SqlStatement.hpp

// SPDX-License-Identifier: Apache-2.0
 
#pragma once
 
// See SqlOdbcPrelude.hpp's header comment for why this replaces a direct <Windows.h> include.
#include "Api.hpp"
#include "DataBinder/Core.hpp"
#include "DataBinder/SqlDate.hpp"
#include "DataBinder/SqlDateTime.hpp"
#include "DataBinder/SqlFixedString.hpp"
#include "DataBinder/SqlGuid.hpp"
#include "DataBinder/SqlNumeric.hpp"
#include "DataBinder/StringInterface.hpp"
#include "DataBinder/UnicodeConverter.hpp"
#include "DataMapper/Record.hpp"
#include "SqlConnection.hpp"
#include "SqlOdbcPrelude.hpp"
#include "SqlQuery.hpp"
#include "SqlQueryFormatter.hpp"
#include "SqlServerType.hpp"
#include "TracyProfiler.hpp"
#include "Utils.hpp"
 
#include <algorithm>
#include <array>
#include <cstdint>
#include <cstring>
#include <expected>
#include <functional>
#include <optional>
#include <ranges>
#include <source_location>
#include <span>
#include <stdexcept>
#include <type_traits>
#include <vector>
 
#include <sql.h>
#include <sqlext.h>
#include <sqlspi.h>
#include <sqltypes.h>
 
namespace Lightweight
{
 
struct SqlRawColumn;
 
/// @brief Represents an SQL query object, that provides a ToSql() method.
template <typename QueryObject>
concept SqlQueryObject = requires(QueryObject const& queryObject) {
    { queryObject.ToSql() } -> std::convertible_to<std::string>;
};
 
class SqlResultCursor;
class SqlVariantRowCursor;
class RowArrayCursor;
 
/// @brief High level API for (prepared) raw SQL statements
///
/// @ingroup CoreApi
/// SQL prepared statement lifecycle:
/// 1. Prepare the statement
/// 2. Optionally bind output columns to local variables
/// 3. Execute the statement (optionally with input parameters)
/// 4. Fetch rows (if any)
/// 5. Repeat steps 3 and 4 as needed
class [[nodiscard]] SqlStatement final: public SqlDataBinderCallback
{
  public:
    /// Construct a new SqlStatement object, using a new connection, and connect to the default database.
    LIGHTWEIGHT_API SqlStatement();
 
    /// Move constructor.
    LIGHTWEIGHT_API SqlStatement(SqlStatement&& other) noexcept;
    /// Move assignment operator.
    LIGHTWEIGHT_API SqlStatement& operator=(SqlStatement&& other) noexcept;
 
    SqlStatement(SqlStatement const&) noexcept = delete;
    SqlStatement& operator=(SqlStatement const&) noexcept = delete;
 
    /// Construct a new SqlStatement object, using the given connection.
    LIGHTWEIGHT_API explicit SqlStatement(SqlConnection& relatedConnection);
 
    /// Construct a new empty SqlStatement object. No SqlConnection is associated with this statement.
    LIGHTWEIGHT_API explicit SqlStatement(std::nullopt_t /*nullopt*/);
 
    LIGHTWEIGHT_API ~SqlStatement() noexcept final;
 
    /// Checks whether the statement's connection is alive and the statement handle is valid.
    [[nodiscard]] LIGHTWEIGHT_API bool IsAlive() const noexcept;
 
    /// Checks whether the statement has been prepared.
    [[nodiscard]] LIGHTWEIGHT_API bool IsPrepared() const noexcept;
 
    /// Retrieves the connection associated with this statement.
    [[nodiscard]] LIGHTWEIGHT_API SqlConnection& Connection() noexcept;
 
    /// Retrieves the connection associated with this statement.
    [[nodiscard]] LIGHTWEIGHT_API SqlConnection const& Connection() const noexcept;
 
    /// Retrieves the last error information with respect to this SQL statement handle.
    [[nodiscard]] LIGHTWEIGHT_API SqlErrorInfo LastError() const;
 
    /// Creates a new query builder for the given table, compatible with the SQL server being connected.
    LIGHTWEIGHT_API SqlQueryBuilder Query(std::string_view const& table = {}) const;
 
    /// Creates a new query builder for the given table with an alias, compatible with the SQL server being connected.
    [[nodiscard]] LIGHTWEIGHT_API SqlQueryBuilder QueryAs(std::string_view const& table,
                                                          std::string_view const& tableAlias) const;
 
    /// Retrieves the native handle of the statement.
    [[nodiscard]] LIGHTWEIGHT_API SQLHSTMT NativeHandle() const noexcept;
 
    /// Prepares the statement for execution.
    ///
    /// @note When preparing a new SQL statement the previously executed statement, yielding a result set,
    ///       must have been closed.
    LIGHTWEIGHT_API void Prepare(std::string_view query) &;
 
    /// Prepares the statement for execution on an rvalue reference and returns the statement.
    LIGHTWEIGHT_API SqlStatement Prepare(std::string_view query) &&;
 
    /// Prepares the statement for execution.
    ///
    /// @note When preparing a new SQL statement the previously executed statement, yielding a result set,
    ///       must have been closed.
    void Prepare(SqlQueryObject auto const& queryObject) &;
 
    /// Prepares the statement from a query object on an rvalue reference and returns the statement.
    SqlStatement Prepare(SqlQueryObject auto const& queryObject) &&;
 
    /// Retrieves the last prepared query string.
    [[nodiscard]] std::string const& PreparedQuery() const noexcept;
 
    /// Binds an input parameter to the prepared statement at the given column index.
    template <SqlInputParameterBinder Arg>
    void BindInputParameter(SQLSMALLINT columnIndex, Arg const& arg);
 
    /// Binds an input parameter to the prepared statement at the given column index with a column name hint.
    template <SqlInputParameterBinder Arg, typename ColumnName>
    void BindInputParameter(SQLSMALLINT columnIndex, Arg const& arg, ColumnName&& columnNameHint);
 
    /// Binds the given arguments to the prepared statement and executes it.
    template <SqlInputParameterBinder... Args>
    [[nodiscard]] SqlResultCursor Execute(Args const&... args);
 
    /// Binds the given arguments to the prepared statement and executes it.
    [[nodiscard]] LIGHTWEIGHT_API SqlResultCursor ExecuteWithVariants(std::vector<SqlVariant> const& args);
 
    /// Executes the prepared statement on a batch of data.
    ///
    /// Each parameter represents a column, to be bound as input parameter.
    /// The element types of each column container must be explicitly supported.
    ///
    /// In order to support column value types, their underlying storage must be contiguous.
    /// Also the input range itself must be contiguous.
    /// If any of these conditions are not met, the function will not compile - use ExecuteBatch() instead.
    template <SqlInputParameterBatchBinder FirstColumnBatch, std::ranges::contiguous_range... MoreColumnBatches>
    [[nodiscard]] SqlResultCursor ExecuteBatchNative(FirstColumnBatch const& firstColumnBatch,
                                                     MoreColumnBatches const&... moreColumnBatches);
 
    /// Executes the prepared statement on a batch of data.
    ///
    /// Each parameter represents a column, to be bound as input parameter,
    /// and the number of elements in these bound column containers will
    /// mandate how many executions will happen.
    ///
    /// This function will bind and execute each row separately,
    /// which is less efficient than ExecuteBatchNative(), but works non-contiguous input ranges.
    template <SqlInputParameterBatchBinder FirstColumnBatch, std::ranges::range... MoreColumnBatches>
    [[nodiscard]] SqlResultCursor ExecuteBatchSoft(FirstColumnBatch const& firstColumnBatch,
                                                   MoreColumnBatches const&... moreColumnBatches);
 
    /// Executes the prepared statement on a batch of data.
    ///
    /// Each parameter represents a column, to be bound as input parameter,
    /// and the number of elements in these bound column containers will
    /// mandate how many executions will happen.
    template <SqlInputParameterBatchBinder FirstColumnBatch, std::ranges::range... MoreColumnBatches>
    [[nodiscard]] SqlResultCursor ExecuteBatch(FirstColumnBatch const& firstColumnBatch,
                                               MoreColumnBatches const&... moreColumnBatches);
 
    /// Executes the prepared statement on a batch of SqlRawColumn-prepared data.
    ///
    /// @param columns The columns to bind as input parameters.
    /// @param rowCount The number of rows to execute.
    [[nodiscard]] LIGHTWEIGHT_API SqlResultCursor ExecuteBatch(std::span<SqlRawColumn const> columns, size_t rowCount);
 
    /// Executes the prepared statement once per row of a *row-major* batch, preferring native ODBC
    /// row-wise array binding (a single zero-copy @c SQLExecute) and transparently falling back to a
    /// prepare-once + per-row execute when native binding is not possible.
    ///
    /// Unlike the column-major @c ExecuteBatch overloads, the data here is laid out as an array of row
    /// structs (e.g. records). Each @p accessors invocable maps a row to one bound column's value,
    /// returning a reference into the row (so the native path binds the value in place):
    /// @code
    /// stmt.ExecuteBatch(std::span { records }, [](Record const& r) -> auto const& { return r.id.Value(); }, ...);
    /// @endcode
    ///
    /// The native row-wise path is taken when every column value type is row-bindable
    /// (@c SqlNativeRowBindableValue, or @c std::optional of such a non-numeric type), every accessor
    /// returns an lvalue reference, the row stride satisfies the indicator-alignment requirement, and the
    /// driver advertises parameter-array support (@ref SqlConnection::SupportsNativeRowBatch). A
    /// per-row runtime stride check guards against accessors that are not constant-offset subobjects.
    /// Otherwise the soft path is used, which correctly binds every supported type (strings, binary,
    /// variant, @c std::optional of any type, …) one row at a time.
    ///
    /// @param rows Contiguous range of row structs (e.g. @c std::span<Record const>).
    /// @param accessors One invocable per bound column; @c accessor(row) yields that column's value.
    /// @return A result cursor for the executed batch (empty when @p rows is empty).
    template <std::ranges::contiguous_range Rows, typename... ColumnAccessors>
        requires(sizeof...(ColumnAccessors) >= 1
                 && (std::invocable<ColumnAccessors const&, std::ranges::range_value_t<Rows> const&> && ...))
    [[nodiscard]] SqlResultCursor ExecuteBatch(Rows const& rows, ColumnAccessors const&... accessors);
 
    /// Executes the given query directly.
    [[nodiscard]] LIGHTWEIGHT_API SqlResultCursor
    ExecuteDirect(std::string_view const& query, std::source_location location = std::source_location::current());
 
    /// Executes the given query directly.
    [[nodiscard]] SqlResultCursor ExecuteDirect(SqlQueryObject auto const& query,
                                                std::source_location location = std::source_location::current());
 
    /// Executes @p query and prepares bulk row-array fetching with up to @p arrayDepth rows per
    /// SQLFetchScroll round-trip.
    ///
    /// This is a fast-path alternative to the per-cell SQLGetData loop used by the regular result
    /// cursor: it binds one contiguous buffer per result column and materializes whole row blocks
    /// per ODBC round-trip. Only fixed-stride column types are supported (integers, floating point,
    /// and bounded character columns). LOB / unbounded columns (varchar(max)/text/varbinary(max))
    /// are rejected by the returned cursor's construction.
    ///
    /// @param query The SQL query to execute.
    /// @param arrayDepth Maximum number of rows materialized per SQLFetchScroll call (must be > 0).
    /// @return A RowArrayCursor bound to this statement's result set.
    [[nodiscard]] LIGHTWEIGHT_API RowArrayCursor ExecuteBatchFetch(std::string_view query, std::size_t arrayDepth);
 
    /// Executes an SQL migration query, as created b the callback.
    template <typename Callable>
        requires std::invocable<Callable, SqlMigrationQueryBuilder&>
    void MigrateDirect(Callable const& callable, std::source_location location = std::source_location::current());
 
    /// Executes the given query, assuming that only one result row and column is affected, that one will be
    /// returned.
    template <typename T>
        requires(!std::same_as<T, SqlVariant>)
    [[nodiscard]] std::optional<T> ExecuteDirectScalar(std::string_view const& query,
                                                       std::source_location location = std::source_location::current());
 
    /// Executes the given query and returns the single result as an SqlVariant.
    template <typename T>
        requires(std::same_as<T, SqlVariant>)
    [[nodiscard]] T ExecuteDirectScalar(std::string_view const& query,
                                        std::source_location location = std::source_location::current());
 
    /// Executes the given query, assuming that only one result row and column is affected, that one will be
    /// returned.
    template <typename T>
        requires(!std::same_as<T, SqlVariant>)
    [[nodiscard]] std::optional<T> ExecuteDirectScalar(SqlQueryObject auto const& query,
                                                       std::source_location location = std::source_location::current());
 
    /// Executes the given query object and returns the single result as an SqlVariant.
    template <typename T>
        requires(std::same_as<T, SqlVariant>)
    [[nodiscard]] T ExecuteDirectScalar(SqlQueryObject auto const& query,
                                        std::source_location location = std::source_location::current());
 
    /// Retrieves the last insert ID of the given table.
    [[nodiscard]] LIGHTWEIGHT_API size_t LastInsertId(std::string_view tableName);
 
  private:
    friend class SqlResultCursor;
    friend class RowArrayCursor;
 
