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MDEV-30218: Incorrect optimization for rowid_filtering 
(Patch from Monty, slightly amended)

Fix rowid filtering optimization in best_access_path():

== Ref access + rowid filtering ==
The cost computations compare #records and index-only scan cost
(keyread_tmp) to find out the per-record advantage one will get if
they skip reading full table record.

The computations produce wrong result when:

- the #records are "clipped down" with s->worst_seeks or
  thd->variables.max_seeks_for_key. keyread_tmp is not clipped
  this way so the numbers are not comparable.

- access_factor is negative. This means index_only read is
  cheaper than non-index-only read.

This patch makes the optimizer not to consider Rowid Filtering in
such cases.
The decision is logged in the Optimizer Trace using
"rowid_filter_skipped" name.

== Range access + rowid filtering ==
when considering to use Rowid Filter with range access, do multiply
keyread_tmp by record_count. That way, it is comparable with the
range access's estimate, which is multiplied by record_count.
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@spetrunia
spetrunia committed Dec 13, 2022
1 parent fdf43b5 commit 87eccd7
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24 mysql-test/main/join_cache.result
View file
@@ -853,7 +853,7 @@ LENGTH(Language) < LENGTH(City.Name) - 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE City ALL Country NULL NULL NULL 4079 Using where
1 SIMPLE Country hash_ALL PRIMARY #hash#PRIMARY 3 world.City.Country 239 Using where; Using join buffer (flat, BNLH join)
1 SIMPLE CountryLanguage hash_ALL PRIMARY,Percentage #hash#PRIMARY 3 world.City.Country 984 Using where; Using join buffer (flat, BNLH join)
1 SIMPLE CountryLanguage hash_ALL|filter PRIMARY,Percentage #hash#PRIMARY|Percentage 3|4 world.City.Country 984 (19%) Using where; Using join buffer (flat, BNLH join); Using rowid filter
SELECT City.Name, Country.Name, CountryLanguage.Language
FROM City,Country,CountryLanguage
WHERE City.Country=Country.Code AND
@@ -1053,7 +1053,7 @@ LENGTH(Language) < LENGTH(City.Name) - 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE City ALL Country NULL NULL NULL 4079 Using where
1 SIMPLE Country hash_ALL PRIMARY #hash#PRIMARY 3 world.City.Country 239 Using where; Using join buffer (flat, BNLH join)
1 SIMPLE CountryLanguage hash_ALL PRIMARY,Percentage #hash#PRIMARY 3 world.City.Country 984 Using where; Using join buffer (incremental, BNLH join)
1 SIMPLE CountryLanguage hash_ALL|filter PRIMARY,Percentage #hash#PRIMARY|Percentage 3|4 world.City.Country 984 (19%) Using where; Using join buffer (incremental, BNLH join); Using rowid filter
SELECT City.Name, Country.Name, CountryLanguage.Language
FROM City,Country,CountryLanguage
WHERE City.Country=Country.Code AND
@@ -1312,7 +1312,7 @@ LENGTH(Language) < LENGTH(City.Name) - 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE City ALL Country NULL NULL NULL 4079 Using where
1 SIMPLE Country eq_ref PRIMARY PRIMARY 3 world.City.Country 1 Using where; Using join buffer (flat, BKA join); Key-ordered Rowid-ordered scan
1 SIMPLE CountryLanguage ref PRIMARY,Percentage PRIMARY 3 world.City.Country 4 Using index condition(BKA); Using where; Using join buffer (flat, BKA join); Key-ordered Rowid-ordered scan
1 SIMPLE CountryLanguage ref|filter PRIMARY,Percentage PRIMARY|Percentage 3|4 world.City.Country 4 (19%) Using index condition(BKA); Using where; Using join buffer (flat, BKA join); Key-ordered Rowid-ordered scan; Using rowid filter
SELECT City.Name, Country.Name, CountryLanguage.Language
FROM City,Country,CountryLanguage
WHERE City.Country=Country.Code AND
