MDEV-30325 Wrong result upon range query using index condition wrong result...

MDEV-30325 Wrong result upon range query using index condition wrong result upon range query using index condition

This was caused by a bug in key_or() when SEL_ARG* key1 has been cloned
and is overlapping with SEL_ARG *key2

Cloning of SEL_ARG's happens only in very special cases, which is why this
bug has remained undetected for years.

It happend in the following query:

SELECT COUNT(*) FROM lineitem force index
(i_l_orderkey_quantity,i_l_shipdate) WHERE
l_shipdate < '1994-01-01' AND l_orderkey < 800 OR
l_quantity > 3 AND l_orderkey NOT IN ( 157, 1444 );

Because there are two different indexes that can be used and the code for
IN causes a 'tree_or', which causes all SEL_ARG's to be cloned.

Other things:
- While checking the code, I found a bug in SEL_ARG::SEL_ARG(SEL_ARG &arg)
 - This was incrementing next_key_part->use_count as part of creating a
   copy of an existing SEL_ARG.
   This is however not enough as the 'reverse operation' when the copy is
   not needed is 'key2_cpy.increment_use_count(-1)', which does something
   completely different.
   Fixed by calling increment_use_count(1) in SEL_ARG::SEL_ARG.

mysql-test/main/range_aria_dbt3.result

+set default_storage_engine=Aria;
+CREATE DATABASE dbt3_s001;
+use dbt3_s001;
+#
+# MDEV-30325 Wrong result upon range query using index condition
+#
+SELECT COUNT(*) FROM lineitem force index (i_l_orderkey_quantity,i_l_shipdate) WHERE l_shipdate < '1994-01-01' AND l_orderkey < 800 OR l_quantity > 3 AND l_orderkey NOT IN ( 157, 1444 );
+COUNT(*)
+5056
+#
+# End of 10.5 tests
+#
+DROP DATABASE dbt3_s001;

mysql-test/main/range_aria_dbt3.test

+#
+# This is generic tests using dbt3_s001 tables
+# This file uses the Aria storage engine
+#
+
+set default_storage_engine=Aria;
+
+CREATE DATABASE dbt3_s001;
+use dbt3_s001;
+--disable_query_log
+--source include/dbt3_s001.inc
+--enable_query_log
+
+--echo #
+--echo # MDEV-30325 Wrong result upon range query using index condition
+--echo #
+
+SELECT COUNT(*) FROM lineitem force index (i_l_orderkey_quantity,i_l_shipdate) WHERE l_shipdate < '1994-01-01' AND l_orderkey < 800 OR l_quantity > 3 AND l_orderkey NOT IN ( 157, 1444 );
+
+--echo #
+--echo # End of 10.5 tests
+--echo #
+
+DROP DATABASE dbt3_s001;

sql/opt_range.cc

@@ -1890,7 +1890,7 @@ SEL_ARG::SEL_ARG(SEL_ARG &arg) :Sql_alloc()
   next= 0;
   if (next_key_part)
   {
-    ++next_key_part->use_count;
+    next_key_part->increment_use_count(1);
     weight += next_key_part->weight;
   }
 }
@@ -10607,8 +10607,7 @@ key_or(RANGE_OPT_PARAM *param, SEL_ARG *key1,SEL_ARG *key2)
             Move on to next range in key2
           */
           key2->increment_use_count(-1); // Free not used tree
-          key2=key2_next;
-          continue;
+          key2= key2_next;
         }
         else
         {
@@ -10622,8 +10621,9 @@ key_or(RANGE_OPT_PARAM *param, SEL_ARG *key1,SEL_ARG *key2)
             tmp:     [---------]
           */
           key2->copy_max_to_min(tmp);
-          continue;
+          key2= key2_next;
         }
+        continue;
       }
 
       /*