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Formerly, the computation of the bucket index involved calling div_var() with a scale determined by select_div_scale(), and then taking the floor of the result. That involved computing anything from 16 to 1000 digits after the decimal point, only for floor_var() to throw them away. In addition, the quotient was computed with rounding in the final digit, which meant that in rare cases the whole result could round up to the wrong bucket, and could exceed count. Thus it was also necessary to clamp the result to the range [1, count], though that didn't prevent the result being in the wrong internal bucket. Instead, compute the quotient using floor division, which guarantees the correct result, as specified by the SQL spec, and doesn't need to be clamped. This is both much simpler and more efficient, since it no longer computes any quotient digits after the decimal point. In addition, it is not necessary to have separate code to handle reversed bounds, since the signs cancel out when dividing. As withb0e9e4d76canda2a0c7c29e, no back-patch. Dean Rasheed, reviewed by Joel Jacobson. Discussion: https://postgr.es/m/CAEZATCVbJH%2BLE9EXW8Rk3AxLe%3DjbOk2yrT_AUJGGh5Rah6zoeg%40mail.gmail.com