Commit graph

78 commits

Author SHA1 Message Date
Monty
ecc7961140 MDEV-34571 Add page accessed and pages read from disk to table_stats
Trivial batch, using the handler statistics already collected for
the slow query log.

The reason for the changes in test cases was mainly to change to use
select TABLE_SCHEMA ... from information_schema.table_statistics instead
of 'show table_statistics' to avoid future changes to test results
if we add more columns to table_statistics.
2024-07-12 11:28:18 +03:00
Alexander Barkov
36eba98817 MDEV-19123 Change default charset from latin1 to utf8mb4
Changing the default server character set from latin1 to utf8mb4.
2024-07-11 10:21:07 +04:00
Monty
94033fcf83 MDEV-33151 Add more columns to TABLE_STATISTICS and USER STATS
Columns added to TABLE_STATISTICS
- ROWS_INSERTED, ROWS_DELETED, ROWS_UPDATED, KEY_READ_HITS and
  KEY_READ_MISSES.

Columns added to CLIENT_STATISTICS and USER_STATISTICS:
- KEY_READ_HITS and KEY_READ_MISSES.

User visible changes (except new columns):
- CLIENT_STATISTICS and USER_STATISTICS has columns KEY_READ_HITS and
  KEY_READ_MISSES added after column ROWS_UPDATED before SELECT_COMMANDS.

Other changes:
- Do not collect table statistics for system tables like index_stats
  table_stats, performance_schema, information_schema etc as the user
  has no control of these and the generate noice in the statistics.
- All row variables that are part of user_stats are moved to
  'struct rows_stats' to make it easy to clear all of them at once.
- ha_read_key_misses added to STATUS_VAR

Notes:
- userstat.result has a change of numbers of rows for handler_read_key.
  This is because use-stat-tables is now disabled for the test.
2024-05-27 12:39:04 +02:00
Monty
775cba4d0f MDEV-33145 Add FLUSH GLOBAL STATUS
- FLUSH GLOBAL STATUS now resets most global_status_vars.
  At this stage, this is mainly to be used for testing.
- FLUSH SESSION STATUS added as an alias for FLUSH STATUS.
- FLUSH STATUS does not require any privilege (before required RELOAD).
- FLUSH GLOBAL STATUS requires RELOAD privilege.
- All global status reset moved to FLUSH GLOBAL STATUS.
- Replication semisync status variables are now reset by
  FLUSH GLOBAL STATUS.
- In test cases, the only changes are:
  - Replace FLUSH STATUS with FLUSH GLOBAL STATUS
  - Replace FLUSH STATUS with FLUSH STATUS; FLUSH GLOBAL STATUS.
    This was only done in a few tests where the test was using SHOW STATUS
    for both local and global variables.
- Uptime_since_flush_status is now always provided, independent if
  ENABLED_PROFILING is enabled when compiling MariaDB.
- @@global.Uptime_since_flush_status is reset on FLUSH GLOBAL STATUS
  and @@session.Uptime_since_flush_status is reset on FLUSH SESSION STATUS.
- When connected, @@session.Uptime_since_flush_status is set to 0.
2024-05-27 12:39:03 +02:00
Monty
a00e99acca MDEV-33152 Add QUERIES to INDEX_STATISTICS
Other changes:
- Do not collect index statistics for system tables like index_stats
  table_stats, performance_schema, information_schema etc as the user
  has no control of these and the generate noise in the statistics.
2024-05-27 12:39:02 +02:00
Sergei Golubchik
7a5448f8da Merge branch '11.0' into 11.1 2023-12-19 20:11:54 +01:00
Sergei Golubchik
8c8bce05d2 Merge branch '10.11' into 11.0 2023-12-19 15:53:18 +01:00
Sergei Golubchik
fd0b47f9d6 Merge branch '10.6' into 10.11 2023-12-18 11:19:04 +01:00
Sergei Golubchik
e95bba9c58 Merge branch '10.5' into 10.6 2023-12-17 11:20:43 +01:00
Oleksandr Byelkin
af2e91d9f2 fix for the test (real fixes will be in 10.4) 2023-12-02 01:03:55 +01:00
Sergei Golubchik
98a39b0c91 Merge branch '10.4' into 10.5 2023-12-02 01:02:50 +01:00
Daniel Black
2fe3e033e6 main.subselect* often fails on CI with ER_SUBQUERY_NO_1_ROW
Using mysql.slow_log was a test table would generate more than
one row if there was more than one row in the table.

