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https://issues.apache.org/jira/browse/IMPALA-8101?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sahil Takiar resolved IMPALA-8101.
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Resolution: Fixed
Fix Version/s: Impala 3.3.0
> Thrift 11 compilation and Thrift ext-data-source compilation are always run
> ---
>
> Key: IMPALA-8101
> URL: https://issues.apache.org/jira/browse/IMPALA-8101
> Project: IMPALA
> Issue Type: Task
>Reporter: Sahil Takiar
>Assignee: Sahil Takiar
>Priority: Major
> Fix For: Impala 3.3.0
>
>
> [~tarmstrong] pointed out that after IMPALA-7924 the build output started
> displaying lines such as: "Running thrift 11 compiler on..." even during
> builds when Thrift files were not modified.
> I dug a bit deeper and found the following:
> * This seems to be happening for Thrift compilation of {{ext-data-source}}
> files as well (e.g. ExternalDataSource.thrift, Types.thrift, etc.); "Running
> thrift compiler for ext-data-source on..." is always printed
> * The issue is that the [custom
> command|https://cmake.org/cmake/help/v3.8/command/add_custom_command.html]
> for ext-data-source and Thrift 11 compilation specify an {{OUTPUT}} file that
> does not exist (and is not generated by Thrift)
> * According to the CMake docs "if the command does not actually create the
> {{OUTPUT}} then the rule will always run" - so Thrift compilation will run
> during every build
> * The issue is that you don't really know what files Thrift is going to
> generate without actually looking into the Thrift file and understanding
> Thrift internals
> * For C++ and Python there is a workaround; for C++ Thrift always generates
> a file \{THRIFT_FILE_NAME}_types.h (similar situation for Python); however,
> for Java no such file necessarily exists (ext-data-source only does Java gen)
> ** This is how regular Thrift compilation works (e.g. compilation of
> beeswax.thrift, ImpalaService.thrift, etc.); which is why we don't see the
> issue for regular Thrift compilation
> A solution for Thrift 11 compilation is to just add generated Python files to
> the {{OUTPUT}} for the custom_command.
> A solution for Thrift compilation of ext-data-source seems trickier, so open
> to suggestions.
> Ideally, Thrift would be provide a way to return the list of files generated
> from a .thrift file, without actually generating the files, but I don't see a
> way to do that.
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