Fix for bug 1974

mysql-test/r/index_merge.result

@@ -270,6 +270,11 @@ explain select * from t0,t1 where t0.key1 = 5 and
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t0	ref	i1	i1	4	const	1	Using where
 1	SIMPLE	t1	index_merge	i1,i8	i1,i8	4,4	NULL	2	Using where
+explain select * from t0,t1 where t0.key1 < 3 and
+(t1.key1 = t0.key1 or t1.key8 = t0.key1);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t0	range	i1	i1	4	NULL	3	Using where
+1	SIMPLE	t1	ALL	i1,i8	NULL	NULL	NULL	1024	Range checked for each record (index map: 0x81)
 explain select * from t1 where key1=3 or key2=4 
 union select * from t1 where key1<4 or key3=5;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

mysql-test/t/index_merge.test

@@ -237,6 +237,10 @@ select * from t0,t1 where (t0.key1=t1.key1) and
 explain select * from t0,t1 where t0.key1 = 5 and 
   (t1.key1 = t0.key1 or t1.key8 = t0.key1);
 
+# Fix for bug#1974
+explain select * from t0,t1 where t0.key1 < 3 and
+  (t1.key1 = t0.key1 or t1.key8 = t0.key1);
+
 #  index_merge inside union
 explain select * from t1 where key1=3 or key2=4 
   union select * from t1 where key1<4 or key3=5;

sql/opt_range.cc

@@ -1018,6 +1018,7 @@ int SQL_SELECT::test_quick_select(THD *thd, key_map keys_to_use,
           List_iterator_fast<SEL_IMERGE> it(tree->merges);
           while ((imerge= it++))
           {
+            bool    imerge_failed= false;
             double  imerge_cost= 0;
             ha_rows imerge_total_records= 0;
             double  tree_read_time;
@@ -1036,21 +1037,23 @@ int SQL_SELECT::test_quick_select(THD *thd, key_map keys_to_use,
                                           &tree_read_time, &tree_records,
                                           &(imerge->best_keys[ptree - 
                                           imerge->trees])))
-                goto imerge_fail;
-
+                imerge_failed= true;
               imerge_cost += tree_read_time;
               imerge_total_records += tree_records;
             }
-            imerge_total_records= min(imerge_total_records, 
-                                      head->file->records);
-            imerge_cost += imerge_total_records / TIME_FOR_COMPARE;
-            if (imerge_cost < min_imerge_cost)
+
+            if (!imerge_failed)
             {
-              min_imerge= imerge;
-              min_imerge_cost= imerge_cost;
-              min_imerge_records= imerge_total_records;
+              imerge_total_records= min(imerge_total_records, 
+                                        head->file->records);
+              imerge_cost += imerge_total_records / TIME_FOR_COMPARE;
+              if (imerge_cost < min_imerge_cost)
+              {
+                min_imerge= imerge;
+                min_imerge_cost= imerge_cost;
+                min_imerge_records= imerge_total_records;
+              }
             }
-imerge_fail:;
           }
           
           if (!min_imerge)