MDEV-35856: implement index hints

Part of an umbrella task MDEV-33281 for implementing optimizer hints.

This commit introduces hints affecting the use of indexes:
  - JOIN_INDEX, NO_JOIN_INDEX
  - GROUP_INDEX, NO_GROUP_INDEX
  - ORDER_INDEX, NO_ORDER_INDEX
  - INDEX, NO_INDEX

Syntax of index hints:
  hint_name([@query_block_name] tbl_name [index_name [, index_name] ...])
  hint_name(tbl_name@query_block_name [index_name [, index_name] ...])

JOIN_INDEX, NO_JOIN_INDEX: Forces the server to use or ignore the specified
index or indexes for any access method, such as ref, range, index_merge,
and so on. Equivalent to FORCE INDEX FOR JOIN, IGNORE INDEX FOR JOIN.

GROUP_INDEX, NO_GROUP_INDEX: Enable or disable the specified index or indexes
for index scans for GROUP BY operations. Equivalent to the index hints
FORCE INDEX FOR GROUP BY, IGNORE INDEX FOR GROUP BY.

ORDER_INDEX, NO_ORDER_INDEX: Causes the server to use or to ignore
the specified index or indexes for sorting rows. Equivalent to
FORCE INDEX FOR ORDER BY, IGNORE INDEX FOR ORDER BY.

INDEX, NO_INDEX: Acts as the combination of JOIN_INDEX, GROUP_INDEX
and ORDER_INDEX, forcing the server to use the specified index or indexes
for any and all scopes, or as the combination of NO_JOIN_INDEX, NO_GROUP_INDEX
and NO_ORDER_INDEX, which causes the server to ignore the specified index
or indexes for any and all scopes. Equivalent to FORCE INDEX, IGNORE INDEX.

Two kinds of index hints were introduced during implementation:
the global kind for [NO_]INDEX hint, and the non-global kind for all others.

Possible conflicts which will generate warnings:
- for a table level hint
  - a hint of the same type or the opposite kind has already been specified
    for the same table
- for a index level hint
  - the same type of hint has already been specified for the same
    table or for the same index, OR
  - the opposite kind of hint has already been specified for the
    same index
- For a multi index hint like JOIN_INDEX(t1 i1, i2, i3), it conflicts
    with a previous hint if any of the JOIN_INDEX(t1 i1), JOIN_INDEX(t1 i2),
    JOIN_INDEX(t1 i3) conflicts with a previous hint

Author: Olernov

mysql-test/main/opt_hints.result

@@ -21,7 +21,7 @@ a
 1
 2
 Warnings:
-Warning	4219	Hint NO_MRR(`t1` `idx_A`) is ignored as conflicting/duplicated
+Warning	4239	Hint NO_MRR(`t1` `idx_A`) is ignored as conflicting/duplicated (an index hint of the same type has already been specified for this key)
 Warning	4222	Unresolved index name `t1`@`select#1` `idx_å` for NO_MRR hint
 DROP TABLE t1;
 # Testing that query block names are accent sensitive case insensitive
@@ -885,7 +885,7 @@ Warning	4219	Hint BKA(`t1`@`q1`) is ignored as conflicting/duplicated
 SELECT /*+ QB_NAME(q1) NO_ICP(@q1 t1 PRIMARY) NO_ICP(@q1 t1 PRIMARY) */ * FROM t1;
 i
 Warnings:
-Warning	4219	Hint NO_ICP(`t1`@`q1` `PRIMARY`) is ignored as conflicting/duplicated
+Warning	4239	Hint NO_ICP(`t1`@`q1` `PRIMARY`) is ignored as conflicting/duplicated (an index hint of the same type has already been specified for this key)
 DROP TABLE t1;
 #
 # Hints inside views are not supported

