implemented estimated_extent() function

git-svn-id: http://svn.osgeo.org/postgis/trunk@1129 b70326c6-7e19-0410-871a-916f4a2858ee

diff --git a/lwgeom/lwgeom_estimate.c b/lwgeom/lwgeom_estimate.c
index 850ddea3a8f20c0ff5b1bc6eedd9ebe903505d9b..33a11d0fa5749045773be8c2987c2bd55d26eeca 100644 (file)
--- a/lwgeom/lwgeom_estimate.c
+++ b/lwgeom/lwgeom_estimate.c
@@ -74,7 +74,9 @@ typedef struct GEOM_STATS_T
        float4 value[1];
 } GEOM_STATS;
 
-#endif
+Datum LWGEOM_estimated_extent(PG_FUNCTION_ARGS);
+
+#endif // USE_VERSION >= 80
 
 #define SHOW_DIGS_DOUBLE 15
 #define MAX_DIGS_DOUBLE (SHOW_DIGS_DOUBLE + 6 + 1 + 3 +1)
@@ -1879,14 +1881,135 @@ Datum LWGEOM_analyze(PG_FUNCTION_ARGS)
        /* Indicate we are done successfully */
        PG_RETURN_BOOL(true);
 }
-       
 
+/*
+ * Return the estimated extent of the table
+ * looking at gathered statistics (or NULL if
+ * no statistics have been gathered).
+ */
+PG_FUNCTION_INFO_V1(LWGEOM_estimated_extent);
+Datum LWGEOM_estimated_extent(PG_FUNCTION_ARGS)
+{
+       text *txnsp = PG_GETARG_TEXT_P(0);
+       text *txtbl = PG_GETARG_TEXT_P(1);
+       text *txcol = PG_GETARG_TEXT_P(2);
+       char *query;
+       char *nsp;
+       char *tbl;
+       char *col;
+       LWHISTOGRAM2D *histo;
+       ArrayType *array = NULL;
+       int SPIcode;
+       SPITupleTable *tuptable;
+       TupleDesc tupdesc ;
+       HeapTuple tuple ;
+       bool isnull;
+       BOX2DFLOAT4 *box;
+
+#if DEBUG_GEOMETRY_STATS
+       elog(NOTICE, "LWGEOM_estimated_extent called");
+#endif
+
+
+       /* Connect to SPI manager */
+       SPIcode = SPI_connect();
+       if (SPIcode != SPI_OK_CONNECT)
+       {
+               elog(ERROR, "LWGEOM_estimated_extent: couldnt open a connection to SPI");
+               PG_RETURN_NULL() ;
+       }
+
+       nsp = palloc(VARSIZE(txnsp)+1);
+       tbl = palloc(VARSIZE(txtbl)+1);
+       col = palloc(VARSIZE(txcol)+1);
+       memcpy(nsp, VARATT_DATA(txnsp), VARSIZE(txnsp)-VARHDRSZ);
+       nsp[VARSIZE(txnsp)-VARHDRSZ]='\0';
+       memcpy(tbl, VARATT_DATA(txtbl), VARSIZE(txtbl)-VARHDRSZ);
+       tbl[VARSIZE(txtbl)-VARHDRSZ]='\0';
+       memcpy(col, VARATT_DATA(txcol), VARSIZE(txcol)-VARHDRSZ);
+       col[VARSIZE(txcol)-VARHDRSZ]='\0';
+
+#if DEBUG_GEOMETRY_STATS
+       elog(NOTICE, " schema:%s table:%s column:%s", nsp, tbl, col);
+#endif
+
+       query = palloc(VARSIZE(txnsp)+VARSIZE(txtbl)+VARSIZE(txcol)+516);
+
+       sprintf(query, "SELECT s.stanumbers1[5:8] FROM pg_statistic s, pg_class c, pg_attribute a, pg_namespace n WHERE c.relname = '%s' AND a.attrelid = c.oid AND a.attname = '%s' AND n.nspname = '%s' AND c.relnamespace = n.oid AND s.starelid=c.oid AND s.staattnum = a.attnum AND staattnum = attnum", tbl, col, nsp);
+
+#if DEBUG_GEOMETRY_STATS > 1
+       elog(NOTICE, " query: %s", query);
+#endif
+
+       SPIcode = SPI_exec(query, 1);
+       if (SPIcode != SPI_OK_SELECT )
+       {
+               SPI_finish();
+               elog(ERROR,"LWGEOM_estimated_extent: couldnt execute sql via SPI");
+               PG_RETURN_NULL();
+       }
+       if (SPI_processed != 1)
+       {
+               SPI_finish();
+#if DEBUG_GEOMETRY_STATS
+               elog(ERROR, " %d stat rows", SPI_processed);
+#endif
+               PG_RETURN_NULL() ;
+       }
+
+       tuptable = SPI_tuptable;
+       tupdesc = SPI_tuptable->tupdesc;
+       tuple = tuptable->vals[0];
+       array = (ArrayType *)SPI_getbinval(tuple, tupdesc, 1, &isnull);
+       if (isnull)
+       {
+               SPI_finish();
+#if DEBUG_GEOMETRY_STATS
+               elog(NOTICE, " stats are NULL");
+#endif
+               PG_RETURN_NULL();
+       }
+       if ( ArrayGetNItems(ARR_NDIM(array), ARR_DIMS(array)) != 4 )
+       {
+               elog(ERROR, " corrupted histogram");
+               PG_RETURN_NULL();
+       }
+
+#if DEBUG_GEOMETRY_STATS
+       elog(NOTICE, " stats array has %d elems", ArrayGetNItems(ARR_NDIM(array), ARR_DIMS(array)));
+#endif
 
