MDEV-20494 ER_NOT_FORM_FILE or assertion upon adding partition to period table

- Fixed mysql_prepare_create_table() constraint duplicate checking;
- Refactored period constraint handling in mysql_prepare_alter_table():
  * No need to allocate new objects;
  * Keep old constraint name but exclude it from dup checking by automatic_name;
- Some minor memory leaks fixed;
- Some conceptual TODOs.

1 files changed, 17 insertions, 0 deletions

diff --git a/sql/field.cc b/sql/field.cc
index ace70c178bc..a9bd97d9844 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -11387,3 +11387,20 @@ void Field::print_key_value_binary(String *out, const uchar* key, uint32 length)
 {
   out->append_semi_hex((const char*)key, length, charset());
 }
+
+
+Virtual_column_info* Virtual_column_info::clone(THD *thd)
+{
+  Virtual_column_info* dst= new (thd->mem_root) Virtual_column_info(*this);
+  if (!dst)
+    return NULL;
+  if (expr)
+  {
+    dst->expr= expr->get_copy(thd);
+    if (!dst->expr)
+      return NULL;
+  }
+  if (!thd->make_lex_string(&dst->name, name.str, name.length))
+    return NULL;
+  return dst;
+};