mysql-test/main/opt_hints_index.result

@@ -0,0 +1,114 @@
+--enable_prepare_warnings
+--disable_view_protocol # Since optimizer hints are not supported inside views
+
+CREATE TABLE t1 (a INT, b INT, c INT, d INT,
+                 KEY i_a(a), KEY i_b(b),
+                 KEY i_ab(a,b), KEY i_c(c), KEY i_d(d));
+INSERT INTO t1 VALUES
+(1,1,1,1),(2,2,2,1),(3,3,3,1),(4,4,4,1),
+(5,5,5,1),(6,6,6,1),(7,7,7,1),(8,8,8,1);
+INSERT INTO t1 SELECT a,b, c + 10, d FROM t1;
+INSERT INTO t1 SELECT a,b, c + 20, d FROM t1;
+INSERT INTO t1 SELECT a,b, c + 40, d FROM t1;
+INSERT INTO t1 SELECT a,b, c + 80, d FROM t1;
+INSERT INTO t1 SELECT a,b, c + 160, d FROM t1;
+ANALYZE TABLE t1;
+
+--echo # Check behavior of duplicated/intersected hints.
+--echo # First specified hint is applied and next conflicting/intersected hints
+--echo # are ignored with warning.
+
+--echo # JOIN_INDEX(t1) is ignored as intersected (INDEX/other hint for the same table)
+EXPLAIN EXTENDED SELECT /*+ INDEX(t1) JOIN_INDEX(t1) */ a FROM t1;
+--echo # INDEX(t1 i_d) is ignored as duplicated (same type of hint for the same table)
+EXPLAIN EXTENDED SELECT /*+ INDEX(t1 i_a, i_b, i_c) NO_INDEX(t1 i_d) */ a FROM t1;
+--echo # JOIN_INDEX(t1 i_a, i_b) is ignored as intersected (INDEX/other hint for the same table)
+EXPLAIN EXTENDED SELECT /*+ INDEX(t1 i_a) JOIN_INDEX(t1 i_a, i_b) JOIN_INDEX(t1 i_b) */ a FROM t1;
+--echo # GROUP_INDEX(t1 i_a, i_b) is ignored as intersected (INDEX/other hint for the same table)
+EXPLAIN EXTENDED SELECT /*+ INDEX(t1 i_a) GROUP_INDEX(t1 i_a, i_b) GROUP_INDEX(t1 i_b) */ a FROM t1;
+--echo # GROUP_INDEX(t1) is ignored as intersected (INDEX/other hint for the same table)
+EXPLAIN EXTENDED SELECT /*+ INDEX(t1 i_a) GROUP_INDEX(t1) */ a FROM t1;
+--echo # ORDER_INDEX(t1 i_a, i_b) is ignored as intersected (INDEX/other hint for the same key)
+EXPLAIN EXTENDED SELECT /*+ INDEX(t1 i_a) ORDER_INDEX(t1 i_a, i_b) ORDER_INDEX(t1 i_b) */ a FROM t1;
+--echo # INDEX(t1 i_b,i_a) is ignored as intersected (INDEX/other hint for the same key)
+EXPLAIN EXTENDED SELECT /*+ ORDER_INDEX(t1 i_a) INDEX(t1 i_b,i_a)*/ a FROM t1;
+--echo # ORDER_INDEX(t1) is ignored as intersected (INDEX/other hint for the same table)
+EXPLAIN EXTENDED SELECT /*+ INDEX(t1 i_a) ORDER_INDEX(t1) */ a FROM t1;
+--echo # ORDER_INDEX(t1 i_b) is ignored as intersected (same hint/INDEX for the same table)
+EXPLAIN EXTENDED SELECT /*+  ORDER_INDEX(t1 i_a, i_b) NO_ORDER_INDEX(t1 i_b) INDEX(t1 i_c)*/ a FROM t1;
+--echo # INDEX(t1) is ignored as intersected (INDEX/other hint for the same table)
+EXPLAIN EXTENDED SELECT /*+  ORDER_INDEX(t1 i_a, i_b) GROUP_INDEX(t1 i_b) INDEX(t1)*/ a FROM t1;
+--echo # INDEX(t1) is ignored as intersected (INDEX/other hint for the same table)
+EXPLAIN EXTENDED SELECT /*+  ORDER_INDEX(t1) GROUP_INDEX(t1) INDEX(t1)*/ a FROM t1;
+--echo # Check the use of index hints.
+--echo # Force the use of i_a, i_b indexes, intersect(i_a,i_b) is used.
+EXPLAIN EXTENDED SELECT /*+ INDEX(t1 i_a, i_b) */ a FROM t1 WHERE a = 1 AND b = 2 AND c = 3;
+--echo # Force the use of i_a, i_ab indexes, i_ab index is used.
+EXPLAIN EXTENDED SELECT /*+ INDEX(t1 i_a, i_ab) */ a FROM t1 WHERE a = 1 AND b = 2 AND c = 3;
+--echo # Force the use of i_a, i_b, i_c indexes, i_c index is used.
+EXPLAIN EXTENDED SELECT /*+ INDEX(t1 i_a, i_b) JOIN_INDEX(t1 i_c) */ * FROM t1 WHERE a = 1 AND b = 2 AND c = 3;
+
+--echo # Test range index access
+EXPLAIN EXTENDED SELECT a FROM t1 WHERE a > 1 AND a < 3;
+--echo # Indexes are forbidden, full scan is employed
+EXPLAIN EXTENDED SELECT /*+ NO_INDEX(t1)*/a FROM t1 WHERE a > 1 AND a < 3;
+EXPLAIN EXTENDED SELECT /*+ NO_JOIN_INDEX(t1)*/a FROM t1 WHERE a > 1 AND a < 3;
+--echo # Indexes are forbidden for grouping and ordering but are usable for data access
