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colblk: Bitmap, BitmapBuilder bug fixes #4112

Merged
merged 2 commits into from
Oct 25, 2024
Merged

colblk: Bitmap, BitmapBuilder bug fixes #4112

merged 2 commits into from
Oct 25, 2024

Commits on Oct 25, 2024

  1. colblk: fix Invert to initialize memory 

    Previously, Invert used slices.Grow to grow the b.words slice if necessary. If
len(b.words) < cap(b.words), words in the unused capacity were not initialized
to zero and were assumed to be zero. Most of the time this was okay, because
Reset zeroed b.words up to len(b.words).

However if the BitmapBuilder was previously used to Finish fewer rows than were
Set, it's possible Finish may have truncated b.words to exclude words with
non-zero bits. Since Reset only reset words within len(b.words), the truncated
words were left unzeroed.

This commit updates Invert to make no assumptions as to the value of words
beyond len(b.words). It also removes the zeroing in Reset which obscured this
bug in most cases, instead relying on Set, Finish and Invert to properly
initialize memory as necessary as it's used.

Fix cockroachdb#4103.
    @jbowens
    jbowens committed Oct 25, 2024
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  2. colblk: fix summary table bounds 

    Fix an off-by-one on the summary table end bound. This could cause SeekSetBitGE
to return the wrong index in bitmaps with more than 4096 represented bits.
    @jbowens
    jbowens committed Oct 25, 2024
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