[GitHub] [arrow] westonpace commented on issue #13030: [JAVA] Is any way reading partial parquet file into arrow

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westonpace commented on issue #13030:
URL: https://github.com/apache/arrow/issues/13030#issuecomment-1113692280

   A parquet file is made up of row groups, columns, and pages.  A page is indivisible as it represents a compressed buffer.  There is no way to read a part of a page and so it cannot be sliced.
   
   However, it is still a popular idea to partition file access based on file size.  One way to handle this is to return every row group whose first byte is in the asked-for range.
   
   For example, if a parquet file has 10 row groups and each row group is 900,000 bytes and you ask for the range [2000000,3000000] you would get the 3rd row group (that starts at byte 2,700,000).


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