+EXPLAIN EXTENDED SELECT /*+ NO_GROUP_INDEX(t1) NO_ORDER_INDEX(t1)*/a FROM t1 WHERE a > 1 AND a < 3;
+--echo # Index "i_a" is forbidden, "i_ab" is used instead
+EXPLAIN EXTENDED SELECT /*+ NO_INDEX(t1 i_a)*/a FROM t1 WHERE a > 1 AND a < 3;
+
+--echo # Usable indexes are forbidden, full scan is employed
+EXPLAIN EXTENDED SELECT /*+ NO_INDEX(t1 i_a, i_ab)*/a FROM t1 WHERE a > 1 AND a < 3;
+
+EXPLAIN EXTENDED SELECT /*+ INDEX(t1 i_ab)*/a FROM t1 WHERE a > 1 AND a < 3;
+
+--echo # Full scan is more efficient for this query, so indexes are not used by default:
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE a < 8;
+--echo # Force using of any index:
+EXPLAIN EXTENDED SELECT /*+ index(t1)*/* FROM t1 WHERE a < 8;
+--echo # Force using of a particular index:
+EXPLAIN EXTENDED SELECT /*+ index(t1 i_a)*/* FROM t1 WHERE a < 8;
+
+--echo # Ignore i_ab index, i_b index is used.
+EXPLAIN EXTENDED SELECT /*+ NO_INDEX(t1 i_ab) */ a, max(b) FROM t1 WHERE b = 2 GROUP BY a;
+--echo # Ignore i_ab index, i_b index is used.
+EXPLAIN EXTENDED SELECT /*+ NO_JOIN_INDEX(t1 i_ab) */ a, max(b) FROM t1 WHERE b = 2 GROUP BY a;
+--echo # Force i_ab index for GROUP BY, i_ab index scan is used.
+EXPLAIN EXTENDED SELECT /*+ GROUP_INDEX(t1 i_ab) */ a, max(b) FROM t1 GROUP BY a;
+--echo # Force i_ab index for JOIN, i_ab loose index scan is used.
+EXPLAIN EXTENDED SELECT /*+ JOIN_INDEX(t1 i_ab) */ a, max(b) FROM t1 GROUP BY a;
+--echo # Ignore i_ab for sorting rows. i_a index is used for sorting.
+EXPLAIN EXTENDED SELECT /*+ NO_ORDER_INDEX(t1 i_ab) */ a FROM t1 ORDER BY a;
+--echo # Ignore i_a for sorting rows. i_ab is used for sorting.
+EXPLAIN EXTENDED SELECT /*+ NO_ORDER_INDEX(t1 i_a) */ a FROM t1 ORDER BY a;
+--echo # Force i_ab index for sorting rows.
+EXPLAIN EXTENDED SELECT /*+ ORDER_INDEX(t1 i_ab) */ a FROM t1 ORDER BY a;
+--echo # Force i_a index for sorting rows.
+EXPLAIN EXTENDED SELECT /*+ ORDER_INDEX(t1 i_a) */ a FROM t1 ORDER BY a;
+--echo # Ignore all indexes.
+EXPLAIN EXTENDED SELECT /*+ NO_INDEX(t1) */ * FROM t1 WHERE a = 1 AND b = 2 AND c = 3;
+--echo # Check if old-style hints work if no new hints are specified.
+EXPLAIN EXTENDED SELECT /*+ NO_MRR(t1) */ * FROM t1 IGNORE INDEX (i_a)
+WHERE a = 1 AND b = 2 AND c = 3;
+
+--echo # Check that old-style hint is silently ignored if a new hint is specified.
+EXPLAIN EXTENDED SELECT /*+ INDEX(t1 i_a) */ * FROM t1 IGNORE INDEX(i_a)
+WHERE a = 1 AND b = 2 AND c = 3;
+
+--echo # No conflicts between different hints for same indexes
+EXPLAIN EXTENDED
+SELECT /*+ MRR(t1 i_a, i_b, i_ab) NO_ICP(t1 i_a, i_b, i_ab) JOIN_INDEX(t1 i_a, i_b) ORDER_INDEX(t1 i_a, i_ab) */
+  a FROM t1;
+
+--echo # Check index hints with UPDATE/DELETE commands.
+--echo # By default, "i_ab" index is used
+EXPLAIN EXTENDED UPDATE t1 SET d = 1 WHERE a = 1 AND b = 2 AND c = 3;
+--echo # Force i_a index to be used.
+EXPLAIN EXTENDED UPDATE /*+ INDEX(t1 i_a) */ t1 SET d = 1 WHERE a = 1 AND b = 2 AND c = 3;
+--echo # By default, "i_ab" index is used
+EXPLAIN EXTENDED DELETE FROM t1 WHERE a = 1 AND b = 2 AND c = 3;
+--echo # Forbid i_ab index for DELETE.
+EXPLAIN EXTENDED DELETE /*+ NO_INDEX(t1 i_ab) */ FROM t1 WHERE a = 1 AND b = 2 AND c = 3;
+
+DROP TABLE t1;

mysql-test/main/opt_hints_index.test

@@ -17,6 +17,7 @@
 #ifndef MEM_ROOT_ARRAY_INCLUDED
 #define MEM_ROOT_ARRAY_INCLUDED
 
+#include <type_traits>
 #include <my_alloc.h>
 
 /**
@@ -44,7 +45,9 @@
           compilers we use.
 */
 
-template<typename Element_type, bool has_trivial_destructor>
+template<typename Element_type,
+         bool has_trivial_destructor=
+                     std::is_trivially_destructible<Element_type>::value>
 class Mem_root_array
 {
 public:
@@ -263,5 +266,4 @@ class Mem_root_array
   }
 };
 
-
 #endif  // MEM_ROOT_ARRAY_INCLUDED