https://mariadb.atlassian.net/browse/MDEV-28
This task implements a new clause LIMIT ROWS EXAMINED <num>
as an extention to the ANSI LIMIT clause. This extension
allows to limit the number of rows and/or keys a query
would access (read and/or write) during query execution.
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.
Problem was that now we can merge derived table (subquery in the FROM clause).
Fix: in case of detected conflict and presence of derived table "over" the table which cased the conflict - try materialization strategy.
sql/sql_insert.cc:
CREATE ... IF NOT EXISTS may do nothing, but
it is still not a failure. don't forget to my_ok it.
******
CREATE ... IF NOT EXISTS may do nothing, but
it is still not a failure. don't forget to my_ok it.
sql/sql_table.cc:
small cleanup
******
small cleanup
Reset 'examined_rows_count' in union to not count same rows twice
mysql-test/r/subselect_mat_cost.result:
Test also slow query logging
mysql-test/t/subselect_mat_cost.test:
Test also slow query logging
sql/sql_union.cc:
Reset 'examined_rows_count' in union to not count same rows twice
We must allocate a larger ref_pointer_array. We failed to account for extra
items allocated here:
#0 find_order_in_list
uint el= all_fields.elements;
all_fields.push_front(order_item); /* Add new field to field list. */
ref_pointer_array[el]= order_item;
order->item= ref_pointer_array + el;
#1 setup_order
#2 setup_without_group
#3 JOIN::prepare
mysql-test/r/order_by.result:
New test case.
mysql-test/r/union.result:
New test case.
mysql-test/t/order_by.test:
New test case.
mysql-test/t/union.test:
New test case.
sql/sql_lex.cc:
find_order_in_list() may need some extra space, so multiply og_num by two.
sql/sql_union.cc:
For UNION, the 'n_sum_items' are accumulated in the "global_parameters" select_lex.
This number must be propagated to setup_ref_array()
When preparing a 'fake_select_lex' we need to use global_parameters->order_list
rather than fake_select_lex->order_list (see comments inside st_select_lex_unit::cleanup)
We must allocate a larger ref_pointer_array. We failed to account for extra
items allocated here:
#0 find_order_in_list
uint el= all_fields.elements;
all_fields.push_front(order_item); /* Add new field to field list. */
ref_pointer_array[el]= order_item;
order->item= ref_pointer_array + el;
#1 setup_order
#2 setup_without_group
#3 JOIN::prepare
Split status variable Rows_read to Rows_read and Rows_tmp_read so that one can see how much real data is read.
Same was done with with Handler_update and Handler_write.
Fixed bug in MEMORY tables where some variables was counted twice.
Added new internal handler call 'ha_close()' to have one place to gather statistics.
Fixed bug where thd->open_options was set to wrong value when doing admin_recreate_table()
mysql-test/r/status.result:
Updated test results and added new tests
mysql-test/r/status_user.result:
Udated test results
mysql-test/t/status.test:
Added new test for temporary table status variables
sql/ha_partition.cc:
Changed to call ha_close() instead of close()
sql/handler.cc:
Added internal_tmp_table variable for easy checking of temporary tables.
Added new internal handler call 'ha_close()' to have one place to gather statistics.
Gather statistics for internal temporary tables.
sql/handler.h:
Added handler variables internal_tmp_table, rows_tmp_read.
Split function update_index_statistics() to two.
Added ha_update_tmp_row() for faster tmp table handling with more statistics.
sql/item_sum.cc:
ha_write_row() -> ha_write_tmp_row()
sql/multi_range_read.cc:
close() -> ha_close()
sql/mysqld.cc:
New status variables: Rows_tmp_read, Handler_tmp_update and Handler_tmp_write
sql/opt_range.cc:
close() -> ha_close()
sql/sql_base.cc:
close() -> ha_close()
sql/sql_class.cc:
Added handling of rows_tmp_read
sql/sql_class.h:
Added new satistics variables.
rows_read++ -> update_rows_read() to be able to correctly count reads to internal temp tables.
