item_subselect.cc File Reference

Implements the subselect Item, used when there is a subselect in a SELECT list, WHERE, etc. More...

#include "sql/item_subselect.h"
#include <climits>
#include <cstdio>
#include <cstring>
#include <initializer_list>
#include <memory>
#include <string>
#include <utility>
#include "decimal.h"
#include "lex_string.h"
#include "my_alloc.h"
#include "my_base.h"
#include "my_compiler.h"
#include "my_dbug.h"
#include "my_pointer_arithmetic.h"
#include "my_sys.h"
#include "mysql/strings/m_ctype.h"
#include "mysql_com.h"
#include "mysqld_error.h"
#include "scope_guard.h"
#include "sql-common/my_decimal.h"
#include "sql/check_stack.h"
#include "sql/current_thd.h"
#include "sql/debug_sync.h"
#include "sql/derror.h"
#include "sql/field.h"
#include "sql/handler.h"
#include "sql/item_cmpfunc.h"
#include "sql/item_func.h"
#include "sql/item_sum.h"
#include "sql/iterators/basic_row_iterators.h"
#include "sql/iterators/composite_iterators.h"
#include "sql/iterators/ref_row_iterators.h"
#include "sql/iterators/row_iterator.h"
#include "sql/iterators/timing_iterator.h"
#include "sql/join_optimizer/access_path.h"
#include "sql/join_optimizer/cost_model.h"
#include "sql/join_optimizer/join_optimizer.h"
#include "sql/key.h"
#include "sql/mysqld.h"
#include "sql/opt_explain_format.h"
#include "sql/opt_trace.h"
#include "sql/opt_trace_context.h"
#include "sql/parse_tree_nodes.h"
#include "sql/query_options.h"
#include "sql/query_result.h"
#include "sql/sql_class.h"
#include "sql/sql_const.h"
#include "sql/sql_error.h"
#include "sql/sql_executor.h"
#include "sql/sql_lex.h"
#include "sql/sql_list.h"
#include "sql/sql_opt_exec_shared.h"
#include "sql/sql_optimizer.h"
#include "sql/sql_select.h"
#include "sql/sql_test.h"
#include "sql/sql_tmp_table.h"
#include "sql/sql_union.h"
#include "sql/system_variables.h"
#include "sql/table.h"
#include "sql/temp_table_param.h"
#include "sql/thd_raii.h"
#include "sql/window.h"
#include "sql_string.h"
#include "string_with_len.h"
#include "template_utils.h"

Classes
class	Query_result_scalar_subquery
	Query result class for scalar and row subqueries. More...
class	Query_result_max_min_subquery
class	Query_result_exists_subquery

Functions
static bool	guaranteed_one_row (const Query_block *qb)
	Check if a query block is guaranteed to return one row. More...
static bool	wrapped_in_intersect_except (Query_term *qb)
	Check if a query block is part of an INTERSECT or EXCEPT set operation. More...
Item *	remove_in2exists_conds (Item *conds)
	Removes every predicate injected by IN->EXISTS. More...
bool	is_quantified_comp_predicate (Item *item)
static Item **	find_subquery_in_select_list (Query_block *select, Item_singlerow_subselect *subquery)
	Find the scalar subquery in Query_block::fields if directly present, i.e., not inside an expression. More...
bool	ExecuteExistsQuery (THD *thd, Query_expression *qe, RowIterator *iterator, bool *found)
	Run a query to see if it returns at least one row (stops after the first has been found, or on error). More...
static int	safe_index_read (TABLE *table, const Index_lookup &ref)

Variables
static const enum_walk	walk_options

Detailed Description

Implements the subselect Item, used when there is a subselect in a SELECT list, WHERE, etc.

Function Documentation

ExecuteExistsQuery()

bool ExecuteExistsQuery	(	THD *	thd,
		Query_expression *	qe,
		RowIterator *	iterator,
		bool *	found
	)

Run a query to see if it returns at least one row (stops after the first has been found, or on error).

Unless there was an error, whether the row was found in "found".

Return values

true

on error

find_subquery_in_select_list()

static Item ** find_subquery_in_select_list ( Query_block *  select, Item_singlerow_subselect *  subquery  )

static

Find the scalar subquery in Query_block::fields if directly present, i.e., not inside an expression.

Parameters

select	The query block owning the transformation.
subquery	The scalar subquery to look for.

Returns

the corresponding ref in Query_block::base_ref_items, or nullptr if not found.

guaranteed_one_row()

static bool guaranteed_one_row ( const Query_block *  qb )

static

Check if a query block is guaranteed to return one row.

We know that this is the case if it has no tables and is not filtered with WHERE, HAVING or LIMIT clauses.

Parameters

qb	the Query_block to check

Returns

true if we are certain that the query block always returns one row, false otherwise

is_quantified_comp_predicate()

bool is_quantified_comp_predicate

(

Item *

item

)

Returns

whether the item is a quantified comparison predicate

remove_in2exists_conds()

Item * remove_in2exists_conds

(

Item *

conds

)

Removes every predicate injected by IN->EXISTS.

This function is different from others:

• it wants to remove all traces of IN->EXISTS (for materialization)
• remove_subq_pushed_predicates() and remove_additional_cond() want to remove only the conditions of IN->EXISTS which index lookup already satisfies (they are just an optimization).

If there are no in2exists conditions, it will return the exact same pointer. If it returns a new Item, the old Item is left alone, so it can be reused in other settings.

Parameters

conds

Condition; may be nullptr.

Returns

new condition

safe_index_read()

static int safe_index_read ( TABLE *  table, const Index_lookup &  ref  )

static

wrapped_in_intersect_except()

static bool wrapped_in_intersect_except ( Query_term *  qb )

static

Check if a query block is part of an INTERSECT or EXCEPT set operation.

Parameters

qb	Query block to check

Returns

true if query block is part of INTERSECT/EXCEPT, false otherwise.

Variable Documentation

walk_options

const enum_walk walk_options

static

Initial value:

=
    enum_walk::PREFIX | enum_walk::POSTFIX | enum_walk::SUBQUERY