Fix MySQL BUG#52344 - Subquery materialization: Assertion if subquery in on-clause of outer join
Original fix and comments from Oysten, adjusted for the different
subquery optimization in MariaDB.
"
Problem: If tables of an outer join are constant tables,
the associated on-clause will be evaluated in the optimization
phase. If the on-clause contains a query that is to be
executed with subquery materialization, this will not work
since the infrastructure for such execution is not yet set up.
Solution: Do not evaluate on-clause in optimization phase if
is_expensive() returns true for this clause. This is how the
problem is currently avoided for where-clauses. This works
because, Item_in_subselect::is_expensive_processor returns true
if query is to be executed with subquery materialization.
"
In addition, after MWL#89, in MariaDB if the IN-EXISTS strategy
is chosen, the in-to-exists predicates are insterted after
join_read_const_table() is called, resulting in evaluation of
the subquery without the in-to-exists predicates.
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.
Analysis:
The send_data method of the result sink class used to collect
data statistics about materialized subqueries incorrectly assumed
that duplicate rows are removed prior to calling send_data. As
a result the collected statistics was wrong, which resulted in
an incorrect maximal number of keys in the Ordered_key buffer.
Solution:
Try to insert each row into the materialized temp table before
collecting statistics, and if the insertion results in a duplicate
row, do not count the current row.
- 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.
Registration of pointer change if we assign it to other pointer which should be identical after statement execution (PS/SP).
mysql-test/r/subselect.result:
Test suite.
mysql-test/t/subselect.test:
Test suite.
sql/sql_class.cc:
The procedure of the pointer registration.
sql/sql_class.h:
The procedure of the pointer registration.
sql/sql_lex.cc:
Registration of pointer change if we assign it to other pointer which should be identical after statement execution (PS/SP).
mysql-test/r/heap_btree.result:
Test of index over bit firld in hash table.
mysql-test/r/heap_hash.result:
Test of index over bit firld in hash table.
mysql-test/t/heap_btree.test:
Test of index over bit firld in hash table.
mysql-test/t/heap_hash.test:
Test of index over bit firld in hash table.
storage/heap/ha_heap.cc:
Adding bit field support for heap tables.
storage/heap/hp_create.c:
Adding bit field support for heap tables.
storage/heap/hp_hash.c:
Adding bit field support for heap tables.
Analysis:
Single-row subqueries are not considered expensive and are
evaluated both during EXPLAIN in to detect errors like
"Subquery returns more than 1 row", and during optimization to
perform constant optimization.
The cause for the failed ASSERT is in JOIN::join_free, where we set
bool full= (!select_lex->uncacheable && !thd->lex->describe);
Thus for EXPLAIN statements full == FALSE, and as a result the call to
JOIN::cleanup doesn't call JOIN_TAB::cleanup which should have
called table->disable_keyread().
Solution:
Consider all kinds of subquery predicates as expensive.
Analysis:
This another instance of the problem fixed in LP BUG#675981 -
evaluation of subqueries during EXPLAIN when the subquery plan
is incomplete because JOIN::optimize() generally doesn't create
complete execution plans for EXPLAIN statements.
In this case the call path is:
mysql_explain_union -> outer_join.exec -> outer_join.init_execution ->
create_sort_index -> filesort -> find_all_keys ->
SQL_SELECT::skip_record -> outer_where_clause.val_int -> ...
-> subselect_join.exec -> ... -> sub_select_cache
When calling sub_select_cache JOIN_TAB::cache is NULL because the cache
objects are not created for EXPLAIN statements.
Solution:
Delay the call to init_execution() after all EXPLAIN related processing
is completed. Thus init_execution() is not called at all during EXPLAIN.
