Bug #12796: Record lost in HEAP table

Two handler objects were present, one was used for an insert and the other for a select
The state of the statistics was local to the handler object and thus the other handler
object didn't notice the insert.
Fix included:
1) Add a new variable key_stat_version added to whenever statistics was considered in need
of update (previously key_stats_ok= FALSE in those places)
2) Add a new handler variable key_stat_version assigned whenever key_stats_ok= TRUE was set
previously
3) Fix records_in_range to return records if records <= 1
4) Fix records_in_range to add 2 to rec_per_key to ensure we don't specify 0 or 1 when it isn't
and thus invoking incorrect optimisations.
5) Fix unique key handling for HEAP table in records_in_range

7 files changed, 71 insertions, 16 deletions

diff --git a/heap/hp_create.c b/heap/hp_create.c
index 2b811dac89b..acd4447fe5c 100644
--- a/heap/hp_create.c
+++ b/heap/hp_create.c
@@ -104,6 +104,7 @@ int heap_create(const char *name, uint keys, HP_KEYDEF *keydef,
       DBUG_RETURN(1);
     }
     share->keydef= (HP_KEYDEF*) (share + 1);
+    share->key_stat_version= 1;
     keyseg= (HA_KEYSEG*) (share->keydef + keys);
     init_block(&share->block, reclength + 1, min_records, max_records);
 	/* Fix keys */
diff --git a/include/heap.h b/include/heap.h
index badec9ce2ef..cfbb6113f86 100644
--- a/include/heap.h
+++ b/include/heap.h
@@ -136,6 +136,7 @@ typedef struct st_heap_share
   HP_KEYDEF  *keydef;
   ulong min_records,max_records;	/* Params to open */
   ulong data_length,index_length,max_table_size;
+  uint key_stat_version;                /* version to indicate insert/delete */
   uint records;				/* records */
   uint blength;				/* records rounded up to 2^n */
   uint deleted;				/* Deleted records in database */
diff --git a/mysql-test/r/heap.result b/mysql-test/r/heap.result
index 53dec294ef8..e3b9f7db984 100644
--- a/mysql-test/r/heap.result
+++ b/mysql-test/r/heap.result
@@ -182,7 +182,7 @@ SELECT * FROM t1 WHERE a=NULL;
 a	b
 explain SELECT * FROM t1 WHERE a IS NULL;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	a	a	5	const	1	Using where
+1	SIMPLE	t1	ref	a	a	5	const	2	Using where
 SELECT * FROM t1 WHERE a<=>NULL;
 a	b
 NULL	99
@@ -296,3 +296,13 @@ insert into t1 values ("abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcd
 insert into t1 values ("abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz");
 ERROR 23000: Duplicate entry 'abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijkl' for key 1
 drop table t1;
+CREATE TABLE t1 (a int, key(a)) engine=heap;
+insert delayed into t1 values (0);
+delete from t1;
+select * from t1;
+a
+insert delayed into t1 values (0), (1);
+select * from t1 where a = 0;
+a
+0
+drop table t1;
diff --git a/mysql-test/t/heap.test b/mysql-test/t/heap.test
index 270b8a1df6f..a8128b79e3b 100644
--- a/mysql-test/t/heap.test
+++ b/mysql-test/t/heap.test
@@ -234,4 +234,15 @@ insert into t1 values ("abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcd
 insert into t1 values ("abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz");
 drop table t1;
 
