MDEV-35616: Add basic optimizer support for virtual column

(Review input addressed)

After this patch, the optimizer can handle virtual column expressions
in WHERE/ON clauses. If the table has an indexed virtual column:

  ALTER TABLE t1
    ADD COLUMN vcol INT AS (col1+1),
    ADD INDEX idx1(vcol);

and the query uses the exact virtual column expression:

  SELECT * FROM t1 WHERE col1+1 <= 100

then the optimizer will be able use index idx1 for it.

This is achieved by walking the WHERE/ON clauses and replacing instances
of virtual column expression (like "col1+1" above) with virtual column's
Item_field (like "vcol"). The latter can be processed by the optimizer.

Replacement is considered (and done) only in items that are potentially
usable to the range optimizer.

Author: spetrunia

libmysqld/CMakeLists.txt

@@ -75,6 +75,7 @@ SET(SQL_EMBEDDED_SOURCES emb_qcache.cc libmysqld.c lib_sql.cc
            ../sql/opt_rewrite_remove_casefold.cc
            ../sql/opt_sargable_left.cc
            ../sql/opt_sum.cc
+           ../sql/opt_vcol_substitution.cc
            ../sql/parse_file.cc ../sql/procedure.cc ../sql/protocol.cc 
            ../sql/records.cc ../sql/repl_failsafe.cc ../sql/rpl_filter.cc
            ../sql/rpl_record.cc ../sql/des_key_file.cc

mysql-test/suite/gcol/r/gcol_keys_innodb.result

@@ -354,28 +354,28 @@ f1	gc
 9	10
 EXPLAIN SELECT * FROM t1 WHERE f1 + 1 > 7;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	10	Using where
+1	SIMPLE	t1	range	gc	gc	5	NULL	3	Using index condition
 SELECT * FROM t1 WHERE f1 + 1 = 7;
 f1	gc
 6	7
 EXPLAIN SELECT * FROM t1 WHERE f1 + 1 = 7;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	10	Using where
+1	SIMPLE	t1	const	gc	gc	5	const	1	
 SELECT * FROM t1 WHERE f1 + 1 IN (7,5);
 f1	gc
 4	5
 6	7
 EXPLAIN SELECT * FROM t1 WHERE f1 + 1 IN(7,5);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	10	Using where
+1	SIMPLE	t1	range	gc	gc	5	NULL	2	Using index condition
 SELECT * FROM t1 WHERE f1 + 1 BETWEEN 5 AND 7;
 f1	gc
 4	5
 5	6
 6	7
 EXPLAIN SELECT * FROM t1 WHERE f1 + 1 BETWEEN 5 AND 7;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	10	Using where
+1	SIMPLE	t1	range	gc	gc	5	NULL	3	Using index condition
 # Check that expression isn't transformed for a disabled key
 SELECT * FROM t1 IGNORE KEY (gc) WHERE f1 + 1 BETWEEN 5 AND 7;
 f1	gc
@@ -432,7 +432,7 @@ f1	gc
 9	10
 EXPLAIN SELECT * FROM t1 WHERE f1 + 1 > 7.0;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	10	Using where
+1	SIMPLE	t1	range	gc	gc	5	NULL	3	Using index condition
 DROP TABLE t1;
 # Pick index with proper type
 CREATE TABLE t1 (f1 int,
@@ -463,7 +463,7 @@ f1	gc_int	gc_date
 # INT column & index should be picked
 EXPLAIN SELECT * FROM t1 WHERE f1 + 1 > 070707;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	18	Using where
+1	SIMPLE	t1	range	gc_int_idx	gc_int_idx	5	NULL	4	Using index condition
 SELECT * FROM t1 WHERE f1 + 1 > CAST(070707 AS DATE);
 f1	gc_int	gc_date
 101010	101011	2010-10-11
@@ -473,7 +473,9 @@ f1	gc_int	gc_date
 # DATE column & index should be picked
 EXPLAIN SELECT * FROM t1 WHERE f1 + 1 > CAST(070707 AS DATE);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	18	Using where
+1	SIMPLE	t1	ALL	gc_int_idx	NULL	NULL	NULL	18	Using where
+Warnings:
+Note	1105	Cannot use key `gc_int_idx` part[0] for lookup: `test`.`t1`.`gc_int` of type `int` > "cast(70707 as date)" of type `date`
 DROP TABLE t1;
 #
 # BUG#21229846: WL8170: SIGNAL 11 IN JOIN::MAKE_SUM_FUNC_LIST
@@ -764,14 +766,14 @@ a	b
 1	1
 EXPLAIN SELECT a, b FROM t WHERE (a XOR b) = 1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t	ALL	NULL	NULL	NULL	NULL	4	Using where
+1	SIMPLE	t	ref	gc_xor	gc_xor	5	const	2	
 SELECT a, b FROM t WHERE (a XOR b) = 1;
 a	b
 0	1
 1	0
 EXPLAIN SELECT a FROM t WHERE (NOT a) = 1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t	ALL	NULL	NULL	NULL	NULL	4	Using where
+1	SIMPLE	t	ref	gc_not	gc_not	5	const	2	
 SELECT a FROM t WHERE (NOT a) = 1;
 a
 0

