*
**********************************************************************
* $Log$
+ * Revision 1.24 2004/06/10 13:42:17 strk
+ * Separated the estimator code in an estimate_selectivity() function.
+ * Handled complete contaiment and complete miss of histogram by searc box.
+ *
* Revision 1.23 2004/06/09 09:35:49 strk
* Removed partial pgsql List API copy
*
*/
#define STATISTIC_KIND_GEOMETRY 100
-#define DEBUG_GEOMETRY_STATS 0
+#define DEBUG_GEOMETRY_STATS 1
/*
* Default geometry selectivity factor
#else // USE_VERSION >= 75
+/*
+ * This function returns an estimate of the selectivity
+ * of a search_box looking at data in the GEOM_STATS
+ * structure.
+ */
+static float8
+estimate_selectivity(BOX *box, GEOM_STATS *geomstats)
+{
+ int x, y;
+ int x_idx_min, x_idx_max, y_idx_min, y_idx_max;
+ double intersect_x, intersect_y, AOI;
+ double cell_area, box_area;
+ double geow, geoh; // width and height of histogram
+ int bps; // boxesPerSide
+ double value;
+ float overlapping_cells;
+ float avg_feat_cells;
+ double gain;
+ float8 selectivity;
+
+
+ /*
+ * Search box completely miss histogram extent
+ */
+ if ( box->high.x < geomstats->xmin ||
+ box->low.x > geomstats->xmax ||
+ box->high.y < geomstats->ymin ||
+ box->low.y > geomstats->ymax )
+ {
+#if DEBUG_GEOMETRY_STATS
+ elog(NOTICE, " search_box does not overlaps histogram, returning 0");
+#endif
+ return 0.0;
+ }
+
+ /*
+ * Search box completely contains histogram extent
+ */
+ if ( box->high.x >= geomstats->xmax &&
+ box->low.x <= geomstats->xmin &&
+ box->high.y >= geomstats->ymax &&
+ box->low.y <= geomstats->ymin )
+ {
+#if DEBUG_GEOMETRY_STATS
+ elog(NOTICE, " search_box contains histogram, returning 1");
+#endif
+ return 1.0;
+ }
+
+ geow = geomstats->xmax-geomstats->xmin;
+ geoh = geomstats->ymax-geomstats->ymin;
+ bps = geomstats->boxesPerSide;
+ cell_area = (geow*geoh) / (bps*bps);
+ box_area = (box->high.x-box->low.x)*(box->high.y-box->low.y);
+ value = 0;
+
+ /* Find first overlapping column */
+ x_idx_min = (box->low.x-geomstats->xmin) / geow * bps;
+ if (x_idx_min < 0) {
+#if DEBUG_GEOMETRY_STATS
+ elog(NOTICE, " search_box overlaps %d columns on the left of histogram grid", -x_idx_min);
+#endif
+ // should increment the value somehow
+ x_idx_min = 0;
+ }
+ if (x_idx_min >= bps)
+ {
+#if DEBUG_GEOMETRY_STATS
+ elog(NOTICE, " search_box overlaps %d columns on the right of histogram grid", x_idx_min-bps+1);
+#endif
+ // should increment the value somehow
+ x_idx_min = bps-1;
+ }
+
+ /* Find first overlapping row */
+ y_idx_min = (box->low.y-geomstats->ymin) / geoh * bps;
+ if (y_idx_min <0)
+ {
+#if DEBUG_GEOMETRY_STATS
+ elog(NOTICE, " search_box overlaps %d columns on the bottom of histogram grid", -y_idx_min);
+#endif
+ // should increment the value somehow
+ y_idx_min = 0;
+ }
+ if (y_idx_min >= bps)
+ {
+#if DEBUG_GEOMETRY_STATS
+ elog(NOTICE, " search_box overlaps %d columns on the top of histogram grid", y_idx_min-bps+1);
+#endif
+ // should increment the value somehow
+ y_idx_min = bps-1;
+ }
+
+ /* Find last overlapping column */
+ x_idx_max = (box->high.x-geomstats->xmin) / geow * bps;
+ if (x_idx_max <0)
+ {
+ // should increment the value somehow
+ x_idx_max = 0;
+ }
+ if (x_idx_max >= bps )
+ {
+ // should increment the value somehow
+ x_idx_max = bps-1;
+ }
+
+ /* Find last overlapping row */
+ y_idx_max = (box->high.y-geomstats->ymin) / geoh * bps;
+ if (y_idx_max <0)
+ {
+ // should increment the value somehow
+ y_idx_max = 0;
+ }
+ if (y_idx_max >= bps)
+ {
+ // should increment the value somehow
+ y_idx_max = bps-1;
+ }
+
+ /*
+ * the {x,y}_idx_{min,max}
+ * define the grid squares that the box intersects
+ */
+ for (y=y_idx_min; y<=y_idx_max; y++)
+ {
+ for (x=x_idx_min; x<=x_idx_max; x++)
+ {
+ double val;
+ double gain;
+
+ val = geomstats->value[x+y*bps];
+
+ /*
+ * Of the cell value we get
+ * only the overlap fraction.