Replace this table with a empty table with PK.

Reviewer: Rex Johnston
2023-11-30 16:15:26 +11:00
Oleg Smirnov
69d294e755 MDEV-29070 SIGSEGV in my_decimal::operator= and Assertion `0' failed and in Item_type_holder::val_decimal on SELECT
The bug is fixed by the patch ported from MySQL. See the comprehensive
description below.

commit 455c4e8810c76430719b1a08a63ca0f69f44678a
Author: Guilhem Bichot <guilhem.bichot@oracle.com>
Date:   Fri Mar 13 17:51:27 2015 +0100

    Bug#17668844: CRASH/ASSERT AT ITEM_TYPE_HOLDER::VAL_STR IN ITEM.C

    We have a predicate of the form:
    literal_row <=> (a UNION)

    The subquery is constant, so Item_cache objects are used for its
    SELECT list.
    In order, this happens:
    - Item_subselect::fix_fields() calls select_lex_unit::prepare,
    where we create Item_type_holder's
    (appended to unit->types list), create the tmp table (using type info
    found in unit->types), and call fill_item_list() to put the
    Item_field's of this table into unit->item_list.
    - Item_subselect::fix_length_and_dec() calls set_row() which
    makes Item_cache's of the subquery wrap the Item_type_holder's
    - When/if a first result row is found for the subquery,
    Item_cache's are re-pointed to unit->item_list
    (i.e. Item_field objects which reference the UNION's tmp table
    columns) (see call to Item_singlerow_subselect::store()).
    - In our subquery, no result row is found, so the Item_cache's
    still wrap Item_type_holder's; evaluating '<=>' reads the
    value of those, but Item_type_holder objects are not expected to be
    evaluated.

    Fix: instead of putting unit->types into Item_cache, and later
    replacing with unit->item_list, put unit->item_list in Item_cache from
    the start.

Approved by Oleksandr Byelkin <sanja@mariadb.com>
2023-11-24 18:30:14 +07:00
Oleksandr Byelkin
0f5613a25f Merge branch '11.0' into 11.1 2023-11-08 18:03:08 +01:00
Oleksandr Byelkin
48af85db21 Merge branch '10.11' into 11.0 2023-11-08 17:09:44 +01:00
Oleksandr Byelkin
04d9a46c41 Merge branch '10.6' into 10.10 2023-11-08 16:23:30 +01:00
Oleksandr Byelkin
fefd6d5559 MDEV-32656: ASAN errors in base_list_iterator::next / setup_table_map upon 2nd execution of PS
Correctly supress error issuing when saving value in field for comporison
2023-11-08 12:08:23 +01:00
Monty
7533062f17 MDEV-32518 Test failure: ./mtr --no-reorder main.log_slow_debug main.subselect
There where two errors left from the previous fix.

- subselect.test assumes that mysql.slow_log is empty. This was not
  enforced.
- subselect.test dropped a file that does not exists (for safety).
  This was fixed by ensuring we don't get a warning if the file does
  not exist.
2023-11-03 11:42:52 +02:00
Sergei Golubchik
cbabb95915 Merge branch '11.0' into 11.1 2023-06-05 20:15:15 +02:00
Sergei Petrunia
c7fe8e51de Merge 10.11 into 11.0 2023-04-17 16:50:01 +03:00
Marko Mäkelä
1d1e0ab2cc Merge 10.6 into 10.8 2023-04-12 15:50:08 +03:00
Oleksandr Byelkin
ac5a534a4c Merge remote-tracking branch '10.4' into 10.5 2023-03-31 21:32:41 +02:00
Igor Babaev
9a3fd1df01 Adjusted test results after rebase against 11.0.1 2023-03-15 17:35:22 -07:00
Igor Babaev
88ca62dc68 MDEV-28965 Assertion failure when preparing UPDATE with derived table in WHERE
This patch fixes not only the assertion failure in the function
Field_iterator_table_ref::set_field_iterator() but also:
 - fixes the problem of forced materialization of derived tables used
   in subqueries contained in WHERE clauses of single-table and multi-table
   UPDATE and DELETE statements
 - fixes the problem of MDEV-17954 that prevented execution of multi-table
   DELETE statements if they use in their WHERE clauses references to
   the tables that are updated.

The patch must be considered a complement to the patch for MDEV-28883.

