- 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.
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.
The problem was in the code (update_const_equal_items()) which marked
index parts constant independently of the place where the equality was used.
In the test suite it marked t2_1.c part constant despite the fact that
it connected by OR with other expression.
Solution is to mark constant only top equalities connected with AND.
The previous patch for the bug (that erroneously identified the bug as
bug 972973 in its comment) was incorrect.
It turned out that the code that triggered the abort complain reported for
the bug was not needed at all.
When the function free_tmp_table deletes the handler object for
a temporary table the field TABLE::file for this table should be
set to NULL. Otherwise an assertion failure may occur.
Bug#13639204 64111: CRASH ON SELECT SUBQUERY WITH NON UNIQUE INDEX
The crash happened due to wrong calculation
of key length during creation of reference for
sort order index. The problem is that
keyuse->used_tables can have OUTER_REF_TABLE_BIT enabled
but used_tables parameter(create_ref_for_key() func) does
not have it. So key parts which have OUTER_REF_TABLE_BIT
are ommited and it could lead to incorrect key length
calculation(zero key length).
mysql-test/r/subselect_innodb.result:
test result
mysql-test/t/subselect_innodb.test:
test case
sql/sql_select.cc:
added OUTER_REF_TABLE_BIT to the used_tables parameter
for create_ref_for_key() function.
storage/innobase/handler/ha_innodb.cc:
added assertion, request from Inno team
storage/innodb_plugin/handler/ha_innodb.cc:
added assertion, request from Inno team
The main problem was a bug in CSV where it provided wrong statistics (it claimed the table was empty when it wasn't)
I also fixed wrong freeing of blob's in the CSV handler. (Any call to handler::read_first_row() on a CSV table with blobs would fail)
mysql-test/r/csv.result:
Added new test case
mysql-test/r/partition_innodb.result:
Updated test results after fixing bug with impossible partitions and const tables
mysql-test/t/csv.test:
Added new test case
sql/sql_select.cc:
Cleaned up code for handling of partitions.
Fixed also a bug where we didn't threat a table with impossible partitions as a const table.
storage/csv/ha_tina.cc:
Allocate blobroot onces.
- When doing join optimization, pre-sort the tables so that they mimic the execution
order we've had with 'semijoin=off'.
- That way, we will not get regressions when there are two query plans (the old and the
new) that have indentical costs but different execution times (because of factors that
the optimizer was not able to take into account).
- This is a regession introduced by fix for BUG#951937
- The problem was that there were scenarios where check_simple_equality() would create an
Item_equal object but would not call item_equal->set_context_field() on it.
- The fix was to add the missing calls.
- Fix equality propagation to work with SJM nests and OR clauses (full descirption of problem and
solution in the comment in the patch)
(The second commit with post-review fixes)
- Remove all references of MAX_TABLES from JOIN struct and make these dynamic
- Updated Join_plan_state to allocate just as many elements as it's needed
sql/opt_subselect.cc:
Optimized version of Join_plan_state
sql/sql_select.cc:
Set join->positions and join->best_positions dynamicly
Don't call update_virtual_fields() if table->vfield is not set.
sql/sql_select.h:
Remove all references of MAX_TABLES from JOIN struct and Join_plan_state and make these dynamic
If the first component of a ref key happened to be a constant appeared
after constant row substitution then no store_key element should be
created for such a component. Yet create_ref_for_key() erroneously could
create such an element that caused construction of invalid ref keys and
wrong results for some joins.
Do not call, directly or indirectly, SQL_SELECT::test_quick_select()
for derived materialized tables / views when optimizing joins referring
to these tables / views to get cost estimates of materialization.
The current code does not create B-tree indexes for materialized
derived tables / views. So now it's not possible to get any estimates
for ranges conditions over the results of the materialization.
The function mysql_derived_create() must take into account the fact
that array of the KEY structures specifying the keys over a derived
table / view may be moved after the optimization phase if the
derived table / view is materialized.
Added 'from_end' as extra parameter to Field::unpack() to detect wrong from data.
Change ha_archive::unpack_row() to detect wrong field lengths.
