MDEV-16711 Crash in Field_blob::store() while reading statistics

          for the small InnoDB table

This bug was introduced by the patch 6c414fcf89510215d6d3466eb9992d444eadae89.
The patch has not taken into account that some objects of the Field_* types
are created only for TABLE_SHARE and the field 'table' is set to NULL
for them. In particular such are objects created to store statistical
min/max values for columns.

1 files changed, 7 insertions, 1 deletions

diff --git a/sql/field.cc b/sql/field.cc
index 64c51677c0f..71fc5684d92 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -7942,7 +7942,13 @@ int Field_blob::store(const char *from,uint length,CHARSET_INFO *cs)
     return 0;
   }
 
-  if (table->blob_storage)    // GROUP_CONCAT with ORDER BY | DISTINCT
+  /*
+    For min/max fields of statistical data 'table' is set to NULL.
+    It could not be otherwise as this data is shared by many instances
+    of the same base table.
+  */
+
+  if (table && table->blob_storage)    // GROUP_CONCAT with ORDER BY | DISTINCT
   {
     DBUG_ASSERT(!f_is_hex_escape(flags));
     DBUG_ASSERT(field_charset == cs);