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https://issues.apache.org/jira/browse/SPARK-57553?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Max Gekk resolved SPARK-57553.
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Resolution: Duplicate
> Support cast between TIME and TIMESTAMP_LTZ
> -------------------------------------------
>
> Key: SPARK-57553
> URL: https://issues.apache.org/jira/browse/SPARK-57553
> Project: Spark
> Issue Type: Sub-task
> Components: SQL
> Affects Versions: 4.3.0
> Reporter: Max Gekk
> Priority: Major
>
> h2. What
> Support {{CAST}} in both directions between {{TIME}} and {{TIMESTAMP}} /
> {{TIMESTAMP_LTZ}}
> (the microsecond {{TimestampType}}).
> h2. Why
> ANSI SQL requires TIME <-> TIMESTAMP to be a valid cast. SPARK-52617 covers
> the
> WITHOUT TIME ZONE variant; this ticket covers the WITH LOCAL TIME ZONE
> variant. Unlike NTZ,
> the LTZ direction is time-zone aware and uses the session time zone.
> h2. Semantics (ANSI / session time zone)
> * {{CAST(time AS TIMESTAMP_LTZ)}}: combine the time-of-day with
> {{CURRENT_DATE}} in the
> session time zone, then store as an absolute instant (epoch micros, UTC).
> * {{CAST(ts_ltz AS TIME(q))}}: convert the instant to the session time zone,
> take the
> time-of-day, truncate fractional seconds to q.
> h2. Scope
> * {{canCast}}/{{canAnsiCast}} + runtime + codegen in {{Cast.scala}},
> threading the session
> {{zoneId}} (as other TIMESTAMP_LTZ casts do).
> * {{TIMESTAMP_LTZ}} has microsecond precision; casting from {{TIME(7..9)}}
> truncates the
> sub-microsecond digits (mark nullable only if applicable).
> h2. Acceptance criteria
> * Both directions correct across DST/zone boundaries; covered with explicit
> session
> time-zone tests.
> * ANSI and non-ANSI modes; tests in {{CastSuiteBase}} and SQL golden files.
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