+       /* Construct box2dfloat4 */
+       box = palloc(sizeof(BOX2DFLOAT4));
+
+       /* Construct the box */
+       memcpy(box, ARR_DATA_PTR(array), sizeof(BOX2DFLOAT4));
+
+#if DEBUG_GEOMETRY_STATS
+       elog(NOTICE, " histogram extent = %g %g, %g %g", box->xmin,
+               box->ymin, box->xmax, box->ymax);
 #endif
 
+       SPIcode = SPI_finish();
+       if (SPIcode != SPI_OK_FINISH )
+       {
+               elog(ERROR, "LWGEOM_estimated_extent: couldnt disconnect from SPI");
+       }
+
+       /* TODO: enlarge the box by some factor */
+
+       PG_RETURN_POINTER(box);
+}
+       
+
+#endif // USE_VERSION >= 80
+
 
 /**********************************************************************
  * $Log$
+ * Revision 1.13  2004/12/10 12:35:11  strk
+ * implemented estimated_extent() function
+ *
  * Revision 1.12  2004/11/04 11:40:08  strk
  * Renamed max/min/avg macros to LW_MAX, LW_MIN, LW_AVG.
  *

diff --git a/lwgeom/lwpostgis.sql.in b/lwgeom/lwpostgis.sql.in
index d68a9398bf491458d6a84068f947687128d6d42c..604ec5eb488232632fa009155344e72f4bec9635 100644 (file)
--- a/lwgeom/lwpostgis.sql.in
+++ b/lwgeom/lwpostgis.sql.in
@@ -1841,6 +1841,22 @@ CREATEFUNCTION estimate_histogram2d(histogram2d,box2d)
        AS '@MODULE_FILENAME@','estimate_lwhistogram2d'
        LANGUAGE 'C'  with (isstrict);
 
+#if USE_VERSION >= 80
+-----------------------------------------------------------------------
+-- ESTIMATED_EXTENT( <schema name>, <table name>, <column name> )
+-----------------------------------------------------------------------
+CREATEFUNCTION estimated_extent(text,text,text) RETURNS box2d AS
+       '@MODULE_FILENAME@', 'LWGEOM_estimated_extent'
+       LANGUAGE 'C' with (isstrict);
+
+-----------------------------------------------------------------------
+-- ESTIMATED_EXTENT( <table name>, <column name> )
+-----------------------------------------------------------------------
+CREATEFUNCTION estimated_extent(text,text) RETURNS box2d AS
+'SELECT estimated_extent(current_schema()::text, $1, $2)'
+LANGUAGE 'SQL' WITH (isstrict);
+
+#endif // USE_VERSION >= 80
 
 -----------------------------------------------------------------------
 -- FIND_EXTENT( <schema name>, <table name>, <column name> )