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.
Made sure that the optimal fields are used by TABLE_REF objects
when building index access keys to joined tables.
Fixed a bug in the template function that sorts the elements of
a list using the bubble sort algorithm. The bug caused poor
performance of the function. Also added an optimization that
skips comparison with the most heavy elements that has been
already properly placed in the list.
Made the comparison of the fields belonging to the same Item_equal
more granular: fields belonging to the same table are also ordered
according to some rules.
- Changed TABLE->alias to String to get fewer reallocs when alias are used.
- Preallocate some buffers
Changed some String->c_ptr() -> String->ptr() when \0 is not needed.
Fixed wrong usage of String->ptr() when we need a \0 terminated string.
Use my_strtod() instead of my_atof() to avoid having to add \0 to string.
c_ptr() -> c_ptr_safe() to avoid warnings from valgrind.
zr
sql/event_db_repository.cc:
Update usage of TABLE->alias
sql/event_scheduler.cc:
c_ptr() -> c_ptr_safe()
sql/events.cc:
c_ptr() -> ptr() as \0 was not needed
sql/field.cc:
Update usage of TABLE->alias
sql/field.h:
Update usage of TABLE->alias
sql/ha_partition.cc:
Update usage of TABLE->alias
sql/handler.cc:
Update usage of TABLE->alias
Fixed wrong usage of str.ptr()
sql/item.cc:
Fixed error where code wrongly assumed string was \0 terminated.
sql/item_func.cc:
c_ptr() -> c_ptr_safe()
Update usage of TABLE->alias
sql/item_sum.h:
Use my_strtod() instead of my_atof() to avoid having to add \0 to string
sql/lock.cc:
Update usage of TABLE->alias
sql/log.cc:
c_ptr() -> ptr() as \0 was not needed
sql/log_event.cc:
c_ptr_quick() -> ptr() as \0 was not needed
sql/opt_range.cc:
ptr() -> c_ptr() as \0 is needed
sql/opt_subselect.cc:
Update usage of TABLE->alias
sql/opt_table_elimination.cc:
Update usage of TABLE->alias
sql/set_var.cc:
ptr() -> c_ptr() as \0 is needed
c_ptr() -> c_ptr_safe()
sql/sp.cc:
c_ptr() -> ptr() as \0 was not needed
sql/sp_rcontext.cc:
Update usage of TABLE->alias
sql/sql_base.cc:
Preallocate buffers
Update usage of TABLE->alias
sql/sql_class.cc:
Fix arguments to sprintf() to work even if string is not \0 terminated
sql/sql_insert.cc:
Update usage of TABLE->alias
c_ptr() -> ptr() as \0 was not needed
sql/sql_load.cc:
Preallocate buffers
Trivial optimizations
sql/sql_parse.cc:
Trivial optimization
sql/sql_plugin.cc:
c_ptr() -> ptr() as \0 was not needed
sql/sql_select.cc:
Update usage of TABLE->alias
sql/sql_show.cc:
Update usage of TABLE->alias
sql/sql_string.h:
Added move() function to move allocated memory from one object to another.
sql/sql_table.cc:
Update usage of TABLE->alias
c_ptr() -> c_ptr_safe()
sql/sql_test.cc:
ptr() -> c_ptr_safe()
sql/sql_trigger.cc:
Update usage of TABLE->alias
c_ptr() -> c_ptr_safe()
sql/sql_update.cc:
Update usage of TABLE->alias
sql/sql_view.cc:
ptr() -> c_ptr_safe()
sql/sql_yacc.yy:
ptr() -> c_ptr()
sql/table.cc:
Update usage of TABLE->alias
sql/table.h:
Changed TABLE->alias to String to get fewer reallocs when alias are used.
storage/federatedx/ha_federatedx.cc:
Use c_ptr_safe() to ensure strings are \0 terminated.
storage/maria/ha_maria.cc:
Update usage of TABLE->alias
storage/myisam/ha_myisam.cc:
Update usage of TABLE->alias
storage/xtradb/row/row0sel.c:
Ensure that null bits in record are properly reset.
(Old code didn't work as row_search_for_mysql() can be called twice while reading fields from one row.
