Download | Release Notes | Changelog | Overview of 5.3

Release date: 28 Aug 2012

For the highlights of this release, see the release notes.

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  • Revision #3564 Fri 2012-08-24 23:43:18 +0200
    • MDEV-336 oqgraph 5.5 crashes in buildbot
    • force -fno-strict-aliasing for oqgraph
  • Revision #3563 Sat 2012-08-25 09:15:57 +0300
    • fix for MDEV-367
    • The problem was that was_null and null_value variables was reset in each reexecution of IN subquery, but engine rerun only for non-constant subqueries.
    • Fixed checking constant in Item_equal sort.
    • Fix constant reporting in Item_subselect.
  • Revision #3562 [merge] Fri 2012-08-24 19:13:34 +0200
  • Revision #3561 [merge] Fri 2012-08-24 15:39:34 +0200
  • Revision #3560 [merge] Fri 2012-08-24 14:26:23 +0200
    • Merge into latest 5.3
    • Revision #3556.1.2 [merge] Fri 2012-08-24 14:02:32 +0200
      • merge from 5.2
      • Revision #2732.59.1 [merge] Fri 2012-08-24 12:32:46 +0200
        • Merge from 5.1.
        • Revision #2643.154.1 Fri 2012-08-24 10:06:16 +0200
          • MDEV-382: Incorrect quoting
          • Various places in the server replication code was incorrectly quoting strings, which could lead to incorrect SQL on the slave/mysqlbinlog.
    • Revision #3556.1.1 [merge] Fri 2012-08-24 13:51:16 +0200
      • Merge from 5.2
  • Revision #3559 Thu 2012-08-23 13:52:36 +0200
    • remove mysql-5.1 assert that is already absent in mysql-5.5
  • Revision #3558 Wed 2012-08-22 18:40:27 +0200
    • MDEV-472 mysql-test-run --valgrind main.ps_2myisam gives warning about not initialized memory
    • Item::get_date() should return 1 unless the value is a valid date.
  • Revision #3557 [merge] Wed 2012-08-22 16:45:25 +0200
    • 5.2 merge.
    • two tests still fail:
      • main.innodb_icp and main.range_vs_index_merge_innodb
      • call records_in_range() with both range ends being open (which triggers an assert)
    • Revision #2732.57.11 [merge] Wed 2012-08-22 16:13:54 +0200
      • 5.1 merge
      • increase xtradb verson from 13.0 to 13.01
      • Revision #2643.153.11 Wed 2012-08-22 16:10:31 +0200
        • merge with XtraDB as of Percona-Server-5.1.63-rel13.4
      • Revision #2643.153.10 [merge] Wed 2012-08-22 11:40:39 +0200
        • merge with MySQL 5.1.65
    • Revision #2732.57.10 Thu 2012-06-21 18:47:13 +0300
      • Fix for Bug #1001505 and Bug #1001510
      • We set correct cmp_context during preparation to avoid changing it later by Item_field::equal_fields_propagator. (see mysql bugs #57135 #57692 during merging)
  • Revision #3556 Tue 2012-08-21 22:24:34 +0400
    • Better comments
  • Revision #3555 Tue 2012-08-14 14:25:56 -0700
    • Corrected the pactch for MDEV-449 to fix valgrind failures.
  • Revision #3554 Mon 2012-08-13 21:13:14 -0700
    • Fixed bug MDEV-449.
    • The bug could caused a crash when the server executed a query with ORDER by and sort_buffer_size was set to a small enough number.
    • It happened because the small sort buffer did not allow to allocate all merge buffers in it.
    • Made sure that the allocated sort buffer would be big enough to contain all possible merge buffers.
  • Revision #3553 [merge] Thu 2012-08-02 00:58:13 +0400
    • MDEV-369 (Mismatches in MySQL engines test suite)
    • Following reasons caused mismatches:
      • different handling of invalid values;
      • different CAST results with fractional seconds;
      • microseconds support in MariaDB;
      • different algorithm of comparing temporal values;
      • differences in error and warning texts and codes;
      • different approach to truncating datetime values to time;
      • additional collations;
      • different record order for queries without ORDER BY;
      • MySQL Bug #66034.
