Bug#33691659 - ON DELETE CASCADE with generated column crashes in innobase_get_computed_value

ANALYSIS
========

1. A cascade delete from the parent table triggers delete
   on the child table. Before a clustered index record is
   deleted in the child table, a copy of row is built to
   remove secondary index record, since the secondary index
   is defined on the virtual column it is necessary to
   materialize the virtual columns.
2. We were skipping this materialization which causes it
   to fail on uninitialized template in
   innobase_get_computed_value() when trying to remove
   the secondary index rows defined on virtual column.

FIX
===

1.  We must initialize virtual column template for
    materializing virtual column if child table has
    an index on a virtual column.

Change-Id: Ib2381d81aa96024ed395261650421f6318f380b8

Author: Aditya A

storage/innobase/row/row0ins.cc

@@ -1309,11 +1309,17 @@ row_ins_foreign_check_on_constraint(
 						 clust_index, tmp_heap);
 	}
 
-	if (cascade->is_delete && foreign->v_cols != NULL
-	    && foreign->v_cols->size() > 0
-	    && table->vc_templ == NULL) {
+	/* A cascade delete from the parent table triggers delete on the child
+	table. Before a clustered index record is deleted in the child table,
+	a copy of row is built to remove secondary index records. This copy of
+	the row requires virtual columns to be materialized. Hence, if child
+	table has any virtual columns which are indexed, we have to initialize
+	virtual column template. */
+	if (cascade->is_delete && dict_table_has_indexed_v_cols(table) &&
+		table->vc_templ == NULL) {
 		innobase_init_vc_templ(table);
 	}
+
 	if (node->is_delete
 	    ? (foreign->type & DICT_FOREIGN_ON_DELETE_SET_NULL)
 	    : (foreign->type & DICT_FOREIGN_ON_UPDATE_SET_NULL)) {