Approved by Oleksandr Byelkin <sanja@mariadb.com>
2023-03-15 17:35:22 -07:00
Igor Babaev
ccec9b1de9 MDEV-30706 Different results of selects from view and CTE with same definition
MDEV-30668 Set function aggregated in outer select used in view definition

This patch fixes two bugs concerning views whose specifications contain
subqueries with set functions aggregated in outer selects.
Due to the first bug those such views that have implicit grouping were
considered as mergeable. This led to wrong result sets for selects from
these views.
Due to the second bug the aggregation select was determined incorrectly and
this led to bogus error messages.
The patch added several test cases for these two bugs and for four other
duplicate bugs.
The patch also enables view-protocol for many other test cases.

Approved by Oleksandr Byelkin <sanja@mariadb.com>
2023-03-02 07:51:33 -08:00
Monty
3fa99f0c0e Change cost for REF to take into account cost for 1 extra key read_next
The main difference in code path between EQ_REF and REF is that for
REF we have to do an extra read_next on the index to check that there
is no more matching rows.

Before this patch we added a preference of EQ_REF by ensuring that REF
would always estimate to find at least 2 rows.

This patch adds the cost of the extra key read_next to REF access and
removes the code that limited REF to at least 2 rows. For some queries
this can have a big effect as the total estimated rows will be halved
for each REF table with 1 rows.

multi_range cost calculations are also changed to take into account
the difference between EQ_REF and REF.

The effect of the patch to the test suite:
- About 80 test case changed
- Almost all changes where for EXPLAIN where estimated rows for REF
  where changed from 2 to 1.
- A few test cases using explain extended had a change of 'filtered'.
  This is because of the estimated rows are now closer to the
  calculated selectivity.
- A very few test had a change of table order.
  This is because the change of estimated rows from 2 to 1 or the small
  cost change for REF
  (main.subselect_sj_jcl6, main.group_by, main.dervied_cond_pushdown,
  main.distinct, main.join_nested, main.order_by, main.join_cache)
- No key statistics and the estimated rows are now smaller which cased
  estimated filtering to be lower.
  (main.subselect_sj_mat)
- The number of total rows are halved.
  (main.derived_cond_pushdown)
- Plans with 1 row changed to use RANGE instead of REF.
  (main.group_min_max)
- ALL changed to REF
  (main.key_diff)
- Key changed from ref + index_only to PRIMARY key for InnoDB, as
  OPTIMIZER_ROW_LOOKUP_COST + OPTIMIZER_ROW_NEXT_FIND_COST is smaller than
  OPTIMIZER_KEY_LOOKUP_COST + OPTIMIZER_KEY_NEXT_FIND_COST.
  (main.join_outer_innodb)
- Cost changes printouts
  (main.opt_trace*)
- Result order change
  (innodb_gis.rtree)
2023-02-10 12:58:50 +02:00
Sergei Petrunia
6c4076fac4 MDEV-30032: EXPLAIN FORMAT=JSON output: part #2: print 'loops'. 2023-02-03 11:22:17 +03:00
Sergei Petrunia
ffe0beca25 MDEV-30032: EXPLAIN FORMAT=JSON output: print costs
Basic printout for join and table execution costs.
2023-02-03 11:01:24 +03:00
Monty
727491b72a Added test cases for preceding test
This includes all test changes from
"Changing all cost calculation to be given in milliseconds"
and forwards.

Some of the things that caused changes in the result files:

- As part of fixing tests, I added 'echo' to some comments to be able to
  easier find out where things where wrong.
- MATERIALIZED has now a higher cost compared to X than before. Because
  of this some MATERIALIZED types have changed to DEPENDEND SUBQUERY.
  - Some test cases that required MATERIALIZED to repeat a bug was
    changed by adding more rows to force MATERIALIZED to happen.
- 'Filtered' in SHOW EXPLAIN has in many case changed from 100.00 to
  something smaller. This is because now filtered also takes into
  account the smallest possible ref access and filters, even if they
  where not used. Another reason for 'Filtered' being smaller is that
  we now also take into account implicit filtering done for subqueries
  using FIRSTMATCH.
  (main.subselect_no_exists_to_in)
  This is caluculated in best_access_path() and stored in records_out.
- Table orders has changed because more accurate costs.
- 'index' and 'ALL' for small tables has changed to use 'range' or
   'ref' because of optimizer_scan_setup_cost.
- index can be changed to 'range' as 'range' optimizer assumes we don't
  have to read the blocks from disk that range optimizer has already read.
  This can be confusing in the case where there is no obvious where clause
  but instead there is a hidden 'key_column > NULL' added by the optimizer.
  (main.subselect_no_exists_to_in)
- Scan on primary clustered key does not report 'Using Index' anymore
  (It's a table scan, not an index scan).
- For derived tables, the number of rows is now 100 instead of 2,
  which can be seen in EXPLAIN.
- More tests have "Using index for group by" as the cost of this
  optimization is now more correct (lower).
- A primary key could be preferred for a normal key, even if it would
  access more rows, as it's faster to do 1 lokoup and 3 'index_next' on a
  clustered primary key than one lookup trough a secondary.
  (main.stat_tables_innodb)

