Open issues:
- A better fix for #57688; Igor is working on this
- Test failure in index_merge_innodb.test ; Igor promised to look at this
- Some Innodb tests fails (need to merge with latest xtradb) ; Kristian promised to look at this.
- Failing tests: innodb_plugin.innodb_bug56143 innodb_plugin.innodb_bug56632 innodb_plugin.innodb_bug56680 innodb_plugin.innodb_bug57255
- Werror is disabled; Should be enabled after merge with xtradb.
Lines below which were added in the patch for Bug#56814 cause this crash:
+ if (table->table)
+ table->table->maybe_null= FALSE;
Consider following test case:
--
CREATE TABLE t1(f1 INT NOT NULL);
INSERT INTO t1 VALUES (16777214),(0);
SELECT COUNT(*) FROM t1 LEFT JOIN t1 t2
ON 1 WHERE t2.f1 > 1 GROUP BY t2.f1;
DROP TABLE t1;
--
We set TABLE::maybe_null to FALSE for t2 table
and in create_tmp_field() we create appropriate tmp table field
using create_tmp_field_from_item() function instead of
create_tmp_field_from_field. As a result we have
LONGLONG field. As we have GROUP BY clause we calculate
group buffer length, see calc_group_buffer().
Item from group list which is used for calculation
refer to the field from real tables and have LONG type.
So group buffer length become insufficient for storing of
LONGLONG value. It leads to overwriting of wrong memory
area in do_field_int() function which is called from
end_update().
After some investigation I found out that
create_tmp_field_from_item() is used only for OLAP
grouping and can not be used for common grouping
as it could be an incompatibility between tmp
table fields and group buffer length.
We can not remove create_tmp_field_from_item() call from
create_tmp_field as OLAP needs it and we can not use this
function for common grouping. So we should remove setting
TABLE::maybe_null to FALSE from simplify_joins().
In this case we'll get wrong behaviour of
list_contains_unique_index() back. To fix it we
could use Field::real_maybe_null() check instead of
Field::maybe_null() and add addition check of
TABLE_LIST::outer_join.
mysql-test/r/group_by.result:
test case
mysql-test/r/join_outer.result:
test case
mysql-test/t/group_by.test:
test case
mysql-test/t/join_outer.test:
test case
sql/sql_select.cc:
--remove wrong code
--use Field::real_maybe_null() check instead of
Field::maybe_null() and add addition check of
TABLE_LIST::outer_join
BUG#26447 prefer a clustered key for an index scan, as secondary index is always slower
... which was fixed to cause
BUG#35850 queries take 50% longer
... and was reverted
and
BUG#39653 prefer a secondary index for an index scan, as clustered key is always slower
... which was fixed to cause
BUG#55656 mysqldump takes six days instead of half an hour
... and was amended with a special case workaround
sql/opt_range.cc:
move get_index_only_read_time() into the handler class
sql/sql_select.cc:
use cost not an index length when choosing a cheaper index
create_sort_index() function overwrites original JOIN_TAB::type field.
At re-execution of subquery overwritten JOIN_TAB::type(JT_ALL) is
used instead of JT_FT. It misleads test_if_skip_sort_order() and
the function tries to find suitable key for the order that should
not be allowed for FULLTEXT(JT_FT) table.
The fix is to restore JOIN_TAB strucures for subselect on re-execution
for EXPLAIN.
Additional fix:
Update TABLE::maybe_null field which
affects list_contains_unique_index() behaviour as it
could have the value(maybe_null==TRUE) based on the
assumption that this join is outer
(see setup_table_map() func).
mysql-test/r/explain.result:
test case
mysql-test/t/explain.test:
test case
sql/item_subselect.cc:
Make subquery uncacheable in case of EXPLAIN. It allows to keep
original JOIN_TAB::type(see JOIN::save_join_tab) and restore it
on re-execution.
sql/sql_select.cc:
-restore JOIN_TAB strucures for subselect on re-execution for EXPLAIN
-Update TABLE::maybe_null field as it could have
the value(maybe_null==TRUE) based on the assumption
that this join is outer(see setup_table_map() func).
