A RowSnapshot that stores rows in shared, immutable chunks. More...

#include <data_source.hpp>

Inheritance diagram for morph::table::TableSnapshot:

Public Member Functions
	TableSnapshot (std::size_t columnCount)
	Constructs an empty snapshot.
std::size_t	rowCount () const override
	The number of rows.
std::size_t	columnCount () const noexcept
	The number of columns.
RowId	rowId (std::size_t row) const override
	A row's key.
Cell	cell (std::size_t row, std::size_t column) const override
	One cell.
void	readColumn (std::size_t column, ColumnSink &sink, std::size_t first, std::size_t last) const override
	Hands rows [first, last) of `column` to `sink`, one run per chunk.
std::shared_ptr< TableSnapshot const >	withRow (std::size_t row, std::vector< Cell > cells) const
	A copy of this snapshot with one row's cells replaced. Only that row's chunk is copied.
std::shared_ptr< TableSnapshot const >	withInserted (std::size_t row, RowId key, std::vector< Cell > cells) const
	A copy with a row inserted before `row`. Chunks before it are shared.
std::shared_ptr< TableSnapshot const >	withRemoved (std::size_t row) const
	A copy with row `row` removed. Chunks before it are shared.
bool	sharesChunk (TableSnapshot const &other, std::size_t row) const noexcept
	Whether this snapshot and `other` share the chunk holding `row`.

Static Public Member Functions
static std::shared_ptr< TableSnapshot const >	fromRows (std::size_t columnCount, std::vector< RowId > ids, std::vector< std::vector< Cell > > rows)
	Builds a snapshot from rows.

Static Public Attributes
static constexpr std::size_t	kChunkRows = 256
	Rows per chunk: small enough that copying one is cheap, large enough that a column read hands long runs.

Additional Inherited Members
Protected Member Functions inherited from morph::table::RowSnapshot
	RowSnapshot (RowSnapshot const &)=default
	Copies the base of a snapshot: a derived snapshot makes a changed copy of itself this way.
	RowSnapshot (RowSnapshot &&)=default
	Moves the base of a snapshot.
RowSnapshot &	operator= (RowSnapshot const &)=default
	Copy-assigns the base of a snapshot.
RowSnapshot &	operator= (RowSnapshot &&)=default
	Move-assigns the base of a snapshot.

Detailed Description

A RowSnapshot that stores rows in shared, immutable chunks.

Changing one row produces a new snapshot that shares every chunk but the one holding the row, so a stream of updates against a table a worker is still reading costs one chunk copy per update, not one table copy.

Definition at line 513 of file data_source.hpp.

Constructor & Destructor Documentation

◆ TableSnapshot()

morph::table::TableSnapshot::TableSnapshot ( std::size_t columnCount )

inlineexplicit

Constructs an empty snapshot.

Parameters

columnCount Number of columns every row has.

Definition at line 521 of file data_source.hpp.

Member Function Documentation

◆ fromRows()

std::shared_ptr< TableSnapshot const > morph::table::TableSnapshot::fromRows	(	std::size_t	columnCount,
		std::vector< RowId >	ids,
		std::vector< std::vector< Cell > >	rows )

inlinestaticnodiscard

Builds a snapshot from rows.

Parameters

columnCount	Number of columns.
ids	The rows' keys.
rows	The rows' cells; each row has `columnCount` cells (missing cells are empty, extra cells are dropped).

Returns: The snapshot.

Definition at line 529 of file data_source.hpp.

◆ rowCount()

std::size_t morph::table::TableSnapshot::rowCount ( ) const

inlinenodiscardoverridevirtual

The number of rows.

Returns: Row count.

Implements morph::table::RowSnapshot.

Definition at line 538 of file data_source.hpp.

◆ columnCount()

std::size_t morph::table::TableSnapshot::columnCount ( ) const

inlinenodiscardnoexcept

The number of columns.

Returns: Column count.

Definition at line 542 of file data_source.hpp.

◆ rowId()

RowId morph::table::TableSnapshot::rowId ( std::size_t row ) const

inlinenodiscardoverridevirtual

A row's key.

Parameters

row	Row index.

Returns: The key.

Implements morph::table::RowSnapshot.

Definition at line 547 of file data_source.hpp.

◆ cell()

Cell morph::table::TableSnapshot::cell	(	std::size_t	row,
		std::size_t	column ) const

inlinenodiscardoverridevirtual

One cell.

Parameters

row	Row index.
column	Column index.

Returns: The cell.

Implements morph::table::RowSnapshot.

Definition at line 555 of file data_source.hpp.

◆ readColumn()

void morph::table::TableSnapshot::readColumn	(	std::size_t	column,
		ColumnSink &	sink,
		std::size_t	first,
		std::size_t	last ) const

inlineoverridevirtual

Hands rows [first, last) of column to sink, one run per chunk.

Parameters

column	Column index.
sink	Receives the cells.
first	First row.
last	One past the last row.

Reimplemented from morph::table::RowSnapshot.

Definition at line 564 of file data_source.hpp.

◆ withRow()

std::shared_ptr< TableSnapshot const > morph::table::TableSnapshot::withRow	(	std::size_t	row,
		std::vector< Cell >	cells ) const

inlinenodiscard

A copy of this snapshot with one row's cells replaced. Only that row's chunk is copied.

Parameters

row	Row index.
cells	The new cells.

Returns: The new snapshot.

Definition at line 579 of file data_source.hpp.

◆ withInserted()

std::shared_ptr< TableSnapshot const > morph::table::TableSnapshot::withInserted	(	std::size_t	row,
		RowId	key,
		std::vector< Cell >	cells ) const

inlinenodiscard

A copy with a row inserted before row. Chunks before it are shared.

Parameters

row	Insert position, at most rowCount().
key	The new row's key.
cells	The new row's cells.

Returns: The new snapshot.

Definition at line 595 of file data_source.hpp.

◆ withRemoved()

std::shared_ptr< TableSnapshot const > morph::table::TableSnapshot::withRemoved ( std::size_t row ) const

inlinenodiscard

A copy with row row removed. Chunks before it are shared.

Parameters

row	Row index.

Returns: The new snapshot.

Definition at line 608 of file data_source.hpp.

◆ sharesChunk()

bool morph::table::TableSnapshot::sharesChunk	(	TableSnapshot const &	other,
		std::size_t	row ) const

inlinenodiscardnoexcept

Whether this snapshot and other share the chunk holding row.

Parameters

other	Another snapshot.
row	Row index valid in both.

Returns: true when the chunk is the same object.

Definition at line 621 of file data_source.hpp.

Member Data Documentation

◆ kChunkRows

std::size_t morph::table::TableSnapshot::kChunkRows = 256

staticconstexpr

Rows per chunk: small enough that copying one is cheap, large enough that a column read hands long runs.

Definition at line 517 of file data_source.hpp.

The documentation for this class was generated from the following file:

morph/table/data_source.hpp

Public Member Functions

Static Public Member Functions

Static Public Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ TableSnapshot()

Member Function Documentation

◆ fromRows()

◆ rowCount()

◆ columnCount()

◆ rowId()

◆ cell()

◆ readColumn()

◆ withRow()

◆ withInserted()

◆ withRemoved()

◆ sharesChunk()

Member Data Documentation

◆ kChunkRows