Bug#30822: ALTER TABLE COALESCE PARTITION causes segmentation fault

Problem was for LINEAR HASH/KEY. Crashes because of wrong partition id
returned when creating the new altered partitions. (because of wrong
linear hash mask)

Solution: Update the linear hash mask before using it for the new
altered table.

mysql-test/r/partition_hash.result

 drop table if exists t1;
+CREATE TABLE t1 (c1 INT)
+PARTITION BY HASH (c1)
+PARTITIONS 15;
+INSERT INTO t1 VALUES (1), (2), (3), (4), (5);
+ALTER TABLE t1 COALESCE PARTITION 13;
+DROP TABLE t1;
+CREATE TABLE t1 (c1 INT)
+PARTITION BY LINEAR HASH (c1)
+PARTITIONS 5;
+INSERT INTO t1 VALUES (1), (2), (3), (4), (5);
+ALTER TABLE t1 COALESCE PARTITION 3;
+DROP TABLE t1;
 create table t1 (a int unsigned)
 partition by hash(a div 2)
 partitions 4;

mysql-test/t/partition_hash.test

@@ -9,6 +9,22 @@
 drop table if exists t1;
 --enable_warnings
 
+#
+# Bug#30822: crash when COALESCE
+#
+CREATE TABLE t1 (c1 INT)
+  PARTITION BY HASH (c1)
+  PARTITIONS 15;
+INSERT INTO t1 VALUES (1), (2), (3), (4), (5);
+ALTER TABLE t1 COALESCE PARTITION 13;
+DROP TABLE t1;
+CREATE TABLE t1 (c1 INT)
+  PARTITION BY LINEAR HASH (c1)
+  PARTITIONS 5;
+INSERT INTO t1 VALUES (1), (2), (3), (4), (5);
+ALTER TABLE t1 COALESCE PARTITION 3;
+DROP TABLE t1;
+
 #
 # More partition pruning tests, especially on interval walking
 #

sql/ha_partition.cc

@@ -1531,6 +1531,14 @@ int ha_partition::copy_partitions(ulonglong *copied, ulonglong *deleted)
   longlong func_value;
   DBUG_ENTER("ha_partition::copy_partitions");
 
+  if (m_part_info->linear_hash_ind)
+  {
+    if (m_part_info->part_type == HASH_PARTITION)
+      set_linear_hash_mask(m_part_info, m_part_info->no_parts);
+    else
+      set_linear_hash_mask(m_part_info, m_part_info->no_subparts);
+  }
+
   while (reorg_part < m_reorged_parts)
   {
     handler *file= m_reorged_file[reorg_part];

sql/sql_partition.cc

@@ -1402,7 +1402,7 @@ static void set_up_partition_func_pointers(partition_info *part_info)
     NONE
 */
 
-static void set_linear_hash_mask(partition_info *part_info, uint no_parts)
+void set_linear_hash_mask(partition_info *part_info, uint no_parts)
 {
   uint mask;
 

sql/sql_partition.h

@@ -65,6 +65,7 @@ int get_part_for_delete(const uchar *buf, const uchar *rec0,
 void prune_partition_set(const TABLE *table, part_id_range *part_spec);
 bool check_partition_info(partition_info *part_info,handlerton **eng_type,
                           TABLE *table, handler *file, HA_CREATE_INFO *info);
+void set_linear_hash_mask(partition_info *part_info, uint no_parts);
 bool fix_partition_func(THD *thd, TABLE *table, bool create_table_ind);
 char *generate_partition_syntax(partition_info *part_info,
                                 uint *buf_length, bool use_sql_alloc,