[ 
https://issues.apache.org/jira/browse/SPARK-31414?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
 ]

Wenchen Fan reassigned SPARK-31414:
-----------------------------------

    Assignee: Kent Yao

> Performance regression with new TimestampFormatter for json and csv
> -------------------------------------------------------------------
>
>                 Key: SPARK-31414
>                 URL: https://issues.apache.org/jira/browse/SPARK-31414
>             Project: Spark
>          Issue Type: Sub-task
>          Components: SQL
>    Affects Versions: 3.0.0
>            Reporter: Kent Yao
>            Assignee: Kent Yao
>            Priority: Major
>
> with benchmark original, where the timestamp values are valid to new parser
> the result is 
> {code:java}
> [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
> {code}
> when we modify the benchmark to 
> {code:java}
>       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()
>       }
> {code}
> where the timestamp values are invalid for the new parser which cause 
> fallback to legacy parser.
> the result is 
> {code:java}
> [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
> {code}
> About 10x perf-regression



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