This change is not related to the crash problem but
affects EXPLAIN results in the test case.
Subquery executes twice, at top level JOIN::optimize and ::execute stages.
At first execution create_sort_index() function is called and
FT_SELECT object is created and destroyed. HANDLER::ft_handler is cleaned up
in the object destructor and at second execution FT_SELECT::get_next() method
returns error.
The fix is to reinit HANDLER::ft_handler field before re-execution of subquery.
mysql-test/r/fulltext.result:
test case
mysql-test/t/fulltext.test:
test case
sql/item_func.cc:
reinit ft_handler before re-execution of subquery
sql/item_func.h:
Fixed method name
sql/sql_select.cc:
reinit ft_handler before re-execution of subquery
The condition over the outer tables now are extracted from
the on condition of any outer join. This condition is
saved in a special field of the JOIN_TAB structure for
the first inner table of the outer join. The condition
is checked before the first inner table is accessed. If
it turns out to be false the table is not accessed at all
and a null complemented row is generated immediately.
ORDER BY computed col
GROUP BY implies ORDER BY in the MySQL dialect of SQL. Therefore, when an
index on the first table in the query is used, and that index satisfies
ordering according to the GROUP BY clause, the query optimizer estimates the
number of tuples that need to be read from this index. If there is a LIMIT
clause, table statistics on tables following this 'sort table' are employed.
There may be a separate ORDER BY clause however, which mandates reading the
whole 'sort table' anyway. But the previous estimate was left untouched.
Fixed by removing the estimate from EXPLAIN output if GROUP BY is used in
conjunction with an ORDER BY clause that mandates using a temporary table.
The problem could be demonstrated with an outer join of two single-row
tables where the values of the join attributes were null. Any query
with such a join could return a wrong result set if the where
condition of the query was not empty. For queries with empty
where conditions the result sets were correct.
This was the consequence of two bugs in the code:
- Item_equal objects for on conditions of outer joins were
not built if the processed query had no where condition
- the check for null values in the code that evaluated constant
Item_equal objects was incorrect.
Fixed both above problems.
Added a test case for the bug and adjusted results for some other
test cases.
When not-exists optimization was applied to a table that
happened to be an inner table of two outer joins, one
embedded into another, then setting the match flag for
the embedding outer join on could be skipped. This caused
generation of extra null complemented rows.
Made sure that the match flags are set correctly in all cases
when not-exists optimization is used.
inited==INDEX
When an error occurs while sending the data in a temporary table there was no
cleanup performed. This caused a failed assertion in the case when different
access methods were used for populating the table vs. retrieving the data from
the table if IGNORE was specified and sql_safe_updates = 0. In this case
execution continues, but the handler expects to continue with the access
method used for row retrieval.
Fixed by doing the cleanup even if errors occur.
Fall back to use ALTER TABLE for engines that doesn't support REPAIR when doing repair for upgrade.
Nicer output from mysql_upgrade and mysql_check
Updated all arrays that used NAME_LEN to use SAFE_NAME_LEN to ensure that we don't break things accidently as names can now have a #mysql50# prefix.
client/mysql_upgrade.c:
If we are using verbose, also run mysqlcheck in verbose mode.
client/mysqlcheck.c:
Add more information if running in verbose mode
Print 'Needs upgrade' instead of complex error if table needs to be upgraded
Don't write connect information if verbose is not 2 or above
mysql-test/r/drop.result:
Updated test and results as we now support full table names
mysql-test/r/grant.result:
Now you get a correct error message if using #mysql with paths
mysql-test/r/show_check.result:
Update results as table names can temporarly be bigger than NAME_LEN (during upgrade)
mysql-test/r/upgrade.result:
Test upgrade for long table names.
mysql-test/suite/funcs_1/r/is_tables_is.result:
Updated old test result (had note been updated in a while)
mysql-test/t/drop.test:
Updated test and results as we now support full table names
mysql-test/t/grant.test:
Now you get a correct error message if using #mysql with paths
mysql-test/t/upgrade.test:
Test upgrade for long table names.