@@ -1509,7 +1509,7 @@ LENGTH(Language) < LENGTH(City.Name) - 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE City ALL Country NULL NULL NULL 4079 Using where
1 SIMPLE Country eq_ref PRIMARY PRIMARY 3 world.City.Country 1 Using where; Using join buffer (flat, BKA join); Key-ordered Rowid-ordered scan
1 SIMPLE CountryLanguage ref PRIMARY,Percentage PRIMARY 3 world.City.Country 4 Using index condition(BKA); Using where; Using join buffer (incremental, BKA join); Key-ordered Rowid-ordered scan
1 SIMPLE CountryLanguage ref|filter PRIMARY,Percentage PRIMARY|Percentage 3|4 world.City.Country 4 (19%) Using index condition(BKA); Using where; Using join buffer (incremental, BKA join); Key-ordered Rowid-ordered scan; Using rowid filter
SELECT City.Name, Country.Name, CountryLanguage.Language
FROM City,Country,CountryLanguage
WHERE City.Country=Country.Code AND
@@ -1706,7 +1706,7 @@ LENGTH(Language) < LENGTH(City.Name) - 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE City ALL Country NULL NULL NULL 4079 Using where
1 SIMPLE Country eq_ref PRIMARY PRIMARY 3 world.City.Country 1 Using where; Using join buffer (flat, BKAH join); Key-ordered Rowid-ordered scan
1 SIMPLE CountryLanguage ref PRIMARY,Percentage PRIMARY 3 world.City.Country 4 Using index condition(BKA); Using where; Using join buffer (flat, BKAH join); Key-ordered Rowid-ordered scan
1 SIMPLE CountryLanguage ref|filter PRIMARY,Percentage PRIMARY|Percentage 3|4 world.City.Country 4 (19%) Using index condition(BKA); Using where; Using join buffer (flat, BKAH join); Key-ordered Rowid-ordered scan; Using rowid filter
SELECT City.Name, Country.Name, CountryLanguage.Language
FROM City,Country,CountryLanguage
WHERE City.Country=Country.Code AND
@@ -1903,7 +1903,7 @@ LENGTH(Language) < LENGTH(City.Name) - 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE City ALL Country NULL NULL NULL 4079 Using where
1 SIMPLE Country eq_ref PRIMARY PRIMARY 3 world.City.Country 1 Using where; Using join buffer (flat, BKAH join); Key-ordered Rowid-ordered scan
1 SIMPLE CountryLanguage ref PRIMARY,Percentage PRIMARY 3 world.City.Country 4 Using index condition(BKA); Using where; Using join buffer (incremental, BKAH join); Key-ordered Rowid-ordered scan
1 SIMPLE CountryLanguage ref|filter PRIMARY,Percentage PRIMARY|Percentage 3|4 world.City.Country 4 (19%) Using index condition(BKA); Using where; Using join buffer (incremental, BKAH join); Key-ordered Rowid-ordered scan; Using rowid filter
SELECT City.Name, Country.Name, CountryLanguage.Language
FROM City,Country,CountryLanguage
WHERE City.Country=Country.Code AND
@@ -2104,7 +2104,7 @@ LENGTH(Language) < LENGTH(City.Name) - 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE City ALL Country NULL NULL NULL 4079 Using where
1 SIMPLE Country hash_ALL PRIMARY #hash#PRIMARY 3 world.City.Country 239 Using where; Using join buffer (flat, BNLH join)
1 SIMPLE CountryLanguage hash_ALL PRIMARY,Percentage #hash#PRIMARY 3 world.City.Country 984 Using where; Using join buffer (flat, BNLH join)
1 SIMPLE CountryLanguage hash_ALL|filter PRIMARY,Percentage #hash#PRIMARY|Percentage 3|4 world.City.Country 984 (19%) Using where; Using join buffer (flat, BNLH join); Using rowid filter
SELECT City.Name, Country.Name, CountryLanguage.Language
FROM City,Country,CountryLanguage
WHERE City.Country=Country.Code AND
@@ -2208,7 +2208,7 @@ LENGTH(Language) < LENGTH(City.Name) - 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE City ALL Country NULL NULL NULL 4079 Using where
1 SIMPLE Country hash_ALL PRIMARY #hash#PRIMARY 3 world.City.Country 239 Using where; Using join buffer (flat, BNLH join)
