[Website] Aggregating Millions of Groups Fast in Apache Arrow DataFusion 28.0.0 #386
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tustvold
approved these changes
Aug 8, 2023
Dandandan
approved these changes
Aug 9, 2023
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I plan to publish this sometime early next week (2023-08-14 or so), to ensure there has been at least a week for anyone who is interested to review Here is the discussion on mailing list: https://lists.apache.org/thread/4lyk9jycr0o6qv5zo5bsw2q9mvvdsp7z Please let me know if anyone would like additional time to review |
yjshen
reviewed
Sep 10, 2023
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| **Figure 5**: Hash group operator structure in DataFusion `28.0.0`. Group values are stored either directly in the hash table, or in a single allocation using the arrow Row format. The hash table contains group indexes. A single `GroupsAccumulator` stores the per-aggregate state for _all_ groups. |
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Primitive group values are also stored in a single allocation using Vec<T::Native>, not directly in the hash table?
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This was a later modification - apache/datafusion#7043
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Closes apache/datafusion#6988
Note: This describes work @tustvold @Dandandan and I did in DataFusion 28.0.0. This content was originally published on the InfluxData Blog but since it is general applicable to Apache Arrow DataFusion I would like to syndicate it here becase:
This is the same model we followed with https://arrow.apache.org/blog/2022/12/26/querying-parquet-with-millisecond-latency/ which was also republished on the arrow blog after the InfluxData blog
It also gives me an example to use my original ASCII art diagrams :)