MySQL  8.0.27
Source Code Documentation
SortFileIterator< Packed_addon_fields > Class Template Referencefinal

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

#include <basic_row_iterators.h>

Inheritance diagram for SortFileIterator< Packed_addon_fields >:
RowIterator

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
 
virtual std::string TimingString () const
 
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 RowIteratorreal_iterator ()
 If this iterator is wrapping a different iterator (e.g. More...
 
virtual const RowIteratorreal_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
THDthd () 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 TABLE_REF) 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_fieldsAre the addon fields packed? This is a compile-time constant, to avoid if (....) tests during execution.
Return values
0Record successfully read.
-1There 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

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