Added EQ_REF chaining to the greedy_optimizer

MDEV-28073 Slow query performance in MariaDB when using many table

The idea is to prefer and chain EQ_REF tables (tables that uses an
unique key to find a row) when searching for the best table combination.
This significantly reduces row combinations that has to be examined.
This is optimization is enabled when setting optimizer_prune_level=2
(which is now default).

Implementation:
- optimizer_prune_level has a new level, 2, which enables EQ_REF
  optimization in addition to the pruning done by level 1.
  Level 2 is now default.
- Added JOIN::eq_ref_tables that contains bits of tables that could use
  potentially use EQ_REF access in the query.  This is calculated
  in sort_and_filter_keyuse()

Under optimizer_prune_level=2:
- When the greedy_optimizer notices that the preceding table was an
  EQ_REF table, it tries to add an EQ_REF table next. If an EQ_REF
  table exists, only this one will be considered at this level.
  We also collect all EQ_REF tables chained by the next levels and these
  are ignored on the starting level as we have already examined these.
  If no EQ_REF table exists, we continue as normal.

This optimization speeds up the greedy_optimizer combination test with
~25%

Other things:
- I ported the changes in MySQL 5.7 to greedy_optimizer.test to MariaDB
  to be able to ensure we can handle all cases that MySQL can do.
- I have run all tests with --mysqld=--optimizer_prune_level=1 to verify that
  there where no test changes.

1 files changed, 571 insertions, 2 deletions

diff --git a/mysql-test/main/greedy_optimizer.test b/mysql-test/main/greedy_optimizer.test
index cac262bca64..1e5b3e0a9b7 100644
--- a/mysql-test/main/greedy_optimizer.test
+++ b/mysql-test/main/greedy_optimizer.test
@@ -1,3 +1,5 @@
+--source include/have_innodb.inc
+
 #
 # A simple test of the greedy query optimization algorithm and the switches that
 # control the optimizationprocess.
@@ -248,7 +250,7 @@ explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c11 = t2.c21 and
 show status like 'Last_query_cost';
 
 
-set optimizer_prune_level=1;
+set optimizer_prune_level=2;
 select @@optimizer_prune_level;
 
 set optimizer_search_depth=0;
@@ -381,6 +383,573 @@ LEFT JOIN (
 SET optimizer_search_depth = DEFAULT;
 DROP TABLE t1,t2,t2_1,t3,t3_1,t4,t4_1,t5,t5_1;
 
