mariadb/sql/sql_derived.cc

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/* Copyright (c) 2002, 2011, Oracle and/or its affiliates. All rights reserved.
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This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License 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
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
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/*
Derived tables
These were introduced by Sinisa <sinisa@mysql.com>
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*/
#include "my_global.h" /* NO_EMBEDDED_ACCESS_CHECKS */
#include "sql_priv.h"
#include "unireg.h"
#include "sql_derived.h"
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#include "sql_select.h"
#include "sql_view.h" // check_duplicate_names
#include "sql_acl.h" // SELECT_ACL
/*
Call given derived table processor (preparing or filling tables)
SYNOPSIS
mysql_handle_derived()
lex LEX for this thread
processor procedure of derived table processing
RETURN
FALSE OK
TRUE Error
*/
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bool
mysql_handle_derived(LEX *lex, bool (*processor)(THD*, LEX*, TABLE_LIST*))
{
bool res= FALSE;
if (lex->derived_tables)
{
lex->thd->derived_tables_processing= TRUE;
for (SELECT_LEX *sl= lex->all_selects_list;
sl;
sl= sl->next_select_in_list())
{
for (TABLE_LIST *cursor= sl->get_table_list();
cursor;
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cursor= cursor->next_local)
{
if ((res= (*processor)(lex->thd, lex, cursor)))
goto out;
}
if (lex->describe)
{
/*
Force join->join_tmp creation, because we will use this JOIN
twice for EXPLAIN and we have to have unchanged join for EXPLAINing
*/
sl->uncacheable|= UNCACHEABLE_EXPLAIN;
sl->master_unit()->uncacheable|= UNCACHEABLE_EXPLAIN;
}
}
}
out:
lex->thd->derived_tables_processing= FALSE;
return res;
}
/**
@brief Create temporary table structure (but do not fill it).
@param thd Thread handle
@param lex LEX for this thread
@param orig_table_list TABLE_LIST for the upper SELECT
@details
This function is called before any command containing derived tables is
executed. Currently the function is used for derived tables, i.e.
- Anonymous derived tables, or
- Named derived tables (aka views) with the @c TEMPTABLE algorithm.
The table reference, contained in @c orig_table_list, is updated with the
fields of a new temporary table.
Derived tables are stored in @c thd->derived_tables and closed by
close_thread_tables().
This function is part of the procedure that starts in
open_and_lock_tables(), a procedure that - among other things - introduces
new table and table reference objects (to represent derived tables) that
don't exist in the privilege database. This means that normal privilege
checking cannot handle them. Hence this function does some extra tricks in
order to bypass normal privilege checking, by exploiting the fact that the
current state of privilege verification is attached as GRANT_INFO structures
on the relevant TABLE and TABLE_REF objects.
For table references, the current state of accrued access is stored inside
TABLE_LIST::grant. Hence this function must update the state of fulfilled
privileges for the new TABLE_LIST, an operation which is normally performed
exclusively by the table and database access checking functions,
check_access() and check_grant(), respectively. This modification is done
for both views and anonymous derived tables: The @c SELECT privilege is set
as fulfilled by the user. However, if a view is referenced and the table
reference is queried against directly (see TABLE_LIST::referencing_view),
the state of privilege checking (GRANT_INFO struct) is copied as-is to the
temporary table.
This function implements a signature called "derived table processor", and
is passed as a function pointer to mysql_handle_derived().
@note This function sets @c SELECT_ACL for @c TEMPTABLE views as well as
anonymous derived tables, but this is ok since later access checking will
distinguish between them.
