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mirror of https://github.com/MariaDB/server.git synced 2025-07-29 05:21:33 +03:00

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

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

View File

@ -127,7 +127,7 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t6.c62 1 Using index
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 1.650935
Last_query_cost 4.284314
explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c12 = t2.c21 and t2.c22 = t3.c31 and t3.c32 = t4.c41 and t4.c42 = t5.c51 and t5.c52 = t6.c61 and t6.c62 = t7.c71;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 3
@ -139,7 +139,7 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t6.c62 1 Using index
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 1.650935
Last_query_cost 4.284314
explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where
@ -198,76 +198,76 @@ select @@optimizer_search_depth;
0
explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c12 = t2.c21 and t2.c22 = t3.c31 and t3.c32 = t4.c41 and t4.c42 = t5.c51 and t5.c52 = t6.c61 and t6.c62 = t7.c71;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 3
1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where
1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t2.c22 1
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t4.c42 1
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t2.c22 1 Using where
1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t4.c42 1 Using where
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t6.c62 1 Using index
1 SIMPLE t1 ALL NULL NULL NULL NULL 3 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 1.405838
Last_query_cost 2.998640
explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c12 = t2.c21 and t2.c22 = t3.c31 and t3.c32 = t4.c41 and t4.c42 = t5.c51 and t5.c52 = t6.c61 and t6.c62 = t7.c71;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 3
1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where
1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t2.c22 1
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t4.c42 1
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t6.c62 1 Using index
1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t4.c42 1 Using where
1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t2.c22 1 Using where
1 SIMPLE t1 ALL NULL NULL NULL NULL 3 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 1.405838
Last_query_cost 2.998640
explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using join buffer (flat, BNL join)
1 SIMPLE t1 eq_ref PRIMARY PRIMARY 4 test.t2.c21 1 Using where
1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using index
1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using index
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using index
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 0.494824
Last_query_cost 0.602062
explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using join buffer (flat, BNL join)
1 SIMPLE t1 eq_ref PRIMARY PRIMARY 4 test.t2.c21 1 Using where
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using index
1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using index
1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using index
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 0.494824
Last_query_cost 0.602062
explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71 and t2.c22 = t3.c32 and t2.c23 = t4.c42 and t2.c24 = t5.c52 and t2.c25 = t6.c62 and t2.c26 = t7.c72 and t3.c33 = t4.c43 and t3.c34 = t5.c53 and t3.c35 = t6.c63 and t3.c36 = t7.c73 and t4.c42 = t5.c54 and t4.c43 = t6.c64 and t4.c44 = t7.c74 and t5.c52 = t6.c65 and t5.c53 = t7.c75 and t6.c62 = t7.c76;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t1 eq_ref PRIMARY PRIMARY 4 test.t2.c21 1 Using where
1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using where
1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using where
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using where
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 0.453844
Last_query_cost 0.621783
explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71 and t2.c22 = t3.c32 and t2.c23 = t4.c42 and t2.c24 = t5.c52 and t2.c25 = t6.c62 and t2.c26 = t7.c72 and t3.c33 = t4.c43 and t3.c34 = t5.c53 and t3.c35 = t6.c63 and t3.c36 = t7.c73 and t4.c42 = t5.c54 and t4.c43 = t6.c64 and t4.c44 = t7.c74 and t5.c52 = t6.c65 and t5.c53 = t7.c75 and t6.c62 = t7.c76;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t1 eq_ref PRIMARY PRIMARY 4 test.t2.c21 1 Using where
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using where
1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using where
1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using where
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 0.453844
Last_query_cost 0.621783
set optimizer_search_depth=1;
select @@optimizer_search_depth;
@@optimizer_search_depth
@ -283,7 +283,7 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 34.291074
