MDEV-4778: Incorrect results from Aria/MyISAM SELECT using index with prefix length on TEXT column

Backport the fix olav.sandstaa@sun.com-20101102184747-qfuntqwj021imy9r:
"Fix for Bug#52660 Perf. regr. using ICP for MyISAM on range queries on an index containing TEXT" 
(together with further fixes in that code) into MyISAM and Aria.

mysql-test/include/icp_tests.inc

@@ -892,3 +892,24 @@ insert into t1 values ('',1);
 select 1 from t1 where b <= 1 and a <> '';
 drop table t1;
 
+--echo #
+--echo # MDEV-4778: Incorrect results from Aria/MyISAM SELECT using index with prefix length on TEXT column
+--echo # 
+CREATE TABLE t1 (
+  c1 TEXT       ,
+  c2 VARCHAR(2) ,
+  INDEX idx1 (c2,c1(2)),
+  INDEX idx2 (c2,c1(1))
+);
+
+INSERT INTO t1 (c1,c2) VALUES ('aa','x'), ('a' ,'y');
+ 
+SELECT * FROM t1 IGNORE INDEX(idx1,idx2) WHERE (c1='aa' AND c2='x') OR (c1='a'  AND c2='y');
+
+EXPLAIN
+SELECT * FROM t1 FORCE INDEX(idx1)       WHERE (c1='aa' AND c2='x') OR (c1='a'  AND c2='y');
+SELECT * FROM t1 FORCE INDEX(idx1)       WHERE (c1='aa' AND c2='x') OR (c1='a'  AND c2='y');
+
+SELECT * FROM t1 FORCE INDEX(idx2)       WHERE (c1='aa' AND c2='x') OR (c1='a'  AND c2='y');
+
+DROP TABLE t1;

mysql-test/r/innodb_icp.result

@@ -852,6 +852,33 @@ select 1 from t1 where b <= 1 and a <> '';
 1
 drop table t1;
 #
+# MDEV-4778: Incorrect results from Aria/MyISAM SELECT using index with prefix length on TEXT column
+# 
+CREATE TABLE t1 (
+c1 TEXT       ,
+c2 VARCHAR(2) ,
+INDEX idx1 (c2,c1(2)),
+INDEX idx2 (c2,c1(1))
+);
+INSERT INTO t1 (c1,c2) VALUES ('aa','x'), ('a' ,'y');
+SELECT * FROM t1 IGNORE INDEX(idx1,idx2) WHERE (c1='aa' AND c2='x') OR (c1='a'  AND c2='y');
+c1	c2
+aa	x
+a	y
+EXPLAIN
+SELECT * FROM t1 FORCE INDEX(idx1)       WHERE (c1='aa' AND c2='x') OR (c1='a'  AND c2='y');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	idx1	idx1	10	NULL	2	Using index condition; Using where
+SELECT * FROM t1 FORCE INDEX(idx1)       WHERE (c1='aa' AND c2='x') OR (c1='a'  AND c2='y');
+c1	c2
+aa	x
+a	y
+SELECT * FROM t1 FORCE INDEX(idx2)       WHERE (c1='aa' AND c2='x') OR (c1='a'  AND c2='y');
+c1	c2
+aa	x
+a	y
+DROP TABLE t1;
+#
 # BUG#920132: Assert trx->n_active_thrs == 1 failed at que0que.c line 1050 
 #
 CREATE TABLE t1 ( a INT )

mysql-test/r/mrr_icp_extra.result

@@ -105,7 +105,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	FieldKey	FieldKey	38	NULL	4	Using index condition; Rowid-ordered scan; Using filesort
 EXPLAIN SELECT * FROM t1 IGNORE INDEX (FieldKey, LongField) WHERE FieldKey > '2' ORDER BY LongVal;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	range	StringField	StringField	38	NULL	4	Using index condition; Using filesort
+1	SIMPLE	t1	range	StringField	StringField	38	NULL	4	Using where; Using filesort
 SELECT * FROM t1 WHERE FieldKey > '2' ORDER BY LongVal;
 FieldKey	LongVal	StringVal
 3	1	2

