sql_opt_exec_shared.h File Reference

Common types of the Optimizer, used by optimization and execution. More...

#include <assert.h>
#include "my_base.h"
#include "sql/item.h"

Go to the source code of this file.

Classes
struct	Index_lookup
	Structure used for index-based lookups. More...
class	QEP_shared
	Holds members common to JOIN_TAB and QEP_TAB. More...
class	QEP_shared_owner
	Owner of a QEP_shared; parent of JOIN_TAB and QEP_TAB. More...

Macros
#define	NO_PLAN_IDX   (-2)
	undefined index More...
#define	PRE_FIRST_PLAN_IDX    (-1)
	right before the first (first's index is 0) More...

Typedefs
using	plan_idx = int
	This represents the index of a JOIN_TAB/QEP_TAB in an array. More...

Enumerations
enum	join_type {   JT_UNKNOWN , JT_SYSTEM , JT_CONST , JT_EQ_REF ,   JT_REF , JT_ALL , JT_RANGE , JT_INDEX_SCAN ,   JT_FT , JT_REF_OR_NULL , JT_INDEX_MERGE }
enum	{   REF_SLICE_ACTIVE = 0 , REF_SLICE_TMP1 , REF_SLICE_TMP2 , REF_SLICE_SAVED_BASE ,   REF_SLICE_WIN_1 }
	Symbolic slice numbers into JOIN's arrays ref_items, tmp_fields and tmp_all_fields. More...

Detailed Description

Common types of the Optimizer, used by optimization and execution.

Macro Definition Documentation

NO_PLAN_IDX

#define NO_PLAN_IDX   (-2)

undefined index

PRE_FIRST_PLAN_IDX

#define PRE_FIRST_PLAN_IDX    (-1)

right before the first (first's index is 0)

Typedef Documentation

plan_idx

using plan_idx = int

This represents the index of a JOIN_TAB/QEP_TAB in an array.

"plan_idx": "Plan Table Index". It is signed, because:

• firstmatch_return may be PRE_FIRST_PLAN_IDX (it can happen that the first table of the plan uses FirstMatch: SELECT ... WHERE literal IN (SELECT ...)).
• it must hold the invalid value NO_PLAN_IDX (which means "no JOIN_TAB/QEP_TAB", equivalent of NULL pointer); this invalid value must itself be different from PRE_FIRST_PLAN_IDX, to distinguish "FirstMatch to before-first-table" (firstmatch_return==PRE_FIRST_PLAN_IDX) from "No FirstMatch" (firstmatch_return==NO_PLAN_IDX).

Enumeration Type Documentation

anonymous enum

anonymous enum

Symbolic slice numbers into JOIN's arrays ref_items, tmp_fields and tmp_all_fields.

See also the comments on JOIN::ref_items.

Enumerator
REF_SLICE_ACTIVE	The slice which is used during evaluation of expressions; Item_ref::ref points there. This is the only slice that is not allocated on the heap; it always points to query_block->base_ref_items. If we have a simple query (no temporary tables or GROUP BY needed), this slice always contains the base slice, i.e., the actual Items used in the original query. However, if we have temporary tables, there are cases where we need to swap out those Items, because they refer to Fields that are no longer in use. As a simple case, consider SELECT REVERSE(t1), COUNT(*) FROM t1 GROUP BY REVERSE(t1); Assuming no index on t1, this will require creating a temporary table consisting only of REVERSE(t1), and then sorting it before grouping. During execution of the query creating the temporary table, we will have an Item_func_reverse pointing to a Field for t1, and the result of this will be stored in the temporary table "tmp". However, when reading from "tmp", it would be wrong to use that Item_func_reverse, as the Field no longer exists. Thus, we create a slice (in REF_SLICE_TMP1) with new Item pointers, where Item_func_reverse is replaced by an Item_field that reads from the right field in the temporary table. Similar logic applies for windowing functions etc.; see below. In such cases, the pointers in this slice are overwritten (using memcpy) by e.g. REF_SLICE_TMP1 for as long as we read from the temporary table. Switch_ref_item_slice provides an encapsulation of the overwriting, and the optimizer stores a copy of the original Item pointers in the REF_SLICE_SAVED_BASE slice so that it is possible to copy them back when we are done.
REF_SLICE_TMP1	The slice with pointers to columns of 1st group-order-distinct tmp table.
REF_SLICE_TMP2	The slice with pointers to columns of 2nd group-order-distinct tmp table.
REF_SLICE_SAVED_BASE	The slice with pointers to columns of table(s), ie., the actual Items. Only used for queries involving temporary tables or the likes; for simple queries, they always live in REF_SLICE_ACTIVE, so we don't need a copy here. See REF_SLICE_ACTIVE for more discussion.
REF_SLICE_WIN_1	The slice with pointers to columns of 1st tmp table of windowing.

join_type

enum join_type

Enumerator
JT_UNKNOWN
JT_SYSTEM
JT_CONST
JT_EQ_REF
JT_REF
JT_ALL
JT_RANGE
JT_INDEX_SCAN
JT_FT
JT_REF_OR_NULL
JT_INDEX_MERGE