SortFileIterator< Packed_addon_fields > Class Template Reference

Fetch the records from a tempoary file. More...

#include <basic_row_iterators.h>

Inheritance diagram for SortFileIterator< Packed_addon_fields >:

Public Member Functions
	SortFileIterator (THD *thd, Mem_root_array< TABLE * > tables, IO_CACHE *tempfile, Filesort_info *sort, ha_rows *examined_rows)
	~SortFileIterator () override
bool	Init () override
	Initialize or reinitialize the iterator. More...
int	Read () override
	Read a result set record from a temporary file after sorting. More...
void	UnlockRow () override
void	SetNullRowFlag (bool) 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...
Public Member Functions inherited from RowIterator
	RowIterator (THD *thd)
virtual	~RowIterator ()=default
	RowIterator (const RowIterator &)=delete
	RowIterator (RowIterator &&)=default
virtual const IteratorProfiler *	GetProfiler () const
	Get profiling data for this iterator (for 'EXPLAIN ANALYZE'). More...
virtual void	SetOverrideProfiler (const IteratorProfiler *profiler)
virtual void	StartPSIBatchMode ()
	Start performance schema batch mode, if supported (otherwise ignored). More...
virtual void	EndPSIBatchModeIfStarted ()
	Ends performance schema batch mode, if started. More...
virtual RowIterator *	real_iterator ()
	If this iterator is wrapping a different iterator (e.g. More...
virtual const RowIterator *	real_iterator () const

Private Attributes
uchar *const	m_rec_buf
const uint	m_buf_length
Mem_root_array< TABLE * >	m_tables
IO_CACHE *const	m_io_cache
Filesort_info *const	m_sort
ha_rows *const	m_examined_rows

Additional Inherited Members
Protected Member Functions inherited from RowIterator
THD *	thd () const

Detailed Description

template<bool Packed_addon_fields>
class SortFileIterator< Packed_addon_fields >

Fetch the records from a tempoary file.

There used to be a comment here saying “should obviously not really happen other than in strange configurations”, but especially with packed addons and InnoDB (where fetching rows needs a primary key lookup), it's not necessarily suboptimal compared to e.g. SortBufferIndirectIterator.

Constructor & Destructor Documentation

SortFileIterator()

template<bool Packed_addon_fields>

SortFileIterator< Packed_addon_fields >::SortFileIterator	(	THD *	thd,
		Mem_root_array< TABLE * >	tables,
		IO_CACHE *	tempfile,
		Filesort_info *	sort,
		ha_rows *	examined_rows
	)

~SortFileIterator()

template<bool Packed_addon_fields>

SortFileIterator< Packed_addon_fields >::~SortFileIterator

override

Member Function Documentation

Init()

template<bool Packed_addon_fields>

bool SortFileIterator< Packed_addon_fields >::Init ( )

inlineoverridevirtual

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 Index_lookup) and allow you to read the records anew.

Implements RowIterator.

Read()

template<bool Packed_addon_fields>

int SortFileIterator< Packed_addon_fields >::Read

overridevirtual

Read a result set record from a temporary file after sorting.

The function first reads the next sorted record from the temporary file. into a buffer. If a success it calls a callback function that unpacks the fields values use in the result set from this buffer into their positions in the regular record buffer.

Template Parameters

Packed_addon_fields

Are the addon fields packed? This is a compile-time constant, to avoid if (....) tests during execution.

Return values

0	Record successfully read.
-1	There is no record to be read anymore.

Implements RowIterator.

SetNullRowFlag()

template<bool Packed_addon_fields>

void SortFileIterator< Packed_addon_fields >::SetNullRowFlag ( bool  is_null_row )

inlineoverridevirtual

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).

This is used for outer joins, when an iterator hasn't produced any rows and we need to produce a NULL-complemented row. Init() or Read() won't necessarily reset this flag, so if you ever set is to true, make sure to also set it to false when needed.

Note that this can be called without Init() having been called first. For example, NestedLoopIterator can hit EOF immediately on the outer iterator, which means the inner iterator doesn't get an Init() call, but will still forward SetNullRowFlag to both inner and outer iterators.

TODO: We shouldn't need this. See the comments on AggregateIterator for a bit more discussion on abstracting out a row interface.

Implements RowIterator.

UnlockRow()

template<bool Packed_addon_fields>

void SortFileIterator< Packed_addon_fields >::UnlockRow ( )

inlineoverridevirtual

Implements RowIterator.

Member Data Documentation

m_buf_length

template<bool Packed_addon_fields>

const uint SortFileIterator< Packed_addon_fields >::m_buf_length

private

m_examined_rows

template<bool Packed_addon_fields>

ha_rows* const SortFileIterator< Packed_addon_fields >::m_examined_rows

private

m_io_cache

template<bool Packed_addon_fields>

IO_CACHE* const SortFileIterator< Packed_addon_fields >::m_io_cache

private

m_rec_buf

template<bool Packed_addon_fields>

uchar* const SortFileIterator< Packed_addon_fields >::m_rec_buf

private

m_sort

template<bool Packed_addon_fields>

Filesort_info* const SortFileIterator< Packed_addon_fields >::m_sort

private

m_tables

template<bool Packed_addon_fields>

Mem_root_array<TABLE *> SortFileIterator< Packed_addon_fields >::m_tables

private

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

• sql/iterators/basic_row_iterators.h
• sql/iterators/sorting_iterator.cc