mysql-test/r/myisam_icp.result

@@ -211,7 +211,7 @@ c-1006=w
 EXPLAIN
 SELECT c1 FROM t3 WHERE c1 >= 'c-1004=w' and c1 <= 'c-1006=w' and i1 > 2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t3	range	c1	c1	12	NULL	2	Using index condition; Using where
+1	SIMPLE	t3	range	c1	c1	12	NULL	2	Using where
 SELECT c1 FROM t3 WHERE c1 >= 'c-1004=w' and c1 <= 'c-1006=w' and i1 > 2;
 c1
 EXPLAIN
@@ -855,6 +855,33 @@ insert into t1 values ('',1);
 select 1 from t1 where b <= 1 and a <> '';
 1
 drop table t1;
+#
+# MDEV-4778: Incorrect results from Aria/MyISAM SELECT using index with prefix length on TEXT column
+# 
+CREATE TABLE t1 (
+c1 TEXT       ,
+c2 VARCHAR(2) ,
+INDEX idx1 (c2,c1(2)),
+INDEX idx2 (c2,c1(1))
+);
+INSERT INTO t1 (c1,c2) VALUES ('aa','x'), ('a' ,'y');
+SELECT * FROM t1 IGNORE INDEX(idx1,idx2) WHERE (c1='aa' AND c2='x') OR (c1='a'  AND c2='y');
+c1	c2
+aa	x
+a	y
+EXPLAIN
+SELECT * FROM t1 FORCE INDEX(idx1)       WHERE (c1='aa' AND c2='x') OR (c1='a'  AND c2='y');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	idx1	idx1	10	NULL	2	Using where
+SELECT * FROM t1 FORCE INDEX(idx1)       WHERE (c1='aa' AND c2='x') OR (c1='a'  AND c2='y');
+c1	c2
+aa	x
+a	y
+SELECT * FROM t1 FORCE INDEX(idx2)       WHERE (c1='aa' AND c2='x') OR (c1='a'  AND c2='y');
+c1	c2
+aa	x
+a	y
+DROP TABLE t1;
 drop table if exists t0, t1, t1i, t1m;
 #
 # BUG#826935 Assertion `!table || (!table->read_set || bitmap_is_set(table->read_set, field_index))' failed

mysql-test/r/null_key.result

@@ -78,13 +78,13 @@ insert into t2 select * from t1;
 alter table t1 modify b blob not null, add c int not null, drop key a, add unique key (a,b(20),c), drop key b, add key (b(10));
 explain select * from t1 where a is null and b = 2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	a,b	a	5	const	3	Using index condition; Using where
+1	SIMPLE	t1	ref	a,b	a	5	const	3	Using where
 explain select * from t1 where a is null and b = 2 and c=0;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	a,b	a	5	const	3	Using index condition; Using where
+1	SIMPLE	t1	ref	a,b	a	5	const	3	Using where
 explain select * from t1 where a is null and b = 7 and c=0;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	a,b	a	5	const	3	Using index condition; Using where
+1	SIMPLE	t1	ref	a,b	a	5	const	3	Using where
 explain select * from t1 where a=2 and b = 2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ref	a,b	a	5	const	1	Using where
@@ -93,25 +93,25 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	12	Using where
 explain select * from t1 where (a is null or a > 0 and a < 3) and b < 5 and c=0 limit 3;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	range	a,b	a	5	NULL	5	Using index condition; Using where
+1	SIMPLE	t1	range	a,b	a	5	NULL	5	Using where
 explain select * from t1 where (a is null or a = 7) and b=7 and c=0;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref_or_null	a,b	a	5	const	4	Using index condition; Using where
+1	SIMPLE	t1	ref_or_null	a,b	a	5	const	4	Using where
 explain select * from t1 where (a is null and b>a) or a is null and b=7 limit 2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	a,b	a	5	const	3	Using index condition; Using where
+1	SIMPLE	t1	ref	a,b	a	5	const	3	Using where
 explain select * from t1 where a is null and b=9 or a is null and b=7 limit 3;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	a,b	a	5	const	3	Using index condition; Using where
+1	SIMPLE	t1	ref	a,b	a	5	const	3	Using where
 explain select * from t1 where a > 1 and a < 3 limit 1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	range	a	a	5	NULL	1	Using index condition
+1	SIMPLE	t1	range	a	a	5	NULL	1	Using where
 explain select * from t1 where a is null and b=7 or a > 1 and a < 3 limit 1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	range	a,b	a	5	NULL	4	Using index condition; Using where
+1	SIMPLE	t1	range	a,b	a	5	NULL	4	Using where
 explain select * from t1 where a > 8 and a < 9;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	range	a	a	5	NULL	1	Using index condition
+1	SIMPLE	t1	range	a	a	5	NULL	1	Using where
 explain select * from t1 where b like "6%";
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	b	b	12	NULL	1	Using where

mysql-test/r/order_by.result

@@ -618,7 +618,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	FieldKey	FieldKey	38	NULL	4	Using index condition; Using filesort
 EXPLAIN SELECT * FROM t1 IGNORE INDEX (FieldKey, LongField) WHERE FieldKey > '2' ORDER BY LongVal;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	range	StringField	StringField	38	NULL	4	Using index condition; Using filesort
+1	SIMPLE	t1	range	StringField	StringField	38	NULL	4	Using where; Using filesort
 SELECT * FROM t1 WHERE FieldKey > '2' ORDER BY LongVal;
 FieldKey	LongVal	StringVal
 3	1	2

