* New index_merge EXPLAIN output format

 * Fixed a problem with wrong query results for partially covering keys in ROR-index_merge
 * ROR-intersection retrieval plan choice algorithm now uses less disk IO
   - and properly processes clustered PK range scans 
 * Fixed several minor range optimizer problems
 * Added more comments
 * Code cleanup

mysql-test/r/index_merge_innodb.result

@@ -8,7 +8,7 @@ INDEX i2(key2),
 ) engine=innodb;
 explain select * from t1 where key1 < 5 or key2 > 197;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	index_merge	i1,i2	i1,i2	4,4	NULL	8	Using where
+1	SIMPLE	t1	index_merge	i1,i2	i1,i2	4,4	NULL	8	Using sort_union(i1,i2); Using where
 select * from t1 where key1 < 5 or key2 > 197;
 key1	key2
 0	200
@@ -18,7 +18,7 @@ key1	key2
 4	196
 explain select * from t1 where key1 < 3 or key2 > 195;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	index_merge	i1,i2	i1,i2	4,4	NULL	8	Using where
+1	SIMPLE	t1	index_merge	i1,i2	i1,i2	4,4	NULL	8	Using sort_union(i1,i2); Using where
 select * from t1 where key1 < 3 or key2 > 195;
 key1	key2
 0	200
@@ -34,7 +34,7 @@ update t1 set str1='aaa', str2='bbb', str3=concat(key2, '-', key1 div 2, '_' ,if
 alter table t1 add primary key (str1, zeroval, str2, str3);
 explain select * from t1 where key1 < 5 or key2 > 197;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	index_merge	i1,i2	i1,i2	4,4	NULL	8	Using where
+1	SIMPLE	t1	index_merge	i1,i2	i1,i2	4,4	NULL	8	Using sort_union(i1,i2); Using where
 select * from t1 where key1 < 5 or key2 > 197;
 key1	key2	str1	zeroval	str2	str3
 4	196	aaa	0	bbb	196-2_a
@@ -44,7 +44,7 @@ key1	key2	str1	zeroval	str2	str3
 0	200	aaa	0	bbb	200-0_a
 explain select * from t1 where key1 < 3 or key2 > 195;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	index_merge	i1,i2	i1,i2	4,4	NULL	8	Using where
+1	SIMPLE	t1	index_merge	i1,i2	i1,i2	4,4	NULL	8	Using sort_union(i1,i2); Using where
 select * from t1 where key1 < 3 or key2 > 195;
 key1	key2	str1	zeroval	str2	str3
 4	196	aaa	0	bbb	196-2_a

mysql-test/r/index_merge_ror_cpk.result

@@ -41,7 +41,7 @@ pk1	pk2	key1	key2	pktail1ok	pktail2ok	pktail3bad	pktail4bad	pktail5bad	pk2copy	b
 1	19	0	0	0	0	0	0	0	19	0	filler-data-19	filler2
 explain select pk1,pk2 from t1 where key1 = 10 and key2=10 and 2*pk1+1 < 2*96+1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	index_merge	key1,key2	key1,key2	4,4	NULL	1	Using where; Using index
+1	SIMPLE	t1	index_merge	key1,key2	key1,key2	4,4	NULL	1	Using intersect(key1,key2); Using where; Using index
 select pk1,pk2 from t1 where key1 = 10 and key2=10 and 2*pk1+1 < 2*96+1;
 pk1	pk2
 95	50
@@ -59,13 +59,19 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ref	key1	key1	4	const	101	Using where
 explain select * from t1 where pk1 < 7500 and key1 = 10;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	index_merge	PRIMARY,key1	key1,PRIMARY	4,4	NULL	38	Using where
+1	SIMPLE	t1	index_merge	PRIMARY,key1	key1,PRIMARY	4,4	NULL	38	Using intersect(key1,PRIMARY); Using where
 explain select * from t1 where pktail1ok=1 and key1=10;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	index_merge	key1,pktail1ok	key1,pktail1ok	4,4	NULL	1	Using where
+1	SIMPLE	t1	index_merge	key1,pktail1ok	key1,pktail1ok	4,4	NULL	1	Using intersect(key1,pktail1ok); Using where
 explain select * from t1 where pktail2ok=1 and key1=10;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	index_merge	key1,pktail2ok	key1,pktail2ok	4,4	NULL	1	Using where
+1	SIMPLE	t1	index_merge	key1,pktail2ok	key1,pktail2ok	4,4	NULL	1	Using intersect(key1,pktail2ok); Using where
+select '  The following is actually a deficiency, it uses sort_union currently:' as 'note:';
+note:
+  The following is actually a deficiency, it uses sort_union currently:
+explain select * from t1 where (pktail2ok=1 and pk1< 50000) or key1=10;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index_merge	PRIMARY,key1,pktail2ok	pktail2ok,key1	8,4	NULL	199	Using sort_union(pktail2ok,key1); Using where
 explain select * from t1 where pktail3bad=1 and key1=10;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ref	key1,pktail3bad	pktail3bad	4	const	98	Using where
@@ -77,7 +83,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ref	key1,pktail5bad	pktail5bad	4	const	99	Using where
 explain select pk1,pk2,key1,key2 from t1 where key1 = 10 and key2=10 limit 10;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	index_merge	key1,key2	key1,key2	4,4	NULL	1	Using where; Using index
+1	SIMPLE	t1	index_merge	key1,key2	key1,key2	4,4	NULL	1	Using intersect(key1,key2); Using where; Using index
 select pk1,pk2,key1,key2 from t1 where key1 = 10 and key2=10 limit 10;
 pk1	pk2	key1	key2
 95	50	10	10