    • More details in MDEV-369 comments.
    • Revision #3552.1.2 Mon 2012-07-30 04:16:49 +0400
      • MDEV-369 (Mismatches in MySQL engines test suite)
    • Revision #3552.1.1 Thu 2012-07-26 23:31:08 +0400
      • Result files were wrong due to MySQL bug#66034
  • Revision #3552 Wed 2012-07-18 15:03:05 +0400
    • MDEV-398: Sergv related to spacial queries
    • index_merge/intersection is unable to work on GIS indexes, because:
      1. index scans have no Rowid-Ordered-Retrieval property
      2. When one does an index-only read over a GIS index, they do not get the index tuple, because index only contains bounding box of the geometry. This is why key_copy() call crashed.
    • This patch fixes #1, which makes the problem go away. Theoretically, it would be nice to check #2, too, but SE API semantics is not sufficiently precise to do it.
  • Revision #3551 Tue 2012-06-26 21:43:34 +0300
    • Fix for Bug #1007622
    • TABLE_LIST::check_single_table made aware about fact that now if table attached to a merged view it can be (unopened) temporary table (in 5.2 it was always leaf table or non (in case of several tables)).
  • Revision #3550 [merge] Sat 2012-06-23 15:00:05 -0700
    • Merge 5.2->5.3
    • Revision #2732.57.9 Sat 2012-06-23 12:19:07 -0700
      • Fixed bug MDEV-360.
      • The bug was the result of the incomplete fix for bug lp bug 1008293.
    • Revision #2732.57.8 Mon 2012-06-18 22:32:17 -0700
      • Fixed bug MDEV-354.
      • Virtual columns of ENUM and SET data types were not supported properly in the original patch that introduced virtual columns into MariaDB 5.2.
      • The problem was that for any virtual column the patch used the interval_id field of the definition of the column in the frm file as a reference to the virtual column expression.
      • The fix stores the optional interval_id of the virtual column in the extended header of the virtual column expression.
  • Revision #3549 Fri 2012-06-22 14:14:22 +0400
    • Added comment about QUICK_RANGE_SELECT::free_cond being unused.
  • Revision #3548 Thu 2012-06-21 14:33:36 +0400
    • Update test results (checked)
  • Revision #3547 Wed 2012-06-20 22:30:24 +0400
    • Update test results.
  • Revision #3546 Wed 2012-06-20 13:41:31 +0400
    • Post-merge fixes:
      • put back the result encoding in func_in.result (messed up by kdiff3)
      • update .result for other tests (checked)
  • Revision #3545 [merge] Mon 2012-06-18 22:38:11 +0400
    • Merge 5.2->5.3
    • Revision #2732.57.7 Tue 2012-06-12 10:06:26 -0700
      • Adjusted results in pbxt.negation_elimination after the fix for lp bug 992380.
    • Revision #2732.57.6 [merge] Tue 2012-06-12 00:09:20 -0700
      • Merge.
      • Revision #2732.58.1 Mon 2012-06-11 22:12:47 -0700
        • Fixed Bug #1008293.
          • One of the reported problems manifested itself in the scenario when one thread tried to to get statistics on a key cache while the second thread had not finished initialization of the key cache structure yet. The problem was resolved by forcing serialization of such operations on key caches.
          •  
          • To serialize function calls to perform certain operations over a key cache a new mutex associated with the key cache now is used. It is stored in the field op_lock of the KEY_CACHE structure. It is locked when the operation is performed. Some of the serialized key cache operations utilize calls for other key cache operations. To avoid recursive locking of op_lock the new functions that perform the operations of key cache initialization, destruction and re-partitioning with an additional parameter were introduced.
          •  
          • The parameter says whether the operation over op_lock are to be performed or are to be omitted. The old functions for the operations of key cache initialization, destruction,and re-partitioning now just call the corresponding new functions with the additional parameter set to true requesting to use op_lock while all other calls of these new function have this parameter set to false.