@see mysql_handle_derived(), mysql_derived_filling(), GRANT_INFO
@return
false OK
true Error
*/
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bool mysql_derived_prepare(THD *thd, LEX *lex, TABLE_LIST *orig_table_list)
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{
SELECT_LEX_UNIT *unit= orig_table_list->derived;
ulonglong create_options;
DBUG_ENTER("mysql_derived_prepare");
bool res= FALSE;
if (unit)
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{
SELECT_LEX *first_select= unit->first_select();
TABLE *table= 0;
select_union *derived_result;
/* prevent name resolving out of derived table */
for (SELECT_LEX *sl= first_select; sl; sl= sl->next_select())
sl->context.outer_context= 0;
if (!(derived_result= new select_union))
DBUG_RETURN(TRUE); // out of memory
Fixed following problems: --Bug#52157 various crashes and assertions with multi-table update, stored function --Bug#54475 improper error handling causes cascading crashing failures in innodb/ndb --Bug#57703 create view cause Assertion failed: 0, file .\item_subselect.cc, line 846 --Bug#57352 valgrind warnings when creating view --Recently discovered problem when a nested materialized derived table is used before being populated and it leads to incorrect result We have several modes when we should disable subquery evaluation. The reasons for disabling are different. It could be uselessness of the evaluation as in case of 'CREATE VIEW' or 'PREPARE stmt', or we should disable subquery evaluation if tables are not locked yet as it happens in bug#54475, or too early evaluation of subqueries can lead to wrong result as it happened in Bug#19077. Main problem is that if subquery items are treated as const they are evaluated in ::fix_fields(), ::fix_length_and_dec() of the parental items as a lot of these methods have Item::val_...() calls inside. We have to make subqueries non-const to prevent unnecessary subquery evaluation. At the moment we have different methods for this. Here is a list of these modes: 1. PREPARE stmt; We use UNCACHEABLE_PREPARE flag. It is set during parsing in sql_parse.cc, mysql_new_select() for each SELECT_LEX object and cleared at the end of PREPARE in sql_prepare.cc, init_stmt_after_parse(). If this flag is set subquery becomes non-const and evaluation does not happen. 2. CREATE|ALTER VIEW, SHOW CREATE VIEW, I_S tables which process FRM files We use LEX::view_prepare_mode field. We set it before view preparation and check this flag in ::fix_fields(), ::fix_length_and_dec(). Some bugs are fixed using this approach, some are not(Bug#57352, Bug#57703). The problem here is that we have a lot of ::fix_fields(), ::fix_length_and_dec() where we use Item::val_...() calls for const items. 3. Derived tables with subquery = wrong result(Bug19077) The reason of this bug is too early subquery evaluation. It was fixed by adding Item::with_subselect field The check of this field in appropriate places prevents const item evaluation if the item have subquery. The fix for Bug19077 fixes only the problem with convert_constant_item() function and does not cover other places(::fix_fields(), ::fix_length_and_dec() again) where subqueries could be evaluated. Example: CREATE TABLE t1 (i INT, j BIGINT); INSERT INTO t1 VALUES (1, 2), (2, 2), (3, 2); SELECT * FROM (SELECT MIN(i) FROM t1 WHERE j = SUBSTRING('12', (SELECT * FROM (SELECT MIN(j) FROM t1) t2))) t3; DROP TABLE t1; 4. Derived tables with subquery where subquery is evaluated before table locking(Bug#54475, Bug#52157) Suggested solution is following: -Introduce new field LEX::context_analysis_only with the following possible flags: #define CONTEXT_ANALYSIS_ONLY_PREPARE 1 #define CONTEXT_ANALYSIS_ONLY_VIEW 2 #define CONTEXT_ANALYSIS_ONLY_DERIVED 4 -Set/clean these flags when we perform context analysis operation -Item_subselect::const_item() returns result depending on LEX::context_analysis_only. If context_analysis_only is set then we return FALSE that means that subquery is non-const. As all subquery types are wrapped by Item_subselect it allow as to make subquery non-const when it's necessary.
