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MDEV-30699: Updated prev_record_reads() to be more exact

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The old code in prev_record_reads() did give wrong estimates when a
join_buffer was used or if the table was depending on more than one
other tables. When join_cache is used, it will cause a re-order of row
combinations, which causes more calls to the engine for tables that
are depending on tables before the join_cached one.

The new prev_records_read() code provides more exact estimates and
should never give a 'too low estimate', assuming that the data to the
function is correct

The definition of prev_record_read() is also updated.
The new definition is:
  "Estimate the number of engine ha_index_read_calls for EQ_REF tables
  when taking into account the one-row-cache in join_read_always_key()"

The cost of using prev_record_reads() value is changed. The value is
now used similar as before to calculate the cost of the storage engine
calls. However the cost of the WHERE cost is changed to take into
account the total number of row combinations as the WHERE has to be
checked even if the one-row-cache is used. This makes the cost
slightly higher than before (for the same prev_record_reads() value).

Other things:
- Cached return value of prev_record_read() in best_access_path() to
  avoid some function calls.
- Fixed bug where position[].use_join_buffer was set in
  best_acess_path() when join buffer was not used. This confused the
  semi join optimizer to try to reoptimize plans that did not need to be
  reoptimized.
  The effect of the bug fix is that we avoid doing some re-optimziations
  with semi-joins when join_buffer is not used. In these cases the value
  shown for the 'Filtering' column in EXPLAIN EXTENDED may change.
- Added 'prev_record.cc' that was used to verify the logic in
  prev_record_reads().

Changes in test suite:
- EQ_REF tables are moved up to be earlier. This is because either the
  higher WHERE cost when EQ_REF is used with more row combination or
  change of cost when using join_cache.
- Filtered has changed (to the better) for some cases using semi-joins
  subselect_sj.test subselect_sj_jcl6.test
This commit is contained in:
Monty
2023-02-14 15:20:14 +02:00
committed by Sergei Petrunia
parent 793caf3a27
commit 15e889c300
15 changed files with 893 additions and 234 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
mysql-test/main/stat_tables.result
View File