          •  
          • Another problem reported in the bug entry concerned the operation of assigning an index to a key cache. This operation can be called while the key cache structures are not initialized yet. In this case any call of flush_key_blocks() should return without any actions.
          •  
          • No test case is provided with this patch.
    • Revision #2732.57.5 [merge] Sun 2012-06-10 14:04:21 +0400
      • Merge
    • Revision #2732.57.4 [merge] Fri 2012-06-01 23:45:54 +0200
      • 5.1 merge
    • Revision #2643.153.9 Fri 2012-06-01 17:53:59 +0200
      • MDEV-256 Bug #995501 - mysqltest attempts to parse Perl code inside a block with false condition, gets confused and throws wrong errors
    • Revision #2732.57.3 Fri 2012-05-25 10:29:53 +0300
      • Fix of Bug #992380 + revise fix_fields about missing with_subselect collection
      • The problem is that some fix_fields do not call Item_func::fix_fields and do not collect with subselect_information.
    • Revision #2732.57.2 Wed 2012-05-23 18:18:08 +0300
      • Fix Bug #1001506
      • This is a backport of the (unchaged) fix for MySQL bug #11764372, 57197.
      • Analysis:
        • When the outer query finishes its main execution and computes GROUP BY, it needs to construct a new temporary table (and a corresponding JOIN) to execute the last DISTINCT operation. At this point JOIN::exec calls JOIN::join_free, which calls JOIN::cleanup -> TMP_TABLE_PARAM::cleanup for both the outer and the inner JOINs. The call to the inner TMP_TABLE_PARAM::cleanup sets copy_field = NULL, but not copy_field_end.
        •  
        • The final execution phase that computes the DISTINCT invokes: evaluate_join_record -> end_write -> copy_funcs The last function copies the results of all functions into the temp table. copy_funcs walks over all functions in join->tmp_table_param.items_to_copy. In this case items_to_copy contains both assignments to user variables. The process of copying user variables invokes Item_func_set_user_var::check which in turn re-evaluates the arguments of the user variable assignment. This in turn triggers re-evaluation of the subquery, and ultimately copy_field.
        •  
        • However, the previous call to TMP_TABLE_PARAM::cleanup for the subquery already set copy_field to NULL but not its copy_field_end. This results in a null pointer access, and a crash.
        •  
      • Fix:
        • Set copy_field_end and save_copy_field_end to null when deleting copy fields in TMP_TABLE_PARAM::cleanup().
    • Revision #2732.57.1 Tue 2012-05-22 08:48:10 +0300
      • Fix of Bug #992380 + revise fix_fields about missing with_subselect collection
      • The problem is that some fix_fields do not call Item_func::fix_fields and do not collect with subselect_information.
  • Revision #3544 Fri 2012-06-15 11:33:24 +0300
    • Fix Bug #1008686
    • Analysis:
      • The fix for bug Bug #985667 implements the method Item_subselect::no_rows_in_result() for all main kinds of subqueries. The purpose of this method is to be called from return_zero_rows() and set Items to some default value in the case when a query returns no rows. Aggregates and subqueries require special treatment in this case.
      •  
      • Every implementation of Item_subselect::no_rows_in_result() called Item_subselect::make_const() to set the subquery predicate to its default value irrespective of where the predicate was located in the query. Once the predicate was set to a constant it was never executed.
      •  
      • At the same time, the JOIN object of the fake select for UNIONs (the one used for the final result of the UNION), was set after all subqueries in the union were executed. Since we set the subquery as constant, it was never executed, and the corresponding JOIN was never created.
      •  
      • In order to decide whether the result of NOT IN is NULL or FALSE, Item_in_optimizer needs to check if the subquery result was empty or not. This is where we got the crash, because subselect_union_engine::no_rows() checks for unit->fake_select_lex->join->send_records, and the join object was NULL.
