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From "Cheng Lian (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SPARK-19737) New analysis rule for reporting unregistered functions without relying on relation resolution
Date Thu, 22 Feb 2018 01:22:00 GMT

    [ https://issues.apache.org/jira/browse/SPARK-19737?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16372289#comment-16372289
] 

Cheng Lian commented on SPARK-19737:
------------------------------------

[~LANDAIS Christophe], I filed SPARK-23486 for this. Should be relatively straightforward
to fix and I'd like to have a new contributor to try it as a starter task. Thanks for reporting!

> New analysis rule for reporting unregistered functions without relying on relation resolution
> ---------------------------------------------------------------------------------------------
>
>                 Key: SPARK-19737
>                 URL: https://issues.apache.org/jira/browse/SPARK-19737
>             Project: Spark
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 2.2.0
>            Reporter: Cheng Lian
>            Assignee: Cheng Lian
>            Priority: Major
>             Fix For: 2.2.0
>
>
> Let's consider the following simple SQL query that reference an undefined function {{foo}}
that is never registered in the function registry:
> {code:sql}
> SELECT foo(a) FROM t
> {code}
> Assuming table {{t}} is a partitioned  temporary view consisting of a large number of
files stored on S3, it may take the analyzer a long time before realizing that {{foo}} is
not registered yet.
> The reason is that the existing analysis rule {{ResolveFunctions}} requires all child
expressions to be resolved first. Therefore, {{ResolveRelations}} has to be executed first
to resolve all columns referenced by the unresolved function invocation. This further leads
to partition discovery for {{t}}, which may take a long time.
> To address this case, we propose a new lightweight analysis rule {{LookupFunctions}}
that
> # Matches all unresolved function invocations
> # Look up the function names from the function registry
> # Report analysis error for any unregistered functions
> Since this rule doesn't actually try to resolve the unresolved functions, it doesn't
rely on {{ResolveRelations}} and therefore doesn't trigger partition discovery.
> We may put this analysis rule in a separate {{Once}} rule batch that sits between the
"Substitution" batch and the "Resolution" batch to avoid running it repeatedly and make sure
it gets executed before {{ResolveRelations}}.



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