    [[nodiscard]] LIGHTWEIGHT_API size_t NumRowsAffected() const;
    [[nodiscard]] LIGHTWEIGHT_API size_t NumColumnsAffected() const;
    [[nodiscard]] LIGHTWEIGHT_API bool FetchRow();
    [[nodiscard]] LIGHTWEIGHT_API std::expected<bool, SqlErrorInfo> TryFetchRow(
        std::source_location location = std::source_location::current()) noexcept;
    void CloseCursor() noexcept;
 
    /// @brief Binds the given output column variables to the result columns of this statement.
    /// @tparam Args ODBC-bindable output column types.
    /// @param args Pointers to caller-owned storage for each result column, in order.
    template <SqlOutputColumnBinder... Args>
    void BindOutputColumns(Args*... args);
 
    /// @brief Binds the members of @p records to the result columns of this statement
    /// in declaration order, via reflection.
    /// @tparam Records Aggregate record types whose members map to result columns.
    /// @param records Pointers to caller-owned record instances.
    template <typename... Records>
        requires(((std::is_class_v<Records> && std::is_aggregate_v<Records>) && ...))
    void BindOutputColumnsToRecord(Records*... records);
 
    /// @brief Binds a single output column variable to the result column at @p columnIndex.
    /// @tparam T An ODBC-bindable output column type.
    /// @param columnIndex 1-based result column index.
    /// @param arg Pointer to caller-owned storage for the column value.
    template <SqlOutputColumnBinder T>
    void BindOutputColumn(SQLUSMALLINT columnIndex, T* arg);
 
    template <SqlGetColumnNativeType T>
    [[nodiscard]] bool GetColumn(SQLUSMALLINT column, T* result) const;
 
    template <SqlGetColumnNativeType T>
    [[nodiscard]] T GetColumn(SQLUSMALLINT column) const;
 
    /// @brief Native row-wise batch execution: binds each column in place over @p rows and submits the
    /// whole batch in a single @c SQLExecute. Precondition: every column is row-bindable.
    template <std::ranges::contiguous_range Rows, typename... ColumnAccessors>
    [[nodiscard]] SqlResultCursor ExecuteBatchNativeRowWise(Rows const& rows, ColumnAccessors const&... accessors);
 
    /// @brief Soft row-major batch execution: binds and executes each row individually. Works for every
    /// supported column type and is the fallback when native row-wise binding does not apply.
    template <std::ranges::contiguous_range Rows, typename... ColumnAccessors>
    [[nodiscard]] SqlResultCursor ExecuteBatchSoftRowMajor(Rows const& rows, ColumnAccessors const&... accessors);
 
    /// @brief Native row-wise array fetch: materializes the already-executed result set into @p out by
    /// binding every result column row-wise over a contiguous block of @p out's records and pulling whole
    /// blocks per @c SQLFetchScroll round-trip. The read-side mirror of @c ExecuteBatchNativeRowWise.
    ///
    /// Each @p accessors invocable maps a record to one bound column's mutable value reference (the same
    /// declaration-order column set the per-row path binds), so the driver writes results in place — no
    /// per-cell @c SQLGetData and no intermediate copy. @p out is grown a block at a time and trimmed to
    /// the exact row count on the final partial block.
    ///
    /// @pre Every accessor's value type satisfies @c SqlRowWiseFetchableColumn and
    ///      @c sizeof(Record) % alignof(SQLLEN) == 0 (so the row-strided indicator slots stay aligned).
    ///      The caller (DataMapper) guarantees both before selecting this path.
    /// @param out Destination vector; results are appended to its current contents.
    /// @param arrayDepth Requested maximum rows per @c SQLFetchScroll (clamped to a memory budget).
    /// @param accessors One invocable per result column; @c accessor(record) yields its mutable value.
    template <typename Record, typename... ColumnAccessors>
    void FetchAllRowWise(std::vector<Record>& out, std::size_t arrayDepth, ColumnAccessors const&... accessors);
 
    /// @brief Row-wise array-binds one output column over a record block; returns the row-strided
    /// indicator buffer to feed @c FinalizeRowWiseOutputColumn. For optional columns every row's
    /// optional is pre-engaged so the contained storage is valid to bind into.
    template <typename ValueType>
    [[nodiscard]] SQLLEN* BindRowWiseOutputColumn(SQLUSMALLINT column,
                                                  void* base0,
                                                  std::size_t rowStride,
                                                  std::size_t depth);
 
    /// @brief Issues the row-wise @c SQLBindCol for one non-optional value type @p Value at @p base0 (the
    /// value slot in record 0; the driver strides it by the active @c SQL_ATTR_ROW_BIND_TYPE). Fixed-
    /// capacity char strings bind their inline buffer as @c SQL_C_CHAR (length fixed up per row
    /// afterwards); all other types bind in place via their @c SqlDataBinder::OutputColumn.
    template <typename Value>
    void BindRowWiseValue(SQLUSMALLINT column, void* base0, SQLLEN* indicators);
 
    /// @brief Post-fetch fixup for one row-wise output column: resets each NULL row's @c std::optional to
    /// @c std::nullopt (no-op for non-optional columns, whose value is materialized in place).
    template <typename ValueType>
    static void FinalizeRowWiseOutputColumn(void* base0,
                                            std::size_t rowStride,
                                            std::size_t rowCount,
                                            SQLLEN const* indicators) noexcept;
 
    template <SqlGetColumnNativeType T>
    [[nodiscard]] std::optional<T> GetNullableColumn(SQLUSMALLINT column) const;
 
    template <SqlGetColumnNativeType T>
    [[nodiscard]] T GetColumnOr(SQLUSMALLINT column, T&& defaultValue) const;
 
    LIGHTWEIGHT_API void RequireSuccess(SQLRETURN error,
                                        std::source_location sourceLocation = std::source_location::current()) const;
    LIGHTWEIGHT_API void PlanPostExecuteCallback(std::function<void()>&& cb) override;
    LIGHTWEIGHT_API void PlanPostProcessOutputColumn(std::function<void()>&& cb) override;
    [[nodiscard]] LIGHTWEIGHT_API SqlServerType ServerType() const noexcept override;
    [[nodiscard]] LIGHTWEIGHT_API std::string const& DriverName() const noexcept override;
    LIGHTWEIGHT_API void ProcessPostExecuteCallbacks();
 
    LIGHTWEIGHT_API SQLLEN* ProvideInputIndicator() override;
    LIGHTWEIGHT_API SQLLEN* ProvideInputIndicators(size_t rowCount) override;
    LIGHTWEIGHT_API std::byte* ProvideBatchStagingBuffer(std::size_t byteCount) override;
    LIGHTWEIGHT_API void ClearBatchIndicators();
    /// Restores single-row, column-bound parameter binding (the ODBC default). @c noexcept so it can run
    /// from a scope guard on the native-batch exception path.
    LIGHTWEIGHT_API void ResetParameterArrayBinding() noexcept;
    /// Throws unless @p result is a success code or @c SQL_NO_DATA (a searched UPDATE/DELETE that matched
    /// no rows). Mirrors @c Execute() so the batch execute paths tolerate zero-row updates.
    LIGHTWEIGHT_API void RequireExecuteSucceededOrNoData(
        SQLRETURN result, std::source_location sourceLocation = std::source_location::current()) const;
    /// Native-batch execute check: tolerates @c SQL_NO_DATA and, on success, verifies the driver
    /// processed all @p expectedCount parameter sets (guards against silent partial array execution).
    LIGHTWEIGHT_API void RequireSuccessfulBatchExecute(
        SQLRETURN result,
        SQLULEN processedCount,
        SQLULEN expectedCount,
        std::source_location sourceLocation = std::source_location::current()) const;
    LIGHTWEIGHT_API void RequireIndicators();
    LIGHTWEIGHT_API SQLLEN* GetIndicatorForColumn(SQLUSMALLINT column) noexcept;
 
    // --- Transparent block-prefetch: backs the classic per-row fetch loops (FetchRow + GetColumn,
    // bound output columns, SqlRowIterator, SqlVariantRowCursor) with the existing RowArrayCursor so a
    // whole block of rows is materialized per SQLFetchScroll round-trip instead of one SQLFetch per row.
    // Out-of-line accessors because the prefetch state lives in the opaque Data struct.
 
    /// @return The effective prefetch depth: the connection default gated by the driver's row-array
    /// capability (1 — i.e. disabled — when unsupported or the connection default is <= 1).
    [[nodiscard]] std::size_t EffectivePrefetchDepth() const noexcept;
    /// @brief Arms (or disables) block-prefetch on the first fetch of a result set; idempotent.
    void ArmPrefetchOnFirstFetch() noexcept;
    /// @brief Fetches the next logical row from the block buffer, refilling the block and running the
    /// recorded bound-column scatters as needed. @return true if a row is available.
    [[nodiscard]] std::expected<bool, SqlErrorInfo> FetchRowPrefetched() noexcept;
    /// @return Whether block-prefetch is currently materializing this result set.
    [[nodiscard]] LIGHTWEIGHT_API bool IsPrefetchActive() const noexcept;
    /// @return The active block-prefetch cursor (precondition: @ref IsPrefetchActive).
    [[nodiscard]] LIGHTWEIGHT_API RowArrayCursor const& PrefetchCursorRef() const noexcept;
    /// @return The 0-based offset of the current logical row within the last fetched block.
    [[nodiscard]] LIGHTWEIGHT_API std::size_t PrefetchRowInBlock() const noexcept;
    /// @return Whether @ref BindOutputColumns should record scatter/deferred-bind closures (prefetch is
    /// enabled and not yet disabled) instead of issuing @c SQLBindCol immediately.
    [[nodiscard]] LIGHTWEIGHT_API bool ShouldRecordPrefetchBinding() const noexcept;
    /// @brief Drops any previously recorded scatter/deferred-bind closures (for idempotent re-binding).
    LIGHTWEIGHT_API void ResetPrefetchBindings() noexcept;
    /// @brief Flags that a bound output column's target type cannot be served from the block buffer, so
    /// arming must decline prefetch for this result set and keep the per-row path.
    LIGHTWEIGHT_API void MarkPrefetchBindingUnsupported() noexcept;
    /// @brief Records, for one output column, the per-row scatter closure (copies the current block cell
    /// into the bound destination) and the real @c SQLBindCol thunk used if the result set turns out
    /// prefetch-ineligible. Indexed by @p column so re-binding the same column overwrites rather than
    /// appends — keeping the bound-column loop, the optional rebind idiom, and the DataMapper's per-row
    /// re-binding all bounded.
    /// @param column 1-based output column index.
    /// @param scatter Copies the current block cell into the bound destination.
    /// @param deferredBind Issues the real @c SQLBindCol when the fast path is declined.
    LIGHTWEIGHT_API void RecordPrefetchColumn(SQLUSMALLINT column,
                                              std::function<void()> scatter,
                                              std::function<void()> deferredBind);
    /// @brief Tears down all block-prefetch state, restoring the handle to single-row fetching.
    LIGHTWEIGHT_API void ResetPrefetchState() noexcept;
    /// @brief Builds an @c SqlVariant cell from the block buffer, mirroring @c SqlDataBinder<SqlVariant>.
    [[nodiscard]] LIGHTWEIGHT_API SqlVariant MakePrefetchVariantCell(RowArrayCursor const& cursor,
                                                                     std::size_t row,
                                                                     SQLUSMALLINT column) const;
    /// @brief Converts a materialized block cell to the requested native type @p T.
    template <typename T>
    [[nodiscard]] T ConvertCell(RowArrayCursor const& cursor, std::size_t row, SQLUSMALLINT column) const;
 
    /// @brief Validates a 1-based column index against the active prefetch cursor, throwing
    /// @c std::invalid_argument for an out-of-range index — matching the per-row path's behaviour for
    /// an invalid descriptor index (ODBC SQLSTATE 07009).
    LIGHTWEIGHT_API void RequirePrefetchColumnInRange(RowArrayCursor const& cursor, SQLUSMALLINT column) const;
 
    /// @brief Records the scatter + deferred-bind closures for one bound output column @p arg of type
    /// @p T (used instead of an immediate @c SQLBindCol while prefetch is pending/active).
    template <SqlOutputColumnBinder T>
    void RecordPrefetchOutputColumn(SQLUSMALLINT column, T* arg);
 
    // private data members
    struct Data;
    std::unique_ptr<Data, void (*)(Data*)> m_data; // The private data of the statement
    SqlConnection* m_connection {};                // Pointer to the connection object
    SQLHSTMT m_hStmt {};                           // The native oDBC statement handle
    std::string m_preparedQuery;                   // The last prepared query
    std::optional<SQLSMALLINT> m_numColumns;       // The number of columns in the result set, if known
    SQLSMALLINT m_expectedParameterCount {};       // The number of parameters expected by the query
};
 
/// @ingroup CoreApi
/// API for reading an SQL query result set.
class [[nodiscard]] SqlResultCursor
{
  public:
    /// Constructs a result cursor for the given SQL statement.
    explicit LIGHTWEIGHT_FORCE_INLINE SqlResultCursor(SqlStatement& stmt) noexcept:
        m_stmt { &stmt }
    {
    }
 
    SqlResultCursor() = delete;
    SqlResultCursor(SqlResultCursor const&) = delete;
    SqlResultCursor& operator=(SqlResultCursor const&) = delete;
 
    /// Move constructor.
    constexpr SqlResultCursor(SqlResultCursor&& other) noexcept:
        m_stmt { other.m_stmt }
    {
        other.m_stmt = nullptr;
    }
 
