Measure the number of all-visible pages for use in index-only scan costing.

Add a column pg_class.relallvisible to remember the number of pages that
were all-visible according to the visibility map as of the last VACUUM
(or ANALYZE, or some other operations that update pg_class.relpages).
Use relallvisible/relpages, instead of an arbitrary constant, to estimate
how many heap page fetches can be avoided during an index-only scan.

This is pretty primitive and will no doubt see refinements once we've
acquired more field experience with the index-only scan mechanism, but
it's way better than using a constant.

Note: I had to adjust an underspecified query in the window.sql regression
test, because it was changing answers when the plan changed to use an
index-only scan.  Some of the adjacent tests perhaps should be adjusted
as well, but I didn't do that here.

6 files changed, 32 insertions, 25 deletions

diff --git a/src/include/access/visibilitymap.h b/src/include/access/visibilitymap.h
index 7d62c126407..4e5c0a0e4ed 100644
--- a/src/include/access/visibilitymap.h
+++ b/src/include/access/visibilitymap.h
@@ -27,6 +27,7 @@ extern bool visibilitymap_pin_ok(BlockNumber heapBlk, Buffer vmbuf);
 extern void visibilitymap_set(Relation rel, BlockNumber heapBlk,
 				  XLogRecPtr recptr, Buffer vmbuf);
 extern bool visibilitymap_test(Relation rel, BlockNumber heapBlk, Buffer *vmbuf);
-extern void visibilitymap_truncate(Relation rel, BlockNumber heapblk);
+extern BlockNumber visibilitymap_count(Relation rel);
+extern void visibilitymap_truncate(Relation rel, BlockNumber nheapblocks);
 
 #endif   /* VISIBILITYMAP_H */
diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index e4eb7b1294f..8fff3675ef2 100644
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201110071
+#define CATALOG_VERSION_NO	201110141
 
 #endif
diff --git a/src/include/catalog/pg_class.h b/src/include/catalog/pg_class.h
index e00618026e4..06120e481e8 100644
--- a/src/include/catalog/pg_class.h
+++ b/src/include/catalog/pg_class.h
@@ -45,6 +45,8 @@ CATALOG(pg_class,1259) BKI_BOOTSTRAP BKI_ROWTYPE_OID(83) BKI_SCHEMA_MACRO
 	Oid			reltablespace;	/* identifier of table space for relation */
 	int4		relpages;		/* # of blocks (not always up-to-date) */
 	float4		reltuples;		/* # of tuples (not always up-to-date) */
+	int4		relallvisible;	/* # of all-visible blocks (not always
+								 * up-to-date) */
 	Oid			reltoastrelid;	/* OID of toast table; 0 if none */
 	Oid			reltoastidxid;	/* if toast table, OID of chunk_id index */
 	bool		relhasindex;	/* T if has (or has had) any indexes */
@@ -92,7 +94,7 @@ typedef FormData_pg_class *Form_pg_class;
  * ----------------
  */
 
-#define Natts_pg_class					26
+#define Natts_pg_class					27
 #define Anum_pg_class_relname			1
 #define Anum_pg_class_relnamespace		2
 #define Anum_pg_class_reltype			3
@@ -103,22 +105,23 @@ typedef FormData_pg_class *Form_pg_class;
 #define Anum_pg_class_reltablespace		8
 #define Anum_pg_class_relpages			9
 #define Anum_pg_class_reltuples			10
-#define Anum_pg_class_reltoastrelid		11
-#define Anum_pg_class_reltoastidxid		12
-#define Anum_pg_class_relhasindex		13
-#define Anum_pg_class_relisshared		14
-#define Anum_pg_class_relpersistence	15
-#define Anum_pg_class_relkind			16
-#define Anum_pg_class_relnatts			17
-#define Anum_pg_class_relchecks			18
-#define Anum_pg_class_relhasoids		19
-#define Anum_pg_class_relhaspkey		20
-#define Anum_pg_class_relhasrules		21
-#define Anum_pg_class_relhastriggers	22
-#define Anum_pg_class_relhassubclass	23
-#define Anum_pg_class_relfrozenxid		24
-#define Anum_pg_class_relacl			25
-#define Anum_pg_class_reloptions		26
+#define Anum_pg_class_relallvisible		11
+#define Anum_pg_class_reltoastrelid		12
+#define Anum_pg_class_reltoastidxid		13
+#define Anum_pg_class_relhasindex		14
+#define Anum_pg_class_relisshared		15
+#define Anum_pg_class_relpersistence	16
+#define Anum_pg_class_relkind			17
+#define Anum_pg_class_relnatts			18
+#define Anum_pg_class_relchecks			19
+#define Anum_pg_class_relhasoids		20
+#define Anum_pg_class_relhaspkey		21
+#define Anum_pg_class_relhasrules		22
+#define Anum_pg_class_relhastriggers	23
+#define Anum_pg_class_relhassubclass	24
+#define Anum_pg_class_relfrozenxid		25
+#define Anum_pg_class_relacl			26
+#define Anum_pg_class_reloptions		27
 