sql/ha_partition.cc:
NAME_LEN -> SAFE_NAME_LEN
sql/item.cc:
NAME_LEN -> SAFE_NAME_LEN
sql/log_event.cc:
NAME_LEN -> SAFE_NAME_LEN
sql/mysql_priv.h:
Added SAFE_NAME_LEN
sql/rpl_filter.cc:
NAME_LEN -> SAFE_NAME_LEN
sql/sp.cc:
NAME_LEN -> SAFE_NAME_LEN
sql/sp_head.cc:
NAME_LEN -> SAFE_NAME_LEN
sql/sql_acl.cc:
NAME_LEN -> SAFE_NAME_LEN
sql/sql_base.cc:
NAME_LEN -> SAFE_NAME_LEN
sql/sql_connect.cc:
NAME_LEN -> SAFE_NAME_LEN
sql/sql_parse.cc:
NAME_LEN -> SAFE_NAME_LEN
sql/sql_prepare.cc:
NAME_LEN -> SAFE_NAME_LEN
sql/sql_select.cc:
NAME_LEN -> SAFE_NAME_LEN
sql/sql_show.cc:
NAME_LEN -> SAFE_NAME_LEN
Enlarge table names for SHOW TABLES to also include optional #mysql50#
sql/sql_table.cc:
Fall back to use ALTER TABLE for engines that doesn't support REPAIR when doing repair for upgrade.
sql/sql_trigger.cc:
NAME_LEN -> SAFE_NAME_LEN
sql/sql_udf.cc:
NAME_LEN -> SAFE_NAME_LEN
sql/sql_view.cc:
NAME_LEN -> SAFE_NAME_LEN
sql/table.cc:
Fixed check_table_name() to not count #mysql50# as part of name
If #mysql50# is part of the name, don't allow path characters in name.
- Changed to still use bcmp() in certain cases becasue
- Faster for short unaligneed strings than memcmp()
- Bettern when using valgrind
- Changed to use my_sprintf() instead of sprintf() to get higher portability for old systems
- Changed code to use MariaDB version of select->skip_record()
- Removed -%::SCCS/s.% from Makefile.am:s to remove automake warnings
Bug#46754: 'rows' field doesn't reflect partition pruning
The EXPLAIN's result in 'rows' field
was evaluated to number of rows when the table was opened
(not from the table cache) and only the partitions left
after pruning was updated with its correct number
of rows.
The evaluation of the 'rows' field was using handler::records()
which is a potentially expensive call, and ignores the partitioning
pruning.
The fix was to use the handlers stats.records after updating it
with ::info(HA_STATUS_VARIABLE) instead.
mysql-test/r/partition_pruning.result:
updated result
mysql-test/t/partition_pruning.test:
Added test.
sql/sql_select.cc:
Use ::info + stats.records instead of ::records().
called twice in a row
Queries with nested joins could cause an infinite loop in the
server when used from SP/PS.
When flattening nested joins, simplify_joins() tracks if the
name resolution list needs to be updated by setting
fix_name_res to TRUE if the current loop iteration has done any
transformations to the join table list. The problem was that
the flag was not reset before the next loop iteration leading
to unnecessary "fixing" of the name resolution list which in
turn could lead to a loop (i.e. circularly-linked part) in that
list. This was causing problems on subsequent execution when
used together with stored procedures or prepared statements.
Fixed by making sure fix_name_res is reset on every loop
iteration.
mysql-test/r/join.result:
Added a test case for bug #53544.
mysql-test/t/join.test:
Added a test case for bug #53544.
sql/sql_select.cc:
Make sure fix_name_res is reset on every loop iteration.
After fix for bug 39653 the shortest available secondary index was used for
full table scan. Primary clustered key was used only if no secondary index
can be used. However, when chosen secondary index includes all fields of the
table being scanned it's better to use primary index since the amount of
data to scan is the same but the primary index is clustered.
Now the find_shortest_key function takes this into account.
mysql-test/suite/innodb/r/innodb_mysql.result:
Added a test case for the bug#55656.
mysql-test/suite/innodb/t/innodb_mysql.test:
Added a test case for the bug#55656.
sql/sql_select.cc:
Bug #55656: mysqldump can be slower after bug #39653 fix.