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lex->context_analysis_only|= CONTEXT_ANALYSIS_ONLY_DERIVED;
// st_select_lex_unit::prepare correctly work for single select
if ((res= unit->prepare(thd, derived_result, 0)))
goto exit;
Fixed following problems: --Bug#52157 various crashes and assertions with multi-table update, stored function --Bug#54475 improper error handling causes cascading crashing failures in innodb/ndb --Bug#57703 create view cause Assertion failed: 0, file .\item_subselect.cc, line 846 --Bug#57352 valgrind warnings when creating view --Recently discovered problem when a nested materialized derived table is used before being populated and it leads to incorrect result We have several modes when we should disable subquery evaluation. The reasons for disabling are different. It could be uselessness of the evaluation as in case of 'CREATE VIEW' or 'PREPARE stmt', or we should disable subquery evaluation if tables are not locked yet as it happens in bug#54475, or too early evaluation of subqueries can lead to wrong result as it happened in Bug#19077. Main problem is that if subquery items are treated as const they are evaluated in ::fix_fields(), ::fix_length_and_dec() of the parental items as a lot of these methods have Item::val_...() calls inside. We have to make subqueries non-const to prevent unnecessary subquery evaluation. At the moment we have different methods for this. Here is a list of these modes: 1. PREPARE stmt; We use UNCACHEABLE_PREPARE flag. It is set during parsing in sql_parse.cc, mysql_new_select() for each SELECT_LEX object and cleared at the end of PREPARE in sql_prepare.cc, init_stmt_after_parse(). If this flag is set subquery becomes non-const and evaluation does not happen. 2. CREATE|ALTER VIEW, SHOW CREATE VIEW, I_S tables which process FRM files We use LEX::view_prepare_mode field. We set it before view preparation and check this flag in ::fix_fields(), ::fix_length_and_dec(). Some bugs are fixed using this approach, some are not(Bug#57352, Bug#57703). The problem here is that we have a lot of ::fix_fields(), ::fix_length_and_dec() where we use Item::val_...() calls for const items. 3. Derived tables with subquery = wrong result(Bug19077) The reason of this bug is too early subquery evaluation. It was fixed by adding Item::with_subselect field The check of this field in appropriate places prevents const item evaluation if the item have subquery. The fix for Bug19077 fixes only the problem with convert_constant_item() function and does not cover other places(::fix_fields(), ::fix_length_and_dec() again) where subqueries could be evaluated. Example: CREATE TABLE t1 (i INT, j BIGINT); INSERT INTO t1 VALUES (1, 2), (2, 2), (3, 2); SELECT * FROM (SELECT MIN(i) FROM t1 WHERE j = SUBSTRING('12', (SELECT * FROM (SELECT MIN(j) FROM t1) t2))) t3; DROP TABLE t1; 4. Derived tables with subquery where subquery is evaluated before table locking(Bug#54475, Bug#52157) Suggested solution is following: -Introduce new field LEX::context_analysis_only with the following possible flags: #define CONTEXT_ANALYSIS_ONLY_PREPARE 1 #define CONTEXT_ANALYSIS_ONLY_VIEW 2 #define CONTEXT_ANALYSIS_ONLY_DERIVED 4 -Set/clean these flags when we perform context analysis operation -Item_subselect::const_item() returns result depending on LEX::context_analysis_only. If context_analysis_only is set then we return FALSE that means that subquery is non-const. As all subquery types are wrapped by Item_subselect it allow as to make subquery non-const when it's necessary.
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lex->context_analysis_only&= ~CONTEXT_ANALYSIS_ONLY_DERIVED;
if ((res= check_duplicate_names(unit->types, 0)))
goto exit;
WL#4738 streamline/simplify @@variable creation process Bug#16565 mysqld --help --verbose does not order variablesBug#20413 sql_slave_skip_counter is not shown in show variables Bug#20415 Output of mysqld --help --verbose is incomplete Bug#25430 variable not found in SELECT @@global.ft_max_word_len; Bug#32902 plugin variables don't know their names Bug#34599 MySQLD Option and Variable Reference need to be consistent in formatting! Bug#34829 No default value for variable and setting default does not raise error Bug#34834 ? Is accepted as a valid sql mode Bug#34878 Few variables have default value according to documentation but error occurs Bug#34883 ft_boolean_syntax cant be assigned from user variable to global var. Bug#37187 `INFORMATION_SCHEMA`.`GLOBAL_VARIABLES`: inconsistent status Bug#40988 log_output_basic.test succeeded though syntactically false. Bug#41010 enum-style command-line options are not honoured (maria.maria-recover fails) Bug#42103 Setting key_buffer_size to a negative value may lead to very large allocations Bug#44691 Some plugins configured as MYSQL_PLUGIN_MANDATORY in can be disabled Bug#44797 plugins w/o command-line options have no disabling option in --help Bug#46314 string system variables don't support expressions Bug#46470 sys_vars.max_binlog_cache_size_basic_32 is broken Bug#46586 When using the plugin interface the type "set" for options caused a crash. Bug#47212 Crash in DBUG_PRINT in mysqltest.cc when trying to print octal number Bug#48758 mysqltest crashes on sys_vars.collation_server_basic in gcov builds Bug#49417 some complaints about mysqld --help --verbose output Bug#49540 DEFAULT value of binlog_format isn't the default value Bug#49640 ambiguous option '--skip-skip-myisam' (double skip prefix) Bug#49644 init_connect and \0 Bug#49645 init_slave and multi-byte characters Bug#49646 mysql --show-warnings crashes when server dies
2009-12-22 10:35:56 +01:00
create_options= (first_select->options | thd->variables.option_bits |
TMP_TABLE_ALL_COLUMNS);
/*
Temp table is created so that it hounours if UNION without ALL is to be
processed
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As 'distinct' parameter we always pass FALSE (0), because underlying
query will control distinct condition by itself. Correct test of
distinct underlying query will be is_union &&
!unit->union_distinct->next_select() (i.e. it is union and last distinct
SELECT is last SELECT of UNION).
