I would like to ask if it is valid to create only ColumnIndex but omit OffsetIndex? My answer is NO according to [1]. If agreed, my inclination is option 1.
[1] https://github.com/apache/parquet-format/blob/079a2dff06e32b7d1ad8c9aa67f2e2128fb5ffa5/src/main/thrift/parquet.thrift#L1019-L1022 On Tue, May 21, 2024 at 6:31 PM wish maple <[email protected]> wrote: > I'm +1 on this, "Offset Index", "Page Index", "Column Index or Offset > Index" all looks good to me. > > Best, > Xuwei Fu > > Andrew Lamb <[email protected]> 于2024年5月21日周二 18:07写道： > > > mapleFU brought up an excellent question[1]. > > > > Upon further research, a "page index" seems to consist of an OffsetIndex > > and ColumnIndex, but some writers may only write OffsetIndex (and not > > ColumnIndex). See discussion on [2] > > > > Thus when we say "repeated fields must start at a page boundary if a page > > index is present OR data-page V2 is present," does that mean: > > 1. an OffsetIndex is present > > 2. both an OffsetIndex and ColumnIndex are present > > 3. Something else > > > > It seems to me that since an OffsetIndex is in terms of numbers of > records, > > if it were present that would require repetition_level=0 at page > > boundaries (aka option 1). > > > > Thoughts? > > Andrew > > > > > > [1] > > https://github.com/apache/parquet-format/pull/244#discussion_r1607878045 > > [2]: https://github.com/apache/parquet-format/pull/245 > > > > On Sun, May 19, 2024 at 7:18 AM Andrew Lamb <[email protected]> > > wrote: > > > > > I have created a PR[1] to the spec to try and encode this mailing list > > > conversation and avoid future confusion. Please have a look and let me > > > know if it captures it correctly. > > > > > > Thanks, > > > Andrew > > > > > > [1]: https://github.com/apache/parquet-format/pull/244 > > > > > > On Wed, May 15, 2024 at 7:03 PM Julien Le Dem <[email protected]> > wrote: > > > > > >> +1 The semantics of a row group is that it contains rows and therefore > > >> starts on R=0 > > >> I generally echo Ed's sentiment here. > > >> > > >> On Wed, May 15, 2024 at 8:01 AM Andrew Lamb <[email protected]> > > >> wrote: > > >> > > >> > Thank you all -- I have filed > > >> > https://issues.apache.org/jira/browse/PARQUET-2473 to track > > clarifying > > >> the > > >> > spec and will make a PR shortly > > >> > > > >> > > > >> > On Sun, May 12, 2024 at 12:18 AM wish maple <[email protected] > > > > >> > wrote: > > >> > > > >> > > IMO when Page V2 is present or PageIndex is enabled, the > boundaries > > >> > > should be check[1] > > >> > > > > >> > > [1] > > >> > > > > >> > > > > >> > > > >> > > > https://github.com/apache/arrow/blob/d10ebf055a393c94a693097db1dca08ff86745bd/cpp/src/parquet/column_writer.cc#L1235-L1237 > > >> > > > > >> > > > > >> > > Jan Finis <[email protected]> 于2024年5月11日周六 01:15写道： > > >> > > > > >> > > > Hey Parquet devs, > > >> > > > > > >> > > > I so far thought that Parquet mandates that records start at > page > > >> > > > boundaries, i.e., at r-level 0, and we have relied on this fact > in > > >> some > > >> > > > places of our engine. That means, there cannot be any data page > > for > > >> a > > >> > > > REPEATED column that starts at an r-level > 0, as this would > mean > > >> that > > >> > a > > >> > > > record would be split between multiple pages. > > >> > > > > > >> > > > I also found the two comments in parquet.thrift: > > >> > > > > > >> > > > /** Number of rows in this data page. which means pages change > > on > > >> > > record > > >> > > > > boundaries (r = 0) **/ > > >> > > > > 3: required i32 num_rows > > >> > > > > > >> > > > > > >> > > > /** > > >> > > > > * Index within the RowGroup of the first row of the page; > > this > > >> > means > > >> > > > > pages > > >> > > > > * change on record boundaries (r = 0). > > >> > > > > */ > > >> > > > > 3: required i64 first_row_index > > >> > > > > > >> > > > > > >> > > > These comments seem to imply that my understanding is correct. > > >> However, > > >> > > > they are worded very weakly, not like a mandate but more like a > > "by > > >> the > > >> > > > way" comment. > > >> > > > > > >> > > > I haven't found any other mention of r-levels and page > boundaries > > in > > >> > the > > >> > > > parquet-format repo (maybe I missed them?). > > >> > > > > > >> > > > I recently noticed that pyarrow.parquet splits repeated fields > > over > > >> > > > multiple pages, so it violates this. This triggers assertions in > > our > > >> > > > engine, so I want to understand what's the right course of > action > > >> here. > > >> > > > > > >> > > > So, can we please clarify: > > >> > > > *Does Parquet mandate that pages need to start at r-level 0?* > > >> > > > > > >> > > > - I.e., is a parquet file with a page that starts at an > r-level > > >> > 0 > > >> > > ill > > >> > > > formed? I.e., is this a bug in pyarrow.parquet? > > >> > > > - Or can pages start at r-level 0? If so, then what is the > > >> > > significance > > >> > > > of the comments in parquet.thrift? > > >> > > > > > >> > > > > > >> > > > Cheers, > > >> > > > Jan > > >> > > > > > >> > > > > >> > > > >> > > > > > >