      •  
    • Solution:
      • If a subquery is in the HAVING clause it must be evaluated in order to know its result, so that we can properly filter the result records. Once subqueries in the HAVING clause are executed even in the case of no result rows, this specific crash will be solved, because the UNION will be executed, and its JOIN will be constructed. Therefore the fix for this crash is to narrow the fix for Bug #985667, and to apply Item_subselect::no_rows_in_result() only when the subquery predicate is in the SELECT clause.
  • Revision #3543 Thu 2012-06-14 17:03:09 +0300
    • Fix Bug #1008773
    • Analysis:
      • Queries with implicit grouping (there is aggregate, but no group by) follow some non-obvious semantics in the case of empty result set. Aggregate functions produce some special "natural" value depending on the function. For instance MIN/MAX return NULL, COUNT returns 0.
      •  
      • The complexity comes from non-aggregate expressions in the select list. If the non-aggregate expression is a constant, it can be computed, so we should return its value, however if the expression is non-constant, and depends on columns from the empty result set, then the only meaningful value is NULL.
      •  
      • The cause of the wrong result was that for subqueries the optimizer didn't make a difference between constant and non-constant ones in the case of empty result for implicit grouping.
    • Solution:
      • In all implementations of Item_subselect::no_rows_in_result() check if the subquery predicate is constant. If it is constant, do not set it to the default value for implicit grouping, instead let it be evaluated.
  • Revision #3542 [merge] Sun 2012-06-10 14:06:11 +0400
    • Merge
    • Revision #3539.1.1 [merge] Sun 2012-06-10 13:53:06 +0400
      • Merge Bug #1010351 from 5.1 to 5.2
      • Revision #2732.53.48 Sun 2012-06-10 13:50:21 +0400
        • Bug #1010351: New "via" keyword in 5.2+ can't be used as identifier anymore
        • Add the VIA_SYM token into keyword_sp list, which makes it allowed for use as keyword and SP label.
  • Revision #3541 Fri 2012-06-08 19:15:01 +0200
    • Bug #1008334 : Speedup specific datetime queries that got slower with introduction of microseconds in 5.3
      • Item::get_seconds() now skips decimal arithmetic, if decimals is 0. This significantly speeds up from_unixtime() if no fractional part is passed.
      • replace sprintfs used to format temporal values by hand-coded formatting
    • Query1 (original query in the bug report)
      • BENCHMARK(10000000,DATE_SUB(FROM_UNIXTIME(RAND() * 2147483648), INTERVAL (FLOOR(1 + RAND() * 365)) DAY))
    • Query2 (Variation of query1 that does not use fractional part in FROM_UNIXTIME parameter)
      • BENCHMARK(10000000,DATE_SUB(FROM_UNIXTIME(FLOOR(RAND() * 2147483648)), INTERVAL (FLOOR(1 + RAND() * 365)) DAY))
    • Prior to the patch, the runtimes were (32 bit compilation/AMD machine)
      • Query1: 41.53 sec
      • Query2: 23.90 sec
    • With the patch, the runtimes are
      • Query1: 32.32 sec (speed up due to removing sprintf)
      • Query2: 12.06 sec (speed up due to skipping decimal arithmetic)
  • Revision #3540 Wed 2012-06-06 23:02:21 +0300
    • Fixed pbxt test case not run by default.
  • Revision #3539 Tue 2012-06-05 17:25:10 +0300
    • Fixed Bug #1000649
    • Analysis:
      • When the method JOIN::choose_subquery_plan() decided to apply the IN-TO-EXISTS strategy, it set the unit and select_lex uncacheable flag to UNCACHEABLE_DEPENDENT_INJECTED unconditionally.
      •  
      • As result, even if IN-TO-EXISTS injected non-correlated predicates, the subquery was still treated as correlated.
    • Solution:
      • Set the subquery as correlated only if the injected predicate(s) depend on the outer query.