Notes:

- There was a 4.7% more calls to best_extension_by_limited_search() in
  the main.greedy_optimizer test.  However examining the test results
  it looked that the plans where slightly better (eq_ref where more
  chained together) so I assume this is ok.
- I have verified a few test cases where there was notable/unexpected
  changes in the plan and in all cases the new optimizer plans where
  faster.  (main.greedy_optimizer and some others)
2023-02-03 00:00:35 +03:00
Monty
07df2029a3 Adjust cost for re-creating a row from the JOIN CACHE
Creating a record from the join cache is faster than getting a row from
the engine (less and simpler code to execute).

Added JOIN_CACHE_ROW_COPY_COST_FACTOR (0.5 for now) as the factor to
take this into account. This is multiplied with ROW_COPY_COST.

Other things:
- Added cost of copying rows to hash join, similar to join_cache joins.
2023-02-02 22:58:52 +03:00
Monty
4515a89814 Fixed cost calculations for materialized tables
One effect of this change in the test suite is that tests with very few
rows changed to use sub queries instead of materialization. This is
correct and expected as for these the materialization overhead is too high.

A lot of tests where fixed to still use materialization by adding a
few rows to the tables (most tests has only 2-3 rows and are thus easily
affected when cost computations are changed).

Other things:
- Added more variables to TMPTABLE_COSTS for better cost calculation
- Added cost of copying rows to TMPTABLE_COSTS lookup and write
- Added THD::optimizer_cache_hit_ratio for easier cost calculations
- Added DISK_FAST_READ_SIZE to be used when calculating costs when
  reading big blocks from a disk
2023-02-02 22:58:38 +03:00
Monty
b6215b9b20 Update row and key fetch cost models to take into account data copy costs
Before this patch, when calculating the cost of fetching and using a
row/key from the engine, we took into account the cost of finding a
row or key from the engine, but did not consistently take into account
index only accessed, clustered key or covered keys for all access
paths.

The cost of the WHERE clause (TIME_FOR_COMPARE) was not consistently
considered in best_access_path().  TIME_FOR_COMPARE was used in
calculation in other places, like greedy_search(), but was in some
cases (like scans) done an a different number of rows than was
accessed.

The cost calculation of row and index scans didn't take into account
the number of rows that where accessed, only the number of accepted
rows.

When using a filter, the cost of index_only_reads and cost of
accessing and disregarding 'filtered rows' where not taken into
account, which made filters cost less than there actually where.

To remedy the above, the following key & row fetch related costs
has been added:

- The cost of fetching and using a row is now split into different costs:
  - key + Row fetch cost (as before) but multiplied with the variable
  'optimizer_cache_cost' (default to 0.5). This allows the user to
  tell the optimizer the likehood of finding the key and row in the
  engine cache.
- ROW_COPY_COST, The cost copying a row from the engine to the
  sql layer or creating a row from the join_cache to the record
  buffer. Mostly affects table scan costs.
- ROW_LOOKUP_COST, the cost of fetching a row by rowid.
- KEY_COPY_COST the cost of finding the next key and copying it from
  the engine to the SQL layer. This is used when we calculate the cost
  index only reads. It makes index scans more expensive than before if
  they cover a lot of rows. (main.index_merge_myisam)
- KEY_LOOKUP_COST, the cost of finding the first key in a range.
  This replaces the old define IDX_LOOKUP_COST, but with a higher cost.
- KEY_NEXT_FIND_COST, the cost of finding the next key (and rowid).
  when doing a index scan and comparing the rowid to the filter.
  Before this cost was assumed to be 0.

All of the above constants/variables are now tuned to be somewhat in
proportion of executing complexity to each other.  There is tuning
need for these in the future, but that can wait until the above are
made user variables as that will make tuning much easier.