 /* ----------------
  *		initial contents of pg_class
@@ -130,13 +133,13 @@ typedef FormData_pg_class *Form_pg_class;
  */
 
 /* Note: "3" in the relfrozenxid column stands for FirstNormalTransactionId */
-DATA(insert OID = 1247 (  pg_type		PGNSP 71 0 PGUID 0 0 0 0 0 0 0 f f p r 29 0 t f f f f 3 _null_ _null_ ));
+DATA(insert OID = 1247 (  pg_type		PGNSP 71 0 PGUID 0 0 0 0 0 0 0 0 f f p r 29 0 t f f f f 3 _null_ _null_ ));
 DESCR("");
-DATA(insert OID = 1249 (  pg_attribute	PGNSP 75 0 PGUID 0 0 0 0 0 0 0 f f p r 21 0 f f f f f 3 _null_ _null_ ));
+DATA(insert OID = 1249 (  pg_attribute	PGNSP 75 0 PGUID 0 0 0 0 0 0 0 0 f f p r 21 0 f f f f f 3 _null_ _null_ ));
 DESCR("");
-DATA(insert OID = 1255 (  pg_proc		PGNSP 81 0 PGUID 0 0 0 0 0 0 0 f f p r 26 0 t f f f f 3 _null_ _null_ ));
+DATA(insert OID = 1255 (  pg_proc		PGNSP 81 0 PGUID 0 0 0 0 0 0 0 0 f f p r 26 0 t f f f f 3 _null_ _null_ ));
 DESCR("");
-DATA(insert OID = 1259 (  pg_class		PGNSP 83 0 PGUID 0 0 0 0 0 0 0 f f p r 26 0 t f f f f 3 _null_ _null_ ));
+DATA(insert OID = 1259 (  pg_class		PGNSP 83 0 PGUID 0 0 0 0 0 0 0 0 f f p r 27 0 t f f f f 3 _null_ _null_ ));
 DESCR("");
 
 
diff --git a/src/include/commands/vacuum.h b/src/include/commands/vacuum.h
index cfbe0c43924..d8fd0caa6b6 100644
--- a/src/include/commands/vacuum.h
+++ b/src/include/commands/vacuum.h
@@ -149,6 +149,7 @@ extern double vac_estimate_reltuples(Relation relation, bool is_analyze,
 extern void vac_update_relstats(Relation relation,
 					BlockNumber num_pages,
 					double num_tuples,
+					BlockNumber num_all_visible_pages,
 					bool hasindex,
 					TransactionId frozenxid);
 extern void vacuum_set_xid_limits(int freeze_min_age, int freeze_table_age,
diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h
index 45ca52e516e..ef84e9f138d 100644
--- a/src/include/nodes/relation.h
+++ b/src/include/nodes/relation.h
@@ -319,6 +319,7 @@ typedef struct PlannerInfo
  *					(always NIL if it's not a table)
  *		pages - number of disk pages in relation (zero if not a table)
  *		tuples - number of tuples in relation (not considering restrictions)
+ *		allvisfrac - fraction of disk pages that are marked all-visible
  *		subplan - plan for subquery (NULL if it's not a subquery)
  *		subroot - PlannerInfo for subquery (NULL if it's not a subquery)
  *
@@ -402,8 +403,9 @@ typedef struct RelOptInfo
 	Relids	   *attr_needed;	/* array indexed [min_attr .. max_attr] */
 	int32	   *attr_widths;	/* array indexed [min_attr .. max_attr] */
 	List	   *indexlist;		/* list of IndexOptInfo */
-	BlockNumber pages;
+	BlockNumber pages;			/* size estimates derived from pg_class */
 	double		tuples;
+	double		allvisfrac;
 	struct Plan *subplan;		/* if subquery */
 	PlannerInfo *subroot;		/* if subquery */
 
diff --git a/src/include/optimizer/plancat.h b/src/include/optimizer/plancat.h
index c0b8eda8137..05843615d66 100644
--- a/src/include/optimizer/plancat.h
+++ b/src/include/optimizer/plancat.h
@@ -29,7 +29,7 @@ extern void get_relation_info(PlannerInfo *root, Oid relationObjectId,
 				  bool inhparent, RelOptInfo *rel);
 
 extern void estimate_rel_size(Relation rel, int32 *attr_widths,
-				  BlockNumber *pages, double *tuples);
+				  BlockNumber *pages, double *tuples, double *allvisfrac);
 
 extern int32 get_relation_data_width(Oid relid, int32 *attr_widths);