NESTED_JOIN Struct Reference

Struct NESTED_JOIN is used to represent how tables are connected through outer join operations and semi-join operations to form a query block. More...

#include <nested_join.h>

Public Member Functions
	NESTED_JOIN ()

Public Attributes
mem_root_deque< Table_ref * >	m_tables
	list of tables referenced in the nested join More...
table_map	used_tables {0}
table_map	not_null_tables {0}
plan_idx	first_nested {0}
	Used for pointing out the first table in the plan being covered by this join nest. More...
bool	natural_join_processed {false}
	Set to true when natural join or using information has been processed. More...
uint	nj_total {0}
	Number of tables and outer join nests administered by this nested join object for the sake of cost analysis. More...
uint	nj_counter {0}
	Used to count tables in the nested join in 2 isolated places: More...
nested_join_map	nj_map {0}
	Bit identifying this nested join. More...
table_map	sj_depends_on {0}
	Tables outside the semi-join that are used within the semi-join's ON condition (ie. More...
table_map	sj_corr_tables {0}
	Outer non-trivially correlated tables, a true subset of sj_depends_on. More...
uint	query_block_id {0}
	Query block id if this struct is generated from a subquery transform. More...
uint	sj_enabled_strategies {0}
	Bitmap of which strategies are enabled for this semi-join nest. More...
mem_root_deque< Item * >	sj_outer_exprs
mem_root_deque< Item * >	sj_inner_exprs
Semijoin_mat_optimize	sjm

Detailed Description

Struct 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 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.

Constructor & Destructor Documentation

NESTED_JOIN()

NESTED_JOIN::NESTED_JOIN ( )

inline

Member Data Documentation

first_nested

plan_idx NESTED_JOIN::first_nested {0}

Used for pointing out the first table in the plan being covered by this join nest.

It is used exclusively within make_outerjoin_info().

m_tables

mem_root_deque<Table_ref *> NESTED_JOIN::m_tables

list of tables referenced in the nested join

natural_join_processed

bool NESTED_JOIN::natural_join_processed {false}

Set to true when natural join or using information has been processed.

nj_counter

uint NESTED_JOIN::nj_counter {0}

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 Query_block::reset_nj_counters.

nj_map

nested_join_map NESTED_JOIN::nj_map {0}

Bit identifying this nested join.

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

nj_total

uint NESTED_JOIN::nj_total {0}

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.

not_null_tables

table_map NESTED_JOIN::not_null_tables {0}

query_block_id

uint NESTED_JOIN::query_block_id {0}

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

sj_corr_tables

table_map NESTED_JOIN::sj_corr_tables {0}

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

Also contains lateral dependencies from materialized derived tables contained inside the semi-join inner tables.

sj_depends_on

table_map NESTED_JOIN::sj_depends_on {0}

Tables outside the semi-join that are used within the semi-join's ON condition (ie.

the subquery WHERE clause and optional IN equalities). Also contains lateral dependencies from materialized derived tables contained inside the semi-join inner tables.

sj_enabled_strategies

uint NESTED_JOIN::sj_enabled_strategies {0}

Bitmap of which strategies are enabled for this semi-join nest.

sj_inner_exprs

mem_root_deque<Item *> NESTED_JOIN::sj_inner_exprs

sj_outer_exprs

mem_root_deque<Item *> NESTED_JOIN::sj_outer_exprs

sjm

Semijoin_mat_optimize NESTED_JOIN::sjm

used_tables

table_map NESTED_JOIN::used_tables {0}

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

• sql/nested_join.h