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https://issues.apache.org/jira/browse/SPARK-57811?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Max Gekk updated SPARK-57811:
-----------------------------
    Shepherd: Max Gekk

> Support string to nanosecond-precision timestamp coercion in comparisons and 
> predicates
> ---------------------------------------------------------------------------------------
>
>                 Key: SPARK-57811
>                 URL: https://issues.apache.org/jira/browse/SPARK-57811
>             Project: Spark
>          Issue Type: Sub-task
>          Components: SQL
>    Affects Versions: 4.3.0
>            Reporter: Max Gekk
>            Priority: Major
>
> This sub-task is part of the umbrella SPARK-56822 (timestamps with nanosecond 
> precision).
> h2. Problem
> {{findCommonTypeForBinaryComparison}} (analysis/TypeCoercion.scala ~L144-147) 
> special-cases only {{TimestampType + StringType}}, and 
> {{StringPromotionTypeCoercion}} (~L58-61) matches only the microsecond 
> {{TimestampTypeExpression}} (DataTypeExpression.scala ~L45). A string operand 
> compared to a nanosecond timestamp column is therefore not coerced like the 
> microsecond case: non-ANSI may promote the timestamp to string, ANSI may 
> fail. Column-vs-column nanos/micro is already correct (SPARK-57454); this is 
> the string-literal path only.
> h2. Goal
> Coerce a string operand compared to a nanosecond timestamp column to the 
> nanosecond type (parity with microsecond), in both the binary-comparison 
> common-type path and the equality string-promotion path, for ANSI and 
> non-ANSI.
> h2. Scope
> Extend {{findCommonTypeForBinaryComparison}} and 
> {{StringPromotionTypeCoercion}} (and the {{DataTypeExpression}} matchers) to 
> include {{AnyTimestampNanoType}}.
> h2. Acceptance criteria
> * {{ts_nanos = '2020-01-02 03:04:05.123456789'}} and range predicates resolve 
> by casting the string to the nanosecond type; results correct in both ANSI 
> and non-ANSI modes.
> h2. Testing
> {{TypeCoercionSuite}} / {{AnsiTypeCoercionSuite}}; nanos golden files.
> h2. Dependencies
> None - independent (widening resolved in SPARK-57454). Feeds the 
> cross-precision test-coverage sub-task.



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