The find_shortest_key function now prefers clustered primary key
if found secondary key includes all fields of the table.
within query
The server could crash after materializing a derived table
which requires a temporary table for grouping.
When destroying the temporary table used to execute a query for
a derived table, JOIN::destroy() did not clean up Item_fields
pointing to fields in the temporary table. This led to
dereferencing a dangling pointer when printing out the items
tree later in the outer SELECT.
The solution is an addendum to the patch for bug37362: in
addition to cleaning up items in tmp_all_fields3, do the same
for items in tmp_all_fields1, since now we have an example
where this is necessary.
mysql-test/r/join.result:
Added test cases for bug#55568 and a duplicate bug #54468.
mysql-test/t/join.test:
Added test cases for bug#55568 and a duplicate bug #54468.
sql/field.cc:
Make sure field->table_name is not set to NULL in
Field::make_field() to avoid assertion failure in
Item_field::make_field() after cleaning up items
(the assertion fired in udf.test when running
the test suite with the patch applied).
sql/sql_select.cc:
In addition to cleaning up items in tmp_all_fields3, do the
same for items in tmp_all_fields1.
Introduce a new helper function to avoid code duplication.
sql/sql_select.h:
Introduce a new helper function to avoid code duplication in
JOIN::destroy().
mysql-test/r/group_by.result:
Added test that showed problems that no_rows_in_results() didn't work for expressions
mysql-test/r/subselect4.result:
Test case for LP#612894
mysql-test/t/group_by.test:
Added test that showed problems that no_rows_in_results() didn't work for expressions
mysql-test/t/subselect4.test:
Test case for LP#612894
sql/item.h:
Added restore_to_before_no_rows_in_result()
Added function processor for no_rows_in_results() and restore_to_before_no_rows_in_results() to ensure it works with functions
Fix that above functions are handled by Item_ref()
sql/item_func.h:
Ensure that no_rows_in_results() and restore_to_before_no_rows_in_result() are called for all function arguments
sql/item_sum.cc:
Added restore_to_before_no_rows_in_result() to restore settings after Item_sum_hybrid::no_rows_in_result() was called.
This is needed to handle the case where we have made 'make_const()' on the item in opt_sum(), but the item will be reused again in a sub query.
Ignore multiple calls to no_rows_in_result() as Item_ref is calling it twice.
sql/item_sum.h:
Added restore_to_before_no_rows_in_result();
sql/sql_select.cc:
Added reset of no_rows_in_result() for JOIN::reinit()
sql/sql_select.h:
Added marker if no_rows_in_result() is called.
The server was not checking for errors generated during
the execution of Item::val_xxx() methods when copying
data to the group, order, or distinct temp table's row.
Fixed by extending the copy_funcs() to return an error
code and by checking for that error code on the places
copy_funcs() is called.
Test case added.
INSERT IGNORE ... SELECT ... UNION SELECT ...
This assert was triggered by INSERT IGNORE ... SELECT. The assert checks that a
statement either sends OK or an error to the client. If the bug was triggered
on release builds, it caused OK to be sent to the client instead of the correct
error message (in this case ER_FIELD_SPECIFIED_TWICE).
The reason the assert was triggered, was that lex->no_error was set to TRUE
during JOIN::optimize() because of IGNORE. This causes all errors to be ignored.
However, not all errors can be ignored. Some, such as ER_FIELD_SPECIFIED_TWICE
will cause the INSERT to fail no matter what. But since lex->no_error was set,
the critical errors were ignored, the INSERT failed and neither OK nor the
error message was sent to the client.
This patch fixes the problem by temporarily turning off lex->no_error in
places where errors cannot be ignored during processing of INSERT ... SELECT.
Test case added to insert.test.
This was triggered by innodb.innodb_multi_update, where we had a static length row without nulls and xtradb didn't fill in the delete-marker byte
include/my_bitmap.h:
Added prototype for bitmap_union_is_set_all()
mysys/my_bitmap.c:
Added function to check if union of two bit maps covers all bits.
sql/mysql_priv.h:
Updated protype for compare_record()
sql/sql_insert.cc:
Send to compare_record() flag if all fields are used.
sql/sql_select.cc:
Set share->null_bytes_for_compare.
sql/sql_update.cc:
In compare_record() don't use the fast cmp_record() (which is basically memcmp) if we don't know that all fields exists.
