Generalize parallel slot result handling.

Instead of having a hard-coded behavior that we ignore missing
tables and report all other errors, let the caller decide what
to do by setting a callback.

Mark Dilger, reviewed and somewhat revised by me. The larger patch
series of which this is a part has also had review from Peter
Geoghegan, Andres Freund, Álvaro Herrera, Michael Paquier, and Amul
Sul, but I don't know whether any of them have reviewed this bit
specifically.

Discussion: http://postgr.es/m/12ED3DA8-25F0-4B68-937D-D907CFBF08E7@enterprisedb.com
Discussion: http://postgr.es/m/5F743835-3399-419C-8324-2D424237E999@enterprisedb.com
Discussion: http://postgr.es/m/70655DF3-33CE-4527-9A4D-DDEB582B6BA0@enterprisedb.com

1 files changed, 29 insertions, 0 deletions

diff --git a/src/include/fe_utils/parallel_slot.h b/src/include/fe_utils/parallel_slot.h
index 99eeb3328d6..8902f8d4f48 100644
--- a/src/include/fe_utils/parallel_slot.h
+++ b/src/include/fe_utils/parallel_slot.h
@@ -15,12 +15,39 @@
 #include "fe_utils/connect_utils.h"
 #include "libpq-fe.h"
 
+typedef bool (*ParallelSlotResultHandler) (PGresult *res, PGconn *conn,
+										   void *context);
+
 typedef struct ParallelSlot
 {
 	PGconn	   *connection;		/* One connection */
 	bool		isFree;			/* Is it known to be idle? */
+
+	/*
+	 * Prior to issuing a command or query on 'connection', a handler callback
+	 * function may optionally be registered to be invoked to process the
+	 * results, and context information may optionally be registered for use
+	 * by the handler.  If unset, these fields should be NULL.
+	 */
+	ParallelSlotResultHandler handler;
+	void	   *handler_context;
 } ParallelSlot;
 
+static inline void
+ParallelSlotSetHandler(ParallelSlot *slot, ParallelSlotResultHandler handler,
+					   void *context)
+{
+	slot->handler = handler;
+	slot->handler_context = context;
+}
+
+static inline void
+ParallelSlotClearHandler(ParallelSlot *slot)
+{
+	slot->handler = NULL;
+	slot->handler_context = NULL;
+}
+
 extern ParallelSlot *ParallelSlotsGetIdle(ParallelSlot *slots, int numslots);
 
 extern ParallelSlot *ParallelSlotsSetup(const ConnParams *cparams,
@@ -31,5 +58,7 @@ extern void ParallelSlotsTerminate(ParallelSlot *slots, int numslots);
 
 extern bool ParallelSlotsWaitCompletion(ParallelSlot *slots, int numslots);
 
+extern bool TableCommandResultHandler(PGresult *res, PGconn *conn,
+									  void *context);
 
 #endif							/* PARALLEL_SLOT_H */