[SPARK-14259] [SQL] Merging small files together based on the cost of opening #12095
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ping @nongli |
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Test build #54661 has finished for PR 12095 at commit
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cc @marmbrus |
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Lgtm, though I still think pipelined reading is the right thing to do long term. |
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Pipelined reading is a good idea to overlap opening and processing, will be done in another PR. After that, this PR is still useful, thinking of lots of tiny files (100ms to open, but 1ms to process), opening these files will be majority of the time, we should not add thousands of tiny files into one partition. |
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Merging this into master, thanks! |
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What changes were proposed in this pull request?
This PR basically re-do the things in #12068 but with a different model, which should work better in case of small files with different sizes.
How was this patch tested?
Updated existing tests.
Ran a query on thousands of partitioned small files locally, with all default settings (the cost to open a file should be over estimated), the durations of tasks become smaller and smaller, which is good (the last few tasks will be shortest).