    /// Move assignment operator.
    constexpr SqlResultCursor& operator=(SqlResultCursor&& other) noexcept
    {
        if (this != &other)
        {
            m_stmt = other.m_stmt;
            other.m_stmt = nullptr;
        }
        return *this;
    }
 
    LIGHTWEIGHT_FORCE_INLINE ~SqlResultCursor()
    {
        if (m_stmt)
        {
            m_stmt->CloseCursor();
            m_stmt = nullptr;
        }
    }
 
    /// Retrieves the number of rows affected by the last query.
    [[nodiscard]] LIGHTWEIGHT_FORCE_INLINE size_t NumRowsAffected() const
    {
        return m_stmt->NumRowsAffected();
    }
 
    /// Retrieves the number of columns affected by the last query.
    [[nodiscard]] LIGHTWEIGHT_FORCE_INLINE size_t NumColumnsAffected() const
    {
        return m_stmt->NumColumnsAffected();
    }
 
    /// Binds the given arguments to the prepared statement to store the fetched data to.
    ///
    /// The statement must be prepared before calling this function.
    template <SqlOutputColumnBinder... Args>
    LIGHTWEIGHT_FORCE_INLINE void BindOutputColumns(Args*... args)
    {
        m_stmt->BindOutputColumns(args...);
    }
 
    /// Binds a single output column at the given index to store fetched data.
    template <SqlOutputColumnBinder T>
    LIGHTWEIGHT_FORCE_INLINE void BindOutputColumn(SQLUSMALLINT columnIndex, T* arg)
    {
        m_stmt->BindOutputColumn(columnIndex, arg);
    }
 
    /// Fetches the next row of the result set.
    [[nodiscard]] LIGHTWEIGHT_FORCE_INLINE bool FetchRow()
    {
        return m_stmt->FetchRow();
    }
 
    /// Attempts to fetch the next row, returning an error info on failure instead of throwing.
    [[nodiscard]] LIGHTWEIGHT_FORCE_INLINE std::expected<bool, SqlErrorInfo> TryFetchRow(
        std::source_location location = std::source_location::current()) noexcept
    {
        return m_stmt->TryFetchRow(location);
    }
 
    /// Binds the given records to the prepared statement to store the fetched data to.
    template <typename... Records>
        requires(((std::is_class_v<Records> && std::is_aggregate_v<Records>) && ...))
    LIGHTWEIGHT_FORCE_INLINE void BindOutputColumnsToRecord(Records*... records)
    {
        m_stmt->BindOutputColumnsToRecord(records...);
    }
 
    /// @brief Fast bulk retrieval: materializes this result set into @p out via native ODBC row-wise
    /// array fetch. Forwards to @c SqlStatement::FetchAllRowWise; see its contract (eligibility and
    /// alignment preconditions are the caller's responsibility).
    /// @param out Destination vector; results are appended.
    /// @param arrayDepth Requested maximum rows per @c SQLFetchScroll round-trip.
    /// @param accessors One invocable per result column; @c accessor(record) yields its mutable value.
    template <typename Record, typename... ColumnAccessors>
    LIGHTWEIGHT_FORCE_INLINE void FetchAllRowWise(std::vector<Record>& out,
                                                  std::size_t arrayDepth,
                                                  ColumnAccessors const&... accessors)
    {
        m_stmt->FetchAllRowWise(out, arrayDepth, accessors...);
    }
 
    /// Retrieves the value of the column at the given index for the currently selected row.
    ///
    /// Returns true if the value is not NULL, false otherwise.
    template <SqlGetColumnNativeType T>
    [[nodiscard]] LIGHTWEIGHT_FORCE_INLINE bool GetColumn(SQLUSMALLINT column, T* result) const
    {
        return m_stmt->GetColumn<T>(column, result);
    }
 
    /// Retrieves the value of the column at the given index for the currently selected row.
    template <SqlGetColumnNativeType T>
    [[nodiscard]] LIGHTWEIGHT_FORCE_INLINE T GetColumn(SQLUSMALLINT column) const
    {
        return m_stmt->GetColumn<T>(column);
    }
 
    /// Retrieves the value of the column at the given index for the currently selected row.
    ///
    /// If the value is NULL, std::nullopt is returned.
    template <SqlGetColumnNativeType T>
    [[nodiscard]] LIGHTWEIGHT_FORCE_INLINE std::optional<T> GetNullableColumn(SQLUSMALLINT column) const
    {
        return m_stmt->GetNullableColumn<T>(column);
    }
 
    /// Retrieves the value of the column at the given index for the currently selected row.
    ///
    /// If the value is NULL, the given @p defaultValue is returned.
    template <SqlGetColumnNativeType T>
    [[nodiscard]] T GetColumnOr(SQLUSMALLINT column, T&& defaultValue) const
    {
        return m_stmt->GetColumnOr(column, std::forward<T>(defaultValue));
    }
 
  private:
    SqlStatement* m_stmt;
};
 
/// @brief Thrown by RowArrayCursor's constructor when the executed result set cannot be fixed-stride
/// array-bound.
///
/// Raised for an unbounded/LOB or over-wide character column (e.g. a column the driver reports
/// as SQL_LONGVARCHAR with no size, common for SQLite's dynamically-typed columns), or a query that
/// produced no result columns. It is a precondition signal, not a database error, so callers that
/// use bulk array-fetch purely as an optimization should catch it and fall back to the single-row
/// path. Distinct from SqlException so transient-error retry logic does not mistake it for one.
class RowArrayCursorUnsupported: public std::runtime_error
{
  public:
    using std::runtime_error::runtime_error;
};
 
/// @brief A cursor that fetches result rows in bulk (ODBC row-array binding) for fast column reads.
///
/// Created via @ref SqlStatement::ExecuteBatchFetch. Instead of issuing one SQLGetData per cell,
/// this cursor binds a contiguous buffer per result column and lets the driver materialize whole
/// blocks of rows per SQLFetchScroll round-trip — eliminating per-cell driver round-trips.
///
/// Supported (fixed-stride) column types, decided per column from SQLDescribeCol:
///  - integer SQL types (SQL_BIT, SQL_TINYINT, SQL_SMALLINT, SQL_INTEGER, SQL_BIGINT)
///    are bound as SQL_C_SBIGINT (an int64 buffer);
///  - floating SQL types (SQL_REAL, SQL_FLOAT, SQL_DOUBLE) are bound as SQL_C_DOUBLE;
///  - all other types (char/varchar/decimal/date/time/timestamp/numeric/...) are bound as
///    SQL_C_CHAR with a per-column buffer sized from the reported column size (plus a margin,
///    capped at @ref RowArrayCursor::MaxCharColumnBytes).
///
/// LOB / unbounded columns (the driver reports column size 0 or an absurdly large size) are
/// rejected: constructing the cursor throws std::runtime_error. Such columns must use the
/// single-row SQLGetData fallback instead.
///
/// The cursor is non-copyable and non-movable: it owns the ODBC statement's array-binding state for
/// its entire lifetime. The constructor binds raw pointers into its own members
/// (SQL_ATTR_ROWS_FETCHED_PTR, SQL_ATTR_ROW_STATUS_PTR) and SQLBindCol into its per-column buffers,
/// so the object must not be relocated after construction — a move would leave the statement handle
/// pointing at the moved-from storage (use-after-free). It is constructed in place via
/// @ref SqlStatement::ExecuteBatchFetch (guaranteed copy elision) and used as a local. The bound
/// buffers must outlive the SQLBindCol binding until fetching completes. Cell indices are 1-based to
/// match SqlResultCursor::GetColumn.
class [[nodiscard]] RowArrayCursor
{
  public:
    /// Maximum byte width allocated for a single bound character column (per row). Columns whose
    /// reported size exceeds this are treated as unbounded/LOB and rejected.
    static constexpr std::size_t MaxCharColumnBytes = 8192;
 
    /// Per-cursor byte budget for the bound column buffers. The effective array depth is
    /// clamp(budget / row-byte-width, MinArrayDepth, requested depth), so wide tables (many or
    /// large character columns) bind fewer rows per round-trip instead of exhausting memory —
    /// the footprint otherwise multiplies across workers x columns x depth on real schemas.
    static constexpr std::size_t MemoryBudgetBytes = 4 * 1024 * 1024;
 
    /// Lower bound for the budget-adapted array depth, so bulk fetch always makes progress even
    /// on extremely wide rows (never reduced below this unless the caller requested less).
    static constexpr std::size_t MinArrayDepth = 16;
 
    RowArrayCursor() = delete;
    RowArrayCursor(RowArrayCursor const&) = delete;
    RowArrayCursor& operator=(RowArrayCursor const&) = delete;
    RowArrayCursor(RowArrayCursor&&) = delete;
    RowArrayCursor& operator=(RowArrayCursor&&) = delete;
 
    /// @brief Constructs the cursor on a statement whose query has already been executed.
    /// Inspects the result columns via SQLDescribeCol, allocates per-column buffers, and binds
    /// them with the row-array statement attributes.
    /// @param stmt The executed statement (must outlive the cursor).
    /// @param arrayDepth Maximum number of rows materialized per FetchArray() (must be > 0). The
    ///                   effective depth may be reduced to fit MemoryBudgetBytes (see ArrayDepth()).
    LIGHTWEIGHT_API RowArrayCursor(SqlStatement& stmt, std::size_t arrayDepth);
 
    /// @brief Resets the statement's row-array attributes and unbinds the columns so the handle
    /// can be safely reused.
    LIGHTWEIGHT_API ~RowArrayCursor() noexcept;
 
    /// @brief Fetches the next block of rows into the bound buffers.
    /// @return The number of rows materialized (0 at end of result set).
    [[nodiscard]] LIGHTWEIGHT_API std::size_t FetchArray();
 
    /// @brief The number of result columns.
    [[nodiscard]] LIGHTWEIGHT_API std::size_t ColumnCount() const noexcept;
 
    /// @brief The effective maximum number of rows per FetchArray() — the requested depth, possibly
    /// reduced so the bound buffers fit MemoryBudgetBytes (never below MinArrayDepth unless the
    /// caller requested less).
    [[nodiscard]] LIGHTWEIGHT_API std::size_t ArrayDepth() const noexcept;
 
    /// @brief Reads an integer cell from the last fetched block.
    /// @param rowInBatch 0-based row offset within the block returned by the last FetchArray().
    /// @param column 1-based result column index.
    /// @return The value, or std::nullopt if the cell is NULL.
    [[nodiscard]] LIGHTWEIGHT_API std::optional<std::int64_t> GetI64(std::size_t rowInBatch, SQLUSMALLINT column) const;
 
    /// @brief Reads a floating-point cell from the last fetched block.
    /// @param rowInBatch 0-based row offset within the block returned by the last FetchArray().
    /// @param column 1-based result column index.
    /// @return The value, or std::nullopt if the cell is NULL.
    [[nodiscard]] LIGHTWEIGHT_API std::optional<double> GetF64(std::size_t rowInBatch, SQLUSMALLINT column) const;
 
    /// @brief Reads a text cell from the last fetched block, however the driver bound it.
    ///
    /// Narrow-bound cells (SQL_C_CHAR) are returned verbatim — identical bytes to a single-row
    /// SQL_C_CHAR read. Wide-bound cells (the driver reported SQL_WCHAR/SQL_WVARCHAR, e.g. MSSQL
    /// NVARCHAR, or SQLite which reports all text as wide) are converted UTF-16 -> UTF-8; for
    /// valid UTF-8 source data that round-trip is byte-lossless, so the result again matches the
    /// single-row read of the same cell.
    ///
    /// @param rowInBatch 0-based row offset within the block returned by the last FetchArray().
    /// @param column 1-based result column index.
    /// @return The UTF-8 value, or std::nullopt if the cell is NULL.
    [[nodiscard]] LIGHTWEIGHT_API std::optional<std::string> GetString(std::size_t rowInBatch, SQLUSMALLINT column) const;
 
    /// @brief Reads a DATE cell from the last fetched block. Valid only for Date-bound columns.
    /// @param rowInBatch 0-based row offset within the block returned by the last FetchArray().
    /// @param column 1-based result column index.
    /// @return The value, or std::nullopt if the cell is NULL.
    [[nodiscard]] LIGHTWEIGHT_API std::optional<SqlDate> GetDate(std::size_t rowInBatch, SQLUSMALLINT column) const;
 
    /// @brief Reads a TIMESTAMP/DATETIME cell from the last fetched block. Valid only for
    /// Timestamp-bound columns.
    /// @param rowInBatch 0-based row offset within the block returned by the last FetchArray().
    /// @param column 1-based result column index.
    /// @return The value, or std::nullopt if the cell is NULL.
    [[nodiscard]] LIGHTWEIGHT_API std::optional<SqlDateTime> GetTimestamp(std::size_t rowInBatch, SQLUSMALLINT column) const;
 
    /// @brief Reads a GUID cell from the last fetched block. Valid only for Guid-bound columns
    /// (drivers that report SQL_GUID, i.e. MSSQL uniqueidentifier / PostgreSQL uuid).
    /// @param rowInBatch 0-based row offset within the block returned by the last FetchArray().
    /// @param column 1-based result column index.
    /// @return The value, or std::nullopt if the cell is NULL.
    [[nodiscard]] LIGHTWEIGHT_API std::optional<SqlGuid> GetGuid(std::size_t rowInBatch, SQLUSMALLINT column) const;
 