mysql-test/suite/gcol/r/gcol_keys_myisam.result

@@ -354,28 +354,28 @@ f1	gc
 9	10
 EXPLAIN SELECT * FROM t1 WHERE f1 + 1 > 7;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	10	Using where
+1	SIMPLE	t1	range	gc	gc	5	NULL	3	Using index condition
 SELECT * FROM t1 WHERE f1 + 1 = 7;
 f1	gc
 6	7
 EXPLAIN SELECT * FROM t1 WHERE f1 + 1 = 7;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	10	Using where
+1	SIMPLE	t1	const	gc	gc	5	const	1	
 SELECT * FROM t1 WHERE f1 + 1 IN (7,5);
 f1	gc
 4	5
 6	7
 EXPLAIN SELECT * FROM t1 WHERE f1 + 1 IN(7,5);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	10	Using where
+1	SIMPLE	t1	range	gc	gc	5	NULL	2	Using index condition
 SELECT * FROM t1 WHERE f1 + 1 BETWEEN 5 AND 7;
 f1	gc
 4	5
 5	6
 6	7
 EXPLAIN SELECT * FROM t1 WHERE f1 + 1 BETWEEN 5 AND 7;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	10	Using where
+1	SIMPLE	t1	range	gc	gc	5	NULL	3	Using index condition
 # Check that expression isn't transformed for a disabled key
 SELECT * FROM t1 IGNORE KEY (gc) WHERE f1 + 1 BETWEEN 5 AND 7;
 f1	gc
@@ -432,7 +432,7 @@ f1	gc
 9	10
 EXPLAIN SELECT * FROM t1 WHERE f1 + 1 > 7.0;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	10	Using where
+1	SIMPLE	t1	range	gc	gc	5	NULL	3	Using index condition
 DROP TABLE t1;
 # Pick index with proper type
 CREATE TABLE t1 (f1 int,
@@ -463,7 +463,7 @@ f1	gc_int	gc_date
 # INT column & index should be picked
 EXPLAIN SELECT * FROM t1 WHERE f1 + 1 > 070707;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	18	Using where
+1	SIMPLE	t1	range	gc_int_idx	gc_int_idx	5	NULL	4	Using index condition
 SELECT * FROM t1 WHERE f1 + 1 > CAST(070707 AS DATE);
 f1	gc_int	gc_date
 101010	101011	2010-10-11
@@ -473,7 +473,9 @@ f1	gc_int	gc_date
 # DATE column & index should be picked
 EXPLAIN SELECT * FROM t1 WHERE f1 + 1 > CAST(070707 AS DATE);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	18	Using where
+1	SIMPLE	t1	ALL	gc_int_idx	NULL	NULL	NULL	18	Using where
+Warnings:
+Note	1105	Cannot use key `gc_int_idx` part[0] for lookup: `test`.`t1`.`gc_int` of type `int` > "cast(70707 as date)" of type `date`
 DROP TABLE t1;
 #
 # BUG#21229846: WL8170: SIGNAL 11 IN JOIN::MAKE_SUM_FUNC_LIST
@@ -764,14 +766,14 @@ a	b
 1	1
 EXPLAIN SELECT a, b FROM t WHERE (a XOR b) = 1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t	ALL	NULL	NULL	NULL	NULL	4	Using where
+1	SIMPLE	t	ref	gc_xor	gc_xor	5	const	2	
 SELECT a, b FROM t WHERE (a XOR b) = 1;
 a	b
 0	1
 1	0
 EXPLAIN SELECT a FROM t WHERE (NOT a) = 1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t	ALL	NULL	NULL	NULL	NULL	4	Using where
+1	SIMPLE	t	ref	gc_not	gc_not	5	const	2	
 SELECT a FROM t WHERE (NOT a) = 1;
 a
 0