MDEV-27753 Incorrect ENGINE type of table after crash for CONNECT table

whenever possible, partitioning should use the full
partition plugin name, not the one byte legacy code.

Normally, ha_partition can get the engine plugin from
table_share->default_part_plugin.

But in some cases, e.g. in DROP TABLE, the table isn't
opened, table_share is NULL, and ha_partition has to parse
the frm, much like dd_frm_type() does.

temporary_tables.cc, sql_table.cc:

When dropping a table, it must be deleted in the engine
first, then frm file. Because frm can be the only true
source of metadata that the engine might need for DROP.

table.cc:

when opening a partitioned table, if the engine for
partitions is not found, do not fallback to MyISAM.

1 files changed, 15 insertions, 0 deletions

diff --git a/sql/unireg.h b/sql/unireg.h
index e9c62334e86..03d63d0fd06 100644
--- a/sql/unireg.h
+++ b/sql/unireg.h
@@ -188,6 +188,21 @@ enum extra2_field_flags {
   VERS_OPTIMIZED_UPDATE= 1 << INVISIBLE_MAX_BITS
 };
 
+static inline size_t extra2_read_len(const uchar **extra2, const uchar *end)
+{
+  size_t length= *(*extra2)++;
+  if (length)
+    return length;
+
+  if ((*extra2) + 2 >= end)
+    return 0;
+  length= uint2korr(*extra2);
+  (*extra2)+= 2;
+  if (length < 256 || *extra2 + length > end)
+    return 0;
+  return length;
+}
+
 int rea_create_table(THD *thd, LEX_CUSTRING *frm,
                      const char *path, const char *db, const char *table_name,
                      HA_CREATE_INFO *create_info, handler *file,