Fix sys.dm_exec_sessions having rows for backends which are already t…

…erminated (babelfish-for-postgresql#3329)

We initialize and keep a local status array which has the entries
for all TDS connections but we did not reset these entries during
connection abort or shmem exit of the backend, which means
future read of this local status array will see these entries as valid.

As a fix, mark the status entry as invalid during proc/shmem exit

Task: [BABEL-5414]

Signed-off-by: Tanzeel Khan [email protected]

contrib/babelfishpg_tds/src/backend/tds/tds.c

@@ -143,7 +143,7 @@ typedef struct LocalTdsStatus
 } LocalTdsStatus;
 
 static TdsStatus *TdsStatusArray = NULL;
-static TdsStatus *MyTdsStatusEntry;
+static TdsStatus *MyTdsStatusEntry = NULL;
 static LocalTdsStatus *localTdsStatusTable = NULL;
 
 uint32_t	MyTdsClientVersion = 0;
@@ -434,9 +434,17 @@ tds_stats_shmem_shutdown(int code, Datum arg)
 		return;
 
 	/* Safety check ... shouldn't get here unless shmem is set up. */
-	if (TdsStatusArray == NULL)
+	if (TdsStatusArray == NULL || MyTdsStatusEntry == NULL)
 		return;
 
+	PGSTAT_BEGIN_WRITE_ACTIVITY(MyTdsStatusEntry);
+
+	MyTdsStatusEntry->st_procpid = 0;	/* mark invalid */
+
+	PGSTAT_END_WRITE_ACTIVITY(MyTdsStatusEntry);
+
+	MyTdsStatusEntry = NULL;
+
 	return;
 }