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Cheolsoo Park commented on PIG-3341: ------------------------------------ +1. > Strict datetime parsing and improve 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 > Assignee: Rohini Palaniswamy > Fix For: 0.12, 0.11.2 > > Attachments: PIG-3341-1.patch, PIG-3341-2.patch, PIG-3341-3.patch > > > 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. -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators For more information on JIRA, see: http://www.atlassian.com/software/jira