+set join_cache_level=@save_join_cache_level;
+
 --echo End of 5.0 tests
 
-set join_cache_level=@save_join_cache_level;
+--echo #
+--echo # Bug #59326: Greedy optimizer produce stupid query execution plans.
+--echo #
+
+CREATE TABLE t10(
+  K INT NOT NULL AUTO_INCREMENT,
+  I INT,
+  PRIMARY KEY(K)
+);
+INSERT INTO t10(I) VALUES (1),(2),(3),(4),(5),(6),(7),(8),(9),(0);
+
+CREATE TABLE t100 LIKE t10;
+INSERT INTO t100(I)
+SELECT X.I FROM t10 AS X,t10 AS Y;
+
+CREATE TABLE t10000 LIKE t10;
+INSERT INTO t10000(I)
+SELECT X.I FROM t100 AS X, t100 AS Y;
+
+--disable_warnings
+let $total_handler_reads=
+select sum(variable_value) from information_schema.session_status
+ where VARIABLE_NAME like 'Handler_read%';
+--enable_warnings
+
+
+## All crossproducts should be executed in order t10,t100,t10000
+EXPLAIN SELECT * FROM t10,t100,t10000;
+EXPLAIN SELECT * FROM t10,t10000,t100;
+EXPLAIN SELECT * FROM t100,t10,t10000;
+EXPLAIN SELECT * FROM t100,t10000,t10;
+EXPLAIN SELECT * FROM t10000,t10,t100;
+EXPLAIN SELECT * FROM t10000,t100,t10;
+
+######
+## Ordering between T100,T10000 EQ-joined T10 will
+## normally be with smallest EQ-table joined first
+######
+let $query=
+SELECT STRAIGHT_JOIN COUNT(*) FROM t10,t100,t10000
+WHERE t100.K=t10.I
+  AND t10000.K=t10.I;
+--source include/expect_qep.inc
+
+## However, swapping EQ_REF-joined tables gives the same cost
+let $query=
+SELECT STRAIGHT_JOIN COUNT(*) FROM t10,t10000,t100
+WHERE t100.K=t10.I
+  AND t10000.K=t10.I;
+--source include/check_qep.inc
+
+#####
+# Expect all variants of EQ joining t100 & t10000 with T10
+# to have same cost # handler_reads:
+let $query=
+SELECT COUNT(*) FROM t10,t100,t10000
+WHERE t100.K=t10.I
+  AND t10000.K=t10.I;
+--source include/check_qep.inc
+
+let $query=
+SELECT COUNT(*) FROM t10,t10000,t100
+WHERE t100.K=t10.I
+  AND t10000.K=t10.I;
+--source include/check_qep.inc
+
+let $query=
+SELECT COUNT(*) FROM t10,t100,t10000
+WHERE t100.K=t10.I
+  AND t10000.K=t10.K;
+--source include/check_qep.inc
+
+let $query=
+SELECT COUNT(*) FROM t10,t10000,t100
+WHERE t100.K=t10.I
+  AND t10000.K=t10.K;
+--source include/check_qep.inc
+
+let $query=
+SELECT COUNT(*) FROM t100,t10,t10000
+WHERE t100.K=t10.I
+  AND t10000.K=t10.K;
+--source include/check_qep.inc
+
+let $query=
+SELECT COUNT(*) FROM t100,t10000,t10
+WHERE t100.K=t10.I
+  AND t10000.K=t10.K;
+--source include/check_qep.inc
+
+let $query=
+SELECT COUNT(*) FROM t10000,t10,t100
+WHERE t100.K=t10.I
+  AND t10000.K=t10.K;
+--source include/check_qep.inc
+
+let $query=
+SELECT COUNT(*) FROM t10000,t100,t10
+WHERE t100.K=t10.I
+  AND t10000.K=t10.K;
+--source include/check_qep.inc
+
+
+#####
+## EQ_REF Should be executed before table scan(ALL)
+## - Independent of #records in table being EQ_REF-joined
+#####
+#####
+# Expect: Join EQ_REF(t100) before ALL(t10000)
+let $query=
+SELECT STRAIGHT_JOIN COUNT(*) FROM t10,t100,t10000
+WHERE t100.K=t10.I
+  AND t10000.I=t10.I;
+--source include/expect_qep.inc
+
+let $query=
+SELECT COUNT(*) FROM t10,t100,t10000
+WHERE t100.K=t10.I
+  AND t10000.I=t10.I;
+--source include/check_qep.inc
+
+let $query=
+SELECT COUNT(*) FROM t10,t10000,t100
+WHERE t100.K=t10.I
+  AND t10000.I=t10.I;
+--source include/check_qep.inc
+
+#####
+# Expect: Join EQ_REF(t10000) before ALL(t100) (star-join)
+let $query=
+SELECT STRAIGHT_JOIN COUNT(*) FROM t10,t10000,t100
+WHERE t100.I=t10.I
+  AND t10000.K=t10.I;
