nd_box_ratio()

static double nd_box_ratio ( const ND_BOX *  b1, const ND_BOX *  b2, int  ndims  )

inlinestatic

Returns the proportion of b2 that is covered by b1.

Definition at line 674 of file gserialized_estimate.c.

References FALSE, ND_BOX_T::max, ND_BOX_T::min, and TRUE.

Referenced by compute_gserialized_stats_mode(), estimate_join_selectivity(), and estimate_selectivity().

{
        int d;
        bool covered = TRUE;
        double ivol = 1.0;
        double vol2 = 1.0;
        double vol1 = 1.0;

        for ( d = 0 ; d < ndims; d++ )
        {
                if ( b1->max[d] <= b2->min[d] || b1->min[d] >= b2->max[d] )
                        return 0.0; /* Disjoint */

                if ( b1->min[d] > b2->min[d] || b1->max[d] < b2->max[d] )
                        covered = FALSE;
        }

        if ( covered )
                return 1.0;

        for ( d = 0; d < ndims; d++ )
        {
                double width1 = b1->max[d] - b1->min[d];
                double width2 = b2->max[d] - b2->min[d];
                double imin, imax, iwidth;

                vol1 *= width1;
                vol2 *= width2;

                imin = Max(b1->min[d], b2->min[d]);
                imax = Min(b1->max[d], b2->max[d]);
                iwidth = imax - imin;
                iwidth = Max(0.0, iwidth);

                ivol *= iwidth;
        }

        if ( vol2 == 0.0 )
                return vol2;

        return ivol / vol2;
}

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