Rewrite of planner statistics-gathering code. ANALYZE is now available as

a separate statement (though it can still be invoked as part of VACUUM, too).
pg_statistic redesigned to be more flexible about what statistics are
stored.  ANALYZE now collects a list of several of the most common values,
not just one, plus a histogram (not just the min and max values).  Random
sampling is used to make the process reasonably fast even on very large
tables.  The number of values and histogram bins collected is now
user-settable via an ALTER TABLE command.

There is more still to do; the new stats are not being used everywhere
they could be in the planner.  But the remaining changes for this project
should be localized, and the behavior is already better than before.

A not-very-related change is that sorting now makes use of btree comparison
routines if it can find one, rather than invoking '<' twice.

1 files changed, 111 insertions, 17 deletions

diff --git a/src/backend/commands/command.c b/src/backend/commands/command.c
index 96d493688e3..13a78f11773 100644
--- a/src/backend/commands/command.c
+++ b/src/backend/commands/command.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/Attic/command.c,v 1.125 2001/03/23 04:49:52 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/Attic/command.c,v 1.126 2001/05/07 00:43:17 tgl Exp $
  *
  * NOTES
  *	  The PerformAddAttribute() code, like most of the relation
@@ -56,6 +56,7 @@
 #include "access/genam.h"
 
 
+static void drop_default(Oid relid, int16 attnum);
 static bool needs_toast_table(Relation rel);
 static bool is_relation(char *name);
 
@@ -408,7 +409,7 @@ AlterTableAddColumn(const char *relationName,
 		HeapTuple	typeTuple;
 		Form_pg_type tform;
 		char	   *typename;
-		int			attnelems;
+		int			attndims;
 
 		if (SearchSysCacheExists(ATTNAME,
 								 ObjectIdGetDatum(reltup->t_data->t_oid),
@@ -425,11 +426,11 @@ AlterTableAddColumn(const char *relationName,
 
 		if (colDef->typename->arrayBounds)
 		{
-			attnelems = length(colDef->typename->arrayBounds);
+			attndims = length(colDef->typename->arrayBounds);
 			typename = makeArrayTypeName(colDef->typename->name);
 		}
 		else
-			attnelems = 0;
+			attndims = 0;
 
 		typeTuple = SearchSysCache(TYPENAME,
 								   PointerGetDatum(typename),
@@ -441,12 +442,12 @@ AlterTableAddColumn(const char *relationName,
 		namestrcpy(&(attribute->attname), colDef->colname);
 		attribute->atttypid = typeTuple->t_data->t_oid;
 		attribute->attlen = tform->typlen;
-		attribute->attdispersion = 0;
+		attribute->attstattarget = DEFAULT_ATTSTATTARGET;
 		attribute->attcacheoff = -1;
 		attribute->atttypmod = colDef->typename->typmod;
 		attribute->attnum = i;
 		attribute->attbyval = tform->typbyval;
-		attribute->attnelems = attnelems;
+		attribute->attndims = attndims;
 		attribute->attisset = (bool) (tform->typtype == 'c');
 		attribute->attstorage = tform->typstorage;
 		attribute->attalign = tform->typalign;
@@ -496,17 +497,13 @@ AlterTableAddColumn(const char *relationName,
 }
 
 
-
-static void drop_default(Oid relid, int16 attnum);
-
-
 /*
  * ALTER TABLE ALTER COLUMN SET/DROP DEFAULT
  */
 void
-AlterTableAlterColumn(const char *relationName,
-					  bool inh, const char *colName,
-					  Node *newDefault)
+AlterTableAlterColumnDefault(const char *relationName,
+							 bool inh, const char *colName,
+							 Node *newDefault)
 {
 	Relation	rel;
 	HeapTuple	tuple;
@@ -551,8 +548,8 @@ AlterTableAlterColumn(const char *relationName,
 			if (childrelid == myrelid)
 				continue;
 			rel = heap_open(childrelid, AccessExclusiveLock);
-			AlterTableAlterColumn(RelationGetRelationName(rel),
-								  false, colName, newDefault);
+			AlterTableAlterColumnDefault(RelationGetRelationName(rel),
+										 false, colName, newDefault);
 			heap_close(rel, AccessExclusiveLock);
 		}
 	}
@@ -560,7 +557,7 @@ AlterTableAlterColumn(const char *relationName,
 	/* -= now do the thing on this relation =- */
 