  • Revision #3538 Mon 2012-06-04 23:22:03 +0200
  • Revision #3537 [merge] Sat 2012-06-02 16:13:05 +0400
    • Merge
    • Revision #3532.1.1 Sat 2012-06-02 03:25:56 +0400
      • Bug #1006164: Multi-table DELETE that uses innodb + index_merge/intersect may fail to delete rows
      • Set index columns to be read when using index_merge, even if TABLE->no_keyread is set for the table (happens for multi-table UPDATEs)
  • Revision #3536 Fri 2012-06-01 14:56:47 +0200
    • MDEV-304: Insufficient buffer allocation for Query_log_event
    • The constructor for Query_log_event allocated 2 bytes too few for extra space needed by Query cache. (Not sure if this is reproducible in practice, as there are often a couple of extra bytes allocated for unused string zero terminators, but better safe than sorry).
  • Revision #3535 Wed 2012-05-30 19:10:18 +0300
    • Fix for Bug #1006231
    • Analysis:
      • When a subquery that needs a temp table is executed during the prepare or optimize phase of the outer query, at the end of the subquery execution all the JOIN_TABs of the subquery are replaced by a new JOIN_TAB that selects from the temp table. However that temp table has no corresponding TABLE_LIST. Once EXPLAIN execution reaches its last phase, it tries to print the names of the subquery tables through its TABLE_LISTs, but in the case of this bug there is no such TABLE_LIST (it is NULL), hence a crash.
    • Solution:
      • The fix is to block subquery evaluation inside Item_func_like::fix_fields and Item_func_like::select_optimize() using the Item::is_expensive() test.
  • Revision #3534 Tue 2012-05-29 09:59:25 +0500
    • MDEV-294 SELECT WHERE ST_CONTAINS doesn't return all the records where ST_CONTAINS() is 1.
    • Optimizator fails using index with ST_Within(g, constant_poly).
    • per-file comments:
      • mysql-test/r/gis-rt-precise.result
        • test result fixed.
      • mysql-test/r/gis-rtree.result
        • test result fixed.
      • mysql-test/suite/maria/r/maria-gis-rtree-dynamic.result
        • test result fixed.
      • mysql-test/suite/maria/r/maria-gis-rtree-trans.result
        • test result fixed.
      • mysql-test/suite/maria/r/maria-gis-rtree.result
        • test result fixed.
      • storage/maria/ma_rt_index.c
        • Use MBR_INTERSECT mode when optimizing the select WITH ST_Within.
      • storage/myisam/rt_index.c
        • Use MBR_INTERSECT mode when optimizing the select WITH ST_Within.
  • Revision #3533 [merge] Fri 2012-05-25 00:44:43 -0700
    • Merge.
    • Revision #3531.1.1 Fri 2012-05-25 00:07:26 -0700
      • Fixed a performance problem: calls of the function imerge_list_and_tree could lead an to exponential growth of the imerge lists.
  • Revision #3532 Fri 2012-05-25 01:20:40 +0400
    • Bug #1002630: Valgrind warnings 'Invalid read' in subselect_engine::calc_const_tables with SELECT
      • In JOIN::exec(), make the having->update_used_tables() call before we've made the JOIN::cleanup(full=true) call. The latter frees SJ-Materialization structures, which correlated subquery predicate items attempt to walk afterwards.
  • Revision #3531 Wed 2012-05-23 21:05:53 +0400
    • Update test results after the latest push
  • Revision #3530 Wed 2012-05-23 11:55:14 +0400
    • Bug #1000051: Query with simple join and ORDER BY takes thousands times longer when run with ICP
      • Correct testcases.
  • Revision #3529 Wed 2012-05-23 11:46:40 +0400
    • Bug #1000051: Query with simple join and ORDER BY takes thousands times longer when run with ICP
      • Disable IndexConditionPushdown for reverse scans.
  • Revision #3528 Tue 2012-05-22 15:22:55 +0300
    • Fix Bug #1002079
    • Analysis:
      • The optimizer detects an empty result through constant table optimization. Then it calls return_zero_rows(), which in turns calls inderctly Item_maxmin_subselect::no_rows_in_result(). The latter method set "value=0", however "value" is pointer to Item_cache, and not just an integer value.