mysql-test/suite/maria/icp.result

@@ -213,7 +213,7 @@ c-1006=w
 EXPLAIN
 SELECT c1 FROM t3 WHERE c1 >= 'c-1004=w' and c1 <= 'c-1006=w' and i1 > 2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t3	range	c1	c1	12	NULL	2	Using index condition; Using where
+1	SIMPLE	t3	range	c1	c1	12	NULL	2	Using where
 SELECT c1 FROM t3 WHERE c1 >= 'c-1004=w' and c1 <= 'c-1006=w' and i1 > 2;
 c1
 EXPLAIN
@@ -857,5 +857,32 @@ insert into t1 values ('',1);
 select 1 from t1 where b <= 1 and a <> '';
 1
 drop table t1;
+#
+# MDEV-4778: Incorrect results from Aria/MyISAM SELECT using index with prefix length on TEXT column
+# 
+CREATE TABLE t1 (
+c1 TEXT       ,
+c2 VARCHAR(2) ,
+INDEX idx1 (c2,c1(2)),
+INDEX idx2 (c2,c1(1))
+);
+INSERT INTO t1 (c1,c2) VALUES ('aa','x'), ('a' ,'y');
+SELECT * FROM t1 IGNORE INDEX(idx1,idx2) WHERE (c1='aa' AND c2='x') OR (c1='a'  AND c2='y');
+c1	c2
+aa	x
+a	y
+EXPLAIN
+SELECT * FROM t1 FORCE INDEX(idx1)       WHERE (c1='aa' AND c2='x') OR (c1='a'  AND c2='y');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	idx1	idx1	10	NULL	2	Using where
+SELECT * FROM t1 FORCE INDEX(idx1)       WHERE (c1='aa' AND c2='x') OR (c1='a'  AND c2='y');
+c1	c2
+aa	x
+a	y
+SELECT * FROM t1 FORCE INDEX(idx2)       WHERE (c1='aa' AND c2='x') OR (c1='a'  AND c2='y');
+c1	c2
+aa	x
+a	y
+DROP TABLE t1;
 set storage_engine= @save_storage_engine;
 set optimizer_switch=@maria_icp_tmp;

sql/handler.h

@@ -2637,7 +2637,33 @@ class handler :public Sql_alloc
    Pops the top if condition stack, if stack is not empty.
  */
  virtual void cond_pop() { return; };
+
+ /**
+   Push down an index condition to the handler.
+
+   The server will use this method to push down a condition it wants
+   the handler to evaluate when retrieving records using a specified
+   index. The pushed index condition will only refer to fields from
+   this handler that is contained in the index (but it may also refer
+   to fields in other handlers). Before the handler evaluates the
+   condition it must read the content of the index entry into the 
+   record buffer.
+
+   The handler is free to decide if and how much of the condition it
+   will take responsibility for evaluating. Based on this evaluation
+   it should return the part of the condition it will not evaluate.
+   If it decides to evaluate the entire condition it should return
+   NULL. If it decides not to evaluate any part of the condition it
+   should return a pointer to the same condition as given as argument.
+
+   @param keyno    the index number to evaluate the condition on
+   @param idx_cond the condition to be evaluated by the handler
+
+   @return The part of the pushed condition that the handler decides
+           not to evaluate
+ */
  virtual Item *idx_cond_push(uint keyno, Item* idx_cond) { return idx_cond; }
+
  /** Reset information about pushed index conditions */
  virtual void cancel_pushed_idx_cond()
  {

storage/maria/ha_maria.cc

@@ -3802,6 +3802,25 @@ int ha_maria::multi_range_read_explain_info(uint mrr_mode, char *str,
 
 Item *ha_maria::idx_cond_push(uint keyno_arg, Item* idx_cond_arg)
 {
+  /*
+    Check if the key contains a blob field. If it does then MyISAM
+    should not accept the pushed index condition since MyISAM will not
+    read the blob field from the index entry during evaluation of the
+    pushed index condition and the BLOB field might be part of the
+    range evaluation done by the ICP code.
+  */
+  const KEY *key= &table_share->key_info[keyno_arg];
+
+  for (uint k= 0; k < key->key_parts; ++k)
+  {
+    const KEY_PART_INFO *key_part= &key->key_part[k];
+    if (key_part->key_part_flag & HA_BLOB_PART)
+    {
+      /* Let the server handle the index condition */
+      return idx_cond_arg;
+    }
+  }
+
   pushed_idx_cond_keyno= keyno_arg;
   pushed_idx_cond= idx_cond_arg;
   in_range_check_pushed_down= TRUE;

storage/myisam/ha_myisam.cc

@@ -2274,6 +2274,25 @@ int ha_myisam::multi_range_read_explain_info(uint mrr_mode, char *str,
 
 Item *ha_myisam::idx_cond_push(uint keyno_arg, Item* idx_cond_arg)
 {
+  /*
+    Check if the key contains a blob field. If it does then MyISAM
+    should not accept the pushed index condition since MyISAM will not
+    read the blob field from the index entry during evaluation of the
+    pushed index condition and the BLOB field might be part of the
+    range evaluation done by the ICP code.
+  */
+  const KEY *key= &table_share->key_info[keyno_arg];
+
+  for (uint k= 0; k < key->key_parts; ++k)
+  {
+    const KEY_PART_INFO *key_part= &key->key_part[k];
+    if (key_part->key_part_flag & HA_BLOB_PART)
+    {
+      /* Let the server handle the index condition */
+      return idx_cond_arg;
+    }
+  }
+
   pushed_idx_cond_keyno= keyno_arg;
   pushed_idx_cond= idx_cond_arg;
   in_range_check_pushed_down= TRUE;