+ */
+
+ intersect_x = min(box->high.x, geomstats->xmin + (x+1) * geow / bps) - max(box->low.x, geomstats->xmin + x * geow / bps );
+ intersect_y = min(box->high.y, geomstats->ymin + (y+1) * geoh / bps) - max(box->low.y, geomstats->ymin+ y * geoh / bps) ;
+
+ AOI = intersect_x*intersect_y;
+ gain = AOI/cell_area;
+
+#if DEBUG_GEOMETRY_STATS > 1
+ elog(NOTICE, " [%d,%d] cell val %.15f",
+ x, y, val);
+ elog(NOTICE, " [%d,%d] gain %.15f",
+ x, y, gain);
+#endif
+
+ val *= gain;
+
+#if DEBUG_GEOMETRY_STATS > 1
+ elog(NOTICE, " [%d,%d] adding %.15f to value",
+ x, y, val);
+#endif
+ value += val;
+ }
+ }
+
+
+ /*
+ * If the search_box is a point, it will
+ * overlap a single cell and thus get
+ * it's value, which is the fraction of
+ * samples (we can presume of row set also)
+ * which bumped to that cell.
+ *
+ * If the table features are points, each
+ * of them will overlap a single histogram cell.
+ * Our search_box value would then be correctly
+ * computed as the sum of the bumped cells values.
+ *
+ * If both our search_box AND the sample features
+ * overlap more then a single histogram cell we
+ * need to consider the fact that our sum computation
+ * will have many duplicated included. E.g. each
+ * single sample feature would have contributed to
+ * raise the search_box value by as many times as
+ * many cells in the histogram are commonly overlapped
+ * by both searc_box and feature. We should then
+ * divide our value by the number of cells in the virtual
+ * 'intersection' between average feature cell occupation
+ * and occupation of the search_box. This is as
+ * fuzzy as you understand it :)
+ *
+ * Consistency check: whenever the number of cells is
+ * one of whichever part (search_box_occupation,
+ * avg_feature_occupation) the 'intersection' must be 1.
+ * If sounds that our 'intersaction' is actually the
+ * minimun number between search_box_occupation and
+ * avg_feat_occupation.
+ *
+ */
+ overlapping_cells = (x_idx_max-x_idx_min+1) *
+ (y_idx_max-y_idx_min+1);
+ avg_feat_cells = geomstats->avgFeatureCells;
+
+#if DEBUG_GEOMETRY_STATS
+elog(NOTICE, " search_box overlaps %f cells", overlapping_cells);
+elog(NOTICE, " avg feat overlaps %f cells", avg_feat_cells);
+#endif
+
+ gain = 1/min(overlapping_cells, avg_feat_cells);
+ selectivity = value*gain;
+
+#if DEBUG_GEOMETRY_STATS
+ elog(NOTICE, " SUM(ov_histo_cells)=%f", value);
+ elog(NOTICE, " gain=%f", gain);
+ elog(NOTICE, " selectivity=%f", selectivity);
+#endif
+
+ /* prevent rounding overflows */
+ if (selectivity > 1.0) selectivity = 1.0;
+ else if (selectivity < 0) selectivity = 0.0;
+
+ return selectivity;
+}
+
/*
* This function should return an estimation of the number of
* rows returned by a query involving an overlap check
* It can make use (if available) of the statistics collected
* by the geometry analyzer function.
*
+ * Note that the good work is done by estimate_selectivity() above.
+ * This function just tries to find the search_box, loads the statistics
+ * and invoke the work-horse.
