Add support for index-only scans in GiST.

This adds a new GiST opclass method, 'fetch', which is used to reconstruct
the original Datum from the value stored in the index. Also, the 'canreturn'
index AM interface function gains a new 'attno' argument. That makes it
possible to use index-only scans on a multi-column index where some of the
opclasses support index-only scans but some do not.

This patch adds support in the box and point opclasses. Other opclasses
can added later as follow-on patches (btree_gist would be particularly
interesting).

Anastasia Lubennikova, with additional fixes and modifications by me.

9 files changed, 28 insertions, 8 deletions

diff --git a/src/include/access/genam.h b/src/include/access/genam.h
index d1d624721d..d86590ac11 100644
--- a/src/include/access/genam.h
+++ b/src/include/access/genam.h
@@ -156,7 +156,7 @@ extern IndexBulkDeleteResult *index_bulk_delete(IndexVacuumInfo *info,
 				  void *callback_state);
 extern IndexBulkDeleteResult *index_vacuum_cleanup(IndexVacuumInfo *info,
 					 IndexBulkDeleteResult *stats);
-extern bool index_can_return(Relation indexRelation);
+extern bool index_can_return(Relation indexRelation, int attno);
 extern RegProcedure index_getprocid(Relation irel, AttrNumber attnum,
 				uint16 procnum);
 extern FmgrInfo *index_getprocinfo(Relation irel, AttrNumber attnum,
diff --git a/src/include/access/gist.h b/src/include/access/gist.h
index 01f0a70fee..50261b8bdd 100644
--- a/src/include/access/gist.h
+++ b/src/include/access/gist.h
@@ -33,7 +33,8 @@
 #define GIST_PICKSPLIT_PROC				6
 #define GIST_EQUAL_PROC					7
 #define GIST_DISTANCE_PROC				8
-#define GISTNProcs						8
+#define GIST_FETCH_PROC					9
+#define GISTNProcs					9
 
 /*
  * strategy numbers for GiST opclasses that want to implement the old
diff --git a/src/include/access/gist_private.h b/src/include/access/gist_private.h
index 9550687916..3693893e26 100644
--- a/src/include/access/gist_private.h
+++ b/src/include/access/gist_private.h
@@ -87,6 +87,7 @@ typedef struct GISTSTATE
 	FmgrInfo	picksplitFn[INDEX_MAX_KEYS];
 	FmgrInfo	equalFn[INDEX_MAX_KEYS];
 	FmgrInfo	distanceFn[INDEX_MAX_KEYS];
+	FmgrInfo	fetchFn[INDEX_MAX_KEYS];
 
 	/* Collations to pass to the support functions */
 	Oid			supportCollation[INDEX_MAX_KEYS];
@@ -118,6 +119,8 @@ typedef struct GISTSearchHeapItem
 {
 	ItemPointerData heapPtr;
 	bool		recheck;		/* T if quals must be rechecked */
+	IndexTuple	ftup;			/* data fetched back from the index, used in
+								 * index-only scans */
 } GISTSearchHeapItem;
 
 /* Unvisited item, either index page or heap tuple */
@@ -157,6 +160,8 @@ typedef struct GISTScanOpaqueData
 	GISTSearchHeapItem pageData[BLCKSZ / sizeof(IndexTupleData)];
 	OffsetNumber nPageData;		/* number of valid items in array */
 	OffsetNumber curPageData;	/* next item to return */
+	MemoryContext pageDataCxt;	/* context holding the fetched tuples, for
+								   index-only scans */
 } GISTScanOpaqueData;
 
 typedef GISTScanOpaqueData *GISTScanOpaque;
@@ -409,6 +414,7 @@ typedef struct GiSTOptions
 /* gist.c */
 extern Datum gistbuildempty(PG_FUNCTION_ARGS);
 extern Datum gistinsert(PG_FUNCTION_ARGS);
+extern Datum gistcanreturn(PG_FUNCTION_ARGS);
 extern MemoryContext createTempGistContext(void);
 extern GISTSTATE *initGISTstate(Relation index);
 extern void freeGISTstate(GISTSTATE *giststate);
@@ -504,7 +510,8 @@ extern void gistMakeUnionItVec(GISTSTATE *giststate, IndexTuple *itvec, int len,
 extern bool gistKeyIsEQ(GISTSTATE *giststate, int attno, Datum a, Datum b);
 extern void gistDeCompressAtt(GISTSTATE *giststate, Relation r, IndexTuple tuple, Page p,
 				  OffsetNumber o, GISTENTRY *attdata, bool *isnull);
-
+extern IndexTuple gistFetchTuple(GISTSTATE *giststate, Relation r,
+			   IndexTuple tuple);
 extern void gistMakeUnionKey(GISTSTATE *giststate, int attno,
 				 GISTENTRY *entry1, bool isnull1,
 				 GISTENTRY *entry2, bool isnull2,
diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index da6035f2c5..3d50f70402 100644
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201503191
+#define CATALOG_VERSION_NO	201503261
 
 #endif
diff --git a/src/include/catalog/pg_am.h b/src/include/catalog/pg_am.h
index 0531222a7e..79609f7774 100644
--- a/src/include/catalog/pg_am.h
+++ b/src/include/catalog/pg_am.h
@@ -123,7 +123,7 @@ DESCR("b-tree index access method");
 DATA(insert OID = 405 (  hash		1 1 f f t f f f f f f f f 23 hashinsert hashbeginscan hashgettuple hashgetbitmap hashrescan hashendscan hashmarkpos hashrestrpos hashbuild hashbuildempty hashbulkdelete hashvacuumcleanup - hashcostestimate hashoptions ));
 DESCR("hash index access method");
 #define HASH_AM_OID 405
-DATA(insert OID = 783 (  gist		0 8 f t f f t t f t t t f 0 gistinsert gistbeginscan gistgettuple gistgetbitmap gistrescan gistendscan gistmarkpos gistrestrpos gistbuild gistbuildempty gistbulkdelete gistvacuumcleanup - gistcostestimate gistoptions ));
+DATA(insert OID = 783 (  gist		0 9 f t f f t t f t t t f 0 gistinsert gistbeginscan gistgettuple gistgetbitmap gistrescan gistendscan gistmarkpos gistrestrpos gistbuild gistbuildempty gistbulkdelete gistvacuumcleanup gistcanreturn gistcostestimate gistoptions ));
 DESCR("GiST index access method");
 #define GIST_AM_OID 783
 DATA(insert OID = 2742 (  gin		0 6 f f f f t t f f t f f 0 gininsert ginbeginscan - gingetbitmap ginrescan ginendscan ginmarkpos ginrestrpos ginbuild ginbuildempty ginbulkdelete ginvacuumcleanup - gincostestimate ginoptions ));
diff --git a/src/include/catalog/pg_amproc.h b/src/include/catalog/pg_amproc.h
index 49d3d13efb..612a9d242e 100644
--- a/src/include/catalog/pg_amproc.h
+++ b/src/include/catalog/pg_amproc.h
@@ -191,6 +191,7 @@ DATA(insert (	1029   600 600 5 2581 ));
 DATA(insert (	1029   600 600 6 2582 ));
 DATA(insert (	1029   600 600 7 2584 ));
 DATA(insert (	1029   600 600 8 3064 ));
+DATA(insert (	1029   600 600 9 3282 ));
 DATA(insert (	2593   603 603 1 2578 ));
 DATA(insert (	2593   603 603 2 2583 ));
 DATA(insert (	2593   603 603 3 2579 ));
@@ -198,6 +199,7 @@ DATA(insert (	2593   603 603 4 2580 ));
 DATA(insert (	2593   603 603 5 2581 ));
 DATA(insert (	2593   603 603 6 2582 ));
 DATA(insert (	2593   603 603 7 2584 ));
+DATA(insert (	2593   603 603 9 3281 ));
 DATA(insert (	2594   604 604 1 2585 ));
 DATA(insert (	2594   604 604 2 2583 ));
 DATA(insert (	2594   604 604 3 2586 ));
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index 3c218a3987..77b77176a3 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -558,7 +558,7 @@ DATA(insert OID = 332 (  btbulkdelete	   PGNSP PGUID 12 1 0 0 0 f f f f t f v 4
 DESCR("btree(internal)");
 DATA(insert OID = 972 (  btvacuumcleanup   PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 2281 "2281 2281" _null_ _null_ _null_ _null_ btvacuumcleanup _null_ _null_ _null_ ));
 DESCR("btree(internal)");
-DATA(insert OID = 276 (  btcanreturn	   PGNSP PGUID 12 1 0 0 0 f f f f t f s 1 0 16 "2281" _null_ _null_ _null_ _null_ btcanreturn _null_ _null_ _null_ ));
+DATA(insert OID = 276 (  btcanreturn	   PGNSP PGUID 12 1 0 0 0 f f f f t f s 2 0 16 "2281 23" _null_ _null_ _null_ _null_ btcanreturn _null_ _null_ _null_ ));
 DESCR("btree(internal)");
 DATA(insert OID = 1268 (  btcostestimate   PGNSP PGUID 12 1 0 0 0 f f f f t f v 7 0 2278 "2281 2281 2281 2281 2281 2281 2281" _null_ _null_ _null_ _null_ btcostestimate _null_ _null_ _null_ ));
 DESCR("btree(internal)");
@@ -987,6 +987,8 @@ DATA(insert OID = 776 (  gistbulkdelete    PGNSP PGUID 12 1 0 0 0 f f f f t f v
 DESCR("gist(internal)");
 DATA(insert OID = 2561 (  gistvacuumcleanup   PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 2281 "2281 2281" _null_ _null_ _null_ _null_ gistvacuumcleanup _null_ _null_ _null_ ));
 DESCR("gist(internal)");
+DATA(insert OID = 3280 (  gistcanreturn	   PGNSP PGUID 12 1 0 0 0 f f f f t f s 2 0 16 "2281 23" _null_ _null_ _null_ _null_ gistcanreturn _null_ _null_ _null_ ));
+DESCR("gist(internal)");
 DATA(insert OID = 772 (  gistcostestimate  PGNSP PGUID 12 1 0 0 0 f f f f t f v 7 0 2278 "2281 2281 2281 2281 2281 2281 2281" _null_ _null_ _null_ _null_ gistcostestimate _null_ _null_ _null_ ));
 DESCR("gist(internal)");
 DATA(insert OID = 2787 (  gistoptions	   PGNSP PGUID 12 1 0 0 0 f f f f t f s 2 0 17 "1009 16" _null_ _null_ _null_ _null_  gistoptions _null_ _null_ _null_ ));
@@ -4089,6 +4091,8 @@ DATA(insert OID = 2579 (  gist_box_compress		PGNSP PGUID 12 1 0 0 0 f f f f t f
 DESCR("GiST support");
 DATA(insert OID = 2580 (  gist_box_decompress	PGNSP PGUID 12 1 0 0 0 f f f f t f i 1 0 2281 "2281" _null_ _null_ _null_ _null_ gist_box_decompress _null_ _null_ _null_ ));
 DESCR("GiST support");
+DATA(insert OID = 3281 (  gist_box_fetch	PGNSP PGUID 12 1 0 0 0 f f f f t f i 1 0 2281 "2281" _null_ _null_ _null_ _null_ gist_box_fetch _null_ _null_ _null_ ));
+DESCR("GiST support");
 DATA(insert OID = 2581 (  gist_box_penalty		PGNSP PGUID 12 1 0 0 0 f f f f t f i 3 0 2281 "2281 2281 2281" _null_ _null_ _null_ _null_	gist_box_penalty _null_ _null_ _null_ ));
 DESCR("GiST support");
 DATA(insert OID = 2582 (  gist_box_picksplit	PGNSP PGUID 12 1 0 0 0 f f f f t f i 2 0 2281 "2281 2281" _null_ _null_ _null_ _null_	gist_box_picksplit _null_ _null_ _null_ ));
@@ -4107,6 +4111,8 @@ DATA(insert OID = 2592 (  gist_circle_compress	PGNSP PGUID 12 1 0 0 0 f f f f t
 DESCR("GiST support");
 DATA(insert OID = 1030 (  gist_point_compress	PGNSP PGUID 12 1 0 0 0 f f f f t f i 1 0 2281 "2281" _null_ _null_ _null_ _null_ gist_point_compress _null_ _null_ _null_ ));
 DESCR("GiST support");
+DATA(insert OID = 3282 (  gist_point_fetch	PGNSP PGUID 12 1 0 0 0 f f f f t f i 1 0 2281 "2281" _null_ _null_ _null_ _null_ gist_point_fetch _null_ _null_ _null_ ));
+DESCR("GiST support");
 DATA(insert OID = 2179 (  gist_point_consistent PGNSP PGUID 12 1 0 0 0 f f f f t f i 5 0 16 "2281 600 23 26 2281" _null_ _null_ _null_ _null_	gist_point_consistent _null_ _null_ _null_ ));
 DESCR("GiST support");
 DATA(insert OID = 3064 (  gist_point_distance	PGNSP PGUID 12 1 0 0 0 f f f f t f i 4 0 701 "2281 600 23 26" _null_ _null_ _null_ _null_	gist_point_distance _null_ _null_ _null_ ));
@@ -5039,7 +5045,7 @@ DATA(insert OID = 4011 (  spgbulkdelete    PGNSP PGUID 12 1 0 0 0 f f f f t f v
 DESCR("spgist(internal)");
 DATA(insert OID = 4012 (  spgvacuumcleanup	 PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 2281 "2281 2281" _null_ _null_ _null_ _null_ spgvacuumcleanup _null_ _null_ _null_ ));
 DESCR("spgist(internal)");
-DATA(insert OID = 4032 (  spgcanreturn	   PGNSP PGUID 12 1 0 0 0 f f f f t f s 1 0 16 "2281" _null_ _null_ _null_ _null_ spgcanreturn _null_ _null_ _null_ ));
+DATA(insert OID = 4032 (  spgcanreturn	   PGNSP PGUID 12 1 0 0 0 f f f f t f s 2 0 16 "2281 23" _null_ _null_ _null_ _null_ spgcanreturn _null_ _null_ _null_ ));
 DESCR("spgist(internal)");
 DATA(insert OID = 4013 (  spgcostestimate  PGNSP PGUID 12 1 0 0 0 f f f f t f v 7 0 2278 "2281 2281 2281 2281 2281 2281 2281" _null_ _null_ _null_ _null_ spgcostestimate _null_ _null_ _null_ ));
 DESCR("spgist(internal)");
diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h
index 334cf51976..401a686664 100644
--- a/src/include/nodes/relation.h
+++ b/src/include/nodes/relation.h
@@ -520,6 +520,8 @@ typedef struct IndexOptInfo
 	Oid		   *sortopfamily;	/* OIDs of btree opfamilies, if orderable */
 	bool	   *reverse_sort;	/* is sort order descending? */
 	bool	   *nulls_first;	/* do NULLs come first in the sort order? */
+	bool	   *canreturn;		/* which index cols can be returned in an
+								   index-only scan? */
 	Oid			relam;			/* OID of the access method (in pg_am) */
 
 	RegProcedure amcostestimate;	/* OID of the access method's cost fcn */
@@ -533,7 +535,6 @@ typedef struct IndexOptInfo
 	bool		unique;			/* true if a unique index */
 	bool		immediate;		/* is uniqueness enforced immediately? */
 	bool		hypothetical;	/* true if index doesn't really exist */
-	bool		canreturn;		/* can index return IndexTuples? */
 	bool		amcanorderbyop; /* does AM support order by operator result? */
 	bool		amoptionalkey;	/* can query omit key for the first column? */
 	bool		amsearcharray;	/* can AM handle ScalarArrayOpExpr quals? */
diff --git a/src/include/utils/geo_decls.h b/src/include/utils/geo_decls.h
index 8da6c6c987..2a91620db7 100644
--- a/src/include/utils/geo_decls.h
+++ b/src/include/utils/geo_decls.h
@@ -410,6 +410,7 @@ extern Datum gist_box_picksplit(PG_FUNCTION_ARGS);
 extern Datum gist_box_consistent(PG_FUNCTION_ARGS);
 extern Datum gist_box_penalty(PG_FUNCTION_ARGS);
 extern Datum gist_box_same(PG_FUNCTION_ARGS);
+extern Datum gist_box_fetch(PG_FUNCTION_ARGS);
 extern Datum gist_poly_compress(PG_FUNCTION_ARGS);
 extern Datum gist_poly_consistent(PG_FUNCTION_ARGS);
 extern Datum gist_circle_compress(PG_FUNCTION_ARGS);
@@ -417,6 +418,8 @@ extern Datum gist_circle_consistent(PG_FUNCTION_ARGS);
 extern Datum gist_point_compress(PG_FUNCTION_ARGS);
 extern Datum gist_point_consistent(PG_FUNCTION_ARGS);
 extern Datum gist_point_distance(PG_FUNCTION_ARGS);
+extern Datum gist_point_fetch(PG_FUNCTION_ARGS);
+
 
 /* geo_selfuncs.c */
 extern Datum areasel(PG_FUNCTION_ARGS);