The MIN/MAX optimizer code from the function opt_sum_query erroneously
did not take into account conjunctive conditions that did not depend on
any table, yet were not identified as constant items. These could be
items containing rand() or PS/SP parameters. These items are supposed
to be evaluated at the execution phase. That's why if such conditions
can be extracted from the WHERE condition the MIN/MAX optimization is
not applied as currently it is always done at the optimization phase.
(In 5.3 expensive subqueries are also evaluated only at the execution
phase. So, if a constant condition with such subquery can be extracted
from the WHERE clause the MIN/MAX optimization should not be applied
in 5.3.)
IF an IN/ALL/SOME predicate with a constant left part is transformed
into an EXISTS subquery the resulting subquery should not be considered
uncacheable if the right part of the predicate is not uncacheable.
Backported the function dbug_print_item() from 5.3. The function is used
only for debugging.
sql/sql_insert.cc:
CREATE ... IF NOT EXISTS may do nothing, but
it is still not a failure. don't forget to my_ok it.
******
CREATE ... IF NOT EXISTS may do nothing, but
it is still not a failure. don't forget to my_ok it.
sql/sql_table.cc:
small cleanup
******
small cleanup
Analysis:
The crash is a result of the same cause as all similar
bugs (lp:827416, lp:718763, lp:778413, lp:806943,
lp:611690). The general pattern is that some optimization
requires the evaluation of some condition (e.g. the WHERE
clause), and this condition contains a subquery, such that
the subquery itself requires a temporary table for its
execution. During the subquery execution the original
tables in the FROM clause are replaced by the temporary
table needed for the final GROUP or ORDER operation. All
this happens during optimization of the outer query. Later
when EXPLAIN is run for the subquery, explain attempts to
print the name of the tables in the FROM clause, but it
finds there a temporary table without a corresponding
TABLE_LIST object. The attempt to print the name of a
NULL table list results in a crash.
Solution:
This patch extends the fix to bug lp:702301, and dissalows
constant substitution of aggregate functions if the filter
condition used to check MIN/MAX keys is an expensive condition.
The problem was that optimization code did not take into account later feature when instad of NOT before BETWEEN it has negated flag into the Item_func_between inherited from Item_func_neg_opt. So optimizer tried process NOT BETWEEN as BETWEEN.
The patch just switches off the optimisation for NOT BETWEEN as it was before when NOT function was really used.
The function matching_cond should take into account that
there may be always false constant conjunctive conditions
that has not been evaluated yet,for example, conjunctive
conditions with non-correlated subqueries.
The function simple_pred did not take into account that a multiple equality
could include ref items (more exactly items of the class Item_direct_view_ref).
It caused crashes for queries over derived tables or views if the
min/max optimization could be applied to these queries.
Resolved all conflicts, bad merges and fixed a few minor bugs in the code.
Commented out the queries from multi_update, view, subselect_sj, func_str,
derived_view, view_grant that failed either with crashes in ps-protocol or
with wrong results.
The failures are clear indications of some bugs in the code and these bugs
are to be fixed.
Both these two bugs happened due to the following problem.
When a view column is referenced in the query an Item_direct_view_ref
object is created that is refers to the Item_field for the column.
All references to the same view column refer to the same Item_field.
Different references can belong to different AND/OR levels and,
as a result, can be included in different Item_equal object.
These Item_equal objects may include different constant objects.
If these constant objects are substituted for the Item_field created
for a view column we have a conflict situation when the second
substitution annuls the first substitution. This leads to
wrong result sets returned by the query. Bug #724942 demonstrates
such an erroneous behaviour.
Test case of the bug #717577 produces wrong result sets because best
equal fields of the multiple equalities built for different OR levels
of the WHERE condition differs. The subsitution for the best equal field
in the second OR branch overwrites the the substitution made for the
first branch.
To avoid such conflicts we have to substitute for the references
to the view columns rather than for the underlying field items.
To make such substitutions possible we have to include into
multiple equalities references to view columns rather than
field items created for such columns.
This patch modifies the Item_equal class to include references
to view columns into multiple equality objects. It also performs
a clean up of the class methods and adds more comments. The methods
of the Item_direct_view_ref class that assist substitutions for
references to view columns has been also added by this patch.
Valgrind warnings were caused by comparing index values to an un-initialized field.
mysql-test/r/subselect.result:
New test cases.
mysql-test/t/subselect.test:
New test cases.
sql/opt_sum.cc:
Add thd to opt_sum_query enabling it to test for errors.
If we have a non-nullable index, we cannot use it to match null values,
since set_null() will be ignored, and we might compare uninitialized data.
sql/sql_select.cc:
Add thd to opt_sum_query, enabling it to test for errors.
sql/sql_select.h:
Add thd to opt_sum_query, enabling it to test for errors.
- Fixed some issues with partitions and connection_string, which also fixed lp:716890 "Pre- and post-recovery crash in Aria"
- Fixed wrong assert in Aria
Now need to merge with latest xtradb before pushing
sql/ha_partition.cc:
Ensure that m_ordered_rec_buffer is not freed before close.
sql/mysqld.cc:
Changed to use opt_stack_trace instead of opt_pstack.
