From: Paul Ramsey <pramsey@cleverelephant.ca>
Date: Tue, 20 Nov 2012 20:51:42 +0000 (+0000)
Subject: #2102, SQL hooks for calling selectivity functions
X-Git-Tag: 2.1.0beta2~375
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=6ed9d34ed3f2482fc83fdccf531bf1ff43f07bc5;p=postgis

#2102, SQL hooks for calling selectivity functions


git-svn-id: http://svn.osgeo.org/postgis/trunk@10720 b70326c6-7e19-0410-871a-916f4a2858ee
---

diff --git a/postgis/geometry_estimate.c b/postgis/geometry_estimate.c
index 54b349fd9..d260ed80f 100644
--- a/postgis/geometry_estimate.c
+++ b/postgis/geometry_estimate.c
@@ -116,6 +116,7 @@ static float8 estimate_selectivity(GBOX *box, GEOM_STATS *geomstats);
 
 Datum geometry_gist_sel_2d(PG_FUNCTION_ARGS);
 Datum geometry_gist_joinsel_2d(PG_FUNCTION_ARGS);
+Datum geometry_gist_read_selectivity(PG_FUNCTION_ARGS);
 Datum geometry_analyze_2d(PG_FUNCTION_ARGS);
 Datum geometry_estimated_extent(PG_FUNCTION_ARGS);
 
@@ -609,6 +610,52 @@ estimate_selectivity(GBOX *box, GEOM_STATS *geomstats)
 	return selectivity;
 }
 
+/**
+* Utility function to read the calculated selectivity for a given search
+* box and table/column. Used for debugging the selectivity code.
+*/
+PG_FUNCTION_INFO_V1(geometry_gist_read_selectivity);
+Datum geometry_gist_read_selectivity(PG_FUNCTION_ARGS)
+{
+	HeapTuple stats_tuple;
+	float4 *floatptr;
+	int32 table_oid = PG_GETARG_INT32(0);
+	int32 attr_num = PG_GETARG_INT32(1);
+	Datum geom_datum = PG_GETARG_DATUM(2);
+	int rv;
+	GBOX gbox;
+	int32 nvalues = 0;
+	float8 selectivity = 0;
+
+	/* Calculate the gbox */
+	if ( ! gserialized_datum_get_gbox_p(geom_datum, &gbox) )
+		elog(ERROR, "Unable to calculate search box from geometry");
+	
+	/* First pull the stats tuple */
+	stats_tuple = SearchSysCache2(STATRELATT, Int32GetDatum(table_oid), Int32GetDatum(attr_num));
+	if ( ! stats_tuple )
+		elog(ERROR, "Unable to retreive stats tuple for oid(%d) attrnum(%d)", table_oid, attr_num);
+		
+	/* Then read the geom status histogram from that */
+	rv = get_attstatsslot(stats_tuple, 0, 0, STATISTIC_KIND_GEOMETRY, InvalidOid, NULL, NULL, NULL, &floatptr, &nvalues);
+	if ( ! rv )
+	{
+		ReleaseSysCache(stats_tuple);
+		elog(ERROR, "Unable to retreive geomstats");		
+	}
+	
+	/* Do the estimation */
+	selectivity = estimate_selectivity(&gbox, (GEOM_STATS*)floatptr);
+
+	/* Clean up */
+	free_attstatsslot(0, NULL, 0, floatptr, nvalues);
+	ReleaseSysCache(stats_tuple);
+	
+	PG_RETURN_FLOAT8(selectivity);
+}
+
+
+
 /**
  * This function should return an estimation of the number of
  * rows returned by a query involving an overlap check
diff --git a/postgis/postgis.sql.in.c b/postgis/postgis.sql.in.c
index 71ec381f3..664aeafb9 100644
--- a/postgis/postgis.sql.in.c
+++ b/postgis/postgis.sql.in.c
@@ -428,6 +428,35 @@ CREATE OR REPLACE FUNCTION geometry_gist_joinsel_2d(internal, oid, internal, sma
 	AS 'MODULE_PATHNAME', 'geometry_gist_joinsel_2d'
 	LANGUAGE 'c';
 
+-- Availability: 2.1.0
+CREATE OR REPLACE FUNCTION geometry_gist_read_selectivity(relid integer, attnum integer, geom geometry)
+	RETURNS float8
+	AS 'MODULE_PATHNAME', 'geometry_gist_read_selectivity'
+	LANGUAGE 'c';
+	
+-- Availability: 2.1.0
+CREATE OR REPLACE FUNCTION geometry_gist_selectivity(schemaname varchar, tablename varchar, attrname varchar, geom geometry)
+	RETURNS float8
+	AS $$
+	  DECLARE
+	  	selectivity float8;
+	  BEGIN
+	  	SELECT geometry_gist_read_selectivity(r.oid::integer, a.attnum::integer, 'SRID=4326;LINESTRING(0 0, 1 1)'::geometry)
+	  	INTO selectivity
+	  	FROM pg_class r 
+	    JOIN pg_attribute a ON (r.oid = a.attrelid) 
+	    JOIN pg_namespace n ON (r.relnamespace = n.oid) 
+	    WHERE  n.nspname = $1 AND r.relname = $2 and a.attname = $3;
+	    IF NOT FOUND THEN
+	  	   RAISE EXCEPTION 'Couldn''t find table? column?';
+	  	END IF;
+	  	RETURN selectivity;
+	  END;
+	$$
+	LANGUAGE 'plpgsql';
+
+
+
 -----------------------------------------------------------------------------
 -- GEOMETRY Operators
 -----------------------------------------------------------------------------