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From "Tim Armstrong (Code Review)" <>
Subject [Impala-ASF-CR] IMPALA-4192: Avoid updating Expr's states from ExprContext
Date Thu, 05 Jan 2017 16:15:24 GMT
Tim Armstrong has posted comments on this change.

Change subject: IMPALA-4192: Avoid updating Expr's states from ExprContext

Patch Set 2:

I do think we need three classes here (the documentation and maybe naming could definitely
be improved). The Expr class is the constant information about the expression itself - the
ExprContext contains thread-local state for the whole expr tree. The FunctionContext contains
thread-local state for specific expr nodes that need it and is part of the UDF interface.

I think having three different classes with those scopes is necessary since there's state
that needs to be stored in each.

I feel like ExprContext is the confusing part - the other two mostly make sense. Maybe it
would be clearer if ExprContext was something like ExprEvalContext or ExprTreeContext? I think
that's the main thing that throws me off since the cardinality of ExprContext compared to
Expr isn't obvious based on the name.

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Gerrit-MessageType: comment
Gerrit-Change-Id: Iefdc9aeeba033355cb9497e3a5d2363627dcf2f3
Gerrit-PatchSet: 2
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Michael Ho <>
Gerrit-Reviewer: Dan Hecht <>
Gerrit-Reviewer: Marcel Kornacker <>
Gerrit-Reviewer: Michael Ho <>
Gerrit-Reviewer: Tim Armstrong <>
Gerrit-HasComments: No

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