    /// @brief How a result column is bound for bulk fetch (the canonical fixed-stride C representation
    /// chosen from the column's SQL type). Public so a transparent prefetch layer can dispatch a generic
    /// cell read to the matching @c Get* accessor.
    enum class BoundType : std::uint8_t
    {
        Int64,     //!< bound as SQL_C_SBIGINT into an int64 buffer
        Double,    //!< bound as SQL_C_DOUBLE into a double buffer
        Char,      //!< bound as SQL_C_CHAR into a per-column byte buffer
        WChar,     //!< bound as SQL_C_WCHAR (UTF-16) into a per-column byte buffer
        Date,      //!< bound as SQL_C_TYPE_DATE into a SQL_DATE_STRUCT buffer
        Timestamp, //!< bound as SQL_C_TYPE_TIMESTAMP into a SQL_TIMESTAMP_STRUCT buffer
        Guid,      //!< bound as SQL_C_GUID into a 16-byte GUID buffer
    };
 
    /// @brief The bound representation chosen for a result column.
    /// @param column 1-based result column index.
    /// @return The @ref BoundType the column was bound as.
    [[nodiscard]] LIGHTWEIGHT_API BoundType ColumnBoundType(SQLUSMALLINT column) const;
 
    /// @brief The raw SQL data type the driver reported for a result column (the @c SQL_* value from
    /// @c SQLDescribeCol), letting callers gate on the exact source type rather than the coarser
    /// @ref BoundType (which collapses e.g. textual TIME/NUMERIC into @c Char).
    /// @param column 1-based result column index.
    /// @return The reported @c SQL_* type code.
    [[nodiscard]] LIGHTWEIGHT_API SQLSMALLINT ColumnSqlType(SQLUSMALLINT column) const;
 
    /// @brief Whether a cell in the last fetched block is SQL NULL.
    /// @param rowInBatch 0-based row offset within the block returned by the last @ref FetchArray.
    /// @param column 1-based result column index.
    /// @return @c true if the cell's length indicator is @c SQL_NULL_DATA.
    [[nodiscard]] LIGHTWEIGHT_API bool IsCellNull(std::size_t rowInBatch, SQLUSMALLINT column) const;
 
  private:
    /// Per-column binding metadata + owning buffers.
    struct BoundColumn
    {
        BoundType type {};              //!< how this column is bound
        SQLSMALLINT sqlType {};         //!< raw SQL_* type reported by SQLDescribeCol
        std::size_t elementWidth {};    //!< byte stride of one row's value in the buffer
        std::vector<char> buffer;       //!< arrayDepth * elementWidth contiguous bytes
        std::vector<SQLLEN> indicators; //!< arrayDepth length indicators (SQL_NULL_DATA etc.)
    };
 
    void ResetStatementState() noexcept;
 
    /// Shared accessor prelude: bounds-checks @p rowInBatch against the last fetched block,
    /// verifies the column is bound as @p expected, and returns the cell's buffer address —
    /// or nullptr when the cell is SQL NULL.
    [[nodiscard]] char const* CheckedCell(std::size_t rowInBatch,
                                          SQLUSMALLINT column,
                                          BoundType expected,
                                          char const* accessorName) const;
 
    SqlStatement* m_stmt;
    std::size_t m_arrayDepth;
    std::size_t m_lastFetched = 0;
    std::vector<BoundColumn> m_columns;
    SQLULEN m_rowsFetched = 0;
    std::vector<SQLUSMALLINT> m_rowStatus;
};
 
struct [[nodiscard]] SqlSentinelIterator
{
};
 
class [[nodiscard]] SqlVariantRowIterator
{
  public:
    explicit SqlVariantRowIterator(SqlSentinelIterator /*sentinel*/) noexcept:
        _cursor { nullptr }
    {
    }
 
    explicit SqlVariantRowIterator(SqlResultCursor& cursor) noexcept:
        _numResultColumns { static_cast<SQLUSMALLINT>(cursor.NumColumnsAffected()) },
        _cursor { &cursor }
    {
        _row.reserve(_numResultColumns);
        ++(*this);
    }
 
    SqlVariantRow& operator*() noexcept
    {
        return _row;
    }
 
    SqlVariantRow const& operator*() const noexcept
    {
        return _row;
    }
 
    SqlVariantRowIterator& operator++() noexcept
    {
        _end = !_cursor->FetchRow();
        if (!_end)
        {
            _row.clear();
            for (auto const i: std::views::iota(SQLUSMALLINT(1), SQLUSMALLINT(_numResultColumns + 1)))
                _row.emplace_back(_cursor->GetColumn<SqlVariant>(i));
        }
        return *this;
    }
 
    bool operator!=(SqlSentinelIterator /*sentinel*/) const noexcept
    {
        return !_end;
    }
 
    bool operator!=(SqlVariantRowIterator const& /*rhs*/) const noexcept
    {
        return !_end;
    }
 
  private:
    bool _end = false;
    SQLUSMALLINT _numResultColumns = 0;
    SqlResultCursor* _cursor;
    SqlVariantRow _row;
};
 
class [[nodiscard]] SqlVariantRowCursor
{
  public:
    explicit SqlVariantRowCursor(SqlResultCursor&& cursor):
        _resultCursor { std::move(cursor) }
    {
    }
 
    SqlVariantRowIterator begin() noexcept
    {
        return SqlVariantRowIterator { _resultCursor };
    }
 
    static SqlSentinelIterator end() noexcept
    {
        return SqlSentinelIterator {};
    }
 
  private:
    SqlResultCursor _resultCursor;
};
 
/// @brief SQL query result row iterator
///
/// Can be used to iterate over rows of the database and fetch them into a record type.
/// @tparam T The record type to fetch the rows into.
/// @code
///
/// struct MyRecord
/// {
///    Field<SqlGuid, PrimaryKey::AutoAssign> field1;
///    Field<int> field2;
///    Field<double> field3;
/// };
///
/// for (auto const& row : SqlRowIterator<MyRecord>(conn))
/// {
///    // row is of type MyRecord
///    // row.field1, row.field2, row.field3 are accessible
/// }
/// @endcode
///
/// Pass a second argument to iterate over a subset of the table only. The callable receives the
/// underlying @ref SqlSelectQueryBuilder with the projection for @c T already applied, so the full
/// WHERE / ORDER BY / LIMIT surface of the query builder is available:
/// @code
///
/// for (auto const& row : SqlRowIterator<MyRecord>(conn, [](auto& query) {
///          return query.Where("field2", 10).OrWhere([](auto& query) {
///              return query.Where("field2", 20).Where("field3", 3.14);
///          });
///      }))
/// {
///    // only the rows matching the condition above are fetched
/// }
/// @endcode
template <typename T>
class SqlRowIterator
{
  public:
    /// Callable refining the SELECT query before it is executed.
    ///
    /// It is invoked with the query builder that already carries the projection for @c T. Any value
    /// the callable returns is ignored, so the builder's chaining methods can be returned directly.
    using QueryCustomizer = std::function<void(SqlSelectQueryBuilder&)>;
 
    /// Constructs a row iterator over all rows of the record's table, using the given SQL connection.
    explicit SqlRowIterator(SqlConnection& conn):
        _connection { &conn }
    {
    }
 
    /// Constructs a row iterator over the subset of rows selected by @p queryCustomizer.
    ///
    /// @param conn The SQL connection to run the query on.
    /// @param queryCustomizer Callable refining the SELECT query, e.g. by adding WHERE conditions.
    SqlRowIterator(SqlConnection& conn, QueryCustomizer queryCustomizer):
        _connection { &conn },
        _queryCustomizer { std::move(queryCustomizer) }
    {
    }
 
    class iterator
    {
      public:
        using difference_type = bool;
        using value_type = T;
 
        iterator& operator++()
        {
            if (_cursor)
            {
                _is_end = !_cursor->FetchRow();
                return *this;
            }
            _is_end = true;
            return *this;
        }
 
        LIGHTWEIGHT_FORCE_INLINE value_type operator*() noexcept
        {
            auto res = T {};
 
            // begin() projects the record via Select().Fields<T>(), which emits one column per
            // RecordColumnMember. Enumerate by column position rather than by member position, so that
            // relation members (HasMany, HasManyThrough, HasOneThrough, ...) neither need a column nor
            // shift the ones that follow them.
            SQLUSMALLINT columnIndex = 0;
            EnumerateRecordMembers(res, [this, &columnIndex]<size_t I, typename FieldType>(FieldType& value) {
                if constexpr (RecordColumnMember<FieldType>)
                {
                    ++columnIndex;
                    if constexpr (FieldWithStorage<FieldType>)
                        value = _cursor->GetColumn<typename FieldType::ValueType>(columnIndex);
                    else
                        value = _cursor->GetColumn<FieldType>(columnIndex);
                }
            });
 
            return res;
        }
 
        LIGHTWEIGHT_FORCE_INLINE constexpr bool operator!=(iterator const& other) const noexcept
        {
            return _is_end != other._is_end;
        }
 
        constexpr iterator(std::default_sentinel_t /*sentinel*/) noexcept:
            _is_end { true },
            _cursor { std::nullopt }
        {
        }
 
        explicit iterator(SqlConnection& conn):
            _stmt { std::make_unique<SqlStatement>(conn) },
            _cursor { std::nullopt }
        {
        }
 
        LIGHTWEIGHT_FORCE_INLINE SqlStatement& Statement() noexcept
        {
            return *_stmt;
        }
 
        void SetCursor(SqlResultCursor cursor) noexcept
        {
            _cursor.emplace(std::move(cursor));
        }
 
      private:
        bool _is_end = false;
        std::unique_ptr<SqlStatement> _stmt;
        std::optional<SqlResultCursor> _cursor;
    };
 
    /// Returns an iterator to the first row of the result set.
    iterator begin()
    {
        auto it = iterator { *_connection };
        auto& stmt = it.Statement();
        stmt.Prepare(it.Statement().Query(RecordTableName<T>).Select().template Fields<T>().Build(_queryCustomizer).All());
        it.SetCursor(stmt.Execute());
        ++it;
        return it;
    }
 
    /// Returns a sentinel iterator representing the end of the result set.
    iterator end() noexcept
    {
        return iterator { std::default_sentinel };
    }
 
  private:
    SqlConnection* _connection;
    QueryCustomizer _queryCustomizer = [](SqlSelectQueryBuilder& /*query*/) {
    };
};
 
// {{{ inline implementation
inline LIGHTWEIGHT_FORCE_INLINE bool SqlStatement::IsAlive() const noexcept
{
    return m_connection && m_connection->IsAlive() && m_hStmt != nullptr;
}
 
inline LIGHTWEIGHT_FORCE_INLINE bool SqlStatement::IsPrepared() const noexcept
{
    return !m_preparedQuery.empty();
}
 
inline LIGHTWEIGHT_FORCE_INLINE SqlConnection& SqlStatement::Connection() noexcept
{
    return *m_connection;
}
 
inline LIGHTWEIGHT_FORCE_INLINE SqlConnection const& SqlStatement::Connection() const noexcept
{
    return *m_connection;
}
 
inline LIGHTWEIGHT_FORCE_INLINE SqlErrorInfo SqlStatement::LastError() const
{
    return SqlErrorInfo::FromStatementHandle(m_hStmt);
}
 
inline LIGHTWEIGHT_FORCE_INLINE SQLHSTMT SqlStatement::NativeHandle() const noexcept
{
    return m_hStmt;
}
 
inline LIGHTWEIGHT_FORCE_INLINE void SqlStatement::Prepare(SqlQueryObject auto const& queryObject) &
{
    Prepare(queryObject.ToSql());
}
 
inline LIGHTWEIGHT_FORCE_INLINE SqlStatement SqlStatement::Prepare(SqlQueryObject auto const& queryObject) &&
{
    return Prepare(queryObject.ToSql());
}
 
inline LIGHTWEIGHT_FORCE_INLINE std::string const& SqlStatement::PreparedQuery() const noexcept
{
    return m_preparedQuery;
}
 
/// @brief Out-of-line definition of `SqlStatement::BindOutputColumns`.
template <SqlOutputColumnBinder... Args>
inline LIGHTWEIGHT_FORCE_INLINE void SqlStatement::BindOutputColumns(Args*... args)
{
    if (ShouldRecordPrefetchBinding())
    {
        // Prefetch is pending/active: defer the SQLBindCol and instead record per-column scatters that
        // copy each block cell into the caller's storage. ResetPrefetchBindings makes the optional
        // rebind idiom (re-calling BindOutputColumns each row) idempotent rather than accumulating.
        ResetPrefetchBindings();
        SQLUSMALLINT i = 0;
        ((++i, RecordPrefetchOutputColumn<Args>(i, args)), ...);
        return;
    }
 
    RequireIndicators();
 
    SQLUSMALLINT i = 0;
    ((++i, RequireSuccess(SqlDataBinder<Args>::OutputColumn(m_hStmt, i, args, GetIndicatorForColumn(i), *this))), ...);
}
 
template <typename... Records>
    requires(((std::is_class_v<Records> && std::is_aggregate_v<Records>) && ...))
void SqlStatement::BindOutputColumnsToRecord(Records*... records)
{
    if (ShouldRecordPrefetchBinding())
    {
        ResetPrefetchBindings();
        SQLUSMALLINT i = 0;
        ((EnumerateRecordMembers(*records,
                                 [this, &i]<size_t I, typename FieldType>(FieldType& value) {
                                     // Only members mapping onto a column occupy a result set index.
                                     if constexpr (RecordColumnMember<FieldType>)
                                     {
                                         ++i;
                                         this->RecordPrefetchOutputColumn<FieldType>(i, &value);
                                     }
                                 })),
         ...);
        return;
    }
 
