xqods9o5ekm3 created SPARK-30335:
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Summary: Clarify behavior of FIRST and LAST without OVER caluse.
Key: SPARK-30335
URL: https://issues.apache.org/jira/browse/SPARK-30335
Project: Spark
Issue Type: New Feature
Components: SQL
Affects Versions: 2.4.0, 3.0.0
Reporter: xqods9o5ekm3
Unlike many databases, Spark SQL allows usage of {{FIRST}} and {{LAST}} in
non-analytic contexts.
At the moment {{FIRST}}
> first(expr[, isIgnoreNull]) - Returns the first value of {{expr}} for a group
> of rows. If {{isIgnoreNull}} is true, returns only non-null values.
and {{LAST}}
> last(expr[, isIgnoreNull]) - Returns the last value of {{expr}} for a group
> of rows. If {{isIgnoreNull}} is true, returns only non-null values.
descriptions, suggest that their behavior is deterministic and many users
assume that it return specific values for example when query
{code:sql}
SELECT first(foo)
FROM (
SELECT * FROM table ORDER BY bar
)
{code}
That however doesn't seem to be the case.
To make situation worse, it seems to work (for example on small samples in
local mode).
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