use dedicated heap for upd_node_t::historical_row and corresponding stuff to

make its lifetime as short as possible

for historical row ROW_COPY_DATA -> ROW_COPY_POINTER for lower memory
consumption and better performance

storage/innobase/include/row0upd.h

@@ -569,7 +569,11 @@ struct upd_node_t{
 				heap) of the row to update; this must be reset
 				to NULL after a successful update */
 	dtuple_t*	historical_row;	/*!< historical row used in
-				CASCADE UPDATE/SET NULL */
+				CASCADE UPDATE/SET NULL;
+				allocated from historical_heap  */
+	mem_heap_t*	historical_heap; /*!< heap for historical row insertion;
+				created when row to update is located;
+				freed right before row update */
 	row_ext_t*	ext;	/*!< NULL, or prefixes of the externally
 				stored columns in the old row */
 	dtuple_t*	upd_row;/* NULL, or a copy of the updated row */

storage/innobase/row/row0ins.cc

@@ -1395,9 +1395,11 @@ row_ins_foreign_check_on_constraint(
 
 	if (table->versioned() && cascade->is_delete != PLAIN_DELETE
 	    && cascade->update->affects_versioned()) {
-		cascade->historical_row =
-			row_build(ROW_COPY_DATA, clust_index, clust_rec, NULL,
-				  table, NULL, NULL, NULL, thr->prebuilt->heap);
+		ut_ad(!cascade->historical_heap);
+		cascade->historical_heap = mem_heap_create(128);
+		cascade->historical_row = row_build(
+			ROW_COPY_POINTERS, clust_index, clust_rec, NULL, table,
+			NULL, NULL, NULL, cascade->historical_heap);
 	}
 
 	/* Store pcur position and initialize or store the cascade node

storage/innobase/row/row0mysql.cc

@@ -2162,16 +2162,18 @@ static dberr_t row_update_vers_insert(que_thr_t* thr, upd_node_t* node)
 	node->historical_row = NULL;
 
 	ins_node_t* insert_node =
-		ins_node_create(INS_DIRECT, table, thr->prebuilt->heap);
+		ins_node_create(INS_DIRECT, table, node->historical_heap);
 
 	ins_node_set_new_row(insert_node, row);
 
 	dfield_t* row_end = dtuple_get_nth_field(row, table->vers_end);
-	char* where = static_cast<char*>(dfield_get_data(row_end));
+	char where[8];
 	if (dict_table_get_nth_col(table, table->vers_end)->vers_native()) {
 		mach_write_to_8(where, trx->id);
+		dfield_set_data(row_end, where, 8);
 	} else {
 		thd_get_query_start_data(trx->mysql_thd, where);
+		dfield_set_data(row_end, where, 7);
 	}
 
 	for (;;) {
@@ -2193,15 +2195,19 @@ static dberr_t row_update_vers_insert(que_thr_t* thr, upd_node_t* node)
 		default:
 			/* Other errors are handled for the parent node. */
 			thr->fk_cascade_depth = 0;
-			return trx->error_state;
+			goto exit;
 
 		case DB_SUCCESS:
 			srv_stats.n_rows_inserted.inc(
 				static_cast<size_t>(trx->id));
 			dict_stats_update_if_needed(table);
-			return DB_SUCCESS;
+			goto exit;
 		}
 	}
+exit:
+	mem_heap_free(node->historical_heap);
+	node->historical_heap = NULL;
+	return trx->error_state;
 }
 
 /**********************************************************************//**