Fix HllSketchHolderObjectStrategy#isSafeToConvertToNullSketch. #15860
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The prior code from apache#15162 was reading only the low-order byte of an int representing the size of a coupon set. As a result, it would erroneously believe that a coupon set with a multiple of 256 elements was empty.
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clintropolis
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Feb 7, 2024
| return false; | ||
| } | ||
| // Based on org.apache.datasketches.hll.PreambleUtil.extractHashSetCount | ||
| int setCount = buf.get(position + 8); // get(HASH_SET_COUNT_INT) | ||
| // Endianness of buf doesn't matter, since we're checking for equality with zero. | ||
| int setCount = buf.getInt(position + 8); // getInt(HASH_SET_COUNT_INT) |
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The changes generally look good to me. We should probably go and ask the apache-datasketches folks if we can get an "isEffectivelyEmpty" method added to the Sketch so that we can remove all of this introspective logic to begin with. That should enable a much more future-proof way of dealing with this. |
imply-cheddar
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Feb 7, 2024
adarshsanjeev
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…e#15860) * Fix HllSketchHolderObjectStrategy#isSafeToConvertToNullSketch. The prior code from apache#15162 was reading only the low-order byte of an int representing the size of a coupon set. As a result, it would erroneously believe that a coupon set with a multiple of 256 elements was empty.
LakshSingla
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Feb 8, 2024
…e#15860) * Fix HllSketchHolderObjectStrategy#isSafeToConvertToNullSketch. The prior code from apache#15162 was reading only the low-order byte of an int representing the size of a coupon set. As a result, it would erroneously believe that a coupon set with a multiple of 256 elements was empty.
LakshSingla
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Feb 8, 2024
… (#15861) * Fix HllSketchHolderObjectStrategy#isSafeToConvertToNullSketch. The prior code from #15162 was reading only the low-order byte of an int representing the size of a coupon set. As a result, it would erroneously believe that a coupon set with a multiple of 256 elements was empty. Co-authored-by: Gian Merlino <gianmerlino@gmail.com>
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The prior code from #15162 was reading only the low-order byte of an int representing the size of a coupon set. As a result, it would erroneously believe that a coupon set with a multiple of 256 elements was empty. At the default lgK (12) this is possible when the sketch has exactly 256 items in it. (At lgK = 12, before it reaches 512, it would be promoted from coupon set to full HLL.)