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Merge pull request #33229 from amosbird/nullableprimarykeyrisk

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Document the risk of enabling allow_nullable_key
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alexey-milovidov 2021-12-28 20:32:58 +03:00 committed by GitHub
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docs/en/operations/settings/settings.md
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@ -3154,6 +3154,12 @@ Possible values:
Default value: `0`.
!!! warning "Warning"
Nullable primary key usually indicates bad design. It is forbidden in almost all main stream DBMS. The feature is mainly for [AggregatingMergeTree](../../engines/table-engines/mergetree-family/aggregatingmergetree.md) and is not heavily tested. Use with care.
!!! warning "Warning"
Do not enable this feature in version `<= 21.8`. It's not properly implemented and may lead to server crash.
## aggregate_functions_null_for_empty {#aggregate_functions_null_for_empty}
Enables or disables rewriting all aggregate functions in a query, adding [-OrNull](../../sql-reference/aggregate-functions/combinators.md#agg-functions-combinator-ornull) suffix to them. Enable it for SQL standard compatibility.