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fix bug with expression virtual column indexes on missing columns for expressions that turn null values into not null values #15959

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merged 1 commit into from Feb 23, 2024

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@clintropolis clintropolis commented Feb 23, 2024

Description

Fixes a mistake in expression virtual column indexes introduced in #15585, which would incorrectly return null from the index supplier, which is a signal to downstream filters that the column is all nulls, even for expressions which translate null values into not null values. This affects filters on stuff like nvl, coalesce, 3 argument lookup, etc. when filtering for the replaced value, for example: ... WHERE NVL(col, 'replaced') = 'replaced'. The workaround I suppose is to just filter for is null without nvl/coalesce/etc.

The added test would incorrectly fail the 2nd case.


This PR has:

  • been self-reviewed.
  • added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
  • added unit tests or modified existing tests to cover new code paths, ensuring the threshold for code coverage is met.
  • been tested in a test Druid cluster.

… expressions that turn null values into not null values
@clintropolis clintropolis merged commit 6145c8d into apache:master Feb 23, 2024
82 of 83 checks passed
@clintropolis clintropolis deleted the fix-expr-index-nil branch February 23, 2024 23:07
cryptoe pushed a commit to cryptoe/druid that referenced this pull request Mar 6, 2024
… expressions that turn null values into not null values (apache#15959)
cryptoe added a commit that referenced this pull request Mar 11, 2024
… expressions that turn null values into not null values (#15959) (#16055)

Co-authored-by: Clint Wylie <cwylie@apache.org>
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