st_nested_join Struct Reference

#include <table.h>

Collaboration diagram for st_nested_join:

Public Attributes
List< TABLE_LIST >	join_list
table_map	used_tables
table_map	not_null_tables
struct st_join_table *	first_nested
uint	nj_total
uint	nj_counter
nested_join_map	nj_map
table_map	sj_depends_on
table_map	sj_corr_tables
uint	query_block_id
List< Item >	sj_outer_exprs
List< Item >	sj_inner_exprs
Semijoin_mat_optimize	sjm

Detailed Description

Struct st_nested_join is used to represent how tables are connected through outer join operations and semi-join operations to form a query block. Out of the parser, inner joins are also represented by st_nested_join structs, but these are later flattened out by simplify_joins(). Some outer join nests are also flattened, when it can be determined that they can be processed as inner joins instead of outer joins.

Definition at line 2211 of file table.h.

Member Data Documentation

struct st_join_table* st_nested_join::first_nested

Used for pointing out the first table in the plan being covered by this join nest. It is used exclusively within make_outerjoin_info().

Definition at line 2220 of file table.h.

uint st_nested_join::nj_counter

Used to count tables in the nested join in 2 isolated places:

1. In make_outerjoin_info().
2. check_interleaving_with_nj/backout_nj_state (these are called by the join optimizer. Before each use the counters are zeroed by reset_nj_counters.

Definition at line 2235 of file table.h.

nested_join_map st_nested_join::nj_map

Bit identifying this nested join. Only nested joins representing the outer join structure need this, other nests have bit set to zero.

Definition at line 2240 of file table.h.

uint st_nested_join::nj_total

Number of tables and outer join nests administered by this nested join object for the sake of cost analysis. Includes direct member tables as well as tables included through semi-join nests, but notice that semi-join nests themselves are not counted.

Definition at line 2227 of file table.h.

uint st_nested_join::query_block_id

Query block id if this struct is generated from a subquery transform.

Definition at line 2253 of file table.h.

table_map st_nested_join::sj_corr_tables

Outer non-trivially correlated tables, a true subset of sj_depends_on

Definition at line 2249 of file table.h.

table_map st_nested_join::sj_depends_on

Tables outside the semi-join that are used within the semi-join's ON condition (ie. the subquery WHERE clause and optional IN equalities).

Definition at line 2245 of file table.h.

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The documentation for this struct was generated from the following file:

• sql/table.h