    RequireIndicators();
 
    SQLUSMALLINT i = 0;
    ((EnumerateRecordMembers(*records,
                             [this, &i]<size_t I, typename FieldType>(FieldType& value) {
                                 // Only members mapping onto a column occupy a result set index.
                                 if constexpr (RecordColumnMember<FieldType>)
                                 {
                                     ++i;
                                     RequireSuccess(SqlDataBinder<FieldType>::OutputColumn(
                                         m_hStmt, i, &value, GetIndicatorForColumn(i), *this));
                                 }
                             })),
     ...);
}
 
/// @brief Out-of-line definition of `SqlStatement::BindOutputColumn`.
template <SqlOutputColumnBinder T>
inline LIGHTWEIGHT_FORCE_INLINE void SqlStatement::BindOutputColumn(SQLUSMALLINT columnIndex, T* arg)
{
    // Singular bind: no ResetPrefetchBindings (callers — e.g. the DataMapper — set columns one at a
    // time); RecordPrefetchColumn overwrites the column's slot so per-row re-binding stays bounded.
    if (ShouldRecordPrefetchBinding())
    {
        RecordPrefetchOutputColumn<T>(columnIndex, arg);
        return;
    }
 
    RequireIndicators();
 
    RequireSuccess(SqlDataBinder<T>::OutputColumn(m_hStmt, columnIndex, arg, GetIndicatorForColumn(columnIndex), *this));
}
 
/// @copydoc SqlStatement::BindInputParameter(SQLSMALLINT, Arg const&)
template <SqlInputParameterBinder Arg>
inline LIGHTWEIGHT_FORCE_INLINE void SqlStatement::BindInputParameter(SQLSMALLINT columnIndex, Arg const& arg)
{
    // tell Execute() that we don't know the expected count
    m_expectedParameterCount = (std::numeric_limits<decltype(m_expectedParameterCount)>::max)();
    RequireSuccess(SqlDataBinder<Arg>::InputParameter(m_hStmt, static_cast<SQLUSMALLINT>(columnIndex), arg, *this));
}
 
/// @copydoc SqlStatement::BindInputParameter(SQLSMALLINT, Arg const&, ColumnName&&)
template <SqlInputParameterBinder Arg, typename ColumnName>
inline LIGHTWEIGHT_FORCE_INLINE void SqlStatement::BindInputParameter(SQLSMALLINT columnIndex,
                                                                      Arg const& arg,
                                                                      ColumnName&& columnNameHint)
{
    SqlLogger::GetLogger().OnBindInputParameter(std::forward<ColumnName>(columnNameHint), arg);
    BindInputParameter(columnIndex, arg);
}
 
template <SqlInputParameterBinder... Args>
SqlResultCursor SqlStatement::Execute(Args const&... args)
{
    // Each input parameter must have an address,
    // such that we can call SQLBindParameter() without needing to copy it.
    // The memory region behind the input parameter must exist until the SQLExecute() call.
 
    ZoneScopedN("SqlStatement::Execute");
    ZoneTextObject(m_preparedQuery);
    SqlLogger::GetLogger().OnExecute(m_preparedQuery);
 
    if (!(m_expectedParameterCount == (std::numeric_limits<decltype(m_expectedParameterCount)>::max)()
          && sizeof...(args) == 0)
        && !(m_expectedParameterCount == sizeof...(args)))
        throw std::invalid_argument { "Invalid argument count" };
 
    SQLUSMALLINT i = 0;
    ((++i,
      SqlLogger::GetLogger().OnBindInputParameter({}, args),
      RequireSuccess(SqlDataBinder<Args>::InputParameter(m_hStmt, i, args, *this))),
     ...);
 
    auto const result = SQLExecute(m_hStmt);
 
    if (result != SQL_NO_DATA && result != SQL_SUCCESS && result != SQL_SUCCESS_WITH_INFO)
        throw SqlException(SqlErrorInfo::FromStatementHandle(m_hStmt), std::source_location::current());
 
    ProcessPostExecuteCallbacks();
    return SqlResultCursor { *this };
}
 
// clang-format off
template <typename T>
concept SqlNativeContiguousValueConcept =
       std::same_as<T, bool>
    || std::same_as<T, char>
    || std::same_as<T, unsigned char>
    || std::same_as<T, wchar_t>
    || std::same_as<T, std::int16_t>
    || std::same_as<T, std::uint16_t>
    || std::same_as<T, std::int32_t>
    || std::same_as<T, std::uint32_t>
    || std::same_as<T, std::int64_t>
    || std::same_as<T, std::uint64_t>
    || std::same_as<T, float>
    || std::same_as<T, double>
    || std::same_as<T, SqlDate>
    || std::same_as<T, SqlTime>
    || std::same_as<T, SqlDateTime>
    || std::same_as<T, SqlFixedString<T::Capacity, typename T::value_type, T::PostRetrieveOperation>>;
 
template <typename FirstColumnBatch, typename... MoreColumnBatches>
concept SqlNativeBatchable =
        std::ranges::contiguous_range<FirstColumnBatch>
    && (std::ranges::contiguous_range<MoreColumnBatches> && ...)
    &&  SqlNativeContiguousValueConcept<std::ranges::range_value_t<FirstColumnBatch>>
    && (SqlNativeContiguousValueConcept<std::ranges::range_value_t<MoreColumnBatches>> && ...);
 
// clang-format on
 
/// @brief A value type that can be bound in a native ODBC row-wise parameter array (fixed-width,
/// inline, indicator-free, bound identically across backends). Backed by the data-driven
/// @c SqlIsNativeRowBindableValue trait that each eligible binder header opts into.
template <typename V>
concept SqlNativeRowBindableValue = SqlIsNativeRowBindableValue<V>;
 
/// @brief A @c std::optional column that can be bound zero-copy in a native row-wise batch: the
/// contained type is row-bindable and non-numeric (numeric optionals are not bound at a uniform
/// offset/representation across backends and therefore use the soft path).
template <typename V>
concept SqlOptionalRowBindable =
    SqlIsStdOptional<V> && SqlNativeRowBindableValue<typename V::value_type> && !SqlIsNumericValue<typename V::value_type>;
 
/// @brief A column value type usable on the native row-wise batch path — either a row-bindable fixed
/// value or a row-bindable optional of one.
template <typename V>
concept SqlRowBindableColumn = SqlNativeRowBindableValue<V> || SqlOptionalRowBindable<V>;
 
/// @brief A column usable on the native row-wise array-FETCH fast path. Intentionally identical to the
/// write-side @c SqlRowBindableColumn — the set of types we can bind row-wise into a record block on
/// fetch matches the set we can bind row-wise as a parameter array on execute: fixed-width primitives,
/// date/time/datetime, numeric, char-based fixed-capacity strings, and non-numeric optionals of those.
///
/// Char fixed strings are materialized by a dedicated SQL_C_CHAR bind plus a per-row length/trim fixup
/// (see @c BindRowWiseOutputColumn / @c FinalizeRowWiseOutputColumn); on PostgreSQL, whose driver
/// transcodes SQL_C_CHAR through the client codepage, records carrying one fall back to the per-row
/// (wide) path instead — see @c SqlConnection::RoundTripsNarrowTextByteExact. Growable strings/binary,
/// GUID and variant are not row-bindable and make the whole record fall back to the per-row fetch path.
template <typename V>
concept SqlRowWiseFetchableColumn = SqlRowBindableColumn<V>;
 
/// @brief Whether @p V's binder provides a row-wise batch entry point (@c BatchRowWiseInputParameter).
///
/// Such types (e.g. @c std::optional of a fixed type, or inline fixed-capacity strings) need a
/// temporary row-strided NULL/length indicator buffer, which in turn requires the row stride to keep
/// @c SQLLEN indicator slots aligned. Plain indicator-free fixed values bind via @c InputParameter and
/// do not satisfy this concept.
template <typename V>
concept SqlHasRowWiseBatchBinder =
    requires(SQLHSTMT stmt, SQLUSMALLINT column, V const* elem0, std::size_t n, SqlDataBinderCallback& cb) {
        { SqlDataBinder<V>::BatchRowWiseInputParameter(stmt, column, elem0, n, n, cb) } -> std::same_as<SQLRETURN>;
    };
 
template <SqlInputParameterBatchBinder FirstColumnBatch, std::ranges::contiguous_range... MoreColumnBatches>
SqlResultCursor SqlStatement::ExecuteBatchNative(FirstColumnBatch const& firstColumnBatch,
                                                 MoreColumnBatches const&... moreColumnBatches)
{
    static_assert(SqlNativeBatchable<FirstColumnBatch, MoreColumnBatches...>,
                  "Must be a supported native contiguous element type.");
 
    ZoneScopedN("SqlStatement::ExecuteBatchNative");
    ZoneTextObject(m_preparedQuery);
 
    if (m_expectedParameterCount != 1 + sizeof...(moreColumnBatches))
        throw std::invalid_argument { "Invalid number of columns" };
 
    auto const rowCount = std::ranges::size(firstColumnBatch);
    ZoneValue(rowCount);
    if (!((std::size(moreColumnBatches) == rowCount) && ...))
        throw std::invalid_argument { "Uneven number of rows" };
 
    size_t rowStart = 0;
 
    // clang-format off
    // NOLINTNEXTLINE(performance-no-int-to-ptr)
    RequireSuccess(SQLSetStmtAttr(m_hStmt, SQL_ATTR_PARAMSET_SIZE, (SQLPOINTER) rowCount, 0));
    RequireSuccess(SQLSetStmtAttr(m_hStmt, SQL_ATTR_PARAM_BIND_OFFSET_PTR, &rowStart, 0));
    RequireSuccess(SQLSetStmtAttr(m_hStmt, SQL_ATTR_PARAM_BIND_TYPE, SQL_PARAM_BIND_BY_COLUMN, 0));
    RequireSuccess(SQLSetStmtAttr(m_hStmt, SQL_ATTR_PARAM_OPERATION_PTR, SQL_PARAM_PROCEED, 0));
    ClearBatchIndicators();
    RequireSuccess(SqlDataBinder<std::remove_cvref_t<decltype(*std::ranges::data(firstColumnBatch))>>::
                       BatchInputParameter(m_hStmt, 1, std::ranges::data(firstColumnBatch), rowCount, *this));
    SQLUSMALLINT column = 1;
    (RequireSuccess(SqlDataBinder<std::remove_cvref_t<decltype(*std::ranges::data(moreColumnBatches))>>::
                        BatchInputParameter(m_hStmt, ++column, std::ranges::data(moreColumnBatches), rowCount, *this)),
     ...);
    RequireSuccess(SQLExecute(m_hStmt));
    ProcessPostExecuteCallbacks();
    // clang-format on
    return SqlResultCursor { *this };
}
 
/// @copydoc SqlStatement::ExecuteBatch
template <SqlInputParameterBatchBinder FirstColumnBatch, std::ranges::range... MoreColumnBatches>
inline LIGHTWEIGHT_FORCE_INLINE SqlResultCursor SqlStatement::ExecuteBatch(FirstColumnBatch const& firstColumnBatch,
                                                                           MoreColumnBatches const&... moreColumnBatches)
{
    // If the input ranges are contiguous and their element types are contiguous and supported as well,
    // we can use the native batch execution.
    if constexpr (SqlNativeBatchable<FirstColumnBatch, MoreColumnBatches...>)
        return ExecuteBatchNative(firstColumnBatch, moreColumnBatches...);
    else
        return ExecuteBatchSoft(firstColumnBatch, moreColumnBatches...);
}
 
template <SqlInputParameterBatchBinder FirstColumnBatch, std::ranges::range... MoreColumnBatches>
SqlResultCursor SqlStatement::ExecuteBatchSoft(FirstColumnBatch const& firstColumnBatch,
                                               MoreColumnBatches const&... moreColumnBatches)
{
    ZoneScopedN("SqlStatement::ExecuteBatchSoft");
    ZoneTextObject(m_preparedQuery);
 
    if (m_expectedParameterCount != 1 + sizeof...(moreColumnBatches))
        throw std::invalid_argument { "Invalid number of columns" };
 
    auto const rowCount = std::ranges::size(firstColumnBatch);
    ZoneValue(rowCount);
    if (!((std::size(moreColumnBatches) == rowCount) && ...))
        throw std::invalid_argument { "Uneven number of rows" };
 
    for (auto const rowIndex: std::views::iota(size_t { 0 }, rowCount))
    {
        std::apply(
            [&]<SqlInputParameterBinder... ColumnValues>(ColumnValues const&... columnsInRow) {
                SQLUSMALLINT column = 0;
                ((++column, SqlDataBinder<ColumnValues>::InputParameter(m_hStmt, column, columnsInRow, *this)), ...);
                RequireSuccess(SQLExecute(m_hStmt));
                ProcessPostExecuteCallbacks();
            },
            std::make_tuple(
                std::ref(*std::ranges::next(std::ranges::begin(firstColumnBatch), static_cast<std::ptrdiff_t>(rowIndex))),
                std::ref(
                    *std::ranges::next(std::ranges::begin(moreColumnBatches), static_cast<std::ptrdiff_t>(rowIndex)))...));
    }
    return SqlResultCursor { *this };
}
 
template <std::ranges::contiguous_range Rows, typename... ColumnAccessors>
    requires(sizeof...(ColumnAccessors) >= 1
             && (std::invocable<ColumnAccessors const&, std::ranges::range_value_t<Rows> const&> && ...))
SqlResultCursor SqlStatement::ExecuteBatch(Rows const& rows, ColumnAccessors const&... accessors)
{
    ZoneScopedN("SqlStatement::ExecuteBatch(row-major)");
    ZoneTextObject(m_preparedQuery);
 
    using RowElem = std::ranges::range_value_t<Rows>;
 
    auto const rowCount = std::ranges::size(rows);
    if (rowCount == 0)
        return SqlResultCursor { *this };
 
    if (m_expectedParameterCount != static_cast<SQLSMALLINT>(sizeof...(accessors)))
        throw std::invalid_argument { "Invalid number of columns" };
 
