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…umns dictionary uniqueness when allowing dimension selector cursor, fixes a bug with unnest on realtime segments with empty rows incorrectly specifying index 0 as the row dictionary value
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abhishekagarwal87
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clintropolis
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sreemanamala
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Aug 6, 2024
changes: * fixes a bug with unnest storage adapter not preserving underlying columns dictionary uniqueness when allowing dimension selector cursor * fixes a bug with unnest on realtime segments with empty rows incorrectly specifying index 0 as the row dictionary value
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Description
Fixes of #16690, but tries to instead fix the attempted behavior of coercing
[]into[null]forUnnestDimensionCursorto be less disruptive while we determine what the correct behavior for unnest on[]for a multi-value string actually is. For regular arrays,[]is skipped per the standard, but for MVDs it looks like theUnnestDimensionCursorwas trying to match group-by behavior. Idk if matching group-by behavior is correct, but the way it was doing it was totally wrong ifnullwasn't id 0 in the dictionary (or if the dictionary had no nulls at all). This PR fixes that by using the idLookup of the underlying dimension selector to lookup the null value id, and if present, using that, and if not, creating a synthetic nullId at position 0 and offsetting all of the real dictionary ids by 1 as we have done in some other places for other reasons (e.g. adapters for default value mode when segments were written in SQL compatible null handling mode).This PR has: