Tanner Clary created CALCITE-6045:
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Summary: CURRENT_TIMESTAMP has incorrect return type
Key: CALCITE-6045
URL: https://issues.apache.org/jira/browse/CALCITE-6045
Project: Calcite
Issue Type: Bug
Reporter: Tanner Clary
When trying to work on CALCITE-6021, I noticed that {{CURRENT_TIMESTAMP}}
currently returns type {{TIMESTAMP}} when it should be
{{TIMESTAMP_WITH_LOCAL_TIME_ZONE}}.
After modifying it, I noticed function was returning the time from (UTC -
System TZ) hours ago. For example, I am in {{America/Los_Angeles}} and if I
called the function at {{2023-10-10 13:28:00 America/Los_Angeles}}, it would
return {{2023-10-10 06:28:00 America/Los_Angeles}}.
I think this is because the DataContext {{CURRENT_TIMESTAMP}} variable, which
is meant to represent milliseconds since epoch UTC, actually has the timezone
offset applied in {{CalciteConnectionImpl#DataContextImpl}}
[here|https://github.com/apache/calcite/blob/main/core/src/main/java/org/apache/calcite/jdbc/CalciteConnectionImpl.java#L442].
To be clear: it is meant to represent millis since epoch UTC, but instead it
is millis since epoch [system tz], as I understand it.
Additionally, I believe the {{getString()}} method for timestamps in
AvaticaResultSet should behave similarly to
[{{SqlFunctions#timestampWithLocalTimezoneToString()}}|https://github.com/apache/calcite/blob/main/core/src/main/java/org/apache/calcite/runtime/SqlFunctions.java#L4021]
when dealing with a {{TIMESTAMP WITH LOCAL TIME ZONE}}. Right now, it does not
take the timezone into consideration so although it represents the accurate
instant in time, it displays differently than {{CAST(CURRENT_TIMESTAMP AS
VARCHAR)}}.
For example, {{SELECT CURRENT_TIMESTAMP, CAST(CURRENT_TIMESTAMP AS VARCHAR)}},
with the correct return type, returns something like:
{{2023-10-10 13:28:00 | 2023-10-10 06:28:00.000 America/Los_Angeles}}
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