If the flag 'optimize_join_buffer_size' is set to 'off' and the value
of the system variable 'join_buffer_size' is greater than the value of
the system variable 'join_buffer_space_limit' than no join cache can
be employed to join tables of the executed query.
A bug in the function JOIN_CACHE::alloc_buffer allowed to use join
buffer even in this case while another bug in the function
revise_cache_usage could cause a crash of the server in this case if the
chosen execution plan for the query contained outer join or semi-join
operation.
of mysql-5.6 code line. The bugs could not be reproduced in the latest release
of mariadb-5.3 as they were fixed either when the code of subquery optimization
was back-ported from mysql-6.0 or later when some other bugs were fixed.
fixed several defects in the greedy optimization:
1) The greedy optimizer calculated the 'compare-cost' (CPU-cost)
for iterating over the partial plan result at each level in
the query plan as 'record_count / (double) TIME_FOR_COMPARE'
This cost was only used locally for 'best' calculation at each
level, and *not* accumulated into the total cost for the query plan.
This fix added the 'CPU-cost' of processing 'current_record_count'
records at each level to 'current_read_time' *before* it is used as
'accumulated cost' argument to recursive
best_extension_by_limited_search() calls. This ensured that the
cost of a huge join-fanout early in the QEP was correctly
reflected in the cost of the final QEP.
To get identical cost for a 'best' optimized query and a
straight_join with the same join order, the same change was also
applied to optimize_straight_join() and get_partial_join_cost()
2) Furthermore to get equal cost for 'best' optimized query and a
straight_join the new code substrcated the same '0.001' in
optimize_straight_join() as it had been already done in
best_extension_by_limited_search()
3) When best_extension_by_limited_search() aggregated the 'best' plan a
plan was 'best' by the check :
'if ((search_depth == 1) || (current_read_time < join->best_read))'
The term '(search_depth == 1' incorrectly caused a new best plan to be
collected whenever the specified 'search_depth' was reached - even if
this partial query plan was more expensive than what we had already
found.
If the duplicate elimination strategy is used for a semi-join and potentially
one of the block-based join algorithms can be employed to join the inner
tables of the semi-join then sorting of the head (first non-constant) table
for a query with ORDER BY / GROUP BY cannot be used.
The execution plan cannot use sorting on the first table from the
sequence of the joined tables if it plans to employ the block-based
hash join algorithm.
KEYUSE elements for a possible hash join key are not sorted by field
numbers of the second table T of the hash join operation. Besides
some of these KEYUSE elements cannot be used to build any key as their
key expressions depend on the tables that are planned to be accessed
after the table T.
The code before the patch did not take this into account and, as a result,
execition of a query the employing block-based hash join algorithm could
cause a crash or return a wrong result set.
The function setup_semijoin_dups_elimination erroneously assumed
that if join_cache_level is set to 3 or 4 then the type of the
access to a table cannot be JT_REF or JT_EQ_REF. This could lead
to wrong query result sets.
The bug happened because in some cases the function JOIN::exec
did not save the value of TABLE::pre_idx_push_select_cond in
TABLE::select->pre_idx_push_select_cond for the sort table.
Noticed and fixed a bug in the function make_cond_remainder
that builds the remainder condition after extraction of an index
pushdown condition from the where condition. The code
erroneously assumed that the function make_cond_for_table left
the value of ICP_COND_USES_INDEX_ONLY in sub-condition markers.
Adjusted many result files from the regression test suite
after this fix .
of the 5.3 code line after a merge with 5.2 on 2010-10-28
in order not to allow the cost to access a joined table to be equal
to 0 ever.
Expanded data sets for many test cases to get the same execution plans
as before.
The bug was caused by an incorrect code of the function
Item_direct_view_ref::replace_equal_field introduced in the
patch for bugs 717577, 724942. The function erroneously
returned the wrapped field instead of the Item_direct_view_ref
object itself in the cases when no replacement happened.
The bug masked two other minor bugs that could result in not
quite correct output of the EXPLAIN command for some queries.
They were fixed in the patch as well.
- Set the default
- Adjust the testcases so that 'new' tests are run with optimizations turned on.
- Pull out relevant tests from "irrelevant" tests and run them with optimizations on.
- Run range.test and innodb.test with both mrr=on and mrr=off
semijoin=on,firstmatch=on,loosescan=on
to
semijoin=off,firstmatch=off,loosescan=off
Adjust the testcases:
- Modify subselect*.test and join_cache.test so that all tests
use the same execution paths as before (i.e. optimizations that
are being tested are enabled)
- Let all other test files run with the new default settings (i.e.
with new optimizations disabled)
- Copy subquery testcases from these files into t/subselect_extra.test
which will run them with new optimizations enabled.
This crashing bug could manifest itself at execution of join queries
over materialized derived tables with IN subquery predicates in the
where clause. If for such a query the optimizer chose to use duplicate
weed-out with duplicates in a materialized derived table and chose to
employ join cache the the execution could cause a crash of the server.
It happened because the JOIN_CACHE::init method assumed that the value
of TABLE::file::ref is set at the moment when the method was called
for the employed join cache. It's true for regular tables, but it's
not true for materialized derived tables that are filled now at the
first access to them, i.e. after the JOIN_CACHE::init has done its job.
