Scan validity from dictionary vectors directly, and skip scanning validity when we encounter a dictionary vector #15737
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…idity when we encounter a dictionary vector
Tishj
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Jan 15, 2025
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Ah I see, that works 👍
Dictionary compression is the only compression method that can create a Dictionary Vector, when we create a DictionaryVector we make sure it has the validity already set.
In the validity compression methods we recognize this and return immediately
(also slightly optimize fetching by not initializing the dictionary)
krlmlr
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Scan validity from dictionary vectors directly, and skip scanning validity when we encounter a dictionary vector (duckdb/duckdb#15737)
Mytherin
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…lues when reading files created by older versions of DuckDB
Mytherin
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…odifies the validity (#16851) Fixes #16836 This regression was caused by #15737 Effectively that change introduced an optimization for dictionary-compressed data where the validity data would be read directly from the dictionary - instead of being read from the separate validity data. This is possible because dictionary-compressed data stores validity data (at offset 0 in the dictionary). However, when doing an `UPDATE`, we would not rewrite the dictionary data when changing only the validity - which would then cause the dictionary column to no longer contain the new (updated) validity data. The fix here is to also rewrite the main column data when updating the validity data. Note that we currently do this for all primitive types - we could limit this to compression methods (like dictionary) that need this - but we can leave that for a future PR. (CC @Tishj).
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This prevents unnecessarily flattening dictionary vectors when scanning.
The two test changes are unrelated but just minor fixes from issues encountered while testing this change.
CC @Tishj