*/
if ((res= derived_result->create_result_table(thd, &unit->types, FALSE,
create_options,
orig_table_list->alias)))
goto exit;
table= derived_result->table;
exit:
/* Hide "Unknown column" or "Unknown function" error */
if (orig_table_list->view)
{
if (thd->is_error() &&
(thd->stmt_da->sql_errno() == ER_BAD_FIELD_ERROR ||
thd->stmt_da->sql_errno() == ER_FUNC_INEXISTENT_NAME_COLLISION ||
thd->stmt_da->sql_errno() == ER_SP_DOES_NOT_EXIST))
{
thd->clear_error();
my_error(ER_VIEW_INVALID, MYF(0), orig_table_list->db,
orig_table_list->table_name);
}
}
/*
if it is preparation PS only or commands that need only VIEW structure
then we do not need real data and we can skip execution (and parameters
is not defined, too)
*/
if (res)
{
if (table)
free_tmp_table(thd, table);
delete derived_result;
}
else
{
if (!thd->fill_derived_tables())
{
delete derived_result;
derived_result= NULL;
}
orig_table_list->derived_result= derived_result;
orig_table_list->table= table;
orig_table_list->table_name= table->s->table_name.str;
orig_table_list->table_name_length= table->s->table_name.length;
table->derived_select_number= first_select->select_number;
table->s->tmp_table= NON_TRANSACTIONAL_TMP_TABLE;
#ifndef NO_EMBEDDED_ACCESS_CHECKS
if (orig_table_list->referencing_view)
table->grant= orig_table_list->grant;
else
table->grant.privilege= SELECT_ACL;
#endif
orig_table_list->db= (char *)"";
orig_table_list->db_length= 0;
// Force read of table stats in the optimizer
table->file->info(HA_STATUS_VARIABLE);
/* Add new temporary table to list of open derived tables */
table->next= thd->derived_tables;
thd->derived_tables= table;
}
}
else if (orig_table_list->merge_underlying_list)
orig_table_list->set_underlying_merge();
DBUG_RETURN(res);
}
/*
fill derived table
SYNOPSIS
mysql_derived_filling()
thd Thread handle
lex LEX for this thread
unit node that contains all SELECT's for derived tables
orig_table_list TABLE_LIST for the upper SELECT
IMPLEMENTATION
Derived table is resolved with temporary table. It is created based on the
queries defined. After temporary table is filled, if this is not EXPLAIN,
then the entire unit / node is deleted. unit is deleted if UNION is used
for derived table and node is deleted is it is a simple SELECT.
If you use this function, make sure it's not called at prepare.
Due to evaluation of LIMIT clause it can not be used at prepared stage.