+--source include/expect_qep.inc
+
+--echo # See BUG#18352936
+let $query=
+SELECT COUNT(*) FROM t10,t100,t10000
+WHERE t100.I=t10.I
+  AND t10000.K=t10.I;
+--source include/check_qep.inc
+
+--echo # See BUG#18352936
+let $query=
+SELECT COUNT(*) FROM t10,t10000,t100
+WHERE t100.I=t10.I
+  AND t10000.K=t10.I;
+--source include/check_qep.inc
+
+#####
+# Expect: Join EQ_REF(t10000) before ALL(t100)
+let $query=
+SELECT STRAIGHT_JOIN COUNT(*) FROM t10,t10000,t100
+WHERE t100.I=t10.I
+  AND t10000.K=t100.I;
+--source include/expect_qep.inc
+
+let $query=
+SELECT COUNT(*) FROM t10,t100,t10000
+WHERE t100.I=t10.I
+  AND t10000.K=t100.I;
+--source include/check_qep.inc
+
+let $query=
+SELECT COUNT(*) FROM t10,t10000,t100
+WHERE t100.I=t10.I
+  AND t10000.K=t100.I;
+--source include/check_qep.inc
+
+
+#####
+## EQ_REF & ALL join two instances of t10000 with t10:
+## Always EQ_REF join first before producing cross product
+#####
+
+#####
+# Expected QEP: 'join EQ_REF(X) on X.K=t10.I' before 'cross' ALL(Y)
+let $query=
+SELECT STRAIGHT_JOIN COUNT(*) FROM t10,t10000 x,t10000 y
+WHERE x.k=t10.i;
+--source include/expect_qep.inc
+
+let $query=
+SELECT COUNT(*) FROM t10,t10000 x,t10000 y
+WHERE x.k=t10.i;
+--source include/check_qep.inc
+
+let $query=
+SELECT COUNT(*) FROM t10,t10000 y,t10000 x
+WHERE x.k=t10.i;
+--source include/check_qep.inc
+
+#####
+# Expected QEP: 'join EQ_REF(X) on X.K=t10.I' before ALL(Y)
+let $query=
+SELECT STRAIGHT_JOIN COUNT(*) FROM t10,t10000 x,t10000 y
+WHERE x.k=t10.i
+  AND y.i=t10.i;
+--source include/expect_qep.inc
+
+let $query=
+SELECT COUNT(*) FROM t10,t10000 x,t10000 y
+WHERE x.k=t10.i
+  AND y.i=t10.i;
+--source include/check_qep.inc
+
+let $query=
+SELECT COUNT(*) FROM t10,t10000 y,t10000 x
+WHERE x.k=t10.i
+  AND y.i=t10.i;
+--source include/check_qep.inc
+
+#####
+# Expected QEP: 'join EQ_REF(X) on X.K=t10.I' before ALL(Y)
+let $query=
+SELECT STRAIGHT_JOIN COUNT(*) FROM t10,t10000 x,t10000 y
+WHERE x.k=t10.i
+  AND y.i=x.k;
+--source include/expect_qep.inc
+
+let $query=
+SELECT COUNT(*) FROM t10,t10000 x,t10000 y
+WHERE x.k=t10.i
+  AND y.i=x.k;
+--source include/check_qep.inc
+
+let $query=
+SELECT COUNT(*) FROM t10,t10000 y,t10000 x
+WHERE x.k=t10.i
+  AND y.i=x.k;
+--source include/check_qep.inc
+
+
+
+## Create indexes to test REF access
+CREATE INDEX IX ON t10(I);
+CREATE INDEX IX ON t100(I);
+CREATE INDEX IX ON t10000(I);
+
+########
+## EQ_REF Should be executed before 'REF'
+## - Independent of #records in table being EQ_REF-joined
+
+####
+# Expected QEP: 'join EQ_REF(t100) on t100.K=t10.I' before REF(t10000)
+let $query=
+SELECT STRAIGHT_JOIN COUNT(*) FROM t10,t100,t10000
+WHERE t100.K=t10.I
+  AND t10000.I=t10.I;
+--source include/expect_qep.inc
+
+let $query=
+SELECT COUNT(*) FROM t10,t100,t10000
+WHERE t100.K=t10.I
+  AND t10000.I=t10.I;
+--source include/check_qep.inc
+
+let $query=
+SELECT COUNT(*) FROM t10,t10000,t100
+WHERE t100.K=t10.I
+  AND t10000.I=t10.I;
+--source include/check_qep.inc
+
+
+#####
+## EQ_REF & REF join two instances of t10000 with t10:
+#####
+
+#####
+## Expect this QEP, cost & #handler_read
+# Expected QEP: 'join EQ_REF(X) on X.K=t10.I' before 'cross' ALL(Y)
+let $query=
+SELECT STRAIGHT_JOIN COUNT(*) FROM t10,t10000 x,t10000 y
+WHERE x.k=t10.i;
+--source include/expect_qep.inc
+
+let $query=
+SELECT COUNT(*) FROM t10,t10000 x,t10000 y
+WHERE x.k=t10.i;