Cause:
The optimize() phase for the subquery selected to use join buffering via setting
JOIN_TAB::next_select= sub_select_cache in make_join_readinfo, however, the call
to check_join_cache_usage() from make_join_readinfo didn't create the corresponding
JOIN_CACHE_BNL object because of the condition:
if ((options & SELECT_DESCRIBE) ||
(((tab->cache= new JOIN_CACHE_BNL(join, tab, prev_cache))) &&
!tab->cache->init()))
Since EXPLAIN for subqueries runs regular execution, the constant predicates that
were delayed to be evaluated at the exec() phase, were evaluated during EXPLAIN.
As a result the outer JOIN::exec called JOIN::exec for the subquery, while the
subquery execution plan was no properly created, which resulted in an failed ASSERT.
Fix:
The patch blocks evaluation of constant expensive conditions during EXPLAIN. Notice
that these conditions are "constant" with respect to the outer query, thus in
general they could be arbitrarily expensive, which may result in very slow EXPLAINs.
The bug happened when BKA join algorithm used an incremental buffer
and some of the fields over which access keys were constructed
- were allocated in the previous join buffers
- were non-nullable
- belonged to inner tables of outer joins.
For such fields an offset to the field value in the record is saved
in the postfix of the record, and a zero offset indicates that the value
is null. Before the key using the field value is constructed the
value is read into the corresponding field of the record buffer and
the null bit is set for the field if the offset is 0. However if
the field is non-nullable the table->null_row must be set to 1
for null values and to 0 for non-null values to ensure proper reading
of the value from the record buffer.
This is a backport of the fix for
MySQL BUG#52317: Assertion failing in Field_varstring::store () at field.cc:6833
The orginal comment by Oystein is:
In order for EXPLAIN to print const-refs, a Store_key_const_item object
is created. This is different for normal execution of subqueries where
a temporary store_key_item object is used instead. The problem is that
EXPLAIN will execute subqueries. This leads to a scenario where a
store_key_const_item object it told to write to its underlying field.
This results in a failing assert since the write set of the underlying
table does not reflect this.
The resolution is to do the same trick as for store_key_item::copy_inner().
That is, temporarily change the write set to allow writes to all columns.
This is only necessary in debug version since non-debug version does not
contain asserts on write_set.
sql/sql_select.h:
Temporarily change write_set in store_key_const_item::copy_inner() to
allow initialization of underlying field. This is necessary since
subqueries are executed for EXPLAIN. (For normal execution,
store_key_item::copy_inner is used.)
The condition that was supposed to check whether a join table
is an inner table of a nested outer join or semi-join was not
quite correct in the code of the function check_join_cache_usage.
That's why some queries with nested outer joins triggered
an assertion failure.
Encapsulated this condition in the new method called
JOIN_TAB::is_nested_inner and provided a proper code for it.
Also corrected a bug in the code of check_join_cache_usage()
that caused a downgrade of not first join buffers of the
level 5 and 7 to level 4 and 6 correspondingly.
The logic for how to check when to update the table cache for
INNODB_LOCKS with real data was flawed. This could result in both
not updating the cache often enough (when the table is queried
repeatedly with less than 100 milliseconds in-between) resulting
in stale data; as well as updating too often (when multiple
queries against the table start at around the same time).
This caused occasional test failures in innodb_information_schema.
Fix by updating the "last updated" timestamp in the right place,
when the cache is updated, not when it is read.
anticipate different execution paths resulting in different
thd->proc_info.
- Fixed subselect_cache to contain correct results. The results
are currently wrong in 5.3, but are correct in 5.2, and 5.3-mwl89.
The cause for the bug was two-fold:
1. Incorrect detection of whether a table is the first one in a query plan -
"used_table & 1" actually checks if used_table is table with number "1".
2. Missing logic to delay the evaluation of (expensive) constant conditions
during the execution phase.
The fix adds/changes:
The patch:
- removes incorrect treatment of expensive predicates from make_cond_for_table,
and lets the caller decide when to evaluate expensive predicates.
- saves expensive constant conditions in JOIN::exec_const_cond,
which is evaluated once in the beginning of JOIN::exec.
Switch makefiles to use libtool to build libmysqld.so, as well as all its
dependencies.
