MDEV-22155 ALTER add default history partitions name clash on non-default partitions

If any of default names clashes with existing names find next large
enough name gap for the requested number of partitions.

mysql-test/suite/versioning/r/partition.result

@@ -1107,3 +1107,45 @@ t1	CREATE TABLE `t1` (
  PARTITION `p2` HISTORY ENGINE = DEFAULT_ENGINE,
  PARTITION `pn` CURRENT ENGINE = DEFAULT_ENGINE)
 drop tables t1;
+#
+# MDEV-22155 ALTER add default history partitions name clash on non-default partitions
+#
+create or replace table t1 (x int) with system versioning
+partition by system_time limit 1
+(partition p2 history, partition p8 history, partition pn current);
+alter table t1 add partition partitions 1;
+alter table t1 add partition partitions 2;
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `x` int(11) DEFAULT NULL
+) ENGINE=DEFAULT_ENGINE DEFAULT CHARSET=latin1 WITH SYSTEM VERSIONING
+ PARTITION BY SYSTEM_TIME LIMIT 1
+(PARTITION `p2` HISTORY ENGINE = DEFAULT_ENGINE,
+ PARTITION `p8` HISTORY ENGINE = DEFAULT_ENGINE,
+ PARTITION `p3` HISTORY ENGINE = DEFAULT_ENGINE,
+ PARTITION `p4` HISTORY ENGINE = DEFAULT_ENGINE,
+ PARTITION `p5` HISTORY ENGINE = DEFAULT_ENGINE,
+ PARTITION `pn` CURRENT ENGINE = DEFAULT_ENGINE)
+alter table t1 add partition partitions 8;
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `x` int(11) DEFAULT NULL
+) ENGINE=DEFAULT_ENGINE DEFAULT CHARSET=latin1 WITH SYSTEM VERSIONING
+ PARTITION BY SYSTEM_TIME LIMIT 1
+(PARTITION `p2` HISTORY ENGINE = DEFAULT_ENGINE,
+ PARTITION `p8` HISTORY ENGINE = DEFAULT_ENGINE,
+ PARTITION `p3` HISTORY ENGINE = DEFAULT_ENGINE,
+ PARTITION `p4` HISTORY ENGINE = DEFAULT_ENGINE,
+ PARTITION `p5` HISTORY ENGINE = DEFAULT_ENGINE,
+ PARTITION `p9` HISTORY ENGINE = DEFAULT_ENGINE,
+ PARTITION `p10` HISTORY ENGINE = DEFAULT_ENGINE,
+ PARTITION `p11` HISTORY ENGINE = DEFAULT_ENGINE,
+ PARTITION `p12` HISTORY ENGINE = DEFAULT_ENGINE,
+ PARTITION `p13` HISTORY ENGINE = DEFAULT_ENGINE,
+ PARTITION `p14` HISTORY ENGINE = DEFAULT_ENGINE,
+ PARTITION `p15` HISTORY ENGINE = DEFAULT_ENGINE,
+ PARTITION `p16` HISTORY ENGINE = DEFAULT_ENGINE,
+ PARTITION `pn` CURRENT ENGINE = DEFAULT_ENGINE)
+drop tables t1;

mysql-test/suite/versioning/t/partition.test

@@ -904,4 +904,20 @@ show create table t1;
 
 drop tables t1;
 
+--echo #
+--echo # MDEV-22155 ALTER add default history partitions name clash on non-default partitions
+--echo #
+create or replace table t1 (x int) with system versioning
+partition by system_time limit 1
+(partition p2 history, partition p8 history, partition pn current);
+alter table t1 add partition partitions 1;
+alter table t1 add partition partitions 2;
+--replace_result $default_engine DEFAULT_ENGINE
+show create table t1;
+alter table t1 add partition partitions 8;
+--replace_result $default_engine DEFAULT_ENGINE
+show create table t1;
+
+drop tables t1;
+
 --source suite/versioning/common_finish.inc

