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https://issues.apache.org/jira/browse/PIG-3341?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13673122#comment-13673122
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Rohini Palaniswamy commented on PIG-3341:
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bq. Before making the fix, I think there needs to be a little more clarity
around exactly what formats are supported. For example, pig 0.11.1 currently
supports datetime strings with no date - "T00:00:00" produces a date in 1970.
Is this intentional?
I don't think anyone is looking for such a behaviour. Not intuitive.
I think we can go with option 1 (more is better) but also state which of those
formats supported are not part of w3c profile. We also need to return null if
it does not confirm to the format instead of throwing an error.
> Improving performance of loading datetime values
> ------------------------------------------------
>
> Key: PIG-3341
> URL: https://issues.apache.org/jira/browse/PIG-3341
> Project: Pig
> Issue Type: Improvement
> Components: impl
> Affects Versions: 0.11.1
> Reporter: pat chan
> Priority: Minor
> Fix For: 0.12, 0.11.2
>
>
> The performance of loading datetime values can be improved by about 25% by
> moving a single line in ToDate.java:
> public static DateTimeZone extractDateTimeZone(String dtStr) {
> Pattern pattern =
> Pattern.compile("(Z|(?<=(T[0-9\\.:]{0,12}))((\\+|-)\\d{2}(:?\\d{2})?))$");;
> should become:
> static Pattern pattern =
> Pattern.compile("(Z|(?<=(T[0-9\\.:]{0,12}))((\\+|-)\\d{2}(:?\\d{2})?))$");
> public static DateTimeZone extractDateTimeZone(String dtStr) {
> There is no need to recompile the regular expression for every value. I'm not
> sure if this function is ever called concurrently, but Pattern objects are
> thread-safe anyways.
> As a test, I created a file of 10M timestamps:
> for i in 0..10000000
> puts '2000-01-01T00:00:00+23'
> end
> I then ran this script:
> grunt> A = load 'data' as (a:datetime); B = filter A by a is null; dump B;
> Before the change it took 160s.
> After the change, the script took 120s.
> ----------------
> Another performance improvement can be made for invalid datetime values. If a
> datetime value is invalid, an exception is created and thrown, which is a
> costly way to fail a validity check. To test the performance impact, I
> created 10M invalid datetime values:
> for i in 0..10000000
> puts '2000-99-01T00:00:00+23'
> end
> In this test, the regex pattern was always recompiled. I then ran this script:
> grunt> A = load 'data' as (a:datetime); B = filter A by a is not null; dump
> B;
> The script took 190s.
> I understand this could be considered an edge case and might not be worth
> changing. However, if there are use cases where invalid dates are part of
> normal processing, then you might consider fixing this.
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