yaooqinn opened a new pull request #28181: [SPARK-31414][SQL] Fix performance regression with new TimestampFormatter for json and csv time parsing URL: https://github.com/apache/spark/pull/28181 <!-- Thanks for sending a pull request! Here are some tips for you: 1. If this is your first time, please read our contributor guidelines: https://spark.apache.org/contributing.html 2. Ensure you have added or run the appropriate tests for your PR: https://spark.apache.org/developer-tools.html 3. If the PR is unfinished, add '[WIP]' in your PR title, e.g., '[WIP][SPARK-XXXX] Your PR title ...'. 4. Be sure to keep the PR description updated to reflect all changes. 5. Please write your PR title to summarize what this PR proposes. 6. If possible, provide a concise example to reproduce the issue for a faster review. 7. If you want to add a new configuration, please read the guideline first for naming configurations in 'core/src/main/scala/org/apache/spark/internal/config/ConfigEntry.scala'. --> ### What changes were proposed in this pull request? With benchmark original, where the timestamp values are valid to the new parser the result is ```scala [info] Running benchmark: Read dates and timestamps [info] Running case: timestamp strings [info] Stopped after 3 iterations, 5781 ms [info] Running case: parse timestamps from Dataset[String] [info] Stopped after 3 iterations, 44764 ms [info] Running case: infer timestamps from Dataset[String] [info] Stopped after 3 iterations, 93764 ms [info] Running case: from_json(timestamp) [info] Stopped after 3 iterations, 59021 ms ``` When we modify the benchmark to def timestampStr: Dataset[String] = { spark.range(0, rowsNum, 1, 1).mapPartitions { iter => iter.map(i => s"""{"timestamp":"1970-01-01T01:02:03.${i % 100}"}""") }.select($"value".as("timestamp")).as[String] } readBench.addCase("timestamp strings", numIters) { _ => timestampStr.noop() } readBench.addCase("parse timestamps from Dataset[String]", numIters) { _ => spark.read.schema(tsSchema).json(timestampStr).noop() } readBench.addCase("infer timestamps from Dataset[String]", numIters) { _ => spark.read.json(timestampStr).noop() } ``` where the timestamp values are invalid for the new parser which causes a fallback to legacy parser(2.4). the result is ```scala [info] Running benchmark: Read dates and timestamps [info] Running case: timestamp strings [info] Stopped after 3 iterations, 5623 ms [info] Running case: parse timestamps from Dataset[String] [info] Stopped after 3 iterations, 506637 ms [info] Running case: infer timestamps from Dataset[String] [info] Stopped after 3 iterations, 509076 ms ``` About 10x perf-regression BUT if we modify the timestamp pattern to `....HH:mm:ss[.SSS][XXX]` which make all timestamp values valid for the new parser to prohibit fallback, the result is ```scala [info] Running benchmark: Read dates and timestamps [info] Running case: timestamp strings [info] Stopped after 3 iterations, 5623 ms [info] Running case: parse timestamps from Dataset[String] [info] Stopped after 3 iterations, 506637 ms [info] Running case: infer timestamps from Dataset[String] [info] Stopped after 3 iterations, 509076 ms ``` ### Why are the changes needed? <!-- Please clarify why the changes are needed. For instance, 1. If you propose a new API, clarify the use case for a new API. 2. If you fix a bug, you can clarify why it is a bug. --> Fix performance regression. ### Does this PR introduce any user-facing change? <!-- If yes, please clarify the previous behavior and the change this PR proposes - provide the console output, description and/or an example to show the behavior difference if possible. If no, write 'No'. --> NO ### How was this patch tested? <!-- If tests were added, say they were added here. Please make sure to add some test cases that check the changes thoroughly including negative and positive cases if possible. If it was tested in a way different from regular unit tests, please clarify how you tested step by step, ideally copy and paste-able, so that other reviewers can test and check, and descendants can verify in the future. If tests were not added, please describe why they were not added and/or why it was difficult to add. --> new tests added.
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