jonmmease opened a new pull request, #4847:
URL: https://github.com/apache/arrow-datafusion/pull/4847
# Which issue does this PR close?
Closes #4843.
# Rationale for this change
Rather than crash when performing a variance-based aggregation on a single
value, follow Postgres' semantics:
- `var`/`stddev` of single element is `NULL`
- `var_pop`/`stddev_pop` of single element is 0
There's documentation of this behavior in Snowflake
(https://docs.snowflake.com/en/sql-reference/functions/stddev.html), and it's
what Postgres does, but in searching briefly I haven't found this behavior
described in the Postgres docs.
# Are these changes tested?
I added a pair of sqllogictest tests for the one and two element cases.
# Are there any user-facing changes?
Queries that used to crash when aggregating single values with
variance-based aggregations will no longer crash.
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