1 SIMPLE CountryLanguage hash_ALL PRIMARY,Percentage #hash#PRIMARY 3 world.City.Country 984 Using where; Using join buffer (incremental, BNLH join)
1 SIMPLE CountryLanguage hash_ALL|filter PRIMARY,Percentage #hash#PRIMARY|Percentage 3|4 world.City.Country 984 (19%) Using where; Using join buffer (incremental, BNLH join); Using rowid filter
SELECT City.Name, Country.Name, CountryLanguage.Language
FROM City,Country,CountryLanguage
WHERE City.Country=Country.Code AND
@@ -2312,7 +2312,7 @@ LENGTH(Language) < LENGTH(City.Name) - 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE City ALL Country NULL NULL NULL 4079 Using where
1 SIMPLE Country eq_ref PRIMARY PRIMARY 3 world.City.Country 1 Using where; Using join buffer (flat, BKA join); Key-ordered Rowid-ordered scan
1 SIMPLE CountryLanguage ref PRIMARY,Percentage PRIMARY 3 world.City.Country 4 Using index condition(BKA); Using where; Using join buffer (flat, BKA join); Key-ordered Rowid-ordered scan
1 SIMPLE CountryLanguage ref|filter PRIMARY,Percentage PRIMARY|Percentage 3|4 world.City.Country 4 (19%) Using index condition(BKA); Using where; Using join buffer (flat, BKA join); Key-ordered Rowid-ordered scan; Using rowid filter
SELECT City.Name, Country.Name, CountryLanguage.Language
FROM City,Country,CountryLanguage
WHERE City.Country=Country.Code AND
@@ -2416,7 +2416,7 @@ LENGTH(Language) < LENGTH(City.Name) - 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE City ALL Country NULL NULL NULL 4079 Using where
1 SIMPLE Country eq_ref PRIMARY PRIMARY 3 world.City.Country 1 Using where; Using join buffer (flat, BKA join); Key-ordered Rowid-ordered scan
1 SIMPLE CountryLanguage ref PRIMARY,Percentage PRIMARY 3 world.City.Country 4 Using index condition(BKA); Using where; Using join buffer (incremental, BKA join); Key-ordered Rowid-ordered scan
1 SIMPLE CountryLanguage ref|filter PRIMARY,Percentage PRIMARY|Percentage 3|4 world.City.Country 4 (19%) Using index condition(BKA); Using where; Using join buffer (incremental, BKA join); Key-ordered Rowid-ordered scan; Using rowid filter
SELECT City.Name, Country.Name, CountryLanguage.Language
FROM City,Country,CountryLanguage
WHERE City.Country=Country.Code AND
@@ -2520,7 +2520,7 @@ LENGTH(Language) < LENGTH(City.Name) - 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE City ALL Country NULL NULL NULL 4079 Using where
1 SIMPLE Country eq_ref PRIMARY PRIMARY 3 world.City.Country 1 Using where; Using join buffer (flat, BKAH join); Key-ordered Rowid-ordered scan
1 SIMPLE CountryLanguage ref PRIMARY,Percentage PRIMARY 3 world.City.Country 4 Using index condition(BKA); Using where; Using join buffer (flat, BKAH join); Key-ordered Rowid-ordered scan
1 SIMPLE CountryLanguage ref|filter PRIMARY,Percentage PRIMARY|Percentage 3|4 world.City.Country 4 (19%) Using index condition(BKA); Using where; Using join buffer (flat, BKAH join); Key-ordered Rowid-ordered scan; Using rowid filter
SELECT City.Name, Country.Name, CountryLanguage.Language
FROM City,Country,CountryLanguage
WHERE City.Country=Country.Code AND
@@ -2624,7 +2624,7 @@ LENGTH(Language) < LENGTH(City.Name) - 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE City ALL Country NULL NULL NULL 4079 Using where
1 SIMPLE Country eq_ref PRIMARY PRIMARY 3 world.City.Country 1 Using where; Using join buffer (flat, BKAH join); Key-ordered Rowid-ordered scan
1 SIMPLE CountryLanguage ref PRIMARY,Percentage PRIMARY 3 world.City.Country 4 Using index condition(BKA); Using where; Using join buffer (incremental, BKAH join); Key-ordered Rowid-ordered scan
1 SIMPLE CountryLanguage ref|filter PRIMARY,Percentage PRIMARY|Percentage 3|4 world.City.Country 4 (19%) Using index condition(BKA); Using where; Using join buffer (incremental, BKAH join); Key-ordered Rowid-ordered scan; Using rowid filter
