gserialized_sel_internal()

float8 gserialized_sel_internal	(	PlannerInfo *	root,
		List *	args,
		int	varRelid,
		int	mode
	)

This function should return an estimation of the number of rows returned by a query involving an overlap check ( it's the restrict function for the && operator )

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.

Definition at line 2070 of file gserialized_estimate.c.

{
        VariableStatData vardata;
        Node *other = NULL;
        bool varonleft;
        ND_STATS *nd_stats = NULL;
 
        GBOX search_box;
        float8 selectivity = 0;
        Const *otherConst;
 
        POSTGIS_DEBUGF(2, "%s: entered function", __func__);
 
        if (!get_restriction_variable(root, args, varRelid, &vardata, &other, &varonleft))
        {
                POSTGIS_DEBUGF(2, "%s: could not find vardata", __func__);
                return DEFAULT_ND_SEL;
        }
 
        if (!IsA(other, Const))
        {
                ReleaseVariableStats(vardata);
                POSTGIS_DEBUGF(2, "%s: no constant argument, returning default selectivity %g", __func__, DEFAULT_ND_SEL);
                return DEFAULT_ND_SEL;
        }
 
        otherConst = (Const*)other;
        if ((!otherConst) || otherConst->constisnull)
        {
                ReleaseVariableStats(vardata);
                POSTGIS_DEBUGF(2, "%s: constant argument is NULL", __func__);
                return DEFAULT_ND_SEL;
        }
 
        if (!gserialized_datum_get_gbox_p(otherConst->constvalue, &search_box))
        {
                ReleaseVariableStats(vardata);
                POSTGIS_DEBUGF(2, "%s: search box is EMPTY", __func__);
                return 0.0;
        }
 
        if (!vardata.statsTuple)
        {
                POSTGIS_DEBUGF(1, "%s: no statistics available on table. Empty? Need to ANALYZE?", __func__);
                return DEFAULT_ND_SEL;
        }
 
        nd_stats = pg_nd_stats_from_tuple(vardata.statsTuple, mode);
        ReleaseVariableStats(vardata);
        selectivity = estimate_selectivity(&search_box, nd_stats, mode);
        if (nd_stats)
                pfree(nd_stats);
 
        return selectivity;
}

References DEFAULT_ND_SEL, estimate_selectivity(), gserialized_datum_get_gbox_p(), and pg_nd_stats_from_tuple().

Referenced by gserialized_gist_sel(), and postgis_index_supportfn().

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