mysql-test/t/index_merge_ror.test

@@ -2,7 +2,7 @@
 #  ROR-index_merge tests. 
 #
 --disable_warnings
-drop table if exists  t1,t0;
+drop table if exists  t0,t1,t2;
 --enable_warnings
 --disable_query_log
 create table t1
@@ -213,3 +213,37 @@ explain select st_a from t1
 
 drop table t0,t1;
 
+# 'Partially' covered fields test
+
+create table t2 (
+  a char(10),
+  b char(10),
+  filler1 char(255),
+  filler2 char(255),
+  key(a(5)),
+  key(b(5))
+);
+
+--disable_query_log
+let $1=8;
+while ($1)
+{
+  eval insert into t2 values (repeat(char($1+64), 8),repeat(char($1+64), 8),'filler1', 'filler2');
+  dec $1;
+}
+insert into t2 select * from t2;
+insert into t2 select * from t2;
+--enable_query_log
+
+# The table row buffer is reused. Fill it with rows that don't match.
+select count(a) from t2 where a='BBBBBBBB';
+select count(a) from t2 where b='BBBBBBBB';
+
+# BUG#1: 
+explain select count(a) from t2 where a='AAAAAAAA' and b='AAAAAAAA';
+select count(a) from t2 where a='AAAAAAAA' and b='AAAAAAAA';
+select count(a) from t2 ignore index(a,b) where a='AAAAAAAA' and b='AAAAAAAA';
+
+insert into t2 values ('ab', 'ab', 'uh', 'oh');
+explain select a from t2 where a='ab';
+drop table t2;

mysql-test/t/index_merge_ror_cpk.test

@@ -69,6 +69,9 @@ explain select * from t1 where pk1 < 7500 and key1 = 10;
 explain select * from t1 where pktail1ok=1 and key1=10;
 explain select * from t1 where pktail2ok=1 and key1=10;
 
+select '  The following is actually a deficiency, it uses sort_union currently:' as 'note:';
+explain select * from t1 where (pktail2ok=1 and pk1< 50000) or key1=10;
+
 explain select * from t1 where pktail3bad=1 and key1=10;
 explain select * from t1 where pktail4bad=1 and key1=10;
 explain select * from t1 where pktail5bad=1 and key1=10;

mysys/my_bitmap.c

@@ -29,6 +29,9 @@
     * bitmap_intersect() is an exception :)
       (for for Bitmap::intersect(ulonglong map2buff))
   
+  If THREAD is defined all bitmap operations except bitmap_init/bitmap_free 
+  are thread-safe.
+
   TODO:
   Make assembler THREAD safe versions of these using test-and-set instructions
 */
@@ -332,29 +335,36 @@ void bitmap_union(MY_BITMAP *map, const MY_BITMAP *map2)
 
 
 /*
-  Get number of set bits in the bitmap 
+  SYNOPSIS
+    bitmap_bits_set()
+      map
+  RETURN
+    Number of set bits in the bitmap.
 */
+
 uint bitmap_bits_set(const MY_BITMAP *map)
 {  
-  uchar *m= map->bitmap,
-        *end= map->bitmap+map->bitmap_size;
+  uchar *m= map->bitmap;
+  uchar *end= m + map->bitmap_size;
   uint res= 0;
 
   DBUG_ASSERT(map->bitmap);
-
   bitmap_lock((MY_BITMAP *)map);
   while (m < end)
   {
     res+= my_count_bits_ushort(*m++);
   }
-
   bitmap_unlock((MY_BITMAP *)map);
   return res;
 }
 
 
 /* 
-  Return number of first zero bit or MY_BIT_NONE if all bits are set.
+  SYNOPSIS
+    bitmap_get_first()
+      map
+  RETURN 
+    Number of first unset bit in the bitmap or MY_BIT_NONE if all bits are set.
 */
 
 uint bitmap_get_first(const MY_BITMAP *map)

sql/sql_select.cc

@@ -10077,7 +10077,7 @@ static void select_describe(JOIN *join, bool need_tmp_table, bool need_order,
   select_result *result=join->result;
   Item *item_null= new Item_null();
   CHARSET_INFO *cs= &my_charset_latin1;
-  int quick_type= -1;
+  int quick_type;
   DBUG_ENTER("select_describe");
   DBUG_PRINT("info", ("Select 0x%lx, type %s, message %s",
 		      (ulong)join->select_lex, join->select_lex->type,
@@ -10104,17 +10104,20 @@ static void select_describe(JOIN *join, bool need_tmp_table, bool need_order,
     {
       JOIN_TAB *tab=join->join_tab+i;
       TABLE *table=tab->table;
-      char buff[512],*buff_ptr=buff;
+      char buff[512]; 
       char buff1[512], buff2[512], buff3[512];
       char keylen_str_buf[64];
       char derived_name[64];
+      String extra(buff, sizeof(buff),cs);
       String tmp1(buff1,sizeof(buff1),cs);
       String tmp2(buff2,sizeof(buff2),cs);
       String tmp3(buff3,sizeof(buff3),cs);
+      extra.length(0);
       tmp1.length(0);
       tmp2.length(0);
       tmp3.length(0);
 