SELECT City.Name, Country.Name, CountryLanguage.Language
FROM City,Country,CountryLanguage
WHERE City.Country=Country.Code AND
11 mysql-test/main/opt_trace.result
View file
@@ -1016,6 +1016,7 @@ explain select * from t1,t2 where t1.a=t2.b+2 and t2.a= t1.b {
"index": "a",
"used_range_estimates": false,
"cause": "not available",
"rowid_filter_skipped": "cost_factor <= 0",
"rows": 1,
"cost": 200,
"chosen": true
@@ -1072,6 +1073,7 @@ explain select * from t1,t2 where t1.a=t2.b+2 and t2.a= t1.b {
"index": "a",
"used_range_estimates": false,
"cause": "not available",
"rowid_filter_skipped": "cost_factor <= 0",
"rows": 1,
"cost": 200,
"chosen": true
@@ -2118,6 +2120,7 @@ explain select * from t1 where a=1 and b=2 order by c limit 1 {
"access_type": "ref",
"index": "a_c",
"used_range_estimates": true,
"rowid_filter_skipped": "worst/max seeks clipping",
"rows": 180,
"cost": 92,
"chosen": true
@@ -3343,6 +3346,7 @@ explain select * from t1 where pk = 2 and a=5 and b=1 {
"access_type": "ref",
"index": "pk",
"used_range_estimates": true,
"rowid_filter_skipped": "cost_factor <= 0",
"rows": 1,
"cost": 2,
"chosen": true
@@ -3351,6 +3355,7 @@ explain select * from t1 where pk = 2 and a=5 and b=1 {
"access_type": "ref",
"index": "pk_a",
"used_range_estimates": true,
"rowid_filter_skipped": "cost_factor <= 0",
"rows": 1,
"cost": 2,
"chosen": false,
@@ -3360,6 +3365,7 @@ explain select * from t1 where pk = 2 and a=5 and b=1 {
"access_type": "ref",
"index": "pk_a_b",
"used_range_estimates": true,
"rowid_filter_skipped": "cost_factor <= 0",
"rows": 1,
"cost": 1.0043,
"chosen": true
@@ -3994,6 +4000,7 @@ explain delete t0,t1 from t0, t1 where t0.a=t1.a and t1.a<3 {
"index": "a",
"used_range_estimates": false,
"cause": "not better than ref estimates",
"rowid_filter_skipped": "cost_factor <= 0",
"rows": 1,
"cost": 3.007,
"chosen": true
@@ -4049,6 +4056,7 @@ explain delete t0,t1 from t0, t1 where t0.a=t1.a and t1.a<3 {
"index": "a",
"used_range_estimates": false,
"cause": "not better than ref estimates",
"rowid_filter_skipped": "worst/max seeks clipping",
"rows": 2,
"cost": 3.014,
"chosen": true
@@ -8145,6 +8153,7 @@ JSON_DETAILED(JSON_EXTRACT(trace, '$**.considered_execution_plans'))
"index": "b",
"used_range_estimates": false,
"cause": "not available",
"rowid_filter_skipped": "cost_factor <= 0",
"rows": 1,
"cost": 20,
"chosen": true
@@ -8370,6 +8379,7 @@ JSON_DETAILED(JSON_EXTRACT(trace, '$**.considered_execution_plans'))
"index": "a",
"used_range_estimates": false,
"cause": "not available",
"rowid_filter_skipped": "cost_factor <= 0",
"rows": 1,
"cost": 20,
"chosen": true
@@ -8445,6 +8455,7 @@ JSON_DETAILED(JSON_EXTRACT(trace, '$**.considered_execution_plans'))
"index": "a",
"used_range_estimates": false,
"cause": "not available",
"rowid_filter_skipped": "cost_factor <= 0",
"rows": 1,
"cost": 200,
"chosen": true
1 mysql-test/main/opt_trace_index_merge_innodb.result
View file
@@ -208,6 +208,7 @@ explain select * from t1 where pk1 != 0 and key1 = 1 {
"access_type": "ref",
"index": "key1",
"used_range_estimates": true,
"rowid_filter_skipped": "cost_factor <= 0",
"rows": 1,
"cost": 2,
"chosen": true
2 mysql-test/main/range.result
View file
@@ -281,7 +281,7 @@ INSERT INTO t1 VALUES
(33,5),(33,5),(33,5),(33,5),(34,5),(35,5);
EXPLAIN SELECT * FROM t1 WHERE a IN(1,2) AND b=5;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref|filter a,b b|a 5|5 const 15 (5%) Using where; Using rowid filter
1 SIMPLE t1 range a,b a 5 NULL 2 Using index condition; Using where
SELECT * FROM t1 WHERE a IN(1,2) AND b=5;
a b
DROP TABLE t1;

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