Don't compare the null_bytes if there is no data there.
sql/table.cc:
Store in share->null_bytes_for_compare the number of bytes that has null or bit fields (but not delete marker)
Store in can_cmp_whole_record if we can use memcmp() (assuming all rows are read) to compare rows in compare_record()
sql/table.h:
Added two elements in table->share to speed up checking how updated rows can be compared.
This assert checks that the server does not try to send OK to the
client if there has been some error during processing. This is done
to make sure that the error is in fact sent to the client.
The problem was that view errors during processing of WHERE conditions
in UPDATE statements where not detected by the update code. It therefore
tried to send OK to the client, triggering the assert.
The bug was only noticeable in debug builds.
This patch fixes the problem by making sure that the update code
checks for errors during condition processing and acts accordingly.
The problem is that QUICK_SELECT_DESC behaviour depends
on used_key_parts value which can be bigger than selected
best_key_parts value if an engine supports clustered key.
But used_key_parts is overwritten with best_key_parts
value that prevents from correct selection of index
access method. The fix is to preserve used_key_parts
value for further use in QUICK_SELECT_DESC.
mysql-test/r/innodb_mysql.result:
test case
mysql-test/t/innodb_mysql.test:
test case
sql/sql_select.cc:
preserve used_key_parts value for further use in QUICK_SELECT_DESC
file .\filesort.cc, line 149 (part II)
Problem: the server didn't disregard sort order
for some zero length tuples.
Fix: skip sort order in such a case
(zero length NOT NULL string functions).
mysql-test/r/select.result:
Fix for bug #54459: Assertion failed: param.sort_length,
file .\filesort.cc, line 149 (part II)
- test result.
mysql-test/t/select.test:
Fix for bug #54459: Assertion failed: param.sort_length,
file .\filesort.cc, line 149 (part II)
- test case.
sql/sql_select.cc:
Fix for bug #54459: Assertion failed: param.sort_length,
file .\filesort.cc, line 149 (part II)
- disregard sort order for zero length NOT NULL string functions
along with zero length NOT NULL fields.
The problem there is that HAVING condition evaluates const
parts of condition despite the condition has references
on aggregate functions. Table t1 became const tables
after make_join_statistics and table1.pk = 1, HAVING is
transformed into MAX(1) < 7 and taken away from HAVING.
The fix is to skip evaluation of HAVING conts parts if
HAVING condition has references on aggregate functions.
mysql-test/r/having.result:
test case
mysql-test/t/having.test:
test case
sql/sql_select.cc:
skip evaluation of HAVING conts parts if
HAVING condition has references on aggregate functions.
strict aliasing violations.
One somewhat major source of strict-aliasing violations and
related warnings is the SQL_LIST structure. For example,
consider its member function `link_in_list` which takes
a pointer to pointer of type T (any type) as a pointer to
pointer to unsigned char. Dereferencing this pointer, which
is done to reset the next field, violates strict-aliasing
rules and might cause problems for surrounding code that
uses the next field of the object being added to the list.
The solution is to use templates to parametrize the SQL_LIST
structure in order to deference the pointers with compatible
types. As a side bonus, it becomes possible to remove quite
a few casts related to acessing data members of SQL_LIST.
sql/handler.h:
Use the appropriate template type argument.
sql/item.cc:
Remove now-unnecessary cast.
sql/item_subselect.cc:
Remove now-unnecessary casts.
sql/item_sum.cc:
Use the appropriate template type argument.
Remove now-unnecessary cast.
sql/mysql_priv.h:
Move SQL_LIST structure to sql_list.h
Use the appropriate template type argument.
sql/sp.cc:
Remove now-unnecessary casts.
sql/sql_delete.cc:
Use the appropriate template type argument.