To make the usage of the above easy, there are new (not virtual)
cost calclation functions in handler:
- ha_read_time(), like read_time(), but take optimizer_cache_cost into
  account.
- ha_read_and_copy_time(), like ha_read_time() but take into account
  ROW_COPY_TIME
- ha_read_and_compare_time(), like ha_read_and_copy_time() but take
  TIME_FOR_COMPARE into account.
- ha_rnd_pos_time(). Read row with row id, taking ROW_COPY_COST
  into account.  This is used with filesort where we don't need
  to execute the WHERE clause again.
- ha_keyread_time(), like keyread_time() but take
  optimizer_cache_cost into account.
- ha_keyread_and_copy_time(), like ha_keyread_time(), but add
  KEY_COPY_COST.
- ha_key_scan_time(), like key_scan_time() but take
  optimizer_cache_cost nto account.
- ha_key_scan_and_compare_time(), like ha_key_scan_time(), but add
  KEY_COPY_COST & TIME_FOR_COMPARE.

I also added some setup costs for doing different types of scans and
creating temporary tables (on disk and in memory). This encourages
the optimizer to not use these for simple 'a few row' lookups if
there are adequate key lookup strategies.
- TABLE_SCAN_SETUP_COST, cost of starting a table scan.
- INDEX_SCAN_SETUP_COST, cost of starting an index scan.
- HEAP_TEMPTABLE_CREATE_COST, cost of creating in memory
  temporary table.
- DISK_TEMPTABLE_CREATE_COST, cost of creating an on disk temporary
  table.

When calculating cost of fetching ranges, we had a cost of
IDX_LOOKUP_COST (0.125) for doing a key div for a new range. This is
now replaced with 'io_cost * KEY_LOOKUP_COST (1.0) *
optimizer_cache_cost', which matches the cost we use for 'ref' and
other key lookups. The effect is that the cost is now a bit higher
when we have many ranges for a key.

Allmost all calculation with TIME_FOR_COMPARE is now done in
best_access_path(). 'JOIN::read_time' now includes the full
cost for finding the rows in the table.

In the result files, many of the changes are now again close to what
they where before the "Update cost for hash and cached joins" commit,
as that commit didn't fix the filter cost (too complex to do
everything in one commit).

The above changes showed a lot of a lot of inconsistencies in
optimizer cost calculation. The main objective with the other changes
was to do calculation as similar (and accurate) as possible and to make
different plans more comparable.

Detailed list of changes:

