MDEV-41606 Support line comments in optimizer hints

mysql-test/main/opt_hints_comments.result

@@ -0,0 +1,115 @@
+# MDEV-41606 Comments in new-style optimizer hints
+CREATE TABLE t1 (a INT, KEY(a));
+CREATE TABLE t2 (a INT, b INT);
+INSERT INTO t1 VALUES (1),(2),(3);
+INSERT INTO t2 VALUES (1,10),(2,20),(3,30);
+# Comments before, between and after hints; commented hints are ignored
+EXPLAIN EXTENDED
+SELECT /*+
+-- NO_INDEX(t1)
+QB_NAME(qb)-- name the query block
+-- INDEX(t1 a)
+NO_INDEX(t1) -- do not use the index
+*/ a FROM t1 WHERE a= 2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
+Warnings:
+Note	1003	select /*+ QB_NAME(`qb`) NO_INDEX(`t1`@`qb`) */ `test`.`t1`.`a` AS `a` from `test`.`t1` where `test`.`t1`.`a` = 2
+# Comments inside hint arguments
+EXPLAIN EXTENDED
+SELECT /*+ QB_NAME(-- query block name
+qb) NO_INDEX(-- table name
+t1@qb -- index name
+a) */ a FROM t1 WHERE a= 2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
+Warnings:
+Note	1003	select /*+ QB_NAME(`qb`) NO_INDEX(`t1`@`qb` `a`) */ `test`.`t1`.`a` AS `a` from `test`.`t1` where `test`.`t1`.`a` = 2
+# Query block paths and join order from the report
+EXPLAIN EXTENDED
+SELECT /*+
+QB_NAME(child_select, derived1.derived2) -- name the nested block
+-- JOIN_ORDER(@child_select t1, t2)
+JOIN_ORDER(@child_select t2, t1) -- reverse the join order
+*/ * FROM
+(SELECT * FROM
+(SELECT t1.a, t2.b FROM t1, t2 WHERE t1.a= t2.a LIMIT 10)
+AS derived2)
+AS derived1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	PRIMARY	<derived3>	ALL	NULL	NULL	NULL	NULL	3	100.00	
+3	DERIVED	t2	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
+3	DERIVED	t1	ref	a	a	5	test.t2.a	1	100.00	Using index
+Warnings:
+Note	1003	/* select#1 */ select /*+ JOIN_ORDER(@`child_select` `t2`,`t1`) */ `derived2`.`a` AS `a`,`derived2`.`b` AS `b` from (/* select#3 */ select /*+ QB_NAME(`child_select`) */ `test`.`t1`.`a` AS `a`,`test`.`t2`.`b` AS `b` from `test`.`t1` join `test`.`t2` where `test`.`t1`.`a` = `test`.`t2`.`a` limit 10) `derived2`
+# A quoted identifier can contain a comment marker
+EXPLAIN EXTENDED
+SELECT /*+ QB_NAME(`-- qb`) NO_INDEX(t1@`-- qb`) */ a
+FROM t1 WHERE a= 2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
+Warnings:
+Note	1003	select /*+ QB_NAME(`-- qb`) NO_INDEX(`t1`@`-- qb`) */ `test`.`t1`.`a` AS `a` from `test`.`t1` where `test`.`t1`.`a` = 2
+EXPLAIN EXTENDED
+SELECT /*+ QB_NAME("-- qb") NO_INDEX(t1@"-- qb") */ a
+FROM t1 WHERE a= 2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
+Warnings:
+Note	1003	select /*+ QB_NAME(`-- qb`) NO_INDEX(`t1`@`-- qb`) */ `test`.`t1`.`a` AS `a` from `test`.`t1` where `test`.`t1`.`a` = 2
+# A line comment can run up to the end of the hint
+EXPLAIN EXTENDED
+SELECT /*+ NO_INDEX(t1) -- INDEX(t1 a) */ a FROM t1 WHERE a= 2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
+Warnings:
+Note	1003	select /*+ NO_INDEX(`t1`@`select#1`) */ `test`.`t1`.`a` AS `a` from `test`.`t1` where `test`.`t1`.`a` = 2
+# Comment-only hints retain the existing empty-hint warning
+SELECT /*+ */ 1;
+1
+1
+Warnings:
+Warning	1064	Optimizer hint syntax error near '*/ 1' at line 1
+SELECT /*+ -- QB_NAME(ignored) */ 1;
+1
+1
+Warnings:
+Warning	1064	Optimizer hint syntax error near '*/ 1' at line 1
+SELECT /*+ --*/ 1;
+1
+1
+Warnings:
+Warning	1064	Optimizer hint syntax error near '*/ 1' at line 1
+# Tabs after the marker and CRLF line endings
+SET @stmt= CONCAT('EXPLAIN EXTENDED SELECT /*+ --', CHAR(9), 'ignored',
+CHAR(13), CHAR(10),
+'NO_INDEX(t1) */ a FROM t1 WHERE a= 2');
+PREPARE stmt FROM @stmt;
+EXECUTE stmt;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
+Warnings:
+Note	1003	select /*+ NO_INDEX(`t1`@`select#1`) */ `test`.`t1`.`a` AS `a` from `test`.`t1` where `test`.`t1`.`a` = 2
+DEALLOCATE PREPARE stmt;
+# Whitespace is required after the two dashes
+SELECT /*+ --not_a_comment */ 1;
+1
+1
+Warnings:
+Warning	1064	Optimizer hint syntax error near '--not_a_comment */ 1' at line 1
+SELECT /*+ - */ 1;
+1
+1
+Warnings:
+Warning	1064	Optimizer hint syntax error near '- */ 1' at line 1
+# Syntax errors after a comment retain their line number
+SELECT /*+
+-- ignored text
+NOT_A_HINT()
+*/ 1;
+1
+1
+Warnings:
+Warning	1064	Optimizer hint syntax error near 'NOT_A_HINT()
+*/ 1' at line 3
+DROP TABLE t1, t2;

