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

Fetch the records from a memory buffer. More...

#include <basic_row_iterators.h>

Inheritance diagram for SortBufferIterator< Packed_addon_fields >:
RowIterator

Public Member Functions

 SortBufferIterator (THD *thd, Mem_root_array< TABLE * > tables, Filesort_info *sort, Sort_result *sort_result, ha_rows *examined_rows)
 
 ~SortBufferIterator () override
 
bool Init () override
 Initialize or reinitialize the iterator. More...
 
int Read () override
 Read a result set record from a buffer 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

Filesort_info *const m_sort
 
Sort_result *const m_sort_result
 
unsigned m_unpack_counter
 
ha_rows *const m_examined_rows
 
Mem_root_array< TABLE * > m_tables
 

Additional Inherited Members

- Protected Member Functions inherited from RowIterator
THDthd () const
 

Detailed Description

template<bool Packed_addon_fields>
class SortBufferIterator< Packed_addon_fields >

Fetch the records from a memory buffer.

This method is used when table->sort.addon_field is allocated. This is allocated for most SELECT queries not involving any BLOB's. In this case the records are fetched from a memory buffer.

Constructor & Destructor Documentation

◆ SortBufferIterator()

template<bool Packed_addon_fields>
SortBufferIterator< Packed_addon_fields >::SortBufferIterator ( THD thd,
Mem_root_array< TABLE * >  tables,
Filesort_info sort,
Sort_result sort_result,
ha_rows examined_rows 
)

◆ ~SortBufferIterator()

template<bool Packed_addon_fields>
SortBufferIterator< Packed_addon_fields >::~SortBufferIterator
override

Member Function Documentation

◆ Init()

template<bool Packed_addon_fields>
bool SortBufferIterator< Packed_addon_fields >::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()

template<bool Packed_addon_fields>
int SortBufferIterator< Packed_addon_fields >::Read
overridevirtual

Read a result set record from a buffer after sorting.

Get the next record from the filesort buffer, then unpack the fields 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.

TODO: consider templatizing on is_varlen as well. Variable / Fixed size key is currently handled by Filesort_info::get_start_of_payload

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

Implements RowIterator.

◆ SetNullRowFlag()

template<bool Packed_addon_fields>
void SortBufferIterator< 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 SortBufferIterator< Packed_addon_fields >::UnlockRow ( )
inlineoverridevirtual

Implements RowIterator.

Member Data Documentation

◆ m_examined_rows

template<bool Packed_addon_fields>
ha_rows* const SortBufferIterator< Packed_addon_fields >::m_examined_rows
private

◆ m_sort

template<bool Packed_addon_fields>
Filesort_info* const SortBufferIterator< Packed_addon_fields >::m_sort
private

◆ m_sort_result

template<bool Packed_addon_fields>
Sort_result* const SortBufferIterator< Packed_addon_fields >::m_sort_result
private

◆ m_tables

template<bool Packed_addon_fields>
Mem_root_array<TABLE *> SortBufferIterator< Packed_addon_fields >::m_tables
private

◆ m_unpack_counter

template<bool Packed_addon_fields>
unsigned SortBufferIterator< Packed_addon_fields >::m_unpack_counter
private

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