Last_query_cost 42.599713
explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c12 = t2.c21 and t2.c22 = t3.c31 and t3.c32 = t4.c41 and t4.c42 = t5.c51 and t5.c52 = t6.c61 and t6.c62 = t7.c71;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t7 index PRIMARY PRIMARY 4 NULL 21 Using index
@ -295,7 +295,7 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 34.291074
Last_query_cost 42.599713
explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t3 index PRIMARY PRIMARY 4 NULL 9 Using index
@ -307,7 +307,7 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 14.789792
Last_query_cost 14.817907
explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t3 index PRIMARY PRIMARY 4 NULL 9 Using index
@ -319,7 +319,7 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 14.789792
Last_query_cost 14.817907
explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71 and t2.c22 = t3.c32 and t2.c23 = t4.c42 and t2.c24 = t5.c52 and t2.c25 = t6.c62 and t2.c26 = t7.c72 and t3.c33 = t4.c43 and t3.c34 = t5.c53 and t3.c35 = t6.c63 and t3.c36 = t7.c73 and t4.c42 = t5.c54 and t4.c43 = t6.c64 and t4.c44 = t7.c74 and t5.c52 = t6.c65 and t5.c53 = t7.c75 and t6.c62 = t7.c76;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL PRIMARY NULL NULL NULL 3 Using where
@ -350,76 +350,76 @@ select @@optimizer_search_depth;
62
explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c12 = t2.c21 and t2.c22 = t3.c31 and t3.c32 = t4.c41 and t4.c42 = t5.c51 and t5.c52 = t6.c61 and t6.c62 = t7.c71;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 3
1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where
1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t2.c22 1
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t4.c42 1
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t2.c22 1 Using where
1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t4.c42 1 Using where
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t6.c62 1 Using index
1 SIMPLE t1 ALL NULL NULL NULL NULL 3 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 1.405838
Last_query_cost 2.998640
explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c12 = t2.c21 and t2.c22 = t3.c31 and t3.c32 = t4.c41 and t4.c42 = t5.c51 and t5.c52 = t6.c61 and t6.c62 = t7.c71;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 3
1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where
1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t2.c22 1
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t4.c42 1
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t6.c62 1 Using index
1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t4.c42 1 Using where
1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t2.c22 1 Using where
1 SIMPLE t1 ALL NULL NULL NULL NULL 3 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 1.405838
Last_query_cost 2.998640
explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using join buffer (flat, BNL join)
1 SIMPLE t1 eq_ref PRIMARY PRIMARY 4 test.t2.c21 1 Using where
1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using index
1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using index
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using index
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 0.494824
Last_query_cost 0.602062
explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using join buffer (flat, BNL join)
1 SIMPLE t1 eq_ref PRIMARY PRIMARY 4 test.t2.c21 1 Using where
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using index
1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using index
1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using index
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 0.494824
Last_query_cost 0.602062
explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71 and t2.c22 = t3.c32 and t2.c23 = t4.c42 and t2.c24 = t5.c52 and t2.c25 = t6.c62 and t2.c26 = t7.c72 and t3.c33 = t4.c43 and t3.c34 = t5.c53 and t3.c35 = t6.c63 and t3.c36 = t7.c73 and t4.c42 = t5.c54 and t4.c43 = t6.c64 and t4.c44 = t7.c74 and t5.c52 = t6.c65 and t5.c53 = t7.c75 and t6.c62 = t7.c76;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t1 eq_ref PRIMARY PRIMARY 4 test.t2.c21 1 Using where
1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using where
1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using where
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using where
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 0.453844
Last_query_cost 0.621783
explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71 and t2.c22 = t3.c32 and t2.c23 = t4.c42 and t2.c24 = t5.c52 and t2.c25 = t6.c62 and t2.c26 = t7.c72 and t3.c33 = t4.c43 and t3.c34 = t5.c53 and t3.c35 = t6.c63 and t3.c36 = t7.c73 and t4.c42 = t5.c54 and t4.c43 = t6.c64 and t4.c44 = t7.c74 and t5.c52 = t6.c65 and t5.c53 = t7.c75 and t6.c62 = t7.c76;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t1 eq_ref PRIMARY PRIMARY 4 test.t2.c21 1 Using where
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using where