 	/* reopen the business */
-	rel = heap_openr((char *) relationName, AccessExclusiveLock);
+	rel = heap_openr(relationName, AccessExclusiveLock);
 
 	/*
 	 * get the number of the attribute
@@ -647,7 +644,6 @@ AlterTableAlterColumn(const char *relationName,
 }
 
 
-
 static void
 drop_default(Oid relid, int16 attnum)
 {
@@ -675,6 +671,104 @@ drop_default(Oid relid, int16 attnum)
 }
 
 
+/*
+ * ALTER TABLE ALTER COLUMN SET STATISTICS
+ */
+void
+AlterTableAlterColumnStatistics(const char *relationName,
+								bool inh, const char *colName,
+								Node *statsTarget)
+{
+	Relation	rel;
+	Oid			myrelid;
+	int			newtarget;
+	Relation	attrelation;
+	HeapTuple	tuple;
+
+#ifndef NO_SECURITY
+	if (!pg_ownercheck(GetUserId(), relationName, RELNAME))
+		elog(ERROR, "ALTER TABLE: permission denied");
+#endif
+
+	rel = heap_openr(relationName, AccessExclusiveLock);
+	if (rel->rd_rel->relkind != RELKIND_RELATION)
+		elog(ERROR, "ALTER TABLE: relation \"%s\" is not a table",
+			 relationName);
+	myrelid = RelationGetRelid(rel);
+	heap_close(rel, NoLock);	/* close rel, but keep lock! */
+
+	/*
+	 * Propagate to children if desired
+	 */
+	if (inh)
+	{
+		List	   *child,
+				   *children;
+
+		/* this routine is actually in the planner */
+		children = find_all_inheritors(myrelid);
+
+		/*
+		 * find_all_inheritors does the recursive search of the
+		 * inheritance hierarchy, so all we have to do is process all of
+		 * the relids in the list that it returns.
+		 */
+		foreach(child, children)
+		{
+			Oid			childrelid = lfirsti(child);
+
+			if (childrelid == myrelid)
+				continue;
+			rel = heap_open(childrelid, AccessExclusiveLock);
+			AlterTableAlterColumnStatistics(RelationGetRelationName(rel),
+											false, colName, statsTarget);
+			heap_close(rel, AccessExclusiveLock);
+		}
+	}
+
+	/* -= now do the thing on this relation =- */
+
+	Assert(IsA(statsTarget, Integer));
+	newtarget = intVal(statsTarget);
+
+	/* Limit target to sane range (should we raise an error instead?) */
+	if (newtarget < 0)
+		newtarget = 0;
+	else if (newtarget > 1000)
+		newtarget = 1000;
+
+	attrelation = heap_openr(AttributeRelationName, RowExclusiveLock);
+
+	tuple = SearchSysCacheCopy(ATTNAME,
+							   ObjectIdGetDatum(myrelid),
+							   PointerGetDatum(colName),
+							   0, 0);
+	if (!HeapTupleIsValid(tuple))
+		elog(ERROR, "ALTER TABLE: relation \"%s\" has no column \"%s\"",
+			 relationName, colName);
+
+	if (((Form_pg_attribute) GETSTRUCT(tuple))->attnum < 0)
+		elog(ERROR, "ALTER TABLE: cannot change system attribute \"%s\"",
+			 colName);
+
+	((Form_pg_attribute) GETSTRUCT(tuple))->attstattarget = newtarget;
+
+	simple_heap_update(attrelation, &tuple->t_self, tuple);
+
+	/* keep system catalog indices current */
+	{
+		Relation	irelations[Num_pg_attr_indices];
+
+		CatalogOpenIndices(Num_pg_attr_indices, Name_pg_attr_indices, irelations);
+		CatalogIndexInsert(irelations, Num_pg_attr_indices, attrelation, tuple);
+		CatalogCloseIndices(Num_pg_attr_indices, irelations);
+	}
+
+	heap_freetuple(tuple);
+	heap_close(attrelation, RowExclusiveLock);
+}
+
+
 #ifdef	_DROP_COLUMN_HACK__
 /*
  *	ALTER TABLE DROP COLUMN trial implementation