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Posted to dev@orc.apache.org by GitBox <gi...@apache.org> on 2021/09/29 12:55:13 UTC

[GitHub] [orc] stiga-huang opened a new pull request #921: ORC-1012: Support specifying columns in orc-scan

stiga-huang opened a new pull request #921:
URL: https://github.com/apache/orc/pull/921


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   ### What changes were proposed in this pull request?
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   The PR adds an option to support specifying columns to be read in the orc-scan tool.
   
   ### Why are the changes needed?
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   Currently the orc-scan tool will scan all columns. I find it useful to specifying columns when profiling read performance on specified data types.
   
   ### How was this patch tested?
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   Manually tested with the new option.
   Added tests in tools/test/TestFileScan.cc.


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[GitHub] [orc] dongjoon-hyun commented on pull request #921: ORC-1012: Support specifying columns in orc-scan

Posted by GitBox <gi...@apache.org>.
dongjoon-hyun commented on pull request #921:
URL: https://github.com/apache/orc/pull/921#issuecomment-995309603


   Since this is `tools`-only change, I backported this to branch-1.7.


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[GitHub] [orc] wgtmac commented on pull request #921: ORC-1012: Support specifying columns in orc-scan

Posted by GitBox <gi...@apache.org>.
wgtmac commented on pull request #921:
URL: https://github.com/apache/orc/pull/921#issuecomment-931023274


   > Currently the other tools (orc-contents and orc-memory) that support specifying columns use fieldId instead of columnId. So only top-level field ids are supported. The new option in orc-scan has the same meaning as these tools. I'd suggest adding another option, e.g. --columnIds=1,2,3, for specifying columnIds. Maybe in a separate PR. Do you think it's ok?
   > 
   > BTW, I slightly modify the test to include a top-level STRUCT column (fieldId=9 in examples/TestOrcFile.testSeek.orc).
   
   I am OK with the current PR (i.e. column selection by the field ids). The orc-scan tool is usually used to verify the integrity of an ORC file. We can add more complex column selection option to it later.


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[GitHub] [orc] dongjoon-hyun merged pull request #921: ORC-1012: Support specifying columns in orc-scan

Posted by GitBox <gi...@apache.org>.
dongjoon-hyun merged pull request #921:
URL: https://github.com/apache/orc/pull/921


   


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[GitHub] [orc] wgtmac commented on pull request #921: ORC-1012: Support specifying columns in orc-scan

Posted by GitBox <gi...@apache.org>.
wgtmac commented on pull request #921:
URL: https://github.com/apache/orc/pull/921#issuecomment-930704093


   > It's great. Thank you, @stiga-huang . BTW, do we support only ordinal column numbers?
   > 
   > Could you give explain how to select columns from complex types like nested columns like `struct`? It would be great if we can have a test coverage for complex types, too.
   > 
   > cc @wgtmac
   
   The RowReaderOptions support column pruning by fieldName (include(list<string>)), fieldId (include(list<int>)), and columnId (includeTypes(list<int>)). The last one supports pruning nested column in the struct. I think that is what @dongjoon-hyun has mentioned. Support nested pruning requires user to specify the exact columnId which is not easy if the schema is rather complex.


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[GitHub] [orc] stiga-huang commented on pull request #921: ORC-1012: Support specifying columns in orc-scan

Posted by GitBox <gi...@apache.org>.
stiga-huang commented on pull request #921:
URL: https://github.com/apache/orc/pull/921#issuecomment-930796037


   Currently the other tools (orc-contents and orc-memory) that support specifying columns use fieldId instead of columnId. So only top-level field ids are supported. The new option in orc-scan has the same meaning as these tools. I'd suggest adding another option, e.g. --columnIds=1,2,3, for specifying columnIds. Maybe in a separate PR. Do you think it's ok?
   
   BTW, I slightly modify the test to include a top-level STRUCT column (fieldId=9 in examples/TestOrcFile.testSeek.orc).


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