HAWQ-1855. Fix access to the uninitialized variable database
diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index 12de33a..8df6518 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -2168,7 +2168,26 @@
estate->es_evTupleNull = NULL;
estate->es_evTuple = NULL;
estate->es_useEvalPlan = false;
-
+
+ /*
+ * In QD, we need to initialize the variable database before
+ * ExecInitNode(), that makes us can access the database
+ * correctly in places such as magma_beginscan(),
+ * magma_insertinit().
+ *
+ * In contrast, if we are in QE, we don't need to do this since
+ * RebuildDatabase() ensures that the database is initialized.
+ *
+ * An example of the uninitialized database:
+ * prepare select_by_id(int) as select * from t where id = 1;
+ * execute select_by_id(1); <- uninitialized when we are in
+ * magma_beginscan()
+ */
+ if (Gp_role == GP_ROLE_DISPATCH)
+ {
+ database = get_database_name(MyDatabaseId);
+ }
+
/*
* Initialize the private state information for all the nodes in the query
* tree. This opens files, allocates storage and leaves us ready to start