@ -251,11 +251,11 @@ and p_name like '%green%') as profit
group by nation, o_year
order by nation, o_year desc;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE part ALL PRIMARY NULL NULL NULL 200 Using where; Using temporary; Using filesort
1 SIMPLE partsupp ref PRIMARY,i_ps_partkey,i_ps_suppkey i_ps_partkey 4 dbt3_s001.part.p_partkey 3
1 SIMPLE supplier ALL PRIMARY,i_s_nationkey NULL NULL NULL 10 Using where; Using join buffer (flat, BNL join)
1 SIMPLE supplier ALL PRIMARY,i_s_nationkey NULL NULL NULL 10 Using where; Using temporary; Using filesort
1 SIMPLE nation eq_ref PRIMARY PRIMARY 4 dbt3_s001.supplier.s_nationkey 1
1 SIMPLE lineitem ref PRIMARY,i_l_suppkey_partkey,i_l_partkey,i_l_suppkey,i_l_orderkey,i_l_orderkey_quantity i_l_suppkey_partkey 10 dbt3_s001.part.p_partkey,dbt3_s001.partsupp.ps_suppkey 8
1 SIMPLE partsupp ref PRIMARY,i_ps_partkey,i_ps_suppkey i_ps_suppkey 4 dbt3_s001.supplier.s_suppkey 70
1 SIMPLE part eq_ref PRIMARY PRIMARY 4 dbt3_s001.partsupp.ps_partkey 1 Using where
1 SIMPLE lineitem ref PRIMARY,i_l_suppkey_partkey,i_l_partkey,i_l_suppkey,i_l_orderkey,i_l_orderkey_quantity i_l_suppkey_partkey 10 dbt3_s001.partsupp.ps_partkey,dbt3_s001.supplier.s_suppkey 8
1 SIMPLE orders eq_ref PRIMARY PRIMARY 4 dbt3_s001.lineitem.l_orderkey 1
EXPLAIN EXTENDED select nation, o_year, sum(amount) as sum_profit
from (select n_name as nation,
@ -269,14 +269,14 @@ and p_name like '%green%') as profit
group by nation, o_year
order by nation, o_year desc;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE part ALL PRIMARY NULL NULL NULL 200 100.00 Using where; Using temporary; Using filesort
1 SIMPLE partsupp ref PRIMARY,i_ps_partkey,i_ps_suppkey i_ps_partkey 4 dbt3_s001.part.p_partkey 3 100.00
1 SIMPLE supplier ALL PRIMARY,i_s_nationkey NULL NULL NULL 10 10.00 Using where; Using join buffer (flat, BNL join)
1 SIMPLE supplier ALL PRIMARY,i_s_nationkey NULL NULL NULL 10 100.00 Using where; Using temporary; Using filesort
1 SIMPLE nation eq_ref PRIMARY PRIMARY 4 dbt3_s001.supplier.s_nationkey 1 100.00
1 SIMPLE lineitem ref PRIMARY,i_l_suppkey_partkey,i_l_partkey,i_l_suppkey,i_l_orderkey,i_l_orderkey_quantity i_l_suppkey_partkey 10 dbt3_s001.part.p_partkey,dbt3_s001.partsupp.ps_suppkey 8 100.00
1 SIMPLE partsupp ref PRIMARY,i_ps_partkey,i_ps_suppkey i_ps_suppkey 4 dbt3_s001.supplier.s_suppkey 70 100.00
1 SIMPLE part eq_ref PRIMARY PRIMARY 4 dbt3_s001.partsupp.ps_partkey 1 100.00 Using where
1 SIMPLE lineitem ref PRIMARY,i_l_suppkey_partkey,i_l_partkey,i_l_suppkey,i_l_orderkey,i_l_orderkey_quantity i_l_suppkey_partkey 10 dbt3_s001.partsupp.ps_partkey,dbt3_s001.supplier.s_suppkey 8 100.00
1 SIMPLE orders eq_ref PRIMARY PRIMARY 4 dbt3_s001.lineitem.l_orderkey 1 100.00
Warnings:
Note 1003 select `dbt3_s001`.`nation`.`n_name` AS `nation`,extract(year from `dbt3_s001`.`orders`.`o_orderDATE`) AS `o_year`,sum(`dbt3_s001`.`lineitem`.`l_extendedprice` * (1 - `dbt3_s001`.`lineitem`.`l_discount`) - `dbt3_s001`.`partsupp`.`ps_supplycost` * `dbt3_s001`.`lineitem`.`l_quantity`) AS `sum_profit` from `dbt3_s001`.`part` join `dbt3_s001`.`supplier` join `dbt3_s001`.`lineitem` join `dbt3_s001`.`partsupp` join `dbt3_s001`.`orders` join `dbt3_s001`.`nation` where `dbt3_s001`.`supplier`.`s_suppkey` = `dbt3_s001`.`partsupp`.`ps_suppkey` and `dbt3_s001`.`lineitem`.`l_suppkey` = `dbt3_s001`.`partsupp`.`ps_suppkey` and `dbt3_s001`.`partsupp`.`ps_partkey` = `dbt3_s001`.`part`.`p_partkey` and `dbt3_s001`.`lineitem`.`l_partkey` = `dbt3_s001`.`part`.`p_partkey` and `dbt3_s001`.`orders`.`o_orderkey` = `dbt3_s001`.`lineitem`.`l_orderkey` and `dbt3_s001`.`nation`.`n_nationkey` = `dbt3_s001`.`supplier`.`s_nationkey` and `dbt3_s001`.`part`.`p_name` like '%green%' group by `dbt3_s001`.`nation`.`n_name`,extract(year from `dbt3_s001`.`orders`.`o_orderDATE`) desc order by `dbt3_s001`.`nation`.`n_name`,extract(year from `dbt3_s001`.`orders`.`o_orderDATE`) desc
Note 1003 select `dbt3_s001`.`nation`.`n_name` AS `nation`,extract(year from `dbt3_s001`.`orders`.`o_orderDATE`) AS `o_year`,sum(`dbt3_s001`.`lineitem`.`l_extendedprice` * (1 - `dbt3_s001`.`lineitem`.`l_discount`) - `dbt3_s001`.`partsupp`.`ps_supplycost` * `dbt3_s001`.`lineitem`.`l_quantity`) AS `sum_profit` from `dbt3_s001`.`part` join `dbt3_s001`.`supplier` join `dbt3_s001`.`lineitem` join `dbt3_s001`.`partsupp` join `dbt3_s001`.`orders` join `dbt3_s001`.`nation` where `dbt3_s001`.`partsupp`.`ps_suppkey` = `dbt3_s001`.`supplier`.`s_suppkey` and `dbt3_s001`.`lineitem`.`l_suppkey` = `dbt3_s001`.`supplier`.`s_suppkey` and `dbt3_s001`.`part`.`p_partkey` = `dbt3_s001`.`partsupp`.`ps_partkey` and `dbt3_s001`.`lineitem`.`l_partkey` = `dbt3_s001`.`partsupp`.`ps_partkey` and `dbt3_s001`.`orders`.`o_orderkey` = `dbt3_s001`.`lineitem`.`l_orderkey` and `dbt3_s001`.`nation`.`n_nationkey` = `dbt3_s001`.`supplier`.`s_nationkey` and `dbt3_s001`.`part`.`p_name` like '%green%' group by `dbt3_s001`.`nation`.`n_name`,extract(year from `dbt3_s001`.`orders`.`o_orderDATE`) desc order by `dbt3_s001`.`nation`.`n_name`,extract(year from `dbt3_s001`.`orders`.`o_orderDATE`) desc
select nation, o_year, sum(amount) as sum_profit
from (select n_name as nation,
extract(year from o_orderdate) as o_year,