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Fix get_last_event_in_room_before_stream_ordering(...) finding the wrong last event #17295

Merged
merged 9 commits into from
Jun 13, 2024
Merged

Fix get_last_event_in_room_before_stream_ordering(...) finding the wrong last event #17295

merged 9 commits into from
Jun 13, 2024

Commits on Jun 12, 2024

  1. Fix get_last_event_in_room_before_stream_ordering(...) not finding … 

    …the last event

Previously, it would use the event with the lowest `stream_ordering` that was
fetched (we want the highest `stream_ordering. `union` does not work how you
might think at first and does not preserve the ordering of the operand queries.

`union all` also doesn't necessarily have that gurantee but it does behave
that way. See https://dba.stackexchange.com/questions/316818/are-results-from-union-all-clauses-always-appended-in-order/316835#316835
    @MadLittleMods
    MadLittleMods committed Jun 12, 2024
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  2. Add actual guranteed order for UNION 

    We use `union all` because we don't need any of the deduplication logic
(`union` is really a union + distinct). `UNION ALL`` does preserve the
ordering of the operand queries but there is no actual gurantee that it
has this behavior in all scenarios so we need the extra `ORDER BY` at the
bottom.

See https://dba.stackexchange.com/questions/316818/are-results-from-union-all-clauses-always-appended-in-order/316835#316835
    @MadLittleMods
    MadLittleMods committed Jun 12, 2024
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  3. Try to better explain why 

    See #17293 (comment)
    @MadLittleMods
    MadLittleMods committed Jun 12, 2024
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  4. Add changelog

    @MadLittleMods
    MadLittleMods committed Jun 12, 2024
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  5. We're actually using sub-query syntax so we can ORDER each query

    @MadLittleMods
    MadLittleMods committed Jun 12, 2024
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  6. Fix invalid syntax

    @MadLittleMods
    MadLittleMods committed Jun 12, 2024
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  7. Merge branch 'develop' into madlittlemods/fix-and-tests-for-get_last_… 

    …event_in_room_before_stream_ordering
    @MadLittleMods
    MadLittleMods committed Jun 12, 2024
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  8. Update wording

    @MadLittleMods
    MadLittleMods committed Jun 12, 2024
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  9. Merge branch 'develop' into madlittlemods/fix-and-tests-for-get_last_… 

    …event_in_room_before_stream_ordering
    @MadLittleMods
    MadLittleMods committed Jun 12, 2024
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