    // Compile-time eligibility for the native row-wise path: every column must be row-bindable, every
    // accessor must return an lvalue reference (so the bound address is a stable subobject), and — when
    // any column needs a row-strided indicator (optionals, inline fixed-capacity strings) — the row
    // stride must keep SQLLEN indicator slots aligned and non-overlapping.
    constexpr bool allColumnsRowBindable =
        (SqlRowBindableColumn<std::remove_cvref_t<std::invoke_result_t<ColumnAccessors const&, RowElem const&>>> && ...);
    constexpr bool allAccessorsReturnReference =
        (std::is_reference_v<std::invoke_result_t<ColumnAccessors const&, RowElem const&>> && ...);
    constexpr bool anyStridedIndicatorColumn =
        (SqlHasRowWiseBatchBinder<std::remove_cvref_t<std::invoke_result_t<ColumnAccessors const&, RowElem const&>>> || ...);
    constexpr bool indicatorAlignmentSatisfied = (sizeof(RowElem) % alignof(SQLLEN)) == 0;
 
    if constexpr (allColumnsRowBindable && allAccessorsReturnReference
                  && (!anyStridedIndicatorColumn || indicatorAlignmentSatisfied))
    {
        auto const* rowData = std::ranges::data(rows);
 
        // Runtime guard: confirm each accessor yields a constant-offset subobject (stride == sizeof row),
        // so binding row 0's address and striding by sizeof(RowElem) addresses every row correctly.
        auto const accessorStrideMatchesRow = [&](auto const& accessor) noexcept -> bool {
            auto const* first = reinterpret_cast<std::byte const*>(std::addressof(accessor(rowData[0])));
            auto const* second = reinterpret_cast<std::byte const*>(std::addressof(accessor(rowData[1])));
            return static_cast<std::size_t>(second - first) == sizeof(RowElem);
        };
        bool const rowStrideOk = rowCount < 2 || (accessorStrideMatchesRow(accessors) && ...);
 
        if (m_connection->SupportsNativeRowBatch() && rowStrideOk)
            return ExecuteBatchNativeRowWise(rows, accessors...);
    }
 
    return ExecuteBatchSoftRowMajor(rows, accessors...);
}
 
template <std::ranges::contiguous_range Rows, typename... ColumnAccessors>
SqlResultCursor SqlStatement::ExecuteBatchNativeRowWise(Rows const& rows, ColumnAccessors const&... accessors)
{
    ZoneScopedN("SqlStatement::ExecuteBatchNativeRowWise");
    ZoneTextObject(m_preparedQuery);
 
    using RowElem = std::ranges::range_value_t<Rows>;
    auto const rowCount = std::ranges::size(rows);
    ZoneValue(rowCount);
    auto const* rowData = std::ranges::data(rows);
 
    // Optimistic init: a driver that ignores SQL_ATTR_PARAMS_PROCESSED_PTR leaves this == rowCount, so the
    // post-execute completeness check never false-trips on such a driver.
    SQLULEN processedCount = rowCount;
 
    // Restore single-row binding and release scratch buffers on EVERY exit — success or exception — so a
    // throwing bind/execute can never leave the handle in a stale multi-paramset/row-wise state for a
    // later reuse (e.g. a single Execute() without re-Prepare). Installed before the attributes are set,
    // so a failure mid-setup is unwound too.
    auto const restoreParameterBinding = detail::Finally([this] {
        ResetParameterArrayBinding();
        ClearBatchIndicators();
    });
 
    // Row-wise array binding: the driver strides every bound value and indicator pointer by sizeof(RowElem).
    // clang-format off
    // NOLINTNEXTLINE(performance-no-int-to-ptr)
    RequireSuccess(SQLSetStmtAttr(m_hStmt, SQL_ATTR_PARAMSET_SIZE, (SQLPOINTER) rowCount, 0));
    // NOLINTNEXTLINE(performance-no-int-to-ptr)
    RequireSuccess(SQLSetStmtAttr(m_hStmt, SQL_ATTR_PARAM_BIND_TYPE, (SQLPOINTER) sizeof(RowElem), 0));
    RequireSuccess(SQLSetStmtAttr(m_hStmt, SQL_ATTR_PARAM_BIND_OFFSET_PTR, nullptr, 0));
    RequireSuccess(SQLSetStmtAttr(m_hStmt, SQL_ATTR_PARAM_OPERATION_PTR, SQL_PARAM_PROCEED, 0));
    RequireSuccess(SQLSetStmtAttr(m_hStmt, SQL_ATTR_PARAMS_PROCESSED_PTR, &processedCount, 0));
    // clang-format on
 
    SQLUSMALLINT column = 0;
    auto const bindColumn = [&](auto const& accessor) {
        ++column;
        using ValueType = std::remove_cvref_t<decltype(accessor(rowData[0]))>;
        // Types needing a per-row indicator (optionals, inline fixed-capacity strings) provide a
        // row-wise batch binder; indicator-free fixed values bind directly via InputParameter.
        if constexpr (SqlHasRowWiseBatchBinder<ValueType>)
            RequireSuccess(SqlDataBinder<ValueType>::BatchRowWiseInputParameter(
                m_hStmt, column, std::addressof(accessor(rowData[0])), sizeof(RowElem), rowCount, *this));
        else
            RequireSuccess(SqlDataBinder<ValueType>::InputParameter(m_hStmt, column, accessor(rowData[0]), *this));
    };
    (bindColumn(accessors), ...);
 
    SqlLogger::GetLogger().OnExecuteBatch();
    // Capture the result before reading processedCount: SQLExecute updates it via the bound pointer, and
    // function-argument evaluation order is unspecified.
    auto const executeResult = SQLExecute(m_hStmt);
    RequireSuccessfulBatchExecute(executeResult, processedCount, static_cast<SQLULEN>(rowCount));
    ProcessPostExecuteCallbacks();
 
    return SqlResultCursor { *this };
}
 
template <std::ranges::contiguous_range Rows, typename... ColumnAccessors>
SqlResultCursor SqlStatement::ExecuteBatchSoftRowMajor(Rows const& rows, ColumnAccessors const&... accessors)
{
    ZoneScopedN("SqlStatement::ExecuteBatchSoftRowMajor");
    ZoneTextObject(m_preparedQuery);
 
    auto const* rowData = std::ranges::data(rows);
    auto const rowCount = std::ranges::size(rows);
    ZoneValue(rowCount);
 
    for (auto const rowIndex: std::views::iota(std::size_t { 0 }, rowCount))
    {
        auto const& row = rowData[rowIndex];
        SQLUSMALLINT column = 0;
        ((++column,
          RequireSuccess(SqlDataBinder<std::remove_cvref_t<decltype(accessors(row))>>::InputParameter(
              m_hStmt, column, accessors(row), *this))),
         ...);
        SqlLogger::GetLogger().OnExecute(m_preparedQuery);
        RequireExecuteSucceededOrNoData(SQLExecute(m_hStmt));
        ProcessPostExecuteCallbacks();
    }
 
    return SqlResultCursor { *this };
}
 
template <typename Value>
void SqlStatement::BindRowWiseValue(SQLUSMALLINT column, void* base0, SQLLEN* indicators)
{
    if constexpr (IsSqlFixedString<Value>)
    {
        // Char fixed-capacity strings are stored inline, so each row's character buffer is reached at
        // Data(row0) + i*rowStride. Bind it as SQL_C_CHAR with the Capacity(+NUL) buffer length (matching
        // the non-PostgreSQL single-row OutputColumn); FinalizeRowWiseOutputColumn sets each row's length
        // from its indicator and applies the trailing-whitespace/NUL trim. PostgreSQL never reaches here:
        // such records take the per-row (wide) path (see SqlConnection::RoundTripsNarrowTextByteExact).
        RequireSuccess(SQLBindCol(m_hStmt,
                                  column,
                                  SQL_C_CHAR,
                                  (SQLPOINTER) SqlBasicStringOperations<Value>::Data(static_cast<Value*>(base0)),
                                  static_cast<SQLLEN>(Value::Capacity) + 1,
                                  indicators));
    }
    else
    {
        // Fixed-width value (primitive, date/time/datetime, numeric): a plain, callback-free SQLBindCol
        // straight into the record field; the driver strides by rowStride.
        RequireSuccess(SqlDataBinder<Value>::OutputColumn(m_hStmt, column, static_cast<Value*>(base0), indicators, *this));
    }
}
 
template <typename ValueType>
SQLLEN* SqlStatement::BindRowWiseOutputColumn(SQLUSMALLINT column, void* base0, std::size_t rowStride, std::size_t depth)
{
    // Row-wise binding strides the indicator pointer by SQL_ATTR_ROW_BIND_TYPE (== rowStride), the same
    // as the value pointer; there is no separate indicator stride. So the indicator array over-allocates
    // to rowStride per row (only sizeof(SQLLEN) of each slot is used) — intrinsic to ODBC row-wise
    // binding, identical to the write side (see SqlDataBinderCallback::ProvideBatchStagingBuffer).
    auto* const indicatorBytes = ProvideBatchStagingBuffer(((depth - 1) * rowStride) + sizeof(SQLLEN));
    auto* const indicators = reinterpret_cast<SQLLEN*>(indicatorBytes);
 
    if constexpr (SqlIsStdOptional<ValueType>)
    {
        using Inner = ValueType::value_type;
        auto* const optBytes = static_cast<std::byte*>(base0);
        // Pre-engage every row's optional so its contained storage is valid to bind into; rows that come
        // back NULL are reset to std::nullopt in FinalizeRowWiseOutputColumn.
        for (auto const i: std::views::iota(std::size_t { 0 }, depth))
            reinterpret_cast<ValueType*>(optBytes + (i * rowStride))->emplace();
        // The contained value of row 0 (constant offset within every optional); the driver strides it by
        // rowStride to reach each row's contained storage in place.
        auto* const contained0 = reinterpret_cast<Inner*>(optBytes + detail::OptionalValueOffset<Inner>());
        BindRowWiseValue<Inner>(column, contained0, indicators);
    }
    else
    {
        BindRowWiseValue<ValueType>(column, base0, indicators);
    }
    return indicators;
}
 
template <typename ValueType>
void SqlStatement::FinalizeRowWiseOutputColumn(void* base0,
                                               std::size_t rowStride,
                                               std::size_t rowCount,
                                               SQLLEN const* indicators) noexcept
{
    auto const indicatorAt = [&](std::size_t i) noexcept {
        return *reinterpret_cast<SQLLEN const*>(reinterpret_cast<std::byte const*>(indicators) + (i * rowStride));
    };
 
    if constexpr (SqlIsStdOptional<ValueType>)
    {
        using Inner = ValueType::value_type;
        auto* const optBytes = static_cast<std::byte*>(base0);
        for (auto const i: std::views::iota(std::size_t { 0 }, rowCount))
        {
            auto* const optional = reinterpret_cast<ValueType*>(optBytes + (i * rowStride));
            if (indicatorAt(i) == SQL_NULL_DATA)
                optional->reset();
            else if constexpr (IsSqlFixedString<Inner>)
            {
                // Engaged char fixed string: set its length and trim, matching the single-row binder.
                // BindRowWiseOutputColumn pre-engages every row and only the NULL branch above ever
                // disengages one, so this holds unconditionally — tested anyway to keep the access
                // provably safe rather than invariant-dependent.
                if (optional->has_value())
                    SqlBasicStringOperations<Inner>::PostProcessOutputColumn(std::addressof(**optional), indicatorAt(i));
            }
            // Engaged fixed-width inner: already materialized in place, nothing more to do.
        }
    }
    else if constexpr (IsSqlFixedString<ValueType>)
    {
        auto* const base = static_cast<std::byte*>(base0);
        for (auto const i: std::views::iota(std::size_t { 0 }, rowCount))
            SqlBasicStringOperations<ValueType>::PostProcessOutputColumn(
                reinterpret_cast<ValueType*>(base + (i * rowStride)), indicatorAt(i));
    }
    // Plain fixed-width non-optional columns: the value is materialized in place; a NULL leaves the
    // default-constructed value untouched, matching the single-row bound-output path.
}
 
template <typename Record, typename... ColumnAccessors>
void SqlStatement::FetchAllRowWise(std::vector<Record>& out, std::size_t arrayDepth, ColumnAccessors const&... accessors)
{
    ZoneScopedN("SqlStatement::FetchAllRowWise");
    ZoneTextObject(m_preparedQuery);
 
    static_assert(sizeof...(ColumnAccessors) >= 1, "FetchAllRowWise requires at least one column accessor");
    constexpr std::size_t columnCount = sizeof...(ColumnAccessors);
 
