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release-24.3: fix spurious LDR DLQ entries #147354

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release-24.3: fix spurious LDR DLQ entries #147354

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Backport:

Please see individual PRs for details.

Release justification: fixes #145994 which was discovered in customer environments.

/cc @cockroachdb/release

@jeffswenson
logical: batch handler exhaustive test
f6b2a25 
This reworks the crud table handler's exhaustive test so that it runs
against the batch handler interface. That allows it to test all of the
LDR handler implementations.

The test was extended to metamorphically define a unique
index/constraint and swap the primary key column id. This allows the
test to reproduce cockroachdb#145994.

Informs: cockroachdb#145994
Release note: none
@jeffswenson
kvcoord: deterministic error ordering
202775d 
DistSender splits requests up in range order and collects errors in the
order requests were dispatched. If there are multiple errors, the
highest priority error is returned and ties are broken by dispatch
order. Now, the merge logic consults the index of the request that
generated the error. This is particularly useful for CPuts as it allows
the caller to observe the first cput in the batch that failed.

The deterministic order allows LDR, `deleteSwap`, and `updateSwap` to
guarantee the cput error is for the primary key. This property is
essential because they are using cput to optimistically guess at the
value of the row in the database. The batches may also contain cput
failures for unique indexes, but those errors should only be raised to
the user if the primary key cput succeeded.

This is still a bit of a hack. In a perfect world, the cput failure
would be treated as a result instead of an error. That would allow the
caller to inspect each cput result independently and would make it clear
that cput failures do not poison any of the other requests in the
batch.

Informs: cockroachdb#146117
Release note: fixes an issue with LDR where the presence of a unique
index may cause spurious DLQ entries if the unique index has a smaller
index id than the primary key index.
@jeffswenson jeffswenson requested review from a team as code owners May 27, 2025 18:15
@blathers-crl blathers[crl]
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blathers-crl bot commented May 27, 2025

Thanks for opening a backport.

Please check the backport criteria before merging:

  • Backports should only be created for serious
    issues     or test-only changes.
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    here).
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If your backport adds new functionality, please ensure that the following additional criteria are satisfied:
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Also, please add a brief release justification to the body of your PR to justify this
backport.

@blathers-crl blathers-crl bot added the backport Label PR's that are backports to older release branches label May 27, 2025
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@arulajmani arulajmani arulajmani approved these changes

@msbutler msbutler msbutler approved these changes

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