Max Gekk created SPARK-57837:
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Summary: Support the precision argument in current_timestamp(p)
and localtimestamp(p)
Key: SPARK-57837
URL: https://issues.apache.org/jira/browse/SPARK-57837
Project: Spark
Issue Type: Sub-task
Components: SQL
Affects Versions: 4.3.0
Reporter: Max Gekk
This sub-task is part of the umbrella SPARK-56822 (timestamps with nanosecond
precision).
h2. Problem
Today {{current_timestamp}} / {{now}} / {{localtimestamp}} take no precision
argument - {{CurrentTimestamp}} / {{Now}} are fixed {{TimestampType}} and
{{LocalTimestamp}} fixed {{TimestampNTZType}} (datetimeExpressions.scala
~L191-268), registered without a builder ({{FunctionRegistry}} ~L701/705), and
the parser produces {{CurrentTimestamp()}} with no args ({{AstBuilder}}
~L3589). ANSI SQL/Foundation defines an optional <timestamp precision> on both
(Feature F555 "Enhanced seconds precision", std lines ~16669-16737), with
{{LOCALTIMESTAMP(p) = CAST(CURRENT_TIMESTAMP(p) AS TIMESTAMP(p) WITHOUT TIME
ZONE)}}.
h2. Goal
Accept an optional precision {{p}} in {{current_timestamp(p)}} and
{{localtimestamp(p)}} for {{p}} in [7, 9] (when nanosecond types are enabled),
returning the corresponding nanosecond LTZ/NTZ type. {{current_time(p)}}
(timeExpressions.scala ~L489-534) is the existing precedent to mirror.
h2. Scope
Add precision-aware expression builders for the current-timestamp functions;
return {{TimestampLTZNanosType(p)}} / {{TimestampNTZNanosType(p)}}; wire the
value from the query's current instant with the nanosecond remainder; keep the
no-arg forms as microsecond defaults.
h2. Acceptance criteria
* {{current_timestamp(9)}} / {{localtimestamp(9)}} return nanosecond-typed
current time; no-arg forms unchanged.
h2. Testing
{{DateExpressionsSuite}} / {{ComputeCurrentTimeSuite}}; nanos golden files.
h2. Dependencies
None hard (builds on resolved ComputeCurrentTime SPARK-57748); reuses the
internal nanosecond make-timestamp expressions surfaced by the make_timestamp
sub-task.
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