Remove now-unnecessary casts.
sql/sql_derived.cc:
Remove now-unnecessary casts.
sql/sql_lex.cc:
Remove now-unnecessary casts.
sql/sql_lex.h:
SQL_LIST now takes a template type argument which must
match the type of the elements of the list. Use forward
declaration when the type is not available, it is used
in pointers anyway.
sql/sql_list.h:
Rename SQL_LIST to SQL_I_List. The template parameter is
the type of object that is stored in the list.
sql/sql_olap.cc:
Remove now-unnecessary casts.
sql/sql_parse.cc:
Remove now-unnecessary casts.
sql/sql_prepare.cc:
Remove now-unnecessary casts.
sql/sql_select.cc:
Remove now-unnecessary casts.
sql/sql_show.cc:
Remove now-unnecessary casts.
sql/sql_table.cc:
Remove now-unnecessary casts.
sql/sql_trigger.cc:
Remove now-unnecessary casts.
sql/sql_union.cc:
Remove now-unnecessary casts.
sql/sql_update.cc:
Remove now-unnecessary casts.
sql/sql_view.cc:
Remove now-unnecessary casts.
sql/sql_yacc.yy:
Remove now-unnecessary casts.
storage/myisammrg/ha_myisammrg.cc:
Remove now-unnecessary casts.
There are two problems:
1. In simplify_joins function we calculate table dependencies. If STRAIGHT_JOIN hint
is used for whole SELECT we do not count it and as result some dependendecies
might be lost. It leads to incorrect table order which is returned by
join_tab_cmp_straight() function.
2. make_join_statistics() calculate the transitive closure for relations a particular
JOIN_TAB is 'dependent on'.
We aggregate the dependent table_map of a JOIN_TAB by adding dependencies from other
tables which we depend on. However, this may also cause new dependencies to be
available after we have completed processing a certain JOIN_TAB.
Both these problems affect condition pushdown and as result condition might be pushed
into wrong table which leads to crash or even omitted which leads to wrong result.
The fix:
1. Use modified 'transitive closure' algorithm provided by Ole John Aske
2. Update table dependences in simplify_joins according to
global STRAIGHT_JOIN hint.
Note: the patch also fixes bugs 46091 & 51492
mysql-test/r/join_outer.result:
test case
mysql-test/t/join_outer.test:
test case
sql/sql_select.cc:
1. Use modified 'transitive closure' algorithm provided by Ole John Aske
2. Update table dependences in simplify_joins according to
global STRAIGHT_JOIN hint.
Fixed some bugs introduced in 5.1.47
Disabled some tests until we have merged with latest Xtradb
configure.in:
Added testing if valgrind/memcheck.h exists
storage/pbxt/src/ha_pbxt.cc:
LOCK_plugin is not anymore locked in init
- 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.
The fix actually reverts the change introduced
by the patch for bug 51494.
The fact is that patches for bugs 52177&48419
fix bugs 51194&50575 as well.
mysql-test/r/innodb_mysql.result:
test case
mysql-test/t/innodb_mysql.test:
test case
sql/sql_select.cc:
reverted wrong fix for bug 51494
greedy_search optimizer_search_depth=0
The algorithm inside restore_prev_nj_state failed to
properly update the counters within the NESTED_JOIN
tree. The counter was decremented each time a table in the
node was removed from the QEP, the correct thing to do being
only to decrement it when the last table in the child node
was removed from the plan. This lead to node counters
getting negative values and the plan thus appeared
impossible. An assertion caught this.
Fixed by not recursing up the tree unless the last table in
the join nest node is removed from the plan
WHERE predicates containing references to empty tables in a
subquery were handled incorrectly by the optimizer when
executing EXPLAIN. As a result, the optimizer could try to
evaluate such predicates rather than just stop with
"Impossible WHERE noticed after reading const tables" as
it would do in a non-subquery case. This led to valgrind
errors and crashes.
Fixed the code checking the above condition so that subqueries
are not excluded and hence are handled in the same way as top
level SELECTs.
mysql-test/r/explain.result:
Added a test case for bug #48419.
mysql-test/r/ps.result:
Updated test results to take the new (and more correct)
"Extra" comments in execution plans.
mysql-test/t/explain.test:
Added a test case for bug #48419.
sql/sql_select.cc:
There is no point in excluding subqueries from checking
for identically false WHERE conditions.