+#
+# Bug 12796: Record doesn't show when selecting through index
+#
+CREATE TABLE t1 (a int, key(a)) engine=heap;
+insert delayed into t1 values (0);
+delete from t1;
+select * from t1;
+insert delayed into t1 values (0), (1);
+select * from t1 where a = 0;
+drop table t1;
+
 # End of 4.1 tests
diff --git a/mysql-test/t/test_heap.test b/mysql-test/t/test_heap.test
new file mode 100644
index 00000000000..851c376ba38
--- /dev/null
+++ b/mysql-test/t/test_heap.test
@@ -0,0 +1,20 @@
+#
+# Test of heap tables.
+#
+
+--disable_warnings
+drop table if exists t1;
+--enable_warnings
+
+#
+# Bug 12796: Record doesn't show when selecting through index
+#
+CREATE TABLE t1 (a int, key(a)) engine=heap;
+insert delayed into t1 values (0);
+delete from t1;
+select * from t1;
+insert delayed into t1 values (0), (1);
+select * from t1 where a = 0;
+drop table t1;
+
+# End of 4.1 tests
diff --git a/sql/ha_heap.cc b/sql/ha_heap.cc
index f8c2e6cc338..61e5ce89693 100644
--- a/sql/ha_heap.cc
+++ b/sql/ha_heap.cc
@@ -68,7 +68,7 @@ int ha_heap::open(const char *name, int mode, uint test_if_locked)
       ha_heap::info(), which is always called before key statistics are
       used.
     */
-    key_stats_ok= FALSE;
+    key_stat_version= file->s->key_stat_version-1;
   }
   return (file ? 0 : 1);
 }
@@ -114,14 +114,21 @@ void ha_heap::update_key_stats()
       continue;
     if (key->algorithm != HA_KEY_ALG_BTREE)
     {
-      ha_rows hash_buckets= file->s->keydef[i].hash_buckets;
-      key->rec_per_key[key->key_parts-1]= 
-        hash_buckets ? file->s->records/hash_buckets : 0;
+      if (key->flags & HA_NOSAME)
+        key->rec_per_key[key->key_parts-1]= 1;
+      else
+      {
+        ha_rows hash_buckets= file->s->keydef[i].hash_buckets;
+        uint no_records= hash_buckets ? file->s->records/hash_buckets : 2;
+        if (no_records < 2)
+          no_records= 2;
+        key->rec_per_key[key->key_parts-1]= no_records;
+      }
     }
   }
   records_changed= 0;
   /* At the end of update_key_stats() we can proudly claim they are OK. */
-  key_stats_ok= TRUE;
+  key_stat_version= file->s->key_stat_version;
 }
 
 int ha_heap::write_row(byte * buf)
@@ -135,7 +142,7 @@ int ha_heap::write_row(byte * buf)
   res= heap_write(file,buf);
   if (!res && ++records_changed*HEAP_STATS_UPDATE_THRESHOLD > 
               file->s->records)
-    key_stats_ok= FALSE;
+    file->s->key_stat_version++;
   return res;
 }
 
@@ -148,7 +155,7 @@ int ha_heap::update_row(const byte * old_data, byte * new_data)
   res= heap_update(file,old_data,new_data);
   if (!res && ++records_changed*HEAP_STATS_UPDATE_THRESHOLD > 
               file->s->records)
-    key_stats_ok= FALSE;
+    file->s->key_stat_version++;
   return res;
 }
 
@@ -159,7 +166,7 @@ int ha_heap::delete_row(const byte * buf)
   res= heap_delete(file,buf);
   if (!res && table->tmp_table == NO_TMP_TABLE && 
       ++records_changed*HEAP_STATS_UPDATE_THRESHOLD > file->s->records)
-    key_stats_ok= FALSE;
+    file->s->key_stat_version++;
   return res;
 }
 
@@ -277,7 +284,7 @@ void ha_heap::info(uint flag)
     have to update the key statistics. Hoping that a table lock is now
     in place.
   */
-  if (! key_stats_ok)
+  if (key_stat_version != file->s->key_stat_version)
     update_key_stats();
 }
 
@@ -290,7 +297,7 @@ int ha_heap::delete_all_rows()
 {
   heap_clear(file);
   if (table->tmp_table == NO_TMP_TABLE)
-    key_stats_ok= FALSE;
+    file->s->key_stat_version++;
   return 0;
 }
 
@@ -451,9 +458,14 @@ ha_rows ha_heap::records_in_range(uint inx, key_range *min_key,
     return HA_POS_ERROR;			// Can only use exact keys
   else
   {
-    /* Assert that info() did run. We need current statistics here. */
-    DBUG_ASSERT(key_stats_ok);
-    return key->rec_per_key[key->key_parts-1];
+    if (records <= 1)
+      return records;
+    else
+    {
+      /* Assert that info() did run. We need current statistics here. */
+      DBUG_ASSERT(key_stat_version == file->s->key_stat_version);
+      return key->rec_per_key[key->key_parts-1];
+    }
   }
 }
 
diff --git a/sql/ha_heap.h b/sql/ha_heap.h
index cbe2474492d..0a087fde1b0 100644
--- a/sql/ha_heap.h
+++ b/sql/ha_heap.h
@@ -29,10 +29,10 @@ class ha_heap: public handler
   key_map btree_keys;
   /* number of records changed since last statistics update */
   uint    records_changed;
-  bool    key_stats_ok;
+  uint    key_stat_version;
 public:
   ha_heap(TABLE *table): handler(table), file(0), records_changed(0),
-      key_stats_ok(0) {}
+      key_stat_version(0) {}
   ~ha_heap() {}
   const char *table_type() const { return "HEAP"; }
   const char *index_type(uint inx)