      •  
      • All of the Item_[maxmin | singlerow]_subselect::val_XXX methods does:
        if (forced_const)
          return value->val_real();
      • which of course crashes when value is a NULL pointer.
    • Solution:
      • When the optimizer discovers an empty result set, set Item_singlerow_subselect::value to a FALSE constant Item instead of NULL.
  • Revision #3527 Mon 2012-05-21 19:37:46 +0500
    • MDEV-136 Non-blocking "set read_only".
    • Handle the 'set read_only=1' in lighter way, than the FLUSH TABLES READ LOCK;
    • For the transactional engines we don't wait for operations on that tables to finish.
    • per-file comments:
      • mysql-test/r/read_only_innodb.result
        • MDEV-136 Non-blocking "set read_only".
          • test result updated.
      • mysql-test/t/read_only_innodb.test
        • MDEV-136 Non-blocking "set read_only".
          • test case added.
      • sql/mysql_priv.h
        • MDEV-136 Non-blocking "set read_only".
          • The close_cached_tables_set_readonly() declared.
      • sql/set_var.cc
        • MDEV-136 Non-blocking "set read_only".
          • Call close_cached_tables_set_readonly() for the read_only::set_var.
      • sql/sql_base.cc
        • MDEV-136 Non-blocking "set read_only".
          • Parameters added to the close_cached_tables implementation, close_cached_tables_set_readonly declared.
          • Prevent blocking on the transactional tables if the set_readonly_mode is on.
  • Revision #3526 [merge] Sun 2012-05-20 14:57:29 +0200
  • Revision #3525 [merge] Fri 2012-05-18 16:28:11 +0400
    • Merge
    • Revision #3522.1.1 Fri 2012-05-18 16:24:12 +0400
      • Bug #1000269: Wrong result (extra rows) with semijoin+materialization, IN subqueries, join_cache_level>0
        • make make_cond_after_sjm() correctly handle OR clauses where one branch refers to the semi-join table while the other branch refers to the non-semijoin table.
  • Revision #3524 Thu 2012-05-17 10:45:20 +0300
  • Revision #3523 Tue 2012-05-15 08:31:07 +0300
    • Fix for Bug #998516
    • If we did nothing in resolving unique table conflict we should not retry (it leed to infinite loop).
    • Now we retry (recheck) unique table check only in case if we materialized a table.
  • Revision #3522 Sun 2012-05-13 13:15:17 +0400
    • Bug #998236: Assertion failure or valgrind errors at best_access_path ...
    • Let fix_semijoin_strategies_for_picked_join_order() set POSITION::prefix_record_count for POSITION records that it copies from SJ_MATERIALIZATION_INFO::tables.
    • (These records do not have prefix_record_count set, because they are optimized as joins-inside-semijoin-nests, without full advance_sj_state() processing).
  • Revision #3521 [merge] Sat 2012-05-12 12:27:26 +0400
  • Revision #3520 [merge] Fri 2012-05-11 11:40:23 +0300
    • Merge 5.2->5.3
    • Revision #2732.53.44 Fri 2012-05-11 09:35:46 +0300
      • fix for Bug #994392
      • The not_null_tables() of Item_func_not_all and Item_in_optimizer was inherited from Item_func by mistake. It made the optimizer think that subquery predicates with ALL/ANY/IN were null-rejecting. This could trigger invalid conversions of outer joins into inner joins.
    • Revision #2732.53.43 Thu 2012-05-10 09:00:21 +0300
      • Fixed typo
    • Revision #2732.53.42 Tue 2012-05-08 12:38:22 +0200
      • MDEV-262 : log_state occationally fails in buildbot.
      • The failures are missing entries in the slow query log. The reason for the failure are sleep() calls with short duration 10ms, which is less than the default system timer resolution for various WaitForXXXObject functions (15.6 ms) and thus can't work reliably.
      • The fix is to make sleeps tiny bit longer (20ms from 10ms) in the test.
    • Revision #2732.53.41 Tue 2012-05-08 00:26:41 +0200
      • fixes Bug #994156
      • MDEV-261 : mysqtest crashes when assigning variable to result of select , like
        let x = `SELECT <something>`
      • The fix is to detect the condition "no active connection", to report error and die.
