rapidsai/cudf

[FEA] Explicitly guarantee row group ordering in the parquet reader.

Open

#15,697 建立於 2024年5月7日

在 GitHub 查看
 (0 留言) (0 反應) (0 負責人)C++ (6,000 star) (735 fork)batch import
cuIOfeature requestgood first issueimprovementlibcudf

描述

From @devavret , the question came up as to whether we guarantee the relative ordering of row groups across multiple input files in the parquet reader. That is, if you have two files [f1, f2] and the row groups within the files (in one column) are specified as [[r0,r3], [r0,r1]], do we guarantee the output ordering would be [f1r0, f1r3, f2r0, f2r1]

The code does in fact do this for both the explicitly specified case and the unspecified (empty user input / all row groups), but we don't make any guarantees about it. Seems like a safe and easy thing to add.

https://github.com/rapidsai/cudf/blob/5d244dfc13f4db0b1e41ded3029942fec50c98f6/cpp/src/io/parquet/reader_impl_helpers.cpp#L663

貢獻者指南

技術棧
cpp
領域
data
議題類型
feature
難度面向新貢獻者的預計實作難度，1 表示很小改動，5 表示專家級工作。
3
預計時間有經驗貢獻者完成調查、實作、測試並準備 pull request 的粗略時間範圍。
1-3 hours
活動狀態議題目前的可參與程度：新鮮、活躍、陳舊、阻塞或等待維護者輸入。
fresh
清晰度議題是否清楚說明預期改動、驗收標準和下一步。
clear
前置要求
Basic understanding of parquet file formatFamiliarity with C++
新手友善度1-100 的估計分數，表示該議題對首次貢獻者的友善程度。
75
研究方向
Examine the code at cpp/src/io/parquet/reader impl helpers.cpp line 663 where row group ordering is currently implicit. The goal is to explicitly guarantee the ordering of row groups across multiple input files. This likely involves adding a comment or documentation in the header or API, ensuring that the existing behavior is contractually guaranteed. Look for any existing tests for row group ordering and consider adding a test to enforce the guarantee.