+--source include/check_qep.inc
+
+let $query=
+SELECT COUNT(*) FROM t10,t10000 y,t10000 x
+WHERE x.k=t10.i;
+--source include/check_qep.inc
+
+#####
+# Expected QEP: 'join EQ_REF(X) on X.K=t10.I' before REF(Y)
+let $query=
+SELECT STRAIGHT_JOIN COUNT(*) FROM t10,t10000 x,t10000 y
+WHERE x.k=t10.i
+  AND y.i=t10.i;
+--source include/expect_qep.inc
+
+let $query=
+SELECT COUNT(*) FROM t10,t10000 x,t10000 y
+WHERE x.k=t10.i
+  AND y.i=t10.i;
+--source include/check_qep.inc
+
+let $query=
+SELECT COUNT(*) FROM t10,t10000 y,t10000 x
+WHERE x.k=t10.i
+  AND y.i=t10.i;
+--source include/check_qep.inc
+
+#####
+# Expected QEP: 'join EQ_REF(X) on X.K=t10.I' before REF(Y)
+let $query=
+SELECT STRAIGHT_JOIN COUNT(*) FROM t10,t10000 x,t10000 y
+WHERE x.k=t10.i
+  AND y.i=x.k;
+--source include/expect_qep.inc
+
+let $query=
+SELECT COUNT(*) FROM t10,t10000 x,t10000 y
+WHERE x.k=t10.i
+  AND y.i=x.k;
+--source include/check_qep.inc
+
+let $query=
+SELECT COUNT(*) FROM t10,t10000 y,t10000 x
+WHERE x.k=t10.i
+  AND y.i=x.k;
+--source include/check_qep.inc
+
+########
+
+
+
+########
+
+--echo #
+--echo # Test improved capabilities of analyzing complex query
+--echo # plans without restricting 'optimizer_search_depth'.
+--echo # Fix problems like those reported as bug#41740 & bug#58225.
+--echo #
+--echo # EPLAIN of queries using T1-T62 will timeout/hang wo/ fixes
+--echo #
+
+DROP TABLE t10, t10000;
+
+--disable_result_log
+
+let $tabledef=
+( K INT NOT NULL AUTO_INCREMENT,
+  I INT,
+  A INT,
+  PRIMARY KEY(K), KEY IX(A)
+) engine = InnoDB;
+
+let $analyze = ANALYZE TABLE t100;
+
+let $i= 1;
+while ($i < 62)
+{
+  let $create= CREATE TABLE t$i $tabledef;
+  eval $create;
+
+  let $insert =
+  INSERT INTO t$i(I,A) SELECT X.K,X.K FROM t100 AS X, t100 AS Y WHERE X.K < 20 AND Y.K <= $i;
+  eval $insert;
+
+  let $analyze = $analyze, t$i;
+  inc $i;
+}
+eval $analyze;
+
+set optimizer_prune_level=default;
+#--enable_result_log
+#select @@optimizer_prune_level;
+#--disable_result_log
+flush status;
+
+#################
+## The EXPLAIN'ed query itself can't be part of the verified
+## result as the QEP is not 100% predictable due to variation
+## in statistics from the engines. This is believed to be
+## caused by:
+##  - Variations in table fill degree.
+##  - 'Fuzzy' statistics provided by engines.
+##  - Round errors caused by 'cost' calculation using
+##    'only' 64-bit double precision.
+##  - Other bugs...?
+##
+###############
+
+## Will test with optimizer_search_depth= [0,1,3,62]
+let $depth= 0;
+while ($depth<4)
+{
+  if ($depth==0)
+  {
+    set optimizer_search_depth=0;
+  }
+  if ($depth==1)
+  {
+    set optimizer_search_depth=1;
+  }
+  if ($depth==2)
+  {
+    set optimizer_search_depth=3;
+  }
+  if ($depth==3)
+  {
+    set optimizer_search_depth=62;
+  }
+  inc $depth;
+
+
+  ## Test pruning of joined table scans (ALL)
+  ## Prepare of QEP without timeout is heavily dependent
+  ## on maintaining correctly '#rows-sorted' plan
+  ##
+  let $query= SELECT COUNT(*) FROM t1 AS x;
+  let $i= 1;
+  while ($i < 61)
+  {
+    let $query= $query JOIN t$i ON t$i.I=x.I;
+    inc $i;
+
+    select @@optimizer_prune_level;
+    select @@optimizer_search_depth;
+    eval EXPLAIN $query;
+  }
+
+  ## Test pruning of joined table scans (ALL)
+  ## with multiple instances of same table.
+  ## (All instances being equally expensive)