- Calculate index_only_cost consistently and correctly for all scan
  and ref accesses. The row fetch_cost and index_only_cost now
  takes into account clustered keys, covered keys and index
  only accesses.
- cost_for_index_read now returns both full cost and index_only_cost
- Fixed cost calculation of get_sweep_read_cost() to match other
  similar costs. This is bases on the assumption that data is more
  often stored on SSD than a hard disk.
- Replaced constant 2.0 with new define TABLE_SCAN_SETUP_COST.
- Some scan cost estimates did not take into account
  TIME_FOR_COMPARE. Now all scan costs takes this into
  account. (main.show_explain)
- Added session variable optimizer_cache_hit_ratio (default 50%). By
  adjusting this on can reduce or increase the cost of index or direct
  record lookups. The effect of the default is that key lookups is now
  a bit cheaper than before. See usage of 'optimizer_cache_cost' in
  handler.h.
- JOIN_TAB::scan_time() did not take into account index only scans,
  which produced a wrong cost when index scan was used. Changed
  JOIN_TAB:::scan_time() to take into consideration clustered and
  covered keys. The values are now cached and we only have to call
  this function once. Other calls are changed to use the cached
  values.  Function renamed to JOIN_TAB::estimate_scan_time().
- Fixed that most index cost calculations are done the same way and
  more close to 'range' calculations. The cost is now lower than
  before for small data sets and higher for large data sets as we take
  into account how many keys are read (main.opt_trace_selectivity,
  main.limit_rows_examined).
- Ensured that index_scan_cost() ==
  range(scan_of_all_rows_in_table_using_one_range) +
  MULTI_RANGE_READ_INFO_CONST. One effect of this is that if there
  is choice of doing a full index scan and a range-index scan over
  almost the whole table then index scan will be preferred (no
  range-read setup cost).  (innodb.innodb, main.show_explain,
  main.range)
  - Fixed the EQ_REF and REF takes into account clustered and covered
    keys.  This changes some plans to use covered or clustered indexes
    as these are much cheaper.  (main.subselect_mat_cost,
    main.state_tables_innodb, main.limit_rows_examined)
  - Rowid filter setup cost and filter compare cost now takes into
    account fetching and checking the rowid (KEY_NEXT_FIND_COST).
    (main.partition_pruning heap.heap_btree main.log_state)
  - Added KEY_NEXT_FIND_COST to
    Range_rowid_filter_cost_info::lookup_cost to account of the time
    to find and check the next key value against the container
  - Introduced ha_keyread_time(rows) that takes into account finding
    the next row and copying the key value to 'record'
    (KEY_COPY_COST).
  - Introduced ha_key_scan_time() for calculating an index scan over
    all rows.
  - Added IDX_LOOKUP_COST to keyread_time() as a startup cost.
  - Added index_only_fetch_cost() as a convenience function to
    OPT_RANGE.
  - keyread_time() cost is slightly reduced to prefer shorter keys.
    (main.index_merge_myisam)
  - All of the above caused some index_merge combinations to be
    rejected because of cost (main.index_intersect). In some cases
    'ref' where replaced with index_merge because of the low
    cost calculation of get_sweep_read_cost().
  - Some index usage moved from PRIMARY to a covering index.
    (main.subselect_innodb)
- Changed cost calculation of filter to take KEY_LOOKUP_COST and
  TIME_FOR_COMPARE into account.  See sql_select.cc::apply_filter().
  filter parameters and costs are now written to optimizer_trace.
- Don't use matchings_records_in_range() to try to estimate the number
  of filtered rows for ranges. The reason is that we want to ensure
  that 'range' is calculated similar to 'ref'. There is also more work
  needed to calculate the selectivity when using ranges and ranges and
  filtering.  This causes filtering column in EXPLAIN EXTENDED to be
  100.00 for some cases where range cannot use filtering.
  (main.rowid_filter)
- Introduced ha_scan_time() that takes into account the CPU cost of
  finding the next row and copying the row from the engine to
  'record'. This causes costs of table scan to slightly increase and
  some test to changed their plan from ALL to RANGE or ALL to ref.
  (innodb.innodb_mysql, main.select_pkeycache)
  In a few cases where scan time of very small tables have lower cost
  than a ref or range, things changed from ref/range to ALL.
  (main.myisam, main.func_group, main.limit_rows_examined,
  main.subselect2)
- Introduced ha_scan_and_compare_time() which is like ha_scan_time()
  but also adds the cost of the where clause (TIME_FOR_COMPARE).
- Added small cost for creating temporary table for
  materialization. This causes some very small tables to use scan
  instead of materialization.
- Added checking of the WHERE clause (TIME_FOR_COMPARE) of the
  accepted rows to ROR costs in get_best_ror_intersect()
- Removed '- 0.001' from 'join->best_read' and optimize_straight_join()
  to ensure that the 'Last_query_cost' status variable contains the
  same value as the one that was calculated by the optimizer.
- Take avg_io_cost() into account in handler::keyread_time() and
  handler::read_time(). This should have no effect as it's 1.0 by
  default, except for heap that overrides these functions.
- Some 'ref_or_null' accesses changed to 'range' because of cost
  adjustments (main.order_by)
- Added scan type "scan_with_join_cache" for optimizer_trace. This is
  just to show in the trace what kind of scan was used.
- When using 'scan_with_join_cache' take into account number of
  preceding tables (as have to restore all fields for all previous
  table combination when checking the where clause)
  The new cost added is:
  (row_combinations * ROW_COPY_COST * number_of_cached_tables).
  This increases the cost of join buffering in proportion of the
  number of tables in the join buffer. One effect is that full scans
  are now done earlier as the cost is then smaller.
  (main.join_outer_innodb, main.greedy_optimizer)
- Removed the usage of 'worst_seeks' in cost_for_index_read as it
  caused wrong plans to be created; It prefered JT_EQ_REF even if it
  would be much more expensive than a full table scan. A related
  issue was that worst_seeks only applied to full lookup, not to
  clustered or index only lookups, which is not consistent. This
  caused some plans to use index scan instead of eq_ref (main.union)
- Changed federated block size from 4096 to 1500, which is the
  typical size of an IO packet.
- Added costs for reading rows to Federated. Needed as there is no
  caching of rows in the federated engine.
- Added ha_innobase::rnd_pos_time() cost function.
- A lot of extra things added to optimizer trace
  - More costs, especially for materialization and index_merge.
  - Make lables more uniform
  - Fixed a lot of minor bugs
  - Added 'trace_started()' around a lot of trace blocks.
- When calculating ORDER BY with LIMIT cost for using an index
  the cost did not take into account the number of row retrivals
  that has to be done or the cost of comparing the rows with the
  WHERE clause. The cost calculated would be just a fraction of
  the real cost. Now we calculate the cost as we do for ranges
  and 'ref'.
- 'Using index for group-by' is used a bit more than before as
  now take into account the WHERE clause cost when comparing
  with 'ref' and prefer the method with fewer row combinations.
  (main.group_min_max).