sql/partition_info.cc

@@ -336,7 +336,8 @@ char *partition_info::create_default_partition_names(THD *thd, uint part_no,
   {
     do
     {
-      sprintf(move_ptr, "p%u", (start_no + i));
+      if (make_partition_name(move_ptr, (start_no + i)))
+        DBUG_RETURN(NULL);
       move_ptr+= MAX_PART_NAME_SIZE;
     } while (++i < num_parts_arg);
   }
@@ -401,17 +402,11 @@ bool partition_info::set_up_default_partitions(THD *thd, handler *file,
   uint i;
   char *default_name;
   bool result= TRUE;
-  bool alter= false;
   DBUG_ENTER("partition_info::set_up_default_partitions");
 
   if (part_type == VERSIONING_PARTITION)
   {
-    if (start_no > 0)
-    {
-      start_no--;
-      alter= true;
-    }
-    else if (use_default_num_partitions)
+    if (start_no == 0 && use_default_num_partitions)
       num_parts= 2;
     use_default_num_partitions= false;
   }
@@ -455,7 +450,7 @@ bool partition_info::set_up_default_partitions(THD *thd, handler *file,
       default_name+=MAX_PART_NAME_SIZE;
       if (part_type == VERSIONING_PARTITION)
       {
-        if (alter || i < num_parts - 1) {
+        if (start_no > 0 || i < num_parts - 1) {
           part_elem->type= partition_element::HISTORY;
         } else {
           part_elem->type= partition_element::CURRENT;

sql/partition_info.h

@@ -34,6 +34,9 @@ typedef bool (*check_constants_func)(THD *thd, partition_info *part_info);
  
 struct st_ddl_log_memory_entry;
 
+#define MAX_PART_NAME_SIZE 8
+
+
 struct Vers_part_info : public Sql_alloc
 {
   Vers_part_info() :
@@ -415,6 +418,7 @@ class partition_info : public Sql_alloc
     }
     return NULL;
   }
+  uint next_part_no(uint new_parts) const;
 };
 
 uint32 get_next_partition_id_range(struct st_partition_iter* part_iter);
@@ -500,4 +504,46 @@ void partition_info::vers_update_el_ids()
   }
 }
 
+
+inline
+bool make_partition_name(char *move_ptr, uint i)
+{
+  int res= snprintf(move_ptr, MAX_PART_NAME_SIZE + 1, "p%u", i);
+  return res < 0 || res > MAX_PART_NAME_SIZE;
+}
+
+
+inline
+uint partition_info::next_part_no(uint new_parts) const
+{
+  if (part_type != VERSIONING_PARTITION)
+    return num_parts;
+  DBUG_ASSERT(new_parts > 0);
+  /* Choose first non-occupied name suffix */
+  uint32 suffix= num_parts - 1;
+  DBUG_ASSERT(suffix > 0);
+  char part_name[MAX_PART_NAME_SIZE + 1];
+  List_iterator_fast<partition_element> it(table->part_info->partitions);
+  for (uint cur_part= 0; cur_part < new_parts; ++cur_part, ++suffix)
+  {
+    uint32 cur_suffix= suffix;
+    if (make_partition_name(part_name, suffix))
+      return 0;
+    partition_element *el;
+    it.rewind();
+    while ((el= it++))
+    {
+      if (0 == my_strcasecmp(&my_charset_latin1, el->partition_name, part_name))
+      {
+        if (make_partition_name(part_name, ++suffix))
+          return 0;
+        it.rewind();
+      }
+    }
+    if (cur_part > 0 && suffix > cur_suffix)
+      cur_part= 0;
+  }
+  return suffix - new_parts;
+}
+
 #endif /* PARTITION_INFO_INCLUDED */

sql/sql_partition.cc

@@ -5135,7 +5135,7 @@ uint prep_alter_part_table(THD *thd, TABLE *table, Alter_info *alter_info,
       alt_part_info->part_type= tab_part_info->part_type;
       alt_part_info->subpart_type= tab_part_info->subpart_type;
       if (alt_part_info->set_up_defaults_for_partitioning(thd, table->file, 0,
-                                                    tab_part_info->num_parts))
+                              tab_part_info->next_part_no(num_new_partitions)))
       {
         goto err;
       }