In Item_ref::fix_fields() do invoke mark_as_dependent() for outside
references in all cases (see email for more details)
sql/item.cc:
In Item_ref::fix_fields() do invoke mark_as_dependent() for outside references in all cases.
sql/item.h:
Change Field_enumerator to enumerate Item_field-s not Field-s.
sql/item_subselect.cc:
Change Field_enumerator to enumerate Item_field-s not Field-s.
sql/opt_table_elimination.cc:
Change Field_enumerator to enumerate Item_field-s not Field-s.
- When analying multiple equalities, take into account that they
may not have a single table field that belongs to one of the tables
that we're trying to eliminate (and they are not useful for table
elimination in that case)
mysql-test/r/table_elim.result:
LPBUG#523593: Running RQG optimizer_no_subquery crashes MariaDB
- Testcase
mysql-test/t/table_elim.test:
LPBUG#523593: Running RQG optimizer_no_subquery crashes MariaDB
- Testcase
include/my_global.h:
MWL#17: Table elimination: fixes for windows
- Add ALIGN_MAX_UNIT (assume malloc returns data aligned to this much)
mysql-test/r/table_elim.result:
MWL#17: Table elimination: fixes for windows
- Use only lower-case as EXPLAIN [EXTENDED] changes case of table names
on windows
mysql-test/t/table_elim.test:
MWL#17: Table elimination: fixes for windows
- Use only lower-case as EXPLAIN [EXTENDED] changes case of table names
on windows
sql/opt_table_elimination.cc:
MWL#17: Table elimination: fixes for windows
- Add extra alignment-padding-space for stack-allocated buffers.
- Fix a trivial problem when OR-merging two multi-equalities
- Amend testsuite to provide full gcov coverage
mysql-test/r/table_elim.result:
MWL#17: Table elimination:
- Amend testsuite to provide full gcov coverage
mysql-test/t/table_elim.test:
MWL#17: Table elimination:
- Amend testsuite to provide full gcov coverage
- Add an @@optimizer_switch flag for table_elimination for debug build
- Better comments
mysql-test/t/index_merge_myisam.test:
MWL#17: Table elimination: last fixes
- Add an @@optimizer_switch flag for table_elimination for debug build
sql/mysql_priv.h:
MWL#17: Table elimination: last fixes
- Add an @@optimizer_switch flag for table_elimination for debug build
sql/mysqld.cc:
MWL#17: Table elimination: last fixes
- Add an @@optimizer_switch flag for table_elimination for debug build
- More testcases
- Set correct dependencies for non-bound multi-equalities.
mysql-test/r/table_elim.result:
MWL#17: Table elimination
- More testcases
mysql-test/t/table_elim.test:
MWL#17: Table elimination
- More testcases
sql/opt_table_elimination.cc:
MWL#17: Table elimination
- Set correct dependencies for non-bound multi-equalities.
- Address review feedback: change expression analyzer used to be a copy-paste
of ref analyzer. ref analyzer, besides doing ref analysis, also collected
info about keys which had sargable predicates. We didn't need that part here.
- Switch from uniform graph to bipartite graph with two kinds of nodes:
"values" (tables and fields) and "modules" (t.col=func(...) equalities,
multi-equalities, unique keys, inner sides of outer joins).
- Rename functions, classes, etc.
Address review feedback:
- Change from Wave-based approach (a-la const table detection) to
building and walking functional dependency graph.
- Change from piggy-backing on ref-access code and KEYUSE structures
to using our own expression analyzer.
sql/item.cc:
MWL#17: Table elimination
- Move from C-ish Field_processor_info to C++ ish and generic Field_enumerator
sql/item.h:
MWL#17: Table elimination
- Move from C-ish Field_processor_info to C++ ish and generic Field_enumerator
sql/sql_bitmap.h:
MWL#17: Table elimination
- Backport of Table_map_iterator from 6.0
- Last fixes
sql/item.cc:
MWL#17: Table elimination
- Don't make multiple calls of ::walk(check_column_usage_processor),
call once and cache the value
sql/item.h:
MWL#17: Table elimination
- s/KEYUSE::usable/KEYUSE::type/, more comments
sql/opt_table_elimination.cc:
MWL#17: Table elimination
- Don't make multiple calls of ::walk(check_column_usage_processor),
call once and cache the value
sql/sql_select.cc:
MWL#17: Table elimination
- s/KEYUSE::usable/KEYUSE::type/, more comments
sql/sql_select.h:
MWL#17: Table elimination
- s/KEYUSE::usable/KEYUSE::type/, more comments
sql/table.h:
MWL#17: Table elimination
- Better comments
