morph::table::RowSnapshot Class Reference

An immutable view of a table's rows at one moment. More...

#include <data_source.hpp>

Inheritance diagram for morph::table::RowSnapshot:

Public Member Functions
virtual std::size_t	rowCount () const =0
	The number of rows.
virtual RowId	rowId (std::size_t row) const =0
	A row's key.
virtual Cell	cell (std::size_t row, std::size_t column) const =0
	One cell.
virtual void	readColumn (std::size_t column, ColumnSink &sink, std::size_t first, std::size_t last) const
	Hands rows [first, last) of column to sink.

Protected Member Functions
	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

An immutable view of a table's rows at one moment.

Nothing changes a snapshot after it is published, so it is safe to read from any thread, concurrently, for as long as it is held.

Definition at line 457 of file data_source.hpp.

Member Function Documentation

rowCount()

virtual std::size_t morph::table::RowSnapshot::rowCount ( ) const

nodiscardpure virtual

The number of rows.

Returns

Row count.

Implemented in morph::table::RowsSnapshot< Row >, and morph::table::TableSnapshot.

rowId()

virtual RowId morph::table::RowSnapshot::rowId ( std::size_t row ) const

nodiscardpure virtual

A row's key.

Parameters

row	Row index, below rowCount().

Returns

The row's RowId.

Implemented in morph::table::RowsSnapshot< Row >, and morph::table::TableSnapshot.

cell()

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

nodiscardpure virtual

One cell.

Parameters

row	Row index, below rowCount().
column	Column index, below the source's column count.

Returns

The cell, by value.

Implemented in morph::table::RowsSnapshot< Row >, and morph::table::TableSnapshot.

readColumn()

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

inlinevirtual

Hands rows [first, last) of column to sink.

The default calls cell per row. A snapshot that stores cells contiguously overrides it to hand whole runs, which is how the engine reads a column of 100,000 rows without as many virtual calls.

Parameters

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

Reimplemented in morph::table::RowsSnapshot< Row >, and morph::table::TableSnapshot.

Definition at line 486 of file data_source.hpp.

operator=() [1/2]

RowSnapshot & morph::table::RowSnapshot::operator= ( RowSnapshot const & )

protecteddefault

Copy-assigns the base of a snapshot.

Returns

*this.

operator=() [2/2]

RowSnapshot & morph::table::RowSnapshot::operator= ( RowSnapshot && )

protecteddefault

Move-assigns the base of a snapshot.

Returns

*this.

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

• morph/table/data_source.hpp