Replication code changed to detect wrong field information in events.
mysql-test/r/archive.result:
dded test case for lp:917689
sql/field.cc:
Added 'from_end' as extra parameter to Field::unpack() to detect wrong from data.
Removed not used 'unpack_key' functions.
sql/field.h:
Added 'from_end' as extra parameter to Field::unpack() to detect wrong from data.
Removed not used 'unpack_key' functions.
Removed some not needed unpack() functions.
sql/filesort.cc:
Added buffer end parameter to unpack_addon_fields()
sql/log_event.h:
Added end of buffer argument to unpack_row()
sql/log_event_old.cc:
Added end of buffer argument to unpack_row()
sql/log_event_old.h:
Added end of buffer argument to unpack_row()
sql/records.cc:
Added buffer end parameter to unpack_addon_fields()
sql/rpl_record.cc:
Added end of buffer argument to unpack_row()
Added detection of wrong field information in events
sql/rpl_record.h:
Added end of buffer argument to unpack_row()
sql/rpl_record_old.cc:
Added end of buffer argument to unpack_row()
Added detection of wrong field information in events
sql/rpl_record_old.h:
Added end of buffer argument to unpack_row()
sql/table.h:
Added buffer end parameter to unpack()
storage/archive/ha_archive.cc:
Change ha_archive::unpack_row() to detect wrong field lengths.
This fixes lp:917689
The function create_hj_key_for_table() that builds the descriptor of
the hash join key to access a table of a materialized subquery must
ignore any equi-join predicate depending on the tables not belonging
to the subquery.
This bug in the function JOIN::drop_unused_derived_keys() could
leave the internal structures for a materialized derived table
in an inconsistent state. This led to a not quite correct EXPLAIN
output when no additional key had been created to access the table.
It also may lead to more serious consequences: so, the test case
added with this fix caused a crash in mariadb-5.5.20.
This bug appeared after the patch for bug 939009 that in the
function merge_key_fields forgot to reset a proper value for
the val field in the result of the merge operation of the key
field created for a regular key access and the key field
created to look for a NULL key.
Adjusted the results of the test case for bug 939009 that
actually were incorrect.
The result of materialization of the right part of an IN subquery predicate
is placed into a temporary table. Each row of the materialized table is
distinct. A unique key over all fields of the temporary table is defined and
created. It allows to perform key look-ups into the table.
The table created for a materialized subquery can be accessed by key as
any other table. The function best_access-path search for the best access
to join a table to a given partial join. With some where conditions this
function considers a possibility of a ref_or_null access. If such access
employs the unique key on the temporary table then when estimating
the cost this access the function tries to use the array rec_per_key. Yet,
such array is not built for this unique key. This causes a crash of the server.
Rows returned by the subquery that contain nulls don't have to be placed
into temporary table, as they cannot be match any row produced by the
left part of the subquery predicate. So all fields of the temporary table
can be defined as non-nullable. In this case any ref_or_null access
to the temporary table does not make any sense and it does not make sense
to estimate such an access.
The fix makes sure that the temporary table for a materialized IN subquery
is defined with columns that are all non-nullable. The also ensures that
any row with nulls returned by the subquery is not placed into the
temporary table.
- After the exec_const_cond->val_int() call, check for error and return.
(if we don't do it, we will eventually hit an error when trying to set status OK in
the diagnostics area, which already has an error status).
- In return_zero_rows(), don't call mark_as_null_row() for semi-join
materialized tables, because 1) they may have been already freed, and
2)there is no real need to call mark_as_null_row() for them.
This bug is the result of an incomplete/inconsistent change introduced into
5.3 code when the cond_equal parameter were added to the function optimize_cond.
The change was made during a merge from 5.2 in October 2010.
The bug could affect only queries with HAVING.
An outer join query with a semi-join subquery could return a wrong result
if the optimizer chose to materialize the subquery.
It happened because when substituting for the best field into a ref item
used to build access keys not all COND_EQUAL objects that could be employed
at substitution were checked.
Also refined some code in the function check_join_cache_usage to make it
safer.