+  let $query= SELECT COUNT(*) FROM t1 AS x;
+  let $i= 1;
+  while ($i <= 56)
+  {
+    let $t= t$i;
+    let $query= $query JOIN $t as t$i ON t$i.I=x.I;
+    inc $i;
+    let $query= $query JOIN $t as t$i ON t$i.I=x.I;
+    inc $i;
+    let $query= $query JOIN $t as t$i ON t$i.I=x.I;
+    inc $i;
+    let $query= $query JOIN $t as t$i ON t$i.I=x.I;
+    inc $i;
+    let $query= $query JOIN $t as t$i ON t$i.I=x.I;
+    inc $i;
+    let $query= $query JOIN $t as t$i ON t$i.I=x.I;
+    inc $i;
+    let $query= $query JOIN $t as t$i ON t$i.I=x.I;
+    inc $i;
+    let $query= $query JOIN $t as t$i ON t$i.I=x.I;
+    inc $i;
+
+    select @@optimizer_prune_level;
+    select @@optimizer_search_depth;
+    eval EXPLAIN $query;
+  }
+
+  ## A mix of 25% EQ_REF / 75% ALL joins
+  ##
+  let $query= SELECT COUNT(*) FROM t1 AS x;
+  let $i= 1;
+  while ($i < 60)
+  {
+    let $query= $query JOIN t$i ON t$i.I = x.I;
+    inc $i;
+    let $query= $query JOIN t$i ON t$i.K = x.I;
+    inc $i;
+    let $query= $query JOIN t$i ON t$i.I = x.I;
+    inc $i;
+    let $query= $query JOIN t$i ON t$i.I = x.I;
+    inc $i;
+
+    eval EXPLAIN $query;
+  }
+
+  ## A mix of 50% EQ_REF / 50% ALL joins
+  ##
+  let $query= SELECT COUNT(*) FROM t1 AS x;
+  let $i= 1;
+  while ($i < 60)
+  {
+    let $query= $query JOIN t$i ON t$i.I = x.I;
+    inc $i;
+    let $query= $query JOIN t$i ON t$i.K = x.I;
+    inc $i;
+    let $query= $query JOIN t$i ON t$i.I = x.I;
+    inc $i;
+    let $query= $query JOIN t$i ON t$i.K = x.I;
+    inc $i;
+
+    eval EXPLAIN $query;
+  }
+
+  ## A mix of 75% EQ_REF / 25% ALL joins
+  ##
+  let $query= SELECT COUNT(*) FROM t1 AS x;
+  let $i= 1;
+  while ($i < 60)
+  {
+    let $query= $query JOIN t$i ON t$i.I = x.I;
+    inc $i;
+    let $query= $query JOIN t$i ON t$i.K = x.I;
+    inc $i;
+    let $query= $query JOIN t$i ON t$i.K = x.I;
+    inc $i;
+    let $query= $query JOIN t$i ON t$i.K = x.I;
+    inc $i;
+
+    eval EXPLAIN $query;
+  }
+
+  ## 100% EQ_REF joins
+  ##
+  let $query= SELECT COUNT(*) FROM t1 AS x;
+  let $i= 1;
+  while ($i < 61)
+  {
+    let $query= $query JOIN t$i ON t$i.K=x.I;
+    inc $i;
+
+    eval EXPLAIN $query;
+  }
+}
+
+let $drop = DROP TABLE t100;
+let $i= 1;
+while ($i < 62)
+{
+  let $drop = $drop, t$i;
+  inc $i;
+}
+eval $drop;
+
+--enable_result_log
+
+show status like "optimizer%";
+SET OPTIMIZER_SEARCH_DEPTH = DEFAULT;
+
+--echo #
+--echo # Bug found when testing greedy optimizer tests
+--echo #
+
+CREATE TABLE t1 (pk INTEGER,
+ col_int_key INTEGER,
+ col_varchar_key VARCHAR(8),
+ PRIMARY KEY (pk),
+ KEY (col_varchar_key, col_int_key, pk));
+
+INSERT INTO t1 values (1,1,"A"),(2,2,"B");
+explain SELECT * FROM t1 AS alias1
+WHERE alias1.col_varchar_key IN (SELECT COUNT(*) FROM t1 AS SQ3_alias2 JOIN t1 AS SQ3_alias3 ON (SQ3_alias3.col_varchar_key = SQ3_alias2.col_varchar_key AND SQ3_alias3.pk = SQ3_alias2.pk));
+drop table t1;
+
+--echo #
+--echo # This triggered an assert failure while testing
+--echo #
+
+CREATE TABLE t1 (a int, b int, key(b));
+INSERT INTO t1 VALUES (7,4),(1,1);
+CREATE TABLE t2 (d int);
+INSERT INTO t2 VALUES (2),(3);
+CREATE TABLE t3 (c int);
+INSERT INTO t3 VALUES (5),(6);
+SELECT * FROM t1 WHERE 5 IN (SELECT t1_a.a FROM t1 as t1_a WHERE 1 IN (SELECT t1_b.a FROM t1 as t1_b LEFT JOIN (t2 JOIN t3) ON (t1_b.a = t2.d) WHERE t1_b.b < 1));
+drop table t1,t2,t3;
+
+--echo End of 10.0 tests