The previous MYSQL_PLUGIN_DEPENDS_ON_MYSQL_INTERNALS() declaration is removed,
as it does not work well with a libtool build. Instead, plugins that need it
can specify an alternate object in MYSQL_PLUGIN_STATIC() that will be used for
embedded library. The plugin must then take care itself of compiling the
special object for embedded, rebuilding the source files previously listed in
MYSQL_PLUGIN_DEPENDS_ON_MYSQL_INTERNALS() with @plugin_embedded_defs@ in
CFLAGS/CXXFLAGS. The extra target @XXX_embedded_static_target@ is available
for the special object, this will be empty when --without-embedded-server.
All in-tree plugins are changed to build their static targets with libtool.
Additional plugins that want to work with libmysqld.so will need to be
similarly modified to build with libtool (or otherwise provide an -fPIC
object). Dynamically loaded plugins are not affected.
The old libraries like libmysys.a, libmyisam.a and similar libraries, which
were installed by `make install` though this is of little use, are still built
and installed to not break package scripts etc. that expect them. These
libraries are kept static to avoid introducing new .so dependencies.
The patch also fixes a handfull of duplicate symbol linker errors, where we
included some object twice during linking; these for one reason or another did
not produce errors before but caused problems on some platforms with this
patch (eg. Mac OS X linker is more strict for shared objects).
This patch only does what is necessary to build libmysqld.so. There are some
more cleanups that are possible now that we are using libtool more fully,
which could done in subsequent patches (though we may not bother as we are
switching from autotools to CMake anyway):
- In libmysql_r/, we should be able to just link libmysys.la etc, instead of
symlinking and re-compiling sources into the directory.
- In libmysql/, we can similarly avoid symlinking and recompiling sources if
we instead build a libmysys_nothread.la library with appropriate CFLAGS and
link that.
- In sql/, we can build a separate target libmysql_int.la with appropriate
CFLAGS for embedded and use that in libmysqld/ instead of symlinking
sources.
- libmysys.a, libmyisam.a and similar libraries could be installed as .so
also to save on code size; or alternatively could be not installed at all.
client/Makefile.am:
Updated for using libtool
config/ac-macros/plugins.m4:
Replace MUSQL_PLUGIN_DEPENDS_ON_MYSQL_INTERNALS with mechanism for plugins
to specify alternate object for embedded.
configure.in:
Fix linking duplicate objects related to THREAD_LOBJECTS.
dbug/Makefile.am:
Updated for using libtool
extra/Makefile.am:
Fix relative paths.
libmysqld/Makefile.am:
Build libmysqld.la using libtool
libmysqld/examples/Makefile.am:
Updated to use libtool
mysys/Makefile.am:
Updated to use libtool.
Fix linking duplicate objects related to THREAD_LOBJECTS.
mysys/my_uuid.c:
Fix conflicting global mutex name by making it static.
regex/Makefile.am:
Updated to use libtool
sql/Makefile.am:
Updated to use libtool
sql/item_func.cc:
Fix conflicting mutex name.
sql/mysql_priv.h:
Fix conflicting mutex name
sql/mysqld.cc:
Fix conflicting mutex name.
Add missing call of my_uuid_end().
storage/archive/Makefile.am:
Updated to use libtool
storage/archive/plug.in:
Updated to use libtool
storage/blackhole/Makefile.am:
Updated to use libtool
storage/blackhole/plug.in:
Updated to use libtool
storage/csv/Makefile.am:
Updated to use libtool
storage/csv/plug.in:
Updated to use libtool
storage/example/Makefile.am:
Updated to use libtool
storage/federated/Makefile.am:
Updated to use libtool
storage/federated/plug.in:
Updated to use libtool
storage/federatedx/Makefile.am:
Updated to use libtool
storage/federatedx/plug.in:
Updated to use libtool
storage/heap/Makefile.am:
Updated to use libtool
storage/heap/plug.in:
Updated to use libtool
storage/innobase/Makefile.am:
Updated to use libtool
storage/innobase/plug.in.disabled:
Updated to use libtool
storage/innodb_plugin/Makefile.am:
Updated to use libtool
storage/maria/CMakeLists.txt:
Fix linking duplicate object in maria_dump_log, causes failure on Mac OS X
storage/maria/Makefile.am:
Updated to use libtool
Fix linking duplicate object in maria_dump_log, causes link failure on Mac OS X
storage/maria/ma_loghandler.c:
Move maria_dump_log code to separate file to fix duplicate object link failures.
