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/* Copyright (c) 2006, 2025, Oracle and/or its affiliates.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License, version 2.0,
as published by the Free Software Foundation.
This program is designed to work with certain software (including
but not limited to OpenSSL) that is licensed under separate terms,
as designated in a particular file or component or in included license
documentation. The authors of MySQL hereby grant you an additional
permission to link the program and your derivative works with the
separately licensed software that they have either included with
the program or referenced in the documentation.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License, version 2.0, for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
#ifndef SQL_DERIVED_INCLUDED
#define SQL_DERIVED_INCLUDED
#include "sql/item.h"
#include "sql/opt_trace_context.h"
#include "sql/sql_const.h"
#include "sql/sql_lex.h"
struct NESTED_JOIN;
/**
Class which handles pushing conditions down to a materialized derived
table. In Query_block::prepare, if it is the outermost query block, and
if we are at the end of preparation, a WHERE condition from the query
block is checked to see if it can be pushed to the materialized derived
table.
Query_block::prepare
push_conditions_to_derived_tables()
For every materialized derived table,
If there is a where condition in this query block,
Make condition that can be pushed down to the derived table.
Extract a part of the condition that has columns belonging to only
this derived table.
Check if this condition can be pushed past window functions if any to
the HAVING clause of the derived table.
Make a condition that could not be pushed past. This will remain in
the outer query block.
Check if this condition can be pushed past group by if present to the
WHERE clause of the derived table.
Make a condition that could not be pushed past. This will be part of
the HAVING clause of the derived table query.
Get the remainder condition which could not be pushed to the derived
table.
Push the condition down to derived table's query expression.
REPEAT THE ABOVE for the rest of the derived tables.
For every query expression inside the current query block
REPEAT THE ABOVE to keep pushing as far down as possible.
*/
class Condition_pushdown {
public:
Condition_pushdown(Item *cond, Table_ref *derived, THD *thd_arg,
Opt_trace_context *trace_arg)
: m_cond_to_check(cond),
m_derived_table(derived),
thd(thd_arg),
trace(trace_arg) {
Query_expression *derived_query_expression =
m_derived_table->derived_query_expression();
m_query_block = derived_query_expression->outer_query_block();
}
bool make_cond_for_derived();
bool make_remainder_cond(Item *cond, Item **remainder_cond);
Item *get_remainder_cond() { return m_remainder_cond; }
/// Used to pass information during condition pushdown.
class Derived_table_info {
public:
Table_ref *m_derived_table;
Query_block *m_derived_query_block;
bool is_set_operation() const {
return m_derived_table->derived_query_expression()->is_set_operation();
}
Derived_table_info(Table_ref *derived_table, Query_block *query_block)
: m_derived_table(derived_table), m_derived_query_block(query_block) {}
};
private:
Item *extract_cond_for_table(Item *cond);
bool replace_columns_in_cond(Item **cond, bool is_having);
bool push_past_window_functions();
bool push_past_group_by();
bool attach_cond_to_derived(Item *derived_cond, Item *cond_to_attach,
bool having);
void update_cond_count(Item *cond);
void check_and_remove_sj_exprs(Item *cond);
void remove_sj_exprs(Item *cond, NESTED_JOIN *sj_nest);
/// Condition that needs to be checked to push down to the derived table.
Item *m_cond_to_check;
/// Derived table to push the condition to.
Table_ref *m_derived_table;
/**
Condition that is extracted from outer WHERE condition to be pushed to
the derived table. This will be a copy when a query expression has
multiple query blocks.
*/
Item *m_cond_to_push{nullptr};
/**
set to m_cond_to_push before cloning (for query expressions with
multiple query blocks).
*/
Item *m_orig_cond_to_push{nullptr};
/**
Condition that would be attached to the HAVING clause of the derived
table. (For each query block in the derived table if UNIONS are present).
*/
Item *m_having_cond{nullptr};
/**
Condition that would be attached to the WHERE clause of the derived table.
(For each query block in the derived table if UNIONS are present).
*/
Item *m_where_cond{nullptr};
/**
Condition that would be left behind in the outer query block. This is the
condition that could not be pushed down to the derived table.
*/
Item *m_remainder_cond{nullptr};
/**
Query block to which m_cond_to_push should be pushed.
*/
Query_block *m_query_block{nullptr};
/**
Enum that represents various stages of checking.
CHECK_FOR_DERIVED - Checking if a condition has only derived table
expressions.
CHECK_FOR_HAVING - Checking if condition could be pushed to HAVING
clause of the derived table.
CHECK_FOR_WHERE - Checking if condition could be pushed to WHERE
clause of the derived table.
*/
enum enum_checking_purpose {
CHECK_FOR_DERIVED,
CHECK_FOR_HAVING,
CHECK_FOR_WHERE
};
enum_checking_purpose m_checking_purpose{CHECK_FOR_DERIVED};
/// Current thread
THD *thd;
/// Optimizer trace context
Opt_trace_context *trace;
};
#endif /* SQL_DERIVED_INCLUDED */
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