mariadb

Tree: bc56dcea9d

Sergey Glukhov fcb83cbf15 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. mysql-test/r/derived.result: test case mysql-test/r/multi_update.result: test case mysql-test/r/view.result: test case mysql-test/suite/innodb/r/innodb_multi_update.result: test case mysql-test/suite/innodb/t/innodb_multi_update.test: test case mysql-test/suite/innodb_plugin/r/innodb_multi_update.result: test case mysql-test/suite/innodb_plugin/t/innodb_multi_update.test: test case mysql-test/t/derived.test: test case mysql-test/t/multi_update.test: test case mysql-test/t/view.test: test case sql/item.cc: --removed unnecessary code sql/item_cmpfunc.cc: --removed unnecessary checks --THD::is_context_analysis_only() is replaced with LEX::is_ps_or_view_context_analysis() sql/item_func.cc: --refactored context analysis checks sql/item_row.cc: --removed unnecessary checks sql/item_subselect.cc: --removed unnecessary code --added DBUG_ASSERT into Item_subselect::exec() which asserts that subquery execution can not happen if LEX::context_analysis_only is set, i.e. at context analysis stage. --Item_subselect::const_item() Return FALSE if LEX::context_analysis_only is set. It prevents subquery evaluation in ::fix_fields & ::fix_length_and_dec at context analysis stage. sql/item_subselect.h: --removed unnecessary code sql/mysql_priv.h: --Added new set of flags. sql/sql_class.h: --removed unnecessary code sql/sql_derived.cc: --added LEX::context_analysis_only analysis intialization/cleanup sql/sql_lex.cc: --init LEX::context_analysis_only field sql/sql_lex.h: --New LEX::context_analysis_only field sql/sql_parse.cc: --removed unnecessary code sql/sql_prepare.cc: --removed unnecessary code --added LEX::context_analysis_only analysis intialization/cleanup sql/sql_select.cc: --refactored context analysis checks sql/sql_show.cc: --added LEX::context_analysis_only analysis intialization/cleanup sql/sql_view.cc: --added LEX::context_analysis_only analysis intialization/cleanup		15 years ago
..
include	Remove unused file	16 years ago
r	Fixed following problems:	15 years ago
t	Fixed following problems:	15 years ago