Bugs fixed:
- Fixed that we don't calculate TIME_FOR_COMPARE twice for some plans,
  like in optimize_straight_join() and greedy_search()
- Fixed bug in save_explain_data where we could test for the wrong
  index when displaying 'Using index'. This caused some old plans to
  show 'Using index'.  (main.subselect_innodb, main.subselect2)
- Fixed bug in get_best_ror_intersect() where 'min_cost' was not
  updated, and the cost we compared with was not the one that was
  used.
- Fixed very wrong cost calculation for priority queues in
  check_if_pq_applicable(). (main.order_by now correctly uses priority
  queue)
- When calculating cost of EQ_REF or REF, we added the cost of
  comparing the WHERE clause with the found rows, not all row
  combinations. This made ref and eq_ref to be regarded way to cheap
  compared to other access methods.
- FORCE INDEX cost calculation didn't take into account clustered or
  covered indexes.
- JT_EQ_REF cost was estimated as avg_io_cost(), which is half the
  cost of a JT_REF key. This may be true for InnoDB primary key, but
  not for other unique keys or other engines. Now we use handler
  function to calculate the cost, which allows us to handle
  consistently clustered, covered keys and not covered keys.
- ha_start_keyread() didn't call extra_opt() if keyread was already
  enabled but still changed the 'keyread' variable (which is wrong).
  Fixed by not doing anything if keyread is already enabled.
- multi_range_read_info_cost() didn't take into account io_cost when
  calculating the cost of ranges.
- fix_semijoin_strategies_for_picked_join_order() used the wrong
  record_count when calling best_access_path() for SJ_OPT_FIRST_MATCH
  and SJ_OPT_LOOSE_SCAN.
- Hash joins didn't provide correct best_cost to the upper level, which
  means that the cost for hash_joins more expensive than calculated
  in best_access_path (a difference of 10x * TIME_OF_COMPARE).
  This is fixed in the new code thanks to that we now include
  TIME_OF_COMPARE cost in 'read_time'.

Other things:
- Added some 'if (thd->trace_started())' to speed up code
- Removed not used function Cost_estimate::is_zero()
- Simplified testing of HA_POS_ERROR in get_best_ror_intersect().
  (No cost changes)
- Moved ha_start_keyread() from join_read_const_table() to join_read_const()
  to enable keyread for all types of JT_CONST tables.
- Made a few very short functions inline in handler.h

Notes:
- In main.rowid_filter the join order of order and lineitem is swapped.
  This is because the cost of doing a range fetch of lineitem(98 rows) is
  almost as big as the whole join of order,lineitem. The filtering will
  also ensure that we only have to do very small key fetches of the rows
  in lineitem.
- main.index_merge_myisam had a few changes where we are now using
  less keys for index_merge. This is because index scans are now more
  expensive than before.
- handler->optimizer_cache_cost is updated in ha_external_lock().
  This ensures that it is up to date per statements.
  Not an optimal solution (for locked tables), but should be ok for now.
- 'DELETE FROM t1 WHERE t1.a > 0 ORDER BY t1.a' does not take cost of
  filesort into consideration when table scan is chosen.
  (main.myisam_explain_non_select_all)
- perfschema.table_aggregate_global_* has changed because an update
  on a table with 1 row will now use table scan instead of key lookup.

TODO in upcomming commits:
- Fix selectivity calculation for ranges with and without filtering and
  when there is a ref access but scan is chosen.
  For this we have to store the lowest known value for
  'accepted_records' in the OPT_RANGE structure.
- Change that records_read does not include filtered rows.
- test_if_cheaper_ordering() needs to be updated to properly calculate
  costs. This will fix tests like main.order_by_innodb,
  main.single_delete_update
- Extend get_range_limit_read_cost() to take into considering
  cost_for_index_read() if there where no quick keys. This will reduce
  the computed cost for ORDER BY with LIMIT in some cases.
  (main.innodb_ext_key)
- Fix that we take into account selectivity when counting the number
  of rows we have to read when considering using a index table scan to
  resolve ORDER BY.
- Add new calculation for rnd_pos_time() where we take into account the
  benefit of reading multiple rows from the same page.
2023-02-02 21:43:30 +03:00
Monty
956980971f Update cost for hash and cached joins
The old code did not't correctly add TIME_FOR_COMPARE to rows that are
part of the scan that will be compared with the attached where clause.

