MDEV-19751 Wrong partitioning by KEY() after primary key dropped

Default (empty) field list in partitioning by KEY() clause is assigned
from primary key. If primary key is changed the partitioning field
list is changed as well, so repartitioning required. Not applicable to
any non-primary keys as default field list may be taken only from
primary key.

1 files changed, 22 insertions, 0 deletions

diff --git a/sql/sql_partition.cc b/sql/sql_partition.cc
index 071c9c05129..2334286b039 100644
--- a/sql/sql_partition.cc
+++ b/sql/sql_partition.cc
@@ -5473,6 +5473,28 @@ the generated partition syntax in a correct manner.
           *partition_changed= TRUE;
         }
       }
+      /*
+        Prohibit inplace when partitioned by primary key and the primary key is dropped.
+      */
+      if (!*partition_changed &&
+          tab_part_info->part_field_array &&
+          !tab_part_info->part_field_list.elements &&
+          table->s->primary_key != MAX_KEY)
+      {
+        KEY *primary_key= table->key_info + table->s->primary_key;
+        List_iterator_fast<Alter_drop> drop_it(alter_info->drop_list);
+        const char *primary_name= primary_key->name;
+        const Alter_drop *drop;
+        drop_it.rewind();
+        while ((drop= drop_it++))
+        {
+          if (drop->type == Alter_drop::KEY &&
+              0 == my_strcasecmp(system_charset_info, primary_name, drop->name))
+            break;
+        }
+        if (drop)
+          *partition_changed= TRUE;
+      }
     }
     if (thd->work_part_info)
     {