filesort.cc File Reference

Sorts a database. More...

#include "sql_priv.h"
#include "filesort.h"
#include "unireg.h"
#include <m_ctype.h>
#include "sql_sort.h"
#include "probes_mysql.h"
#include "opt_range.h"
#include "bounded_queue.h"
#include "filesort_utils.h"
#include "sql_select.h"
#include "debug_sync.h"
#include "opt_trace.h"
#include "sql_optimizer.h"
#include "sql_base.h"
#include <algorithm>
#include <utility>

Defines
#define	DBL_EXP_DIG   (sizeof(double)*8-DBL_MANT_DIG)
Functions
ha_rows	filesort (THD *thd, TABLE *table, Filesort *filesort, bool sort_positions, ha_rows *examined_rows, ha_rows *found_rows)
void	filesort_free_buffers (TABLE *table, bool full)
void	copy_native_longlong (uchar *to, int to_length, longlong val, bool is_unsigned)
void	make_sortkey (Sort_param *param, uchar *to, uchar *ref_pos)
	Declared here so we can unit test it.
int	merge_many_buff (Sort_param *param, uchar *sort_buffer, BUFFPEK *buffpek, uint *maxbuffer, IO_CACHE *t_file)
uint	read_to_buffer (IO_CACHE *fromfile, BUFFPEK *buffpek, uint rec_length)
void	reuse_freed_buff (QUEUE *queue, BUFFPEK *reuse, uint key_length)
int	merge_buffers (Sort_param *param, IO_CACHE *from_file, IO_CACHE *to_file, uchar *sort_buffer, BUFFPEK *lastbuff, BUFFPEK *Fb, BUFFPEK *Tb, int flag)
uint	sortlength (THD *thd, SORT_FIELD *sortorder, uint s_length, bool *multi_byte_charset)
	Declared here so we can unit test it.
void	change_double_for_sort (double nr, uchar *to)
Variables
const bool	Is_big_endian = false

---

Detailed Description

Sorts a database.

---

Function Documentation

ha_rows filesort	(	THD *	thd,
		TABLE *	table,
		Filesort *	filesort,
		bool	sort_positions,
		ha_rows *	examined_rows,
		ha_rows *	found_rows
	)

Sort a table. Creates a set of pointers that can be used to read the rows in sorted order. This should be done with the functions in records.cc.

Before calling filesort, one must have done table->file->info(HA_STATUS_VARIABLE)

The result set is stored in table->io_cache or table->record_pointers.

Parameters:

	thd	Current thread
	table	Table to sort
	filesort	How to sort the table
	sort_positions	Set to TRUE if we want to force sorting by position (Needed by UPDATE/INSERT or ALTER TABLE or when rowids are required by executor)
[out]	examined_rows	Store number of examined rows here This is the number of found rows before applying WHERE condition.
[out]	found_rows	Store the number of found rows here. This is the number of found rows after applying WHERE condition.

Note:

If we sort by position (like if sort_positions is 1) filesort() will call table->prepare_for_position().

Return values:

HA_POS_ERROR	Error
\::	Number of rows in the result, could be less than found_rows if LIMIT were provided.

void make_sortkey	(	Sort_param *	param,
		uchar *	to,
		uchar *	ref_pos
	)

Declared here so we can unit test it.

Make a sort-key from record.

int merge_buffers	(	Sort_param *	param,
		IO_CACHE *	from_file,
		IO_CACHE *	to_file,
		uchar *	sort_buffer,
		BUFFPEK *	lastbuff,
		BUFFPEK *	Fb,
		BUFFPEK *	Tb,
		int	flag
	)

Merge buffers to one buffer.

Parameters:

param	Sort parameter
from_file	File with source data (BUFFPEKs point to this file)
to_file	File to write the sorted result data.
sort_buffer	Buffer for data to store up to MERGEBUFF2 sort keys.
lastbuff	OUT Store here BUFFPEK describing data written to to_file
Fb	First element in source BUFFPEKs array
Tb	Last element in source BUFFPEKs array
flag

Return values:

0	OK
other	error

int merge_many_buff	(	Sort_param *	param,
		uchar *	sort_buffer,
		BUFFPEK *	buffpek,
		uint *	maxbuffer,
		IO_CACHE *	t_file
	)

Merge buffers to make < MERGEBUFF2 buffers.

uint read_to_buffer	(	IO_CACHE *	fromfile,
		BUFFPEK *	buffpek,
		uint	rec_length
	)

Read data to buffer.

Return values:

(uint)-1

if something goes wrong

void reuse_freed_buff	(	QUEUE *	queue,
		BUFFPEK *	reuse,
		uint	key_length
	)

Put all room used by freed buffer to use in adjacent buffer.

Note, that we can't simply distribute memory evenly between all buffers, because new areas must not overlap with old ones.

Parameters:

[in]	queue	list of non-empty buffers, without freed buffer
[in]	reuse	empty buffer
[in]	key_length	key length

uint sortlength	(	THD *	thd,
		SORT_FIELD *	sortorder,
		uint	s_length,
		bool *	multi_byte_charset
	)

Declared here so we can unit test it.

Calculate length of sort key.

Parameters:

	thd	Thread handler
	sortorder	Order of items to sort
	s_length	Number of items to sort
[out]	multi_byte_charset	Set to 1 if we are using multi-byte charset (In which case we have to use strxnfrm())

Note:

sortorder->length is updated for each sort item.
sortorder->need_strxnfrm is set 1 if we have to use strxnfrm

Returns:

Total length of sort buffer in bytes