ConstIterator Class Reference

An iterator that reads from a table where only a single row is known to be matching, no matter what's on the left side, i.e., WHERE column=<const>. More...

#include <ref_row_iterators.h>

Inheritance diagram for ConstIterator:

Public Member Functions
	ConstIterator (THD *thd, TABLE *table, TABLE_REF *table_ref, ha_rows *examined_rows)
bool	Init () override
	Initialize or reinitialize the iterator. More...
int	Read () override
	Read a constant table when there is at most one matching row, using an index lookup. More...
void	UnlockRow () override
	Rows from const tables are read once but potentially used multiple times during execution of a query. More...
Public Member Functions inherited from TableRowIterator
	TableRowIterator (THD *thd, TABLE *table)
void	UnlockRow () override
	The default implementation of unlock-row method of RowIterator, used in all access methods except EQRefIterator. More...
void	SetNullRowFlag (bool is_null_row) override
	Mark the current row buffer as containing a NULL row or not, so that if you read from it and the flag is true, you'll get only NULLs no matter what is actually in the buffer (typically some old leftover row). More...
void	StartPSIBatchMode () override
	Start performance schema batch mode, if supported (otherwise ignored). More...
void	EndPSIBatchModeIfStarted () override
	Ends performance schema batch mode, if started. More...
Public Member Functions inherited from RowIterator
	RowIterator (THD *thd)
virtual	~RowIterator ()=default
	RowIterator (const RowIterator &)=delete
	RowIterator (RowIterator &&)=default
virtual std::string	TimingString () const
virtual RowIterator *	real_iterator ()
	If this iterator is wrapping a different iterator (e.g. More...
virtual const RowIterator *	real_iterator () const

Private Attributes
TABLE_REF *const	m_ref
bool	m_first_record_since_init
ha_rows *const	m_examined_rows

Additional Inherited Members
Protected Member Functions inherited from TableRowIterator
int	HandleError (int error)
void	PrintError (int error)
TABLE *	table () const
Protected Member Functions inherited from RowIterator
THD *	thd () const

Detailed Description

An iterator that reads from a table where only a single row is known to be matching, no matter what's on the left side, i.e., WHERE column=<const>.

Constructor & Destructor Documentation

ConstIterator()

ConstIterator::ConstIterator	(	THD *	thd,
		TABLE *	table,
		TABLE_REF *	table_ref,
		ha_rows *	examined_rows
	)

Member Function Documentation

Init()

bool ConstIterator::Init ( )

overridevirtual

Initialize or reinitialize the iterator.

You must always call Init() before trying a Read() (but Init() does not imply Read()).

You can call Init() multiple times; subsequent calls will rewind the iterator (or reposition it, depending on whether the iterator takes in e.g. a TABLE_REF) and allow you to read the records anew.

Implements RowIterator.

Read()

int ConstIterator::Read ( )

overridevirtual

Read a constant table when there is at most one matching row, using an index lookup.

Return values

0	Row was found
-1	Row was not found
1	Got an error (other than row not found) during read

Implements RowIterator.

UnlockRow()

void ConstIterator::UnlockRow ( )

inlineoverridevirtual

Rows from const tables are read once but potentially used multiple times during execution of a query.

Ensure such rows are never unlocked during query execution.

Implements RowIterator.

Member Data Documentation

m_examined_rows

ha_rows* const ConstIterator::m_examined_rows

private

m_first_record_since_init

bool ConstIterator::m_first_record_since_init

private

m_ref

TABLE_REF* const ConstIterator::m_ref

private

---

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

• sql/iterators/ref_row_iterators.h
• sql/iterators/ref_row_iterators.cc