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https://issues.apache.org/jira/browse/HIVE-18430?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jason Dere updated HIVE-18430:
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Attachment: HIVE-18430.1.patch
> Add new determinism category for runtime constants (current_date,
> current_timestamp)
> ------------------------------------------------------------------------------------
>
> Key: HIVE-18430
> URL: https://issues.apache.org/jira/browse/HIVE-18430
> Project: Hive
> Issue Type: Bug
> Components: UDF
> Reporter: Jason Dere
> Assignee: Jason Dere
> Attachments: HIVE-18430.1.patch
>
>
> Add a new piece of metadata to the UDFs to specify if whether a UDF is a
> runtime constant. Runtime constants also exist in SQL Server, and this is
> similar to Postgres' concept of STABLE functions. This metadata may be useful
> for materialized views and query caching.
> Some Hive functions such as the ones listed below are currently labelled as
> deterministic, but really are runtime constants:
> current_timestamp
> current_date
> current_user
> current_database
> The values for these functions are not deterministic between different
> queries - for example current_timestamp will most likely be different every
> query executed. This makes these functions ineligible for things like
> materialized views or cached query results.
> However the value for the current_timestamp should not change during the life
> of a single query, which allows these values to be used in optimizations such
> as constant folding.
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