MySQL  8.0.27
Source Code Documentation
SortBufferIndirectIterator Class Referencefinal

Fetch the record IDs from a memory buffer, but the records themselves from the table on disk. More...

#include <basic_row_iterators.h>

Inheritance diagram for SortBufferIndirectIterator:
RowIterator

Public Member Functions

 SortBufferIndirectIterator (THD *thd, Mem_root_array< TABLE * > tables, Sort_result *sort_result, bool ignore_not_found_rows, bool has_null_flags, ha_rows *examined_rows)
 
 ~SortBufferIndirectIterator () override
 
bool Init () override
 Initialize or reinitialize the iterator. More...
 
int Read () override
 Read a single row. More...
 
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...
 
void UnlockRow () override
 
- 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

Sort_result *const m_sort_result
 
Mem_root_array< TABLE * > m_tables
 
uint m_sum_ref_length
 
ha_rows *const m_examined_rows
 
ucharm_cache_pos = nullptr
 
ucharm_cache_end = nullptr
 
bool m_ignore_not_found_rows
 
bool m_has_null_flags
 

Additional Inherited Members

- Protected Member Functions inherited from RowIterator
THDthd () const
 

Detailed Description

Fetch the record IDs from a memory buffer, but the records themselves from the table on disk.

Used when the above (comment on SortBufferIterator) is not true, UPDATE, DELETE and so forth and SELECT's involving large BLOBs. It is also used for the result of Unique, which returns row IDs in the same format as filesort. In this case the record data is fetched from the handler using the saved reference using the rnd_pos handler call.

Constructor & Destructor Documentation

◆ SortBufferIndirectIterator()

SortBufferIndirectIterator::SortBufferIndirectIterator ( THD thd,
Mem_root_array< TABLE * >  tables,
Sort_result sort_result,
bool  ignore_not_found_rows,
bool  has_null_flags,
ha_rows examined_rows 
)

◆ ~SortBufferIndirectIterator()

SortBufferIndirectIterator::~SortBufferIndirectIterator ( )
override

Member Function Documentation

◆ Init()

bool SortBufferIndirectIterator::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 SortBufferIndirectIterator::Read ( )
overridevirtual

Read a single row.

The row data is not actually returned from the function; it is put in the table's (or tables', in case of a join) record buffer, ie., table->records[0].

Return values
0OK
-1End of records
1Error

Implements RowIterator.

◆ SetNullRowFlag()

void SortBufferIndirectIterator::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()

void SortBufferIndirectIterator::UnlockRow ( )
inlineoverridevirtual

Implements RowIterator.

Member Data Documentation

◆ m_cache_end

uchar * SortBufferIndirectIterator::m_cache_end = nullptr
private

◆ m_cache_pos

uchar* SortBufferIndirectIterator::m_cache_pos = nullptr
private

◆ m_examined_rows

ha_rows* const SortBufferIndirectIterator::m_examined_rows
private

◆ m_has_null_flags

bool SortBufferIndirectIterator::m_has_null_flags
private

◆ m_ignore_not_found_rows

bool SortBufferIndirectIterator::m_ignore_not_found_rows
private

◆ m_sort_result

Sort_result* const SortBufferIndirectIterator::m_sort_result
private

◆ m_sum_ref_length

uint SortBufferIndirectIterator::m_sum_ref_length
private

◆ m_tables

Mem_root_array<TABLE *> SortBufferIndirectIterator::m_tables
private

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