1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using where
1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using where
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 0.453844
Last_query_cost 0.621783
set optimizer_prune_level=2;
select @@optimizer_prune_level;
@@optimizer_prune_level
@ -439,7 +439,7 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t6.c62 1 Using index
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 1.650935
Last_query_cost 4.284314
explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c12 = t2.c21 and t2.c22 = t3.c31 and t3.c32 = t4.c41 and t4.c42 = t5.c51 and t5.c52 = t6.c61 and t6.c62 = t7.c71;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 3
@ -451,7 +451,7 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t6.c62 1 Using index
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 1.650935
Last_query_cost 4.284314
explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where
@ -515,7 +515,7 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 34.291074
Last_query_cost 42.599713
explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c12 = t2.c21 and t2.c22 = t3.c31 and t3.c32 = t4.c41 and t4.c42 = t5.c51 and t5.c52 = t6.c61 and t6.c62 = t7.c71;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t7 index PRIMARY PRIMARY 4 NULL 21 Using index
@ -527,7 +527,7 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 34.291074
Last_query_cost 42.599713
explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t3 index PRIMARY PRIMARY 4 NULL 9 Using index
@ -539,7 +539,7 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 14.789792
Last_query_cost 14.817907
explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t3 index PRIMARY PRIMARY 4 NULL 9 Using index
@ -551,7 +551,7 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 14.789792
Last_query_cost 14.817907
explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71 and t2.c22 = t3.c32 and t2.c23 = t4.c42 and t2.c24 = t5.c52 and t2.c25 = t6.c62 and t2.c26 = t7.c72 and t3.c33 = t4.c43 and t3.c34 = t5.c53 and t3.c35 = t6.c63 and t3.c36 = t7.c73 and t4.c42 = t5.c54 and t4.c43 = t6.c64 and t4.c44 = t7.c74 and t5.c52 = t6.c65 and t5.c53 = t7.c75 and t6.c62 = t7.c76;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL PRIMARY NULL NULL NULL 3 Using where
@ -591,7 +591,7 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t6.c62 1 Using index
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 1.650935
Last_query_cost 4.284314
explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c12 = t2.c21 and t2.c22 = t3.c31 and t3.c32 = t4.c41 and t4.c42 = t5.c51 and t5.c52 = t6.c61 and t6.c62 = t7.c71;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 3
@ -603,7 +603,7 @@ id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t6.c62 1 Using index
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 1.650935
Last_query_cost 4.284314
explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where
@ -1194,14 +1194,17 @@ AND t10000.I=t10.I;
COUNT(*)
9000
### NOTE: Handler_reads: 9030, expected: 9045 ###
#####
## EQ_REF & REF join two instances of t10000 with t10:
#####
flush status;
EXPLAIN SELECT STRAIGHT_JOIN COUNT(*) FROM t10000 y, t10, t10000 x
EXPLAIN SELECT STRAIGHT_JOIN COUNT(*) FROM t10,t10000 x,t10000 y
WHERE x.k=t10.i;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE y index NULL PRIMARY 4 NULL 10000 Using index
1 SIMPLE t10 range IX IX 5 NULL 10 Using where; Using index; Using join buffer (flat, BNL join)
1 SIMPLE t10 index IX IX 5 NULL 10 Using where; Using index
1 SIMPLE x eq_ref PRIMARY PRIMARY 4 test.t10.I 1 Using index
SELECT STRAIGHT_JOIN COUNT(*) FROM t10000 y, t10, t10000 x
1 SIMPLE y index NULL PRIMARY 4 NULL 10000 Using index; Using join buffer (flat, BNL join)
SELECT STRAIGHT_JOIN COUNT(*) FROM t10,t10000 x,t10000 y
WHERE x.k=t10.i;
COUNT(*)
90000
@ -1209,9 +1212,9 @@ flush status;
EXPLAIN SELECT COUNT(*) FROM t10,t10000 x,t10000 y
WHERE x.k=t10.i;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE y index NULL PRIMARY 4 NULL 10000 Using index
1 SIMPLE t10 range IX IX 5 NULL 10 Using where; Using index; Using join buffer (flat, BNL join)
1 SIMPLE t10 index IX IX 5 NULL 10 Using where; Using index
1 SIMPLE x eq_ref PRIMARY PRIMARY 4 test.t10.I 1 Using index
1 SIMPLE y index NULL PRIMARY 4 NULL 10000 Using index; Using join buffer (flat, BNL join)
SELECT COUNT(*) FROM t10,t10000 x,t10000 y
WHERE x.k=t10.i;
COUNT(*)
@ -1220,9 +1223,9 @@ flush status;
EXPLAIN SELECT COUNT(*) FROM t10,t10000 y,t10000 x
WHERE x.k=t10.i;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE y index NULL PRIMARY 4 NULL 10000 Using index
1 SIMPLE t10 range IX IX 5 NULL 10 Using where; Using index; Using join buffer (flat, BNL join)
1 SIMPLE t10 index IX IX 5 NULL 10 Using where; Using index
1 SIMPLE x eq_ref PRIMARY PRIMARY 4 test.t10.I 1 Using index
1 SIMPLE y index NULL PRIMARY 4 NULL 10000 Using index; Using join buffer (flat, BNL join)
SELECT COUNT(*) FROM t10,t10000 y,t10000 x
WHERE x.k=t10.i;
COUNT(*)