Support parallel btree index builds.

To make this work, tuplesort.c and logtape.c must also support
parallelism, so this patch adds that infrastructure and then applies
it to the particular case of parallel btree index builds.  Testing
to date shows that this can often be 2-3x faster than a serial
index build.

The model for deciding how many workers to use is fairly primitive
at present, but it's better than not having the feature.  We can
refine it as we get more experience.

Peter Geoghegan with some help from Rushabh Lathia.  While Heikki
Linnakangas is not an author of this patch, he wrote other patches
without which this feature would not have been possible, and
therefore the release notes should possibly credit him as an author
of this feature.  Reviewed by Claudio Freire, Heikki Linnakangas,
Thomas Munro, Tels, Amit Kapila, me.

Discussion: http://postgr.es/m/CAM3SWZQKM=Pzc=CAHzRixKjp2eO5Q0Jg1SoFQqeXFQ647JiwqQ@mail.gmail.com
Discussion: http://postgr.es/m/CAH2-Wz=AxWqDoVvGU7dq856S4r6sJAj6DBn7VMtigkB33N5eyg@mail.gmail.com

3 files changed, 8 insertions, 11 deletions

diff --git a/src/include/access/nbtree.h b/src/include/access/nbtree.h
index d28f413c663..0f6a40168ca 100644
--- a/src/include/access/nbtree.h
+++ b/src/include/access/nbtree.h
@@ -21,6 +21,7 @@
 #include "catalog/pg_index.h"
 #include "lib/stringinfo.h"
 #include "storage/bufmgr.h"
+#include "storage/shm_toc.h"
 
 /* There's room for a 16-bit vacuum cycle ID in BTPageOpaqueData */
 typedef uint16 BTCycleId;
@@ -430,8 +431,6 @@ typedef BTScanOpaqueData *BTScanOpaque;
 /*
  * external entry points for btree, in nbtree.c
  */
-extern IndexBuildResult *btbuild(Relation heap, Relation index,
-		struct IndexInfo *indexInfo);
 extern void btbuildempty(Relation index);
 extern bool btinsert(Relation rel, Datum *values, bool *isnull,
 		 ItemPointer ht_ctid, Relation heapRel,
@@ -547,13 +546,8 @@ extern bool btvalidate(Oid opclassoid);
 /*
  * prototypes for functions in nbtsort.c
  */
-typedef struct BTSpool BTSpool; /* opaque type known only within nbtsort.c */
-
-extern BTSpool *_bt_spoolinit(Relation heap, Relation index,
-			  bool isunique, bool isdead);
-extern void _bt_spooldestroy(BTSpool *btspool);
-extern void _bt_spool(BTSpool *btspool, ItemPointer self,
-		  Datum *values, bool *isnull);
-extern void _bt_leafbuild(BTSpool *btspool, BTSpool *spool2);
+extern IndexBuildResult *btbuild(Relation heap, Relation index,
+		struct IndexInfo *indexInfo);
+extern void _bt_parallel_build_main(dsm_segment *seg, shm_toc *toc);
 
 #endif							/* NBTREE_H */
diff --git a/src/include/access/parallel.h b/src/include/access/parallel.h
index d0c218b1854..025691fd82d 100644
--- a/src/include/access/parallel.h
+++ b/src/include/access/parallel.h
@@ -59,7 +59,9 @@ extern PGDLLIMPORT bool InitializingParallelWorker;
 
 #define		IsParallelWorker()		(ParallelWorkerNumber >= 0)
 
-extern ParallelContext *CreateParallelContext(const char *library_name, const char *function_name, int nworkers);
+extern ParallelContext *CreateParallelContext(const char *library_name,
+					  const char *function_name, int nworkers,
+					  bool serializable_okay);
 extern void InitializeParallelDSM(ParallelContext *pcxt);
 extern void ReinitializeParallelDSM(ParallelContext *pcxt);
 extern void LaunchParallelWorkers(ParallelContext *pcxt);
diff --git a/src/include/access/relscan.h b/src/include/access/relscan.h
index 9c603ca637a..18c7dedd5d3 100644
--- a/src/include/access/relscan.h
+++ b/src/include/access/relscan.h
@@ -39,6 +39,7 @@ typedef struct ParallelHeapScanDescData
 	BlockNumber phs_startblock; /* starting block number */
 	pg_atomic_uint64 phs_nallocated;	/* number of blocks allocated to
 										 * workers so far. */
+	bool		phs_snapshot_any;	/* SnapshotAny, not phs_snapshot_data? */
 	char		phs_snapshot_data[FLEXIBLE_ARRAY_MEMBER];
 }			ParallelHeapScanDescData;