+      quick_type= -1;
       item_list.empty();
       item_list.push_back(new Item_int((int32)
 				       join->select_lex->select_number));
@@ -10165,7 +10168,7 @@ static void select_describe(JOIN *join, bool need_tmp_table, bool need_order,
       else
 	item_list.push_back(item_null);
 
-      /* Build key,key_len, and ref values and add them to item_list */
+      /* Build "key", "key_len", and "ref" values and add them to item_list */
       if (tab->ref.key_parts)
       {
 	KEY *key_info=table->key_info+ tab->ref.key;
@@ -10200,7 +10203,7 @@ static void select_describe(JOIN *join, bool need_tmp_table, bool need_order,
       }
       else if (tab->select && tab->select->quick)
       {
-        tab->select->quick->fill_keys_and_lengths(&tmp2, &tmp3);
+        tab->select->quick->add_keys_and_lengths(&tmp2, &tmp3);
 	item_list.push_back(new Item_string(tmp2.ptr(),tmp2.length(),cs));
 	item_list.push_back(new Item_string(tmp3.ptr(),tmp3.length(),cs));
 	item_list.push_back(item_null);
@@ -10211,9 +10214,11 @@ static void select_describe(JOIN *join, bool need_tmp_table, bool need_order,
 	item_list.push_back(item_null);
 	item_list.push_back(item_null);
       }
+      /* Add "rows" field to item_list. */
       item_list.push_back(new Item_int((longlong) (ulonglong)
 				       join->best_positions[i]. records_read,
 				       21));
+      /* Build "Extra" field and add it to item_list. */
       my_bool key_read=table->key_read;
       if (tab->type == JT_NEXT && table->used_keys.is_set(tab->index))
 	key_read=1;
@@ -10225,38 +10230,51 @@ static void select_describe(JOIN *join, bool need_tmp_table, bool need_order,
 	item_list.push_back(new Item_string(tab->info,strlen(tab->info),cs));
       else
       {
+        if (quick_type == QUICK_SELECT_I::QS_TYPE_ROR_UNION || 
+            quick_type == QUICK_SELECT_I::QS_TYPE_ROR_INTERSECT ||
+            quick_type == QUICK_SELECT_I::QS_TYPE_INDEX_MERGE)
+        {
+          extra.append("; Using ");
+          tab->select->quick->add_info_string(&extra);
+        }
 	if (tab->select)
 	{
 	  if (tab->use_quick == 2)
 	  {
             char buf[MAX_KEY/8+1];
-	    sprintf(buff_ptr,"; Range checked for each record (index map: 0x%s)",
-                tab->keys.print(buf));
-	    buff_ptr=strend(buff_ptr);
+            extra.append("; Range checked for each record (index map: 0x");
+            extra.append(tab->keys.print(buf));
+            extra.append(')');
 	  }
 	  else
-	    buff_ptr=strmov(buff_ptr,"; Using where");
+            extra.append("; Using where");
 	}
 	if (key_read)
-	  buff_ptr= strmov(buff_ptr,"; Using index");
+	  extra.append("; Using index");
 	if (table->reginfo.not_exists_optimize)
-	  buff_ptr= strmov(buff_ptr,"; Not exists");
+	  extra.append("; Not exists");
 	if (need_tmp_table)
 	{
 	  need_tmp_table=0;
-	  buff_ptr= strmov(buff_ptr,"; Using temporary");
+	  extra.append("; Using temporary");
 	}
 	if (need_order)
 	{
 	  need_order=0;
-	  buff_ptr= strmov(buff_ptr,"; Using filesort");
+	  extra.append("; Using filesort");
 	}
 	if (distinct & test_all_bits(used_tables,thd->used_tables))
-	  buff_ptr= strmov(buff_ptr,"; Distinct");
-	if (buff_ptr == buff)
-	  buff_ptr+= 2;				// Skip inital "; "
-	item_list.push_back(new Item_string(buff+2,(uint) (buff_ptr - buff)-2,
-					    cs));
+	  extra.append("; Distinct");
+        
+        /* Skip initial "; "*/
+        const char *str= extra.ptr();
+        uint32 len= extra.length();
+        if (len)
+        {
+          str += 2;
+          len -= 2;
+        }
+	item_list.push_back(new Item_string(str, len, cs));
       }
       // For next iteration
       used_tables|=table->map;