      • Note, that the check for no active connection was already in place for ordinary commands, and was missing only for assign-variable command.
    • Revision #2732.53.40 Mon 2012-05-07 13:26:34 +0300
      • Fix for Bug #993726
      • Optimization of aggregate functions detected constant under max() and evalueted it, but condition in the WHWRE clause (which is always FALSE) was not taken into account
    • Revision #2732.53.39 Mon 2012-05-07 11:02:58 +0300
      • Fix for bug Bug #992405
      • The patch backports two patches from mysql 5.6:
        • BUG#12640437: USING SQL_BUFFER_RESULT RESULTS IN A DIFFERENT QUERY OUTPUT
        • Bug#12578908: SELECT SQL_BUFFER_RESULT OUTPUTS TOO MANY ROWS WHEN GROUP IS OPTIMIZED AWAY
          Original comment:
          -----------------
          3714 Jorgen Loland	2012-03-01
                BUG#12640437 - USING SQL_BUFFER_RESULT RESULTS IN A DIFFERENT 
                                QUERY OUTPUT
                .
                For all but simple grouped queries, temporary tables are used to
                resolve grouping. In these cases, the list of grouping fields is
                stored in the temporary table and grouping is resolved
                there (e.g. by adding a unique constraint on the involved
                fields). Because of this, grouping is already done when the rows
                are read from the temporary table.
                .
                In the case where a group clause may be optimized away, grouping
                does not have to be resolved using a temporary table. However, if
                a temporary table is explicitly requested (e.g. because the
                SQL_BUFFER_RESULT hint is used, or the statement is
                INSERT...SELECT), a temporary table is used anyway. In this case,
                the temporary table is created with an empty group list (because
                the group clause was optimized away) and it will therefore not
                create groups. Since the temporary table does not take care of
                grouping, JOIN::group shall not be set to false in 
                make_simple_join(). This was fixed in bug 12578908. 
                .
                However, there is an exception where make_simple_join() should
                set JOIN::group to false even if the query uses a temporary table
                that was explicitly requested but is not strictly needed. That
                exception is if the loose index scan access method (explain
                says "Using index for group-by") is used to read into the 
                temporary table. With loose index scan, grouping is resolved 
                by the access method. This is exactly what happens in this bug.
    • Revision #2732.53.38 Thu 2012-05-03 14:49:52 +0300
      • Fix Bug #993745
      • This is a backport of the fix for MySQL bug #13723054 in 5.6.
      • Original comment:
        The crash is caused by arbitrary memory area owerwriting in case of
        BLOB fields during attempt to copy BLOB field key image into record
        buffer(record buffer is too small to get BLOB key part image).
        note:
        QUICK_GROUP_MIN_MAX_SELECT can not work with BLOB fields
        because it uses record buffer as temporary buffer for key values
        however this case is filtered out by covering_keys() check
        in get_best_group_min_max() as BLOBs always require key length
        modificator in the key declaration and if the key has a BLOB
        then it can not be covered key.
        The fix is to use 'max_used_key_length' key length instead of 0.
      • Analysis:
        • Spcifically the crash in this bug was a result of the call to key_copy() that copied the whole key, inlcuding the BLOB field which is not used for index access. Copying the blob field overwrote memory as far as the function parameter 'key_info'. As a result the contents of key_info was all 0, which resulted in a crash when this key_info was accessed few lines below in key_cmp().
  • Revision #3519 Tue 2012-05-08 20:58:41 +0300
    • Fix compiler warnings.
  • Revision #3518 Tue 2012-05-08 19:13:26 +0300
    • Addition to the fix to Bug #994275.
    • It is problem of constant propagated to ref* access method (the problem was hiden by using debug binaries for testing).
  • Revision #3517 Mon 2012-05-07 21:14:37 +0300
    • Bug #994275 fix.
    • In 5.3 we substitute constants in ref access values it can't be null so we do not need add NOT NULL for early NULL filtering.

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