Added handler::ha_update_tmp_row()
sql/sql_connect.cc:
Added comment
sql/sql_expression_cache.cc:
ha_write_row() -> ha_write_tmp_row()
sql/sql_select.cc:
close() -> ha_close()
ha_update_row() -> ha_update_tmp_row()
sql/sql_show.cc:
ha_write_row() -> ha_write_tmp_row()
sql/sql_table.cc:
Fixed bug where thd->open_options was set to wrong value when doing admin_recreate_table()
sql/sql_union.cc:
ha_write_row() -> ha_write_tmp_row()
sql/sql_update.cc:
ha_write_row() -> ha_write_tmp_row()
sql/table.cc:
close() -> ha_close()
storage/heap/ha_heap.cc:
Removed double counting of statistic variables.
close -> ha_close() to get tmp table statistics.
storage/maria/ha_maria.cc:
close -> ha_close() to get tmp table statistics.
The patch imposes unconditional materialization for derived tables
used in update and multi-update statements.
Fixed a bug with a wrong order of processing derived tables/views
at the prepare stage that caused a crash for the variant of the
query from test case for bug 52157.
Resolved all conflicts, bad merges and fixed a few minor bugs in the code.
Commented out the queries from multi_update, view, subselect_sj, func_str,
derived_view, view_grant that failed either with crashes in ps-protocol or
with wrong results.
The failures are clear indications of some bugs in the code and these bugs
are to be fixed.
mysql-test/r/union.result:
Added test for lp:732124
mysql-test/t/union.test:
Added test for lp:732124
sql/sp_rcontext.cc:
Updated function definition for ::send_data()
sql/sp_rcontext.h:
Updated function definition for ::send_data()
sql/sql_analyse.cc:
Test if send_data() returned an error
sql/sql_class.cc:
Updated function definition for ::send_data()
sql/sql_class.h:
Changed select_result::send_data(List<Item> &items) to return -1 in case of duplicate row that should not be counted as part of LIMIT
sql/sql_cursor.cc:
Check if send_data returned error
sql/sql_delete.cc:
Updated function definition for ::send_data()
sql/sql_insert.cc:
Updated function definition for ::send_data()
sql/sql_select.cc:
Don't count rows which send_data() tells you to ignore
sql/sql_union.cc:
Inform caller that the row should be ignored. This is the real bug fix for lp:732124
sql/sql_update.cc:
Updated function definition for ::send_data()
- Fixed problem with oqgraph and 'make dist'
Note that after this merge we have a problem show in join_outer where we examine too many rows in one specific case (related to BUG#57024).
This will be fixed when mwl#128 is merged into 5.3.
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.
This bug was introduced in this revision:
kostja@sun.com-20100727102553-b4n2ojcyfj79l2x7
("A pre-requisite patch for the fix for Bug#52044.")
It happens because close_thread_tables() is now called in
open_and_lock_tables upon failure. Hence, table is no longer
open when optimizer tries to do cleanup.
Fix: Make sure to do cleanup in st_select_lex_unit::prepare()
upon failure. This way, cleanup() is called before tables are
released.
mysql-test/r/subselect.result:
Added test case for Bug#57704.
mysql-test/t/subselect.test:
Added test case for Bug#57704.
sql/sql_union.cc:
st_select_lex_unit::prepare(): On failure, make sure cleanup()
is called.
This bug was introduced in this revision:
kostja@sun.com-20100727102553-b4n2ojcyfj79l2x7
("A pre-requisite patch for the fix for Bug#52044.")
It happens because close_thread_tables() is now called in
open_and_lock_tables upon failure. Hence, table is no longer
open when optimizer tries to do cleanup.
Fix: Make sure to do cleanup in st_select_lex_unit::prepare()
upon failure. This way, cleanup() is called before tables are
released.
Merge 5.3-mwl89 into 5.3 main.
There is one remaining test failure in this merge:
innodb_mysql_lock2. All other tests have been checked to
deliver the same results/explains as 5.3-mwl89, including
the few remaining wrong results.
