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release-23.2: sql/stats: evict stats cache entry if user-defined types have changed #124853

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Jun 6, 2024

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@michae2 michae2 commented May 30, 2024

Backport 1/3 commits from #124603.

/cc @cockroachdb/release


sql/stats: evict stats cache entry if user-defined types have changed

When adding table statistics to the stats cache, we decode histogram upper bounds into datums. If the histogram column uses a user-defined type, we hydrate the type and use this to decode.

In statistics builder, these histogram upper bound datums are compared against datums in spans and constraints. The comparisons assume that the datums are of equivalent type, but if the user-defined type has changed sometime after loading the stats cache entry, this might not be true.

If the user-defined type has changed, we need to evict and re-load the stats cache entry so that we decode histogram datums with a freshly-hydrated type.

(We were already checking UDT versions when building the optTable in sql.(*optCatalog).dataSourceForTable, but the newly-built optTable used the existing table statistics instead of refreshing those, too.)

Fixes: #124181

Release note (bug fix): Fix a bug where a change to a user-defined type could cause queries against tables using that type to fail with an error message like:

histogram.go:694: span must be fully contained in the bucket

The change to the user-defined type could come directly from an ALTER TYPE statement, or indirectly from an ALTER DATABASE ADD REGION or DROP REGION statement (which implicitly change the crdb_internal_region type).

This bug has existed since UDTs were introduced in v20.2.


Release justification: fix for a serious production issue.

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blathers-crl bot commented May 30, 2024

Thanks for opening a backport.

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@blathers-crl blathers-crl bot added the backport Label PR's that are backports to older release branches label May 30, 2024
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@michae2 michae2 force-pushed the backport23.2-124603 branch 2 times, most recently from 789ada7 to 9987c33 Compare June 4, 2024 06:07
@michae2 michae2 requested review from mgartner and rafiss June 5, 2024 15:34
@michae2 michae2 marked this pull request as ready for review June 5, 2024 15:34
@michae2 michae2 requested a review from a team as a code owner June 5, 2024 15:34
When adding table statistics to the stats cache, we decode histogram
upper bounds into datums. If the histogram column uses a user-defined
type, we hydrate the type and use this to decode.

In statistics builder, these histogram upper bound datums are compared
against datums in spans and constraints. The comparisons assume that the
datums are of equivalent type, but if the user-defined type has changed
sometime after loading the stats cache entry, this might not be true.

If the user-defined type has changed, we need to evict and re-load the
stats cache entry so that we decode histogram datums with a freshly-
hydrated type.

(We were already checking UDT versions when building the optTable in
sql.(*optCatalog).dataSourceForTable, but the newly-built optTable used
the existing table statistics instead of refreshing those, too.)

Fixes: cockroachdb#124181

Release note (bug fix): Fix a bug where a change to a user-defined type
could cause queries against tables using that type to fail with an error
message like:

  "histogram.go:694: span must be fully contained in the bucket"

The change to the user-defined type could come directly from an ALTER
TYPE statement, or indirectly from an ALTER DATABASE ADD REGION or DROP
REGION statement (which implicitly change the crdb_internal_region
type).

This bug has existed since UDTs were introduced in v20.2.
@michae2 michae2 merged commit e705886 into cockroachdb:release-23.2 Jun 6, 2024
5 of 6 checks passed
@michae2 michae2 deleted the backport23.2-124603 branch June 6, 2024 22:48
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3 participants