To fix this problem for any ROWID field of materialized derived table
the procedure that copies fields from record buffers into the employed
join buffer first checks whether the value of TABLE::file::ref has
been set for the table, and if it's not so the procedure sets this value.
A lot of small fixes and new test cases.
client/mysqlbinlog.cc:
Cast removed
client/mysqltest.cc:
Added missing DBUG_RETURN
include/my_pthread.h:
set_timespec_time_nsec() now only takes one argument
mysql-test/t/date_formats.test:
Remove --disable_ps_protocl as now also ps supports microseconds
mysys/my_uuid.c:
Changed to use my_interval_timer() instead of my_getsystime()
mysys/waiting_threads.c:
Changed to use my_hrtime()
sql/field.h:
Added bool special_const_compare() for fields that may convert values before compare (like year)
sql/field_conv.cc:
Added test to get optimal copying of identical temporal values.
sql/item.cc:
Return that item_int is equal if it's positive, even if unsigned flag is different.
Fixed Item_cache_str::save_in_field() to have identical null check as other similar functions
Added proper NULL check to Item_cache_int::save_in_field()
sql/item_cmpfunc.cc:
Don't call convert_constant_item() if there is nothing that is worth converting.
Simplified test when years should be converted
sql/item_sum.cc:
Mark cache values in Item_sum_hybrid as not constants to ensure they are not replaced by other cache values in compare_datetime()
sql/item_timefunc.cc:
Changed sec_to_time() to take a my_decimal argument to ensure we don't loose any sub seconds.
Added Item_temporal_func::get_time() (This simplifies some things)
sql/mysql_priv.h:
Added Lazy_string_decimal()
sql/mysqld.cc:
Added my_decimal constants max_seconds_for_time_type, time_second_part_factor
sql/table.cc:
Changed expr_arena to be of type CONVENTIONAL_EXECUTION to ensure that we don't loose any items that are created by fix_fields()
sql/tztime.cc:
TIME_to_gmt_sec() now sets *in_dst_time_gap in case of errors
This is needed to be able to detect if timestamp is 0
storage/maria/lockman.c:
Changed from my_getsystime() to set_timespec_time_nsec()
storage/maria/ma_loghandler.c:
Changed from my_getsystime() to my_hrtime()
storage/maria/ma_recovery.c:
Changed from my_getsystime() to mmicrosecond_interval_timer()
storage/maria/unittest/trnman-t.c:
Changed from my_getsystime() to mmicrosecond_interval_timer()
storage/xtradb/handler/ha_innodb.cc:
Added support for new time,datetime and timestamp
unittest/mysys/thr_template.c:
my_getsystime() -> my_interval_timer()
unittest/mysys/waiting_threads-t.c:
my_getsystime() -> my_interval_timer()
- "Using MRR" is no longer shown with range access.
- Instead, both range and BKA accesses will show one of the following:
= "Rowid-ordered scan"
= "Key-ordered scan"
= "Key-ordered Rowid-ordered scan"
depending on whether DS-MRR implementation will do scan keys in order, rowids in order,
or both.
- The patch also introduces a way for other storage engines/MRR implementations to
pass information to EXPLAIN output about the properties of employed MRR scans.
The bug in the function print_keyuse() caused crashes if
hash join could be used. It happened because the function
ignored the fact that KEYUSE structures could be created
for hash joins as well.
even in the cases when there existed range/index-merge scans that
were cheaper than the full table scan.
This was a defect/bug of the implementation of mwl #128.
Now hash join can work not only with full table scan of the joined
table, but also with full index scan, range and index-merge scans.
Accordingly, in the cases when hash join is used the column 'type'
in the EXPLAINs can contain now 'hash_ALL', 'hash_index', 'hash_range'
and 'hash_index_merge'. If hash join is coupled with a range/index_merge
scan then the columns 'key' and 'key_len' contain info not only on
the used hash index, but also on the indexes used for the scan.
This bug could manifest itself when hash join over a varchar column
with NULL values in some rows was used. It happened because the
function key_buf_cmp erroneously returned FALSE when one of the joined
key fields was null while the second was not.
Also fixed two other bugs in the functions key_hashnr and key_buf_cmp
that could possibly lead to wrong results for some queries that
used hash join over several columns with nulls.
Also reverted the latest addition of the test case for bug #45092. It
had been already backported earlier.
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.
One of the hash functions employed by the BNLH join algorithm
calculates the the value of hash index for key value utilizing
every byte of the key buffer. To make this calculation valid
one has to ensure that for any key value unused bytes of the
buffer are filled with with a certain filler. We choose 0 as
a filler for these bytes.
Added an optional boolean parameter with_zerofill to the function
key_copy. If the value of the parameter is TRUE all unused bytes
of the key buffer is filled with 0.
In some cases the function make_cond_for_index() was mistaken
when detecting index only pushdown conditions for a table:
a pushdown condition that was not index only could be marked
as such.
It happened because the procedure erroneously used the markers
for index only conditions that remained from the calls of
this function that extracted the index conditions for other
tables.
Fixed by erasing index only markers as soon as they are need
anymore.
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.
