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65fbc1dcdb
Adding support for UPDATE .. RETURNING .. INTO queries.
For example:
UPDATE t1 SET a=10,b=20 RETURNING a,b INTO va,vb;
UPDATE t1 SET a=10,b=20 RETURNING a,b INTO @a,@b;
Limitations:
1. These types of queries:
- REPLACE .. RETURNING .. INTO
- DELETE .. RETURNING .. INTO
- INSERT .. RETURNING .. INTO
do not work - they return an error.
They will be implemented separately, when needed.
2. UPDATE..RETURNING..INTO with --binlog_format=statement is not allowed
and an error is raised.
3. Using OLD_VALUE(col) inside UPDATE..RETURNING..INTO is not allowed
and an error is raised.
4. Multi-table updates, as well as single table updates with a subquery
to the same table in WHERE (which get converted to multi-table) do
not work and an error is raised.
Notes:
1. ANALYZE and EXPLAIN
Both
ANALYZE UPDATE .. RETURNING .. INTO ..
EXPLAIN UPDATE .. RETURNING .. INTO ..
return this error:
'RETURNING..INTO' is not allowed in this context
2. Behavior on no data
a. In case of degenerated plans (WHERE 1=0, LIMIT 0),
no errors are raised.
b. If the updated table contains no rows, the behavior depends on the engine,
for example:
- MyISAM returns no errors
- InnoDB raises
No data - zero rows fetched, selected, or processed
This behavior is engine dependent because some engines (e.g. MyISAM)
quickly know that the table has no records and execute the statement
using a degenerated plan.
c. If there are some rows, but non of them match the WHERE condition,
then this error is raised:
No data - zero rows fetched, selected, or processed
d. If some rows where found but none of them actually
got changed by the SET, still this error is raised:
No data - zero rows fetched, selected, or processed
The error message might be misleading. However, if we read
it as "zero rows [that required updates] fetched", it looks OK.
Let's not introduce a new error message for now.
Helper changes:
1. The grammar in analyze_stmt_command was changed to have
LEX::analyze_stmt set to true earlier, so
LEX::set_returning_into_result() already knows if this
is an ANALYZE statement.
2. The Sql_cmd_update constructor is now called earlier in the grammar,
to be able to call Sql_cmd_update::set_with_old_value_items()
in the SET and RETURNING clauses.
3. Sql_cmd_dml::lex is now set during the constructor time.
It makes things easier:
- Sql_cmd_update::returns_result_set() needs the lex.
- Sql_cmd_delete::orig_multitable and Sql_cmd_update::orig_multitable
are not needed any more.
They were used only in Sql_cmd_delete::sql_command_code() and
Sql_cmd_update::sql_command_code().
Sql_cmd_dml::sql_command_code() now returns lex->sql_command.
The overrides Sql_cmd_delete::sql_command_code() and
Sql_cmd_update::sql_command_code() were removed.
116 lines
3.5 KiB
Objective-C
116 lines
3.5 KiB
Objective-C
/* Copyright (c) 2006, 2010, Oracle and/or its affiliates. All rights reserved.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335 USA */
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#ifndef SQL_DELETE_INCLUDED
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#define SQL_DELETE_INCLUDED
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#include "my_base.h" /* ha_rows */
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#include "sql_class.h" /* enum_duplicates */
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#include "sql_cmd.h" // Sql_cmd_dml
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#include "sql_base.h"
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class THD;
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struct TABLE_LIST;
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class Item;
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class select_result;
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typedef class Item COND;
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template <typename T> class SQL_I_List;
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/**
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@class Sql_cmd_delete - class used for any DELETE statements
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This class is derived from Sql_cmd_dml and contains implementations
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for abstract virtual function of the latter such as precheck() and
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prepare_inner(). It also overrides the implementation of execute_inner()
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providing a special handling for single-table delete statements that
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are not converted to multi-table delete.
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The class provides an object of the DML_prelocking_strategy class
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for the virtual function get_dml_prelocking_strategy().
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*/
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class Sql_cmd_delete final : public Sql_cmd_dml
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{
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public:
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ha_rows deleted{0};
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Sql_cmd_delete(LEX *lex, bool multitable_arg)
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: Sql_cmd_dml(lex),
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multitable(multitable_arg),
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save_protocol(NULL)
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{}
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/**
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@brief Check if the statement returns a result set
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*/
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bool returns_result_set() const override
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{
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return returns_result_set_generic(lex);
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}
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DML_prelocking_strategy *get_dml_prelocking_strategy() override
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{
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return &multidelete_prelocking_strategy;
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}
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bool processing_as_multitable_delete_prohibited(THD *thd);
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bool is_multitable() const { return multitable; }
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void set_as_multitable() { multitable= true; }
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void remove_order_by_without_limit(THD *thd);
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void get_dml_stat (ha_rows &found, ha_rows &changed) override
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{
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found= 0;
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changed= deleted;
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}
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protected:
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/**
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@brief Perform precheck of table privileges for delete statements
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*/
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bool precheck(THD *thd) override;
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/**
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@brief Perform context analysis for delete statements
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*/
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bool prepare_inner(THD *thd) override;
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/**
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@brief Perform optimization and execution actions needed for deletes
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*/
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bool execute_inner(THD *thd) override;
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private:
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/**
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@biefSpecial handling of single-table deletes after prepare phase
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*/
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bool delete_from_single_table(THD *thd);
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/*
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True if the statement is a multitable delete or converted to such.
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For a single-table delete this flag is set to true if the statement
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is supposed to be converted to multi-table delete.
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*/
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bool multitable;
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/* The prelocking strategy used when opening the used tables */
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Multidelete_prelocking_strategy multidelete_prelocking_strategy;
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List<Item> empty_list; /**< auxiliary empty list used by prepare_inner() */
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Protocol *save_protocol; /**< needed for ANALYZE .. DELETE .. RETURNING */
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};
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#endif /* SQL_DELETE_INCLUDED */
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