Now the cost calculation for hash join and full join cache join are
identical except for HASH_FANOUT (10%)

The cost for a join with keys is now also uniform.
The total cost for a using a key for lookup is calculated in one place as:

(cost_of_finding_rows_through_key(records) + records/TIME_FOR_COMPARE)*
record_count_of_previous_row_combinations + startup_cost

startup_cost is the cost of a creating a temporary table (if needed)

Best_cost now includes the cost of comparing all WHERE clauses and also
cost of joining with previous row combinations.

Other things:
- Optimizer trace is now printing the total costs, including testing the
  WHERE clause (TIME_FOR_COMPARE) and comparing with all previous rows.
- In optimizer trace, include also total cost of query together with the
  final join order. This makes it easier to find out where the cost was
  calculated.
- Old code used filter even if the cost for it was higher than not using a
  filter. This is not corrected.
- When rebasing on 10.11, I noticed some changes to access_cost_factor
  calculation. These changes was not picked as the coming changes
  to filtering will make that code obsolete.
2023-02-02 20:49:35 +03:00
Monty
b67144893a Update matching_candidates_in_table() to treat all conditions similar
Fixed also that the 'with_found_constraint parameter' to
matching_candidates_in_table() is as documented: It is now true only
if there is a reference to a previous table in the WHERE condition for
the current examined table (as it was originally documented)

Changes in test results:
- Filtered was 25% smaller for some queries (expected).
- Some join order changed (probably because the tables had very few rows).
- Some more table scans, probably because there would be fewer returned
  rows.
- Some tests exposes a bug that if there is more filtered rows, then the
  cost for table scan will be higher. This will be fixed in a later commit.
2023-02-02 20:19:32 +03:00
Oleksandr Byelkin
33825755c7 Merge branch '10.7' into 10.8 2022-11-02 16:07:38 +01:00
Oleksandr Byelkin
177d858e38 Merge branch '10.4' into 10.5 2022-11-02 13:14:54 +01:00
Oleksandr Byelkin
0946c99e7d Merge branch '10.3' into 10.4 2022-11-02 13:13:45 +01:00
Oleksandr Byelkin
3303748fd1 MDEV-29926: ASAN heap-use-after-free in Explain_query::~Explain_query
Make sure that EXPLAIN object allocated on runtime arena.
2022-11-02 12:49:24 +01:00
Marko Mäkelä
4345d93100 Merge 10.7 into 10.8 2022-09-21 09:52:09 +03:00
Alexander Barkov
fe844c16b6 Merge remote-tracking branch 'origin/10.4' into 10.5 2022-09-14 16:24:51 +04:00
Marko Mäkelä
18795f5512 Merge 10.3 into 10.4 2022-09-13 16:36:38 +03:00
Alexander Barkov
f1544424de MDEV-29446 Change SHOW CREATE TABLE to display default collation 2022-09-12 22:10:39 +04:00
Marko Mäkelä
f79cebb4d0 Merge 10.7 into 10.8 2022-07-28 10:33:26 +03:00
Marko Mäkelä
098c0f2634 Merge 10.4 into 10.5 2022-07-27 17:17:24 +03:00
Oleksandr Byelkin
3bb36e9495 Merge branch '10.3' into 10.4 2022-07-27 11:02:57 +02:00
Alexander Barkov
57f5c319af MDEV-21445 Strange/inconsistent behavior of IN condition when mixing numbers and strings 2022-07-06 15:42:21 +04:00
Sergei Golubchik
443c2a715d Merge branch '10.7' into 10.8 2022-05-11 12:21:36 +02:00
Sergei Golubchik
ef781162ff Merge branch '10.4' into 10.5 2022-05-09 22:04:06 +02:00
Sergei Golubchik
a70a1cf3f4 Merge branch '10.3' into 10.4 2022-05-08 23:03:08 +02:00
Oleksandr Byelkin
9614fde1aa Merge branch '10.2' into 10.3 2022-05-03 10:59:54 +02:00