mysql-test/main/opt_hints_comments.test

@@ -0,0 +1,76 @@
+--echo # MDEV-41606 Comments in new-style optimizer hints
+--enable_prepare_warnings
+
+CREATE TABLE t1 (a INT, KEY(a));
+CREATE TABLE t2 (a INT, b INT);
+INSERT INTO t1 VALUES (1),(2),(3);
+INSERT INTO t2 VALUES (1,10),(2,20),(3,30);
+
+--echo # Comments before, between and after hints; commented hints are ignored
+EXPLAIN EXTENDED
+SELECT /*+
+  -- NO_INDEX(t1)
+  QB_NAME(qb)-- name the query block
+  -- INDEX(t1 a)
+  NO_INDEX(t1) -- do not use the index
+*/ a FROM t1 WHERE a= 2;
+
+--echo # Comments inside hint arguments
+EXPLAIN EXTENDED
+SELECT /*+ QB_NAME(-- query block name
+  qb) NO_INDEX(-- table name
+  t1@qb -- index name
+  a) */ a FROM t1 WHERE a= 2;
+
+--echo # Query block paths and join order from the report
+EXPLAIN EXTENDED
+SELECT /*+
+  QB_NAME(child_select, derived1.derived2) -- name the nested block
+  -- JOIN_ORDER(@child_select t1, t2)
+  JOIN_ORDER(@child_select t2, t1) -- reverse the join order
+*/ * FROM
+  (SELECT * FROM
+    (SELECT t1.a, t2.b FROM t1, t2 WHERE t1.a= t2.a LIMIT 10)
+    AS derived2)
+  AS derived1;
+
+--echo # A quoted identifier can contain a comment marker
+EXPLAIN EXTENDED
+SELECT /*+ QB_NAME(`-- qb`) NO_INDEX(t1@`-- qb`) */ a
+FROM t1 WHERE a= 2;
+EXPLAIN EXTENDED
+SELECT /*+ QB_NAME("-- qb") NO_INDEX(t1@"-- qb") */ a
+FROM t1 WHERE a= 2;
+
+--echo # A line comment can run up to the end of the hint
+EXPLAIN EXTENDED
+SELECT /*+ NO_INDEX(t1) -- INDEX(t1 a) */ a FROM t1 WHERE a= 2;
+
+--echo # Comment-only hints retain the existing empty-hint warning
+SELECT /*+ */ 1;
+SELECT /*+ -- QB_NAME(ignored) */ 1;
+SELECT /*+ --*/ 1;
+
+--echo # Tabs after the marker and CRLF line endings
+SET @stmt= CONCAT('EXPLAIN EXTENDED SELECT /*+ --', CHAR(9), 'ignored',
+                  CHAR(13), CHAR(10),
+                  'NO_INDEX(t1) */ a FROM t1 WHERE a= 2');
+PREPARE stmt FROM @stmt;
+EXECUTE stmt;
+DEALLOCATE PREPARE stmt;
+
+--echo # Whitespace is required after the two dashes
+--disable_ps_protocol
+--disable_view_protocol
+SELECT /*+ --not_a_comment */ 1;
+SELECT /*+ - */ 1;
+
+--echo # Syntax errors after a comment retain their line number
+SELECT /*+
+  -- ignored text
+  NOT_A_HINT()
+*/ 1;
+--enable_ps_protocol
+--enable_view_protocol
+
+DROP TABLE t1, t2;

sql/opt_hints_parser.cc

@@ -224,7 +224,18 @@ Optimizer_hint_tokenizer::find_keyword(const LEX_CSTRING &str)
 Optimizer_hint_tokenizer::Token
 Optimizer_hint_tokenizer::get_token(CHARSET_INFO *cs)
 {
-  get_spaces();
+  for ( ; ; )
+  {
+    get_spaces();
+    if (m_end - m_ptr < 2 || m_ptr[0] != '-' || m_ptr[1] != '-')
+      break;
+    // Match the SQL lexer's whitespace requirement after --.
+    if (m_end - m_ptr > 2 &&
+        !my_isspace(cs, m_ptr[2]) && !my_iscntrl(cs, m_ptr[2]))
+      break;
+    for (m_ptr+= 2; !eof() && *m_ptr != '\n'; m_ptr++)
+    { }
+  }
   if (eof())
     return Token(Lex_cstring(m_ptr, m_ptr), TokenID::tEOF);
   const char head= m_ptr[0];