kkewwei commented on code in PR #16896:
URL: https://github.com/apache/lucene/pull/16896#discussion_r4412165211
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lucene/core/src/java/org/apache/lucene/codecs/lucene90/Lucene90DocValuesProducer.java:
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@@ -547,21 +547,34 @@ static void rangeIntoBitSet(
* values satisfy {@code stored = raw * mul + delta}. Returns {@code
{encodedMin, encodedMax}} or
* {@code null} if the range is empty (no raw value can match).
*/
- private static long[] transformGcdBounds(long minValue, long maxValue, long
mul, long delta) {
+ static long[] transformGcdBounds(
+ long minValue, long maxValue, long mul, long delta, int bitsPerValue) {
assert mul > 0;
- long encodedMin = saturatingShiftLower(minValue, delta);
- long encodedMax = saturatingShiftUpper(maxValue, delta);
- if (mul != 1) {
- encodedMin = Math.ceilDiv(encodedMin, mul);
- encodedMax = Math.floorDiv(encodedMax, mul);
+ if (maxValue < delta) {
+ return null;
}
- encodedMin = Math.max(0, encodedMin);
+ assert canTransformGcdBounds(minValue, maxValue, delta, bitsPerValue);
+ long encodedMin = minValue <= delta ? 0 : Math.ceilDiv(minValue - delta,
mul);
+ long encodedMax =
+ maxValue == Long.MAX_VALUE ? Long.MAX_VALUE : Math.floorDiv(maxValue -
delta, mul);
if (encodedMin > encodedMax) {
return null;
}
return new long[] {encodedMin, encodedMax};
}
+ /** Checks whether query bounds can be safely transformed to encoded bounds.
*/
+ static boolean canTransformGcdBounds(long minValue, long maxValue, long
delta, int bitsPerValue) {
Review Comment:
1. delta >= 0:
minValue <= delta -> encodedMin = 0
maxValue < delta -> empty range
otherwise -> subtraction is safe
We can see it's aways safe to transform gcdBounds for the case
2. delta < 0:
minValue <= delta
-> encodedMin = 0
maxValue < delta
-> empty range
(minValue/maxValue) <= Long.MAX_VALUE + delta -> subtraction is
safe
otherwise
-> fallback
3. delta < 0 && maxValue == Long.MAX_VALUE:
bitsPerValue < 64 -> encodedMax = Long.MAX_VALUE
otherwise -> fallback
Special case3: when bitsPerValue < 64, the stored value must be <
Long.MAX_VALUE, encodedMax = Long.MAX_VALUE is safe
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