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https://issues.apache.org/jira/browse/IMPALA-7899?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Paul Rogers reassigned IMPALA-7899:
-----------------------------------
Assignee: (was: Paul Rogers)
> RuntimeFilterGenerator uses Preconditions for normal conditions
> ---------------------------------------------------------------
>
> Key: IMPALA-7899
> URL: https://issues.apache.org/jira/browse/IMPALA-7899
> Project: IMPALA
> Issue Type: Bug
> Components: Frontend
> Affects Versions: Impala 3.0
> Reporter: Paul Rogers
> Priority: Minor
>
> The {{RuntimeFilterGenerator.computeTargetExpr()}} checks if a value can be
> cast to a given type. It does so by calling {{Expr.castTo()}}, which uses the
> following technique to report that the cast is not valid:
> {code:java}
> Preconditions.checkArgument(targetType.equals(type),
> "targetType=" + targetType + " type=" + type);
> {code}
> This condition occurs in {{PlannerTest}}. So, if I have a breakpoint set to
> catch {{Preconditions}} failures, that breakpoint is hit on every run. I have
> to remember, "oh, yeah, it is OK that we are violating this invariant."
> In general, it is bad practice to use things like {{assert}},
> {{Preconditions}} or unchecked exceptions to report "expected" conditions: it
> muddies the water about what is an invariant or is not.
> Instead, use a checked, purpose-built exception, such as
> {{SqlCastException}}, to report such errors, and include comments that the
> exception will be thrown for expected illegal casts.
> Or, better, restructure the method so that there is one version that is
> expected to succeed (the current one), and another that returns null if the
> cast is not legal. Have the enforcing version call the returning-null version.
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