storage/maria/ma_loghandler.h:
Move maria_dump_log code to separate file to fix duplicate object link failures.
storage/maria/maria_dump_log.c:
Move maria_dump_log code to separate file to fix duplicate object link failures.
storage/maria/plug.in:
Updated to use libtool
storage/myisam/Makefile.am:
Updated to use libtool
storage/myisam/plug.in:
Updated to use libtool
storage/myisammrg/Makefile.am:
Updated to use libtool
storage/myisammrg/plug.in:
Updated to use libtool
storage/pbxt/plug.in:
Updated to use libtool
storage/pbxt/src/Makefile.am:
Updated to use libtool
storage/xtradb/Makefile.am:
Updated to use libtool
storage/xtradb/plug.in:
Updated to use libtool
strings/Makefile.am:
Updated to use libtool
unittest/unit.pl:
Don't attempt to run libtool internal files as unit tests.
vio/Makefile.am:
Updated to use libtool
When pushing the condition for a table in the function
JOIN_TAB::make_scan_filter the optimizer must not push
conditions from WHERE if the table is some inner table
of an outer join..
The condition over outer tables extracted from the on expression
for a outer join must be ANDed to the condition pushed to the
first inner table of this outer join only.
Nested outer joins cannot use flat join buffers. So if join_cache_level
is set to 1 then any join algorithm employing join buffers cannot be used
for nested outer joins.
The patch that introduced the new enumeration type Match_flag
for the values of match flags in the records put into join buffers
missed the necessary modifications in JOIN_CACHE::set_match_flag_if_none.
This could cause wrong results for outer joins with on expressions
only over outer tables.
A non-incremental join buffer cannot be used for inner tables of nested
outer joins. That's why when join_cache_level is set to 7 it must
be downgraded to level 6 for the inner tables of nested outer joins.
For the same reason with join_cache_level set to 3 no join buffer is
used for the inner tables of outer joins (we could downgrade it to
level 2, but this level does not support ref access).
Miscalculation of the minimum possible buffer size could trigger
an assert in JOIN_CACHE_HASHED::put_record when if join_buffer_size
was set to the values that is less than the length of one record to
stored in the join buffer.
It happened due to the following mistakes:
- underestimation of space needed for a key in the hash table
(we have to take into account that hash table can have more
buckets than the expected number of records).
- the value of maximum total length of all records stored in
the join buffer was not saved in the field max_used_fieldlength
by the function calc_used_field_length.
better MYSQL_PLUGIN_WITHOUT that works correctly in all of the following:
--with-plugin-XXX
--without-plugin-XXX
--with-plugins=XXX
--with-plugins=META
--with-plugins=XXX --without-plugin-XXX
--with-plugins=META --without-plugin-XXX
This patch removes most remaining delays due to uninteruptible sleep()
during shutdown, as found using PMP. This makes standard test run very
close in speed to with --loose-innodb-fast-shutdown=2, and greatly
speeds up running the test suite.
sql/mysqld.cc:
Poll for threads to die every 20 msec during shutdown, rather than force
a wait for 2 full seconds should one thread be a little slow to exit
(this was seen occasionally in mysql-test-run).
storage/xtradb/include/srv0srv.h:
Rename the event, as we now use it to wakeup more threads during shutdown.
storage/xtradb/log/log0log.c:
Rename the event, as we now use it to wakeup more threads during shutdown.
storage/xtradb/srv/srv0srv.c:
Replace some hardcoded sleep()s with os_wait_event_time() that can be
interrupted early during server shutdown to avoid unnecessary delays.
