feat: Actually decode dictionary arrays#861
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## main #861 +/- ##
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- Coverage 79.96% 79.44% -0.53%
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Files 105 106 +1
Lines 15461 15881 +420
Branches 1738 1834 +96
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+ Hits 12364 12616 +252
- Misses 1998 2115 +117
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I'm pretty happy with this! If there are no objections I'll merge later today and move on to the shared dictionary problem. |
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For #861 (actual decoding of dictionary arrays), we really need shared arrays for this to be reasonable (e.g., to not deep copy each dictionary for each batch!). This PR (1) moves shared buffers to the C library instead of the IPC extension, (2) implements a second kind of shared buffer, which is borrowed from an owned reference-counted array, and (3) implements a "clone" that mostly uses the second concept to explode an array into 100% reference counted buffers that we can clone. I had hoped we could replace the R and Python versions of these but the logic is fuzzier there because once an array has been referenced we can't mess with it or any of its parents (or it will cause a crash). My mind explodes (and I get a lot of failing R tests cases) whenever I mess with that piece and so I'll try to deal with that a different day. This still needs tests for the shared array move and clone. --------- Co-authored-by: Copilot <copilot@github.com>
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This PR uses the previous steps to output arrays (including the ArrowArrayStream reader). This lets us wire it in to all the tests as well.
The main follow up is that this PR currently deep copies the dictionary for every batch that arrives, negating much of the point of dictionary encoding. This is a fairly self-contained change that I'll do separately: #864
I also added dictionary index validation while I was here! It is fairly compact (compared to the other code).
Closes #845.