+ *
* This is the one used for PG version >= 7.5
*
*/
/*
* Do the estimation
*/
- {
- int x, y;
- int x_idx_min, x_idx_max, y_idx_min, y_idx_max;
- double intersect_x, intersect_y, AOI;
- double cell_area, box_area;
- double geow, geoh; // width and height of histogram
- int bps; // boxesPerSide
- BOX *box;
- double value;
- float overlapping_cells;
- float avg_feat_cells;
- double gain;
-
- box = search_box;
- geow = geomstats->xmax-geomstats->xmin;
- geoh = geomstats->ymax-geomstats->ymin;
- bps = geomstats->boxesPerSide;
- cell_area = (geow*geoh) / (bps*bps);
- box_area = (box->high.x-box->low.x)*(box->high.y-box->low.y);
- value = 0;
-
- /* Find first overlapping column */
- x_idx_min = (box->low.x-geomstats->xmin) / geow * bps;
- if (x_idx_min < 0) {
-#if DEBUG_GEOMETRY_STATS
- elog(NOTICE, " search_box overlaps %d columns on the left of histogram grid", -x_idx_min);
-#endif
- // should increment the value somehow
- x_idx_min = 0;
- }
- if (x_idx_min >= bps)
- {
-#if DEBUG_GEOMETRY_STATS
- elog(NOTICE, " search_box overlaps %d columns on the right of histogram grid", x_idx_min-bps+1);
-#endif
- // should increment the value somehow
- x_idx_min = bps-1;
- }
-
- /* Find first overlapping row */
- y_idx_min = (box->low.y-geomstats->ymin) / geoh * bps;
- if (y_idx_min <0)
- {
-#if DEBUG_GEOMETRY_STATS
- elog(NOTICE, " search_box overlaps %d columns on the bottom of histogram grid", -y_idx_min);
-#endif
- // should increment the value somehow
- y_idx_min = 0;
- }
- if (y_idx_min >= bps)
- {
-#if DEBUG_GEOMETRY_STATS
- elog(NOTICE, " search_box overlaps %d columns on the top of histogram grid", y_idx_min-bps+1);
-#endif
- // should increment the value somehow
- y_idx_min = bps-1;
- }
-
- /* Find last overlapping column */
- x_idx_max = (box->high.x-geomstats->xmin) / geow * bps;
- if (x_idx_max <0)
- {
- // should increment the value somehow
- x_idx_max = 0;
- }
- if (x_idx_max >= bps )
- {
- // should increment the value somehow
- x_idx_max = bps-1;
- }
-
- /* Find last overlapping row */
- y_idx_max = (box->high.y-geomstats->ymin) / geoh * bps;
- if (y_idx_max <0)
- {
- // should increment the value somehow
- y_idx_max = 0;
- }
- if (y_idx_max >= bps)
- {
- // should increment the value somehow
- y_idx_max = bps-1;
- }
-
- /*
- * the {x,y}_idx_{min,max}
- * define the grid squares that the box intersects
- */
- for (y=y_idx_min; y<=y_idx_max; y++)
- {
- for (x=x_idx_min; x<=x_idx_max; x++)
- {
- double val;
- double gain;
-
- val = geomstats->value[x+y*bps];
-
- /*
- * Of the cell value we get
- * only the overlap fraction.
- */
-
- intersect_x = min(box->high.x, geomstats->xmin + (x+1) * geow / bps) - max(box->low.x, geomstats->xmin + x * geow / bps );
- intersect_y = min(box->high.y, geomstats->ymin + (y+1) * geoh / bps) - max(box->low.y, geomstats->ymin+ y * geoh / bps) ;
-
- AOI = intersect_x*intersect_y;
- gain = AOI/cell_area;
-
-#if DEBUG_GEOMETRY_STATS > 1
- elog(NOTICE, " [%d,%d] cell val %.15f",
- x, y, val);
- elog(NOTICE, " [%d,%d] gain %.15f",
- x, y, gain);
-#endif
-
- val *= gain;
-
-#if DEBUG_GEOMETRY_STATS > 1
- elog(NOTICE, " [%d,%d] adding %.15f to value",
- x, y, val);
-#endif
- value += val;
- }
- }
-
-
- /*
- * If the search_box is a point, it will
- * overlap a single cell and thus get
- * it's value, which is the fraction of
- * samples (we can presume of row set also)
- * which bumped to that cell.
- *
- * If the table features are points, each
- * of them will overlap a single histogram cell.
- * Our search_box value would then be correctly
- * computed as the sum of the bumped cells values.
- *
- * If both our search_box AND the sample features
- * overlap more then a single histogram cell we
- * need to consider the fact that our sum computation
- * will have many duplicated included. E.g. each
- * single sample feature would have contributed to
- * raise the search_box value by as many times as
- * many cells in the histogram are commonly overlapped
- * by both searc_box and feature. We should then
- * divide our value by the number of cells in the virtual
- * 'intersection' between average feature cell occupation
- * and occupation of the search_box. This is as
- * fuzzy as you understand it :)
- *
- * Consistency check: whenever the number of cells is
- * one of whichever part (search_box_occupation,
- * avg_feature_occupation) the 'intersection' must be 1.
- * If sounds that our 'intersaction' is actually the
- * minimun number between search_box_occupation and
- * avg_feat_occupation.
- *
- */
- overlapping_cells = (x_idx_max-x_idx_min+1) *
- (y_idx_max-y_idx_min+1);
- avg_feat_cells = geomstats->avgFeatureCells;
-
-#if DEBUG_GEOMETRY_STATS
- elog(NOTICE, " search_box overlaps %f cells", overlapping_cells);
- elog(NOTICE, " avg feat overlaps %f cells", avg_feat_cells);
-#endif
-
- gain = 1/min(overlapping_cells, avg_feat_cells);
- selectivity = value*gain;
-
-#if DEBUG_GEOMETRY_STATS
- elog(NOTICE, " SUM(ov_histo_cells)=%f", value);
- elog(NOTICE, " gain=%f", gain);
- elog(NOTICE, " selectivity=%f", selectivity);
-#endif
-
- /* prevent rounding overflows */
- if (selectivity > 1.0) selectivity = 1.0;
- else if (selectivity < 0) selectivity = 0.0;
- }
-
+ selectivity = estimate_selectivity(search_box, geomstats);
#if DEBUG_GEOMETRY_STATS
/* Indicate we are done successfully */
PG_RETURN_BOOL(true);
}
+
+
#endif
projects / postgis / commitdiff