    // Adapt the depth to the per-cursor memory budget. The row-strided indicator staging over-allocates
    // to sizeof(Record) per row per column, so the per-row footprint is sizeof(Record) * (1 + columns)
    // (data block + one indicator buffer per column). Clamp like RowArrayCursor so wide rows bind fewer
    // rows per round-trip instead of exhausting memory.
    {
        auto const perRow = sizeof(Record) * (1 + columnCount);
        auto const budgetDepth = RowArrayCursor::MemoryBudgetBytes / std::max<std::size_t>(perRow, 1);
        auto const minDepth = std::min(RowArrayCursor::MinArrayDepth, arrayDepth); // never raise above the request
        arrayDepth = std::clamp(budgetDepth, minDepth, arrayDepth);
    }
 
    std::vector<SQLUSMALLINT> rowStatus(arrayDepth);
    SQLULEN rowsFetched = 0;
 
    // Restore single-row, column-bound fetch state and release staging buffers on EVERY exit — success or
    // exception — so a throwing bind/fetch can never leave the handle in a stale row-array state for a
    // later reuse. Mirrors ExecuteBatchNativeRowWise's restoreParameterBinding guard.
    auto const restoreFetchState = detail::Finally([this] {
        SQLFreeStmt(m_hStmt, SQL_UNBIND);
        // clang-format off
        // NOLINTNEXTLINE(performance-no-int-to-ptr)
        SQLSetStmtAttr(m_hStmt, SQL_ATTR_ROW_ARRAY_SIZE, (SQLPOINTER) 1, 0);
        SQLSetStmtAttr(m_hStmt, SQL_ATTR_ROW_BIND_TYPE, SQL_BIND_BY_COLUMN, 0);
        SQLSetStmtAttr(m_hStmt, SQL_ATTR_ROW_STATUS_PTR, nullptr, 0);
        SQLSetStmtAttr(m_hStmt, SQL_ATTR_ROWS_FETCHED_PTR, nullptr, 0);
        // clang-format on
        ClearBatchIndicators();
    });
 
    // clang-format off
    // NOLINTNEXTLINE(performance-no-int-to-ptr)
    RequireSuccess(SQLSetStmtAttr(m_hStmt, SQL_ATTR_ROW_BIND_TYPE, (SQLPOINTER) sizeof(Record), 0));
    // NOLINTNEXTLINE(performance-no-int-to-ptr)
    RequireSuccess(SQLSetStmtAttr(m_hStmt, SQL_ATTR_ROW_ARRAY_SIZE, (SQLPOINTER) arrayDepth, 0));
    RequireSuccess(SQLSetStmtAttr(m_hStmt, SQL_ATTR_ROW_STATUS_PTR, rowStatus.data(), 0));
    RequireSuccess(SQLSetStmtAttr(m_hStmt, SQL_ATTR_ROWS_FETCHED_PTR, &rowsFetched, 0));
    // clang-format on
 
    for (;;)
    {
        std::size_t const base = out.size();
        out.resize(base + arrayDepth);
        Record* const row0 = out.data() + base;
 
        // Rebind each column into this block's records (the value pointer follows out's storage across a
        // reallocation) and refresh the per-column row-strided indicator buffers.
        ClearBatchIndicators();
        std::array<SQLLEN*, columnCount> indicators {};
        SQLUSMALLINT column = 0;
        std::size_t bindIndex = 0;
        ((indicators[bindIndex++] = BindRowWiseOutputColumn<std::remove_cvref_t<decltype(accessors(*row0))>>(
              ++column, std::addressof(accessors(*row0)), sizeof(Record), arrayDepth)),
         ...);
 
        rowsFetched = 0;
        auto const fetchResult = SQLFetchScroll(m_hStmt, SQL_FETCH_NEXT, 0);
        if (fetchResult == SQL_NO_DATA)
        {
            out.resize(base);
            break;
        }
        // SQL_SUCCESS_WITH_INFO is acceptable: rowsFetched stays valid. The fixed-width eligibility gate
        // keeps the bound columns from truncating, so it should not occur for these columns in practice.
        if (!SQL_SUCCEEDED(fetchResult))
            RequireSuccess(fetchResult);
 
        auto const fetched = static_cast<std::size_t>(rowsFetched);
        SqlLogger::GetLogger().OnFetchRow(); // one block-fetch round-trip (vs. one per row on the slow path)
 
        std::size_t finalizeIndex = 0;
        (FinalizeRowWiseOutputColumn<std::remove_cvref_t<decltype(accessors(*row0))>>(
             std::addressof(accessors(*row0)), sizeof(Record), fetched, indicators[finalizeIndex++]),
         ...);
 
        out.resize(base + fetched);
        if (fetched < arrayDepth)
            break;
    }
 
    SqlLogger::GetLogger().OnFetchEnd();
}
 
template <SqlGetColumnNativeType T>
inline bool SqlStatement::GetColumn(SQLUSMALLINT column, T* result) const
{
    if (IsPrefetchActive())
    {
        auto const& cursor = PrefetchCursorRef();
        auto const row = PrefetchRowInBlock();
        RequirePrefetchColumnInRange(cursor, column);
        if (cursor.IsCellNull(row, column))
            return false;
        *result = ConvertCell<T>(cursor, row, column);
        return true;
    }
    SQLLEN indicator {}; // TODO: Handle NULL values if we find out that we need them for our use-cases.
    RequireSuccess(SqlDataBinder<T>::GetColumn(m_hStmt, column, result, &indicator, *this));
    return indicator != SQL_NULL_DATA;
}
 
namespace detail
{
 
    template <typename T>
    concept SqlNullableType = (std::same_as<T, SqlVariant> || IsSpecializationOf<std::optional, T>);
 
    /// Detects @c SqlFixedString<N, Char, Mode> specializations (the inline fixed-capacity strings).
    template <typename T>
    struct IsSqlFixedStringSpec: std::false_type
    {
    };
    template <std::size_t N, typename Char, SqlFixedStringMode Mode>
    struct IsSqlFixedStringSpec<SqlFixedString<N, Char, Mode>>: std::true_type
    {
    };
    template <typename T>
    concept SqlFixedStringCell = IsSqlFixedStringSpec<std::remove_cvref_t<T>>::value;
 
    /// The plain standard string flavours the block-prefetch reader converts to from UTF-8 bytes.
    template <typename T>
    concept PlainStringCell =
        std::same_as<T, std::string> || std::same_as<T, std::u8string> || std::same_as<T, std::u16string>
        || std::same_as<T, std::u32string> || std::same_as<T, std::wstring>;
 
    /// Detects @c SqlNumeric<Precision, Scale> specializations.
    template <typename T>
    struct IsSqlNumericSpec: std::false_type
    {
    };
    template <std::size_t Precision, std::size_t Scale>
    struct IsSqlNumericSpec<SqlNumeric<Precision, Scale>>: std::true_type
    {
    };
    template <typename T>
    concept SqlNumericCell = IsSqlNumericSpec<std::remove_cvref_t<T>>::value;
 
    /// Views a UTF-8 @c std::string (opaque byte container) as a @c std::u8string_view for conversion.
    [[nodiscard]] inline std::u8string_view AsU8View(std::string const& utf8) noexcept
    {
        return std::u8string_view { reinterpret_cast<char8_t const*>(utf8.data()), utf8.size() };
    }
 
    /// @brief Trims the trailing bytes of a fetched fixed-string value to match
    /// @c SqlFixedString::PostProcessOutputColumn (which the single-row @c GetColumn path applies), so a
    /// prefetched value is byte-identical to a per-row read. Every mode strips trailing NULs;
    /// @c FIXED_SIZE_RIGHT_TRIMMED additionally strips trailing ASCII whitespace (e.g. @c CHAR(N) space
    /// padding). Operates on the raw UTF-8 bytes before any wide conversion — ASCII whitespace/NUL are
    /// single bytes that map one-to-one to their wide code units, so the result matches a trim applied
    /// after conversion.
    /// @tparam Mode The fixed string's @c SqlFixedStringMode (its @c PostRetrieveOperation).
    /// @param bytes The fetched UTF-8 bytes, trimmed in place.
    template <SqlFixedStringMode Mode>
    inline void TrimFixedStringBytes(std::string& bytes) noexcept
    {
        auto const isTrailingTrimmable = [](char c) noexcept {
            if (c == '\0')
                return true;
            if constexpr (Mode == SqlFixedStringMode::FIXED_SIZE_RIGHT_TRIMMED)
                return c == ' ' || c == '\t' || c == '\n' || c == '\r' || c == '\v' || c == '\f';
            else
                return false;
        };
        while (!bytes.empty() && isTrailingTrimmable(bytes.back()))
            bytes.pop_back();
    }
 
    /// @brief Decodes the fetched UTF-8 bytes into a @c std::basic_string of the target character type
    /// @p Char, reusing the project's UnicodeConverter. The block-prefetch reader stores text as UTF-8
    /// (RowArrayCursor::GetString); this re-encodes it to the string target's element type.
    /// @tparam Char The target character type (@c char / @c char8_t / @c char16_t / @c char32_t / @c wchar_t).
    /// @param utf8 The fetched UTF-8 bytes.
    /// @return The decoded string in the target encoding.
    template <typename Char>
    [[nodiscard]] inline std::basic_string<Char> DecodeUtf8To(std::string const& utf8)
    {
        if constexpr (std::same_as<Char, char>)
            return utf8;
        else if constexpr (std::same_as<Char, char8_t>)
            return std::u8string { AsU8View(utf8) };
        else if constexpr (std::same_as<Char, char16_t>)
            return ToUtf16(AsU8View(utf8));
        else if constexpr (std::same_as<Char, char32_t>)
            return ToUtf32<std::u32string>(AsU8View(utf8));
        else
            return ToStdWideString(AsU8View(utf8));
    }
 
    /// @brief Any string-like target the block-prefetch reader reconstructs from UTF-8 bytes: the plain
    /// standard strings plus the Lightweight string wrappers (fixed- and dynamic-capacity). Each exposes a
    /// @c value_type and is constructible from a @c std::basic_string of that type.
    template <typename T>
    concept StringLikeCell = PlainStringCell<T> || SqlStringInterface<T>;
 
    /// A scalar target type the block-prefetch reader can reconstruct faithfully (mirrors the non-throwing
    /// branches of @c SqlStatement::ConvertCell). Excludes types whose faithful reconstruction needs the
    /// dedicated single-row binder (e.g. @c SqlNumeric, @c SqlTime, binary, user types).
    template <typename T>
    concept PrefetchConvertibleScalar =
        std::same_as<T, SqlVariant> || std::same_as<T, SqlDate> || std::same_as<T, SqlDateTime> || std::same_as<T, SqlGuid>
        || StringLikeCell<T> || std::is_floating_point_v<T> || std::is_integral_v<T> || std::is_enum_v<T>;
 
    template <typename T>
    struct PrefetchConvertibleOptional: std::false_type
    {
    };
    template <typename U>
    struct PrefetchConvertibleOptional<std::optional<U>>: std::bool_constant<PrefetchConvertibleScalar<U>>
    {
    };
 
    /// A bound output target the prefetch scatter can serve: a convertible scalar or an optional of one.
    template <typename T>
    concept PrefetchConvertible = PrefetchConvertibleScalar<T> || PrefetchConvertibleOptional<T>::value;
 
    /// @brief Reconstructs a temporal or GUID cell from the block buffer. Each target reads its matching
    /// bound representation; a mismatched bound type (only reachable via a cross-type @c GetColumn) yields
    /// a default, mirroring the lenient single-row path. A GUID stored as text (SQLite) is parsed back.
    template <typename T>
    [[nodiscard]] inline T ReadTemporalGuidCell(RowArrayCursor const& cursor, std::size_t row, SQLUSMALLINT column)
    {
        using BoundType = RowArrayCursor::BoundType;
        auto const boundType = cursor.ColumnBoundType(column);
        if constexpr (std::same_as<T, SqlDate>)
            return boundType == BoundType::Date ? cursor.GetDate(row, column).value_or(SqlDate {}) : SqlDate {};
        else if constexpr (std::same_as<T, SqlDateTime>)
            return boundType == BoundType::Timestamp ? cursor.GetTimestamp(row, column).value_or(SqlDateTime {})
                                                     : SqlDateTime {};
        else // SqlGuid
        {
            if (boundType == BoundType::Guid)
                return cursor.GetGuid(row, column).value_or(SqlGuid {});
            if (boundType == BoundType::Char || boundType == BoundType::WChar)
                return SqlGuid::TryParse(cursor.GetString(row, column).value_or(std::string {})).value_or(SqlGuid {});
            return SqlGuid {};
        }
    }
 
    /// @brief Reconstructs a @c SqlNumeric cell from the block buffer (driver-reported as a fixed-width
    /// numeric, bound @c Int64 or @c Double). A non-numeric bound type yields a default.
    template <typename T>
    [[nodiscard]] inline T ReadNumericCell(RowArrayCursor const& cursor, std::size_t row, SQLUSMALLINT column)
    {
        using BoundType = RowArrayCursor::BoundType;
        switch (cursor.ColumnBoundType(column))
        {
            case BoundType::Double:
                return T { cursor.GetF64(row, column).value_or(0.0) };
            case BoundType::Int64:
                return T { static_cast<double>(cursor.GetI64(row, column).value_or(0)) };
            default:
                return T {};
        }
    }
 