RETURN
FALSE OK
TRUE Error
*/
bool mysql_derived_filling(THD *thd, LEX *lex, TABLE_LIST *orig_table_list)
{
TABLE *table= orig_table_list->table;
SELECT_LEX_UNIT *unit= orig_table_list->derived;
bool res= FALSE;
/*check that table creation pass without problem and it is derived table */
if (table && unit)
{
SELECT_LEX *first_select= unit->first_select();
select_union *derived_result= orig_table_list->derived_result;
SELECT_LEX *save_current_select= lex->current_select;
if (unit->is_union())
{
// execute union without clean up
res= unit->exec();
}
else
{
unit->set_limit(first_select);
if (unit->select_limit_cnt == HA_POS_ERROR)
first_select->options&= ~OPTION_FOUND_ROWS;
lex->current_select= first_select;
res= mysql_select(thd, &first_select->ref_pointer_array,
first_select->table_list.first,
first_select->with_wild,
first_select->item_list, first_select->where,
(first_select->order_list.elements+
first_select->group_list.elements),
first_select->order_list.first,
first_select->group_list.first,
first_select->having, (ORDER*) NULL,
WL#4738 streamline/simplify @@variable creation process Bug#16565 mysqld --help --verbose does not order variablesBug#20413 sql_slave_skip_counter is not shown in show variables Bug#20415 Output of mysqld --help --verbose is incomplete Bug#25430 variable not found in SELECT @@global.ft_max_word_len; Bug#32902 plugin variables don't know their names Bug#34599 MySQLD Option and Variable Reference need to be consistent in formatting! Bug#34829 No default value for variable and setting default does not raise error Bug#34834 ? Is accepted as a valid sql mode Bug#34878 Few variables have default value according to documentation but error occurs Bug#34883 ft_boolean_syntax cant be assigned from user variable to global var. Bug#37187 `INFORMATION_SCHEMA`.`GLOBAL_VARIABLES`: inconsistent status Bug#40988 log_output_basic.test succeeded though syntactically false. Bug#41010 enum-style command-line options are not honoured (maria.maria-recover fails) Bug#42103 Setting key_buffer_size to a negative value may lead to very large allocations Bug#44691 Some plugins configured as MYSQL_PLUGIN_MANDATORY in can be disabled Bug#44797 plugins w/o command-line options have no disabling option in --help Bug#46314 string system variables don't support expressions Bug#46470 sys_vars.max_binlog_cache_size_basic_32 is broken Bug#46586 When using the plugin interface the type "set" for options caused a crash. Bug#47212 Crash in DBUG_PRINT in mysqltest.cc when trying to print octal number Bug#48758 mysqltest crashes on sys_vars.collation_server_basic in gcov builds Bug#49417 some complaints about mysqld --help --verbose output Bug#49540 DEFAULT value of binlog_format isn't the default value Bug#49640 ambiguous option '--skip-skip-myisam' (double skip prefix) Bug#49644 init_connect and \0 Bug#49645 init_slave and multi-byte characters Bug#49646 mysql --show-warnings crashes when server dies
2009-12-22 10:35:56 +01:00
(first_select->options | thd->variables.option_bits |
SELECT_NO_UNLOCK),
derived_result, unit, first_select);
}
2003-06-12 15:52:36 +02:00
if (!res)
{
/*
Here we entirely fix both TABLE_LIST and list of SELECT's as
there were no derived tables
*/
if (derived_result->flush())
res= TRUE;
}
lex->current_select= save_current_select;
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}
return res;
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}
Bug #58730 Assertion failed: table->key_read == 0 in close_thread_table, temptable views The TABLE::key_read field indicates if the optimizer has found that row retrieval only should access the index tree. The triggered assert inside close_thread_table() checks that this field has been reset when the table is about to be closed. During normal execution, these fields are reset right before tables are closed at the end of mysql_execute_command(). But in the case of errors, tables are closed earlier. The patch for Bug#52044 refactored the open tables code so that close_thread_tables() is called immediately if opening of tables fails. At this point in the execution, it could happend that all TABLE::key_read fields had not been properly reset, therefore triggering the assert. The problematic statement in this case was EXPLAIN where the query accessed two derived tables and where the first derived table was processed successfully while the second derived table was not. Since it was an EXPLAIN, TABLE::key_read fields were not reset after successful derived table processing since the state needs to be accessible afterwards. When processing of the second derived table failed, it's corresponding SELECT_LEX_UNIT was cleaned, which caused it's TABLE::key_read fields to be reset. Since processing failed, the error path of open_and_lock_tables() was entered and close_thread_tables() was called. The assert was then triggered due to the TABLE::key_read fields set during processing of the first derived table. This patch fixes the problem by adding a new derived table processor, mysql_derived_cleanup() that is called after mysql_derived_filling(). It causes cleanup of all SELECT_LEX_UNITs to be called, resetting all relevant TABLE::key_read fields. Test case added to derived.test.
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/**
Cleans up the SELECT_LEX_UNIT for the derived table (if any).
*/
bool mysql_derived_cleanup(THD *thd, LEX *lex, TABLE_LIST *derived)
{
SELECT_LEX_UNIT *unit= derived->derived;
if (unit)
unit->cleanup();
return false;
}