Removed references to pstack
sql/partition_element.h:
Ensure that connect_string is initialized
storage/maria/ma_key_recover.c:
Fixed wrong assert
when semijoin=on
When setting the aggregate function as having no rows to report
the function no_rows_in_result() was calling Item_sum::reset().
However this function in addition to cleaning up the aggregate
value by calling aggregator_clear() was also adding the current
value to the aggregate value by calling aggregator_add().
Fixed by making no_rows_in_result() to call aggregator_clear()
directly.
Renamed Item_sum::reset to Item_sum::reset_and_add() to
and added a comment to avoid misinterpretation of what the
function does.
Item*) at opt_sum.cc:305
Queries applying MIN/MAX functions to indexed columns are
optimized to read directly from the index if all key parts
of the index preceding the aggregated key part are bound to
constants by the WHERE clause. A prefix length is also
produced, equal to the total length of the bound key
parts. If the aggregated column itself is bound to a
constant, however, it is also included in the prefix.
Such full search keys are read as closed intervals for
reasons beyond the scope of this bug. However, the procedure
missed one case where a key part meant for use as range
endpoint was being overwritten with a NULL value destined
for equality checking. In this case the key part was
overwritten but the range flag remained, causing open
interval reading to be performed.
Bug was fixed by adding more stringent checking to the
search key building procedure (matching_cond) and never
allow overwrites of range predicates with non-range
predicates.
An assertion was added to make sure open intervals are never
used with full search keys.
- INSERT with RAND() doesn't require row based logging again
- Some bugs fixed in opt_range() where we table->key_read was wrongly used
.bzrignore:
Ignore new xtstat binary
mysql-test/r/index_merge_myisam.result:
Update results (old result was wrong)
mysql-test/suite/binlog/r/binlog_stm_binlog.result:
Added drop table first
mysql-test/suite/binlog/r/binlog_stm_unsafe_warning.result:
Added test for when RAND() requires row based logging
mysql-test/suite/binlog/t/binlog_stm_binlog.test:
Added drop table first
mysql-test/suite/binlog/t/binlog_stm_unsafe_warning.test:
Added test for when RAND() requires row based logging
scripts/make_binary_distribution.sh:
Removed type from last commit
sql/item_create.cc:
Don't require row based logging when using RAND() with INSERT
sql/opt_range.cc:
Revert wrong patch from Oracle:
- As QUICK_RANGE_SELECT uses it's own 'file' handler to the tables, one can't use 'table->key_read' as a flag to detect if index only read (keyread) is used or not
- Don't set keyread if keyread is already enabled
- Don't disable key read, if we didn't enable it ourselves
- Simplify code (and ensure that we do proper cleanup of index only read)
sql/opt_range.h:
Added flags to detect if the range optimizer enabled index only read (key read) or not
sql/opt_sum.cc:
Use our more optimized macros
sql/sql_lex.h:
Added 'readable' function to check if we are in a sub query function or not (not normal query or sub query in FROM clause)
sql/sql_select.cc:
Use our more optimized keyread macros
Added ASSERTS early
Simplify code on eliminate_item_equal()
Fixed that substitute_for_best_equal_field() doesn't core dump in case of out of memory conditions.
Removed not needed test for 'field->maybe_null()'
Replaced master_unit()->item with is_subquery_function() (More readable)
sql/sql_update.cc:
Use our more optimized keyread macros
sql/table.cc:
Use our more optimized keyread macros
sql/table.h:
Use separate functions to enable/disable Index only reads
- Safer, more readable, better logging and faster.
NULL from outer join query
Problem: optimising MIN/MAX() queries without GROUP BY clause
by replacing the aggregate expression with a constant, we may set it
to NULL disregarding the fact that there may be outer joins involved.
Fix: don't replace MIN/MAX() with NULL if there're outer joins.
Note: the fix itself is just
- if (!count)
+ if (!count && !outer_tables)
set to NULL
The rest of the patch eliminates repeated code to improve speed
and for easy maintenance of the code.
mysql-test/r/group_by.result:
Fix for bug#52051: Aggregate functions incorrectly returns
NULL from outer join query
- test result.
mysql-test/t/group_by.test:
Fix for bug#52051: Aggregate functions incorrectly returns
NULL from outer join query
- test case.
sql/opt_sum.cc:
Fix for bug#52051: Aggregate functions incorrectly returns
NULL from outer join query
- optimising MIN/MAX() queries without GROUP BY clause by
replacing them with a constant, take into account that
there're may be outer joins involved.
- repeated code for MIN/MAX optimization in the opt_sum_query()
eliminated by introducing new functions that read MIN/MAX values
using index and combining MIN/MAX cases to one.
This patch:
- Moves all definitions from the mysql_priv.h file into
header files for the component where the variable is
defined
- Creates header files if the component lacks one
- Eliminates all include directives from mysql_priv.h
- Eliminates all circular include cycles
- Rename time.cc to sql_time.cc
- Rename mysql_priv.h to sql_priv.h