    /// @brief Renders a block-buffer cell to UTF-8 text. Character columns are returned verbatim;
    /// numeric, temporal and GUID columns are formatted to their text form. This mirrors the driver's
    /// @c SQL_C_CHAR conversion on the single-row @c GetColumn path so that reading a non-character column
    /// as a string (e.g. a generic "print every column as text" loop) yields the value rather than an
    /// empty string. Integer text is identical to the driver's; floating/temporal text uses the value
    /// type's @c std::formatter, which is backend-independent.
    [[nodiscard]] inline std::string RenderCellAsUtf8(RowArrayCursor const& cursor, std::size_t row, SQLUSMALLINT column)
    {
        switch (cursor.ColumnBoundType(column))
        {
            case RowArrayCursor::BoundType::Char:
            case RowArrayCursor::BoundType::WChar:
                return cursor.GetString(row, column).value_or(std::string {});
            case RowArrayCursor::BoundType::Int64:
                return std::format("{}", cursor.GetI64(row, column).value_or(0));
            case RowArrayCursor::BoundType::Double:
                return std::format("{}", cursor.GetF64(row, column).value_or(0.0));
            case RowArrayCursor::BoundType::Date:
                return std::format("{}", cursor.GetDate(row, column).value_or(SqlDate {}));
            case RowArrayCursor::BoundType::Timestamp:
                return std::format("{}", cursor.GetTimestamp(row, column).value_or(SqlDateTime {}));
            case RowArrayCursor::BoundType::Guid:
                return std::format("{}", cursor.GetGuid(row, column).value_or(SqlGuid {}));
        }
        return std::string {};
    }
 
    /// @brief Reconstructs a string-like cell (plain @c std::string flavours and the Lightweight string
    /// wrappers) from the block buffer, rendering any bound type to text via @ref RenderCellAsUtf8.
    /// Fixed-capacity strings get the same trailing trim the single-row @c GetColumn path applies via
    /// @c SqlFixedString::PostProcessOutputColumn; the UTF-8 bytes are then re-encoded to the target's
    /// element type.
    template <typename T>
    [[nodiscard]] inline T ReadStringLikeCell(RowArrayCursor const& cursor, std::size_t row, SQLUSMALLINT column)
    {
        auto utf8 = RenderCellAsUtf8(cursor, row, column);
        if constexpr (SqlFixedStringCell<T>)
            TrimFixedStringBytes<T::PostRetrieveOperation>(utf8);
        return T { DecodeUtf8To<typename T::value_type>(utf8) };
    }
 
    /// @brief Reconstructs an arithmetic or enum cell from the block buffer, coercing whichever fixed-width
    /// representation the column was bound as (@c Int64 or @c Double) to @p T. A non-arithmetic bound type
    /// yields a default.
    template <typename T>
    [[nodiscard]] inline T ReadArithmeticCell(RowArrayCursor const& cursor, std::size_t row, SQLUSMALLINT column)
    {
        using BoundType = RowArrayCursor::BoundType;
        switch (cursor.ColumnBoundType(column))
        {
            case BoundType::Int64:
                return static_cast<T>(cursor.GetI64(row, column).value_or(0));
            case BoundType::Double:
                return static_cast<T>(cursor.GetF64(row, column).value_or(0.0));
            default:
                return T {};
        }
    }
 
} // end namespace detail
 
template <typename T>
inline T SqlStatement::ConvertCell(RowArrayCursor const& cursor, std::size_t row, SQLUSMALLINT column) const
{
    // Dispatch the target type to the matching reconstruction helper. The arming allowlist keeps the
    // column's bound representation in step with the natural target type; each helper additionally guards
    // on the bound type so a cross-type raw GetColumn read degrades to a default rather than throwing.
    if constexpr (std::same_as<T, SqlVariant>)
        return MakePrefetchVariantCell(cursor, row, column);
    else if constexpr (IsSpecializationOf<std::optional, T>)
    {
        if (cursor.IsCellNull(row, column))
            return std::nullopt;
        return T { ConvertCell<typename T::value_type>(cursor, row, column) };
    }
    else if constexpr (std::same_as<T, SqlDate> || std::same_as<T, SqlDateTime> || std::same_as<T, SqlGuid>)
        return detail::ReadTemporalGuidCell<T>(cursor, row, column);
    else if constexpr (detail::SqlNumericCell<T>)
        return detail::ReadNumericCell<T>(cursor, row, column);
    else if constexpr (detail::StringLikeCell<T>)
        return detail::ReadStringLikeCell<T>(cursor, row, column);
    else if constexpr (std::is_floating_point_v<T> || std::is_integral_v<T> || std::is_enum_v<T>)
        return detail::ReadArithmeticCell<T>(cursor, row, column);
    else
        // A target type the block buffer cannot reconstruct (e.g. a user type with a custom binder). The
        // bound path declines prefetch for such targets (see PrefetchConvertible); reaching here via a raw
        // GetColumn returns a default rather than crashing.
        return T {};
}
 
template <SqlOutputColumnBinder T>
inline void SqlStatement::RecordPrefetchOutputColumn(SQLUSMALLINT column, T* arg)
{
    auto deferredBind = [this, column, arg] {
        RequireIndicators();
        RequireSuccess(SqlDataBinder<T>::OutputColumn(m_hStmt, column, arg, GetIndicatorForColumn(column), *this));
    };
    if constexpr (detail::PrefetchConvertible<T>)
    {
        RecordPrefetchColumn(
            column,
            [this, column, arg] { *arg = ConvertCell<T>(PrefetchCursorRef(), PrefetchRowInBlock(), column); },
            std::move(deferredBind));
    }
    else
    {
        // The target type cannot be reconstructed from the block buffer; record only the real bind and
        // flag the set so arming declines prefetch and the deferred binds drive the per-row path.
        RecordPrefetchColumn(column, {}, std::move(deferredBind));
        MarkPrefetchBindingUnsupported();
    }
}
 
template <SqlGetColumnNativeType T>
inline T SqlStatement::GetColumn(SQLUSMALLINT column) const
{
    if (IsPrefetchActive())
    {
        auto const& cursor = PrefetchCursorRef();
        auto const row = PrefetchRowInBlock();
        RequirePrefetchColumnInRange(cursor, column);
        if constexpr (!detail::SqlNullableType<T>)
            if (cursor.IsCellNull(row, column))
                throw std::runtime_error { "Column value is NULL" };
        return ConvertCell<T>(cursor, row, column);
    }
    T result {};
    SQLLEN indicator {};
    {
        // SQLGetData is where the ODBC driver materializes the column value (driver/network I/O).
        // Isolating it lets a profiler separate I/O-bound retrieval from CPU-bound value conversion
        // done by the caller — the key question for deciding what to parallelize.
        ZoneScopedN("SqlStatement::ColumnGetData");
        RequireSuccess(SqlDataBinder<T>::GetColumn(m_hStmt, column, &result, &indicator, *this));
    }
    if constexpr (!detail::SqlNullableType<T>)
        if (indicator == SQL_NULL_DATA)
            throw std::runtime_error { "Column value is NULL" };
    return result;
}
 
template <SqlGetColumnNativeType T>
inline std::optional<T> SqlStatement::GetNullableColumn(SQLUSMALLINT column) const
{
    if (IsPrefetchActive())
    {
        auto const& cursor = PrefetchCursorRef();
        auto const row = PrefetchRowInBlock();
        RequirePrefetchColumnInRange(cursor, column);
        if (cursor.IsCellNull(row, column))
            return std::nullopt;
        return ConvertCell<T>(cursor, row, column);
    }
    T result {};
    SQLLEN indicator {}; // TODO: Handle NULL values if we find out that we need them for our use-cases.
    {
        ZoneScopedN("SqlStatement::ColumnGetData");
        RequireSuccess(SqlDataBinder<T>::GetColumn(m_hStmt, column, &result, &indicator, *this));
    }
    if (indicator == SQL_NULL_DATA)
        return std::nullopt;
    return { std::move(result) };
}
 
template <SqlGetColumnNativeType T>
T SqlStatement::GetColumnOr(SQLUSMALLINT column, T&& defaultValue) const
{
    return GetNullableColumn<T>(column).value_or(std::forward<T>(defaultValue));
}
 
inline LIGHTWEIGHT_FORCE_INLINE SqlResultCursor SqlStatement::ExecuteDirect(SqlQueryObject auto const& query,
                                                                            std::source_location location)
{
    return ExecuteDirect(query.ToSql(), location);
}
 
template <typename Callable>
    requires std::invocable<Callable, SqlMigrationQueryBuilder&>
void SqlStatement::MigrateDirect(Callable const& callable, std::source_location location)
{
    ZoneScopedN("SqlStatement::MigrateDirect");
    auto migration = SqlMigrationQueryBuilder { Connection().QueryFormatter() };
    callable(migration);
    auto const queries = migration.GetPlan().ToSql();
    ZoneValue(queries.size());
 
    // A comment-only `-- LIGHTWEIGHT_SQLITE_GUARD:` script (e.g. ALTER COLUMN or a foreign-key change on
    // SQLite) carries no executable DDL: the schema change is performed by the migration executor's
    // table-rebuild path, which only runs via MigrationManager. Executing such a script directly here
    // would silently do nothing, so fail loudly and point at the supported entry point instead.
    auto const isCommentOnlyGuardScript = [](std::string_view script) {
        constexpr std::string_view marker = "-- LIGHTWEIGHT_SQLITE_GUARD:";
        if (!script.starts_with(marker))
            return false;
        auto const newline = script.find('\n');
        if (newline == std::string_view::npos)
            return true; // sentinel line only, nothing executable follows
        auto const body = script.substr(newline + 1);
        auto const bodyStart = body.find_first_not_of(" \t\r\n");
        return bodyStart == std::string_view::npos || body.substr(bodyStart).starts_with("--");
    };
 
    for (auto const& query: queries)
    {
        if (isCommentOnlyGuardScript(query))
            throw std::runtime_error(
                std::format("SqlStatement::MigrateDirect cannot apply this SQLite schema change directly because it "
                            "requires a table rebuild (e.g. ALTER COLUMN or a foreign-key change). Apply it through "
                            "MigrationManager::ApplyPendingMigrations, which runs the rebuild executor.\n  Script: {}",
                            query));
        [[maybe_unused]] auto cursor = ExecuteDirect(query, location);
    }
}
 
template <typename T>
    requires(!std::same_as<T, SqlVariant>)
inline std::optional<T> SqlStatement::ExecuteDirectScalar(std::string_view const& query, std::source_location location)
{
    auto cursor = ExecuteDirect(query, location);
    RequireSuccess(FetchRow());
    return GetNullableColumn<T>(1);
}
 
template <typename T>
    requires(std::same_as<T, SqlVariant>)
inline T SqlStatement::ExecuteDirectScalar(std::string_view const& query, std::source_location location)
{
    auto cursor = ExecuteDirect(query, location);
    RequireSuccess(FetchRow());
    if (auto result = GetNullableColumn<T>(1); result.has_value())
        return *result;
    return SqlVariant { SqlNullValue };
}
 
template <typename T>
    requires(!std::same_as<T, SqlVariant>)
inline std::optional<T> SqlStatement::ExecuteDirectScalar(SqlQueryObject auto const& query, std::source_location location)
{
    return ExecuteDirectScalar<T>(query.ToSql(), location);
}
 
template <typename T>
    requires(std::same_as<T, SqlVariant>)
inline T SqlStatement::ExecuteDirectScalar(SqlQueryObject auto const& query, std::source_location location)
{
    return ExecuteDirectScalar<T>(query.ToSql(), location);
}
 
inline LIGHTWEIGHT_FORCE_INLINE void SqlStatement::CloseCursor() noexcept
{
    // Tear down any block-prefetch first: the RowArrayCursor destructor unbinds the columns and
    // restores SQL_ATTR_ROW_ARRAY_SIZE so the SQLFreeStmt(SQL_CLOSE) below — and the next query on this
    // statement — start from a clean single-row state. Resets the prefetch lifecycle to Unarmed.
    ResetPrefetchState();
 
    // SQL Server batches and DML/DDL row-count tokens produce multiple result
    // sets per SQLExecDirect. SQLFreeStmt(SQL_CLOSE) only discards the current
    // cursor — remaining result sets stay pending on the *connection*, and
    // without MARS every subsequent statement on that connection fails with
    // HY000 "Connection is busy with results for another command". Drain via
    // SQLMoreResults until SQL_NO_DATA (or an error), then close.
    //
    // SQLMoreResults is standard ODBC; SQLite and PostgreSQL drivers return
    // SQL_NO_DATA on the first call when nothing is pending, so the cost on
    // single-statement queries is one no-op driver call.
    while (true)
    {
        auto const rc = SQLMoreResults(m_hStmt);
        if (rc == SQL_NO_DATA || !SQL_SUCCEEDED(rc))
            break;
    }
    SQLFreeStmt(m_hStmt, SQL_CLOSE);
    SqlLogger::GetLogger().OnFetchEnd();
}
 
// }}}
 
} // namespace Lightweight