Refactor and generalize the ParallelSlot machinery.

Create a wrapper object, ParallelSlotArray, to encapsulate the
number of slots and the slot array itself, plus some other relevant
bits of information. This reduces the number of parameters we have
to pass around all over the place.

Allow for a ParallelSlotArray to contain slots connected to
different databases within a single cluster. The current clients
of this mechanism don't need this, but it is expected to be used
by future patches.

Defer connecting to databases until we actually need the connection
for something. This is a slight behavior change for vacuumdb and
reindexdb. If you specify a number of jobs that is larger than the
number of objects, the extra connections will now not be used.
But, on the other hand, if you specify a number of jobs that is
so large that it's going to fail, the failure would previously have
happened before any operations were actually started, and now it
won't.

Mark Dilger, reviewed by me.

Discussion: http://postgr.es/m/12ED3DA8-25F0-4B68-937D-D907CFBF08E7@enterprisedb.com
Discussion: http://postgr.es/m/BA592F2D-F928-46FF-9516-2B827F067F57@enterprisedb.com

1 files changed, 20 insertions, 7 deletions

diff --git a/src/include/fe_utils/parallel_slot.h b/src/include/fe_utils/parallel_slot.h
index 8902f8d4f48..b7e2b0a29b8 100644
--- a/src/include/fe_utils/parallel_slot.h
+++ b/src/include/fe_utils/parallel_slot.h
@@ -21,7 +21,7 @@ typedef bool (*ParallelSlotResultHandler) (PGresult *res, PGconn *conn,
 typedef struct ParallelSlot
 {
 	PGconn	   *connection;		/* One connection */
-	bool		isFree;			/* Is it known to be idle? */
+	bool		inUse;			/* Is the slot being used? */
 
 	/*
 	 * Prior to issuing a command or query on 'connection', a handler callback
@@ -33,6 +33,16 @@ typedef struct ParallelSlot
 	void	   *handler_context;
 } ParallelSlot;
 
+typedef struct ParallelSlotArray
+{
+	int			numslots;
+	ConnParams *cparams;
+	const char *progname;
+	bool		echo;
+	const char *initcmd;
+	ParallelSlot slots[FLEXIBLE_ARRAY_MEMBER];
+} ParallelSlotArray;
+
 static inline void
 ParallelSlotSetHandler(ParallelSlot *slot, ParallelSlotResultHandler handler,
 					   void *context)
@@ -48,15 +58,18 @@ ParallelSlotClearHandler(ParallelSlot *slot)
 	slot->handler_context = NULL;
 }
 
-extern ParallelSlot *ParallelSlotsGetIdle(ParallelSlot *slots, int numslots);
+extern ParallelSlot *ParallelSlotsGetIdle(ParallelSlotArray *slots,
+										  const char *dbname);
+
+extern ParallelSlotArray *ParallelSlotsSetup(int numslots, ConnParams *cparams,
+											 const char *progname, bool echo,
+											 const char *initcmd);
 
-extern ParallelSlot *ParallelSlotsSetup(const ConnParams *cparams,
-										const char *progname, bool echo,
-										PGconn *conn, int numslots);
+extern void ParallelSlotsAdoptConn(ParallelSlotArray *sa, PGconn *conn);
 
-extern void ParallelSlotsTerminate(ParallelSlot *slots, int numslots);
+extern void ParallelSlotsTerminate(ParallelSlotArray *sa);
 
-extern bool ParallelSlotsWaitCompletion(ParallelSlot *slots, int numslots);
+extern bool ParallelSlotsWaitCompletion(ParallelSlotArray *sa);
 
 extern bool TableCommandResultHandler(PGresult *res, PGconn *conn,
 									  void *context);