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https://issues.apache.org/jira/browse/IMPALA-5298?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jinchul Kim resolved IMPALA-5298.
---------------------------------
Resolution: Fixed
Fix Version/s: Impala 2.9.0
> Investigate and fix from_unixtime() slowness, currently 100x slower than
> scanning Bigint
> ----------------------------------------------------------------------------------------
>
> Key: IMPALA-5298
> URL: https://issues.apache.org/jira/browse/IMPALA-5298
> Project: IMPALA
> Issue Type: Bug
> Components: Backend
> Affects Versions: Impala 2.6.0
> Reporter: Mostafa Mokhtar
> Labels: newbie, performance
> Fix For: Impala 2.9.0
>
> Attachments: Screen Shot 2017-05-09 at 5.26.30 PM.png, hotspots.csv,
> top-down.csv
>
>
> Noticed that applying from_unixtime against a Bigint results in ~100x
> slowdown compared to just scanning the Bigint column
> {code}
> select max(from_unixtime (l_orderkey)) from lineitem where l_shipdate <
> "1993-01-01"
> Fetched 1 row(s) in 75.67s
> {code}
> {code}
> select max (l_orderkey) from lineitem where l_shipdate < "1993-01-01"
> Fetched 1 row(s) in 0.87s
> {code}
> {code}
> Function / Call Stack CPU Time
> std::basic_ios<char, std::char_traits<char>>::init 36.50%
> std::basic_ios<char, std::char_traits<char>>::imbue 10.50%
> std::__ostream_insert<char, std::char_traits<char>> 7.10%
> std::ostream::_M_insert<long> 4.90%
> std::locale::locale 4.00%
> operator delete 3.40%
> std::locale::~locale 2.80%
> std::ostream::operator<< 2.60%
> operator new 2.40%
> std::ostream::operator<< 2.00%
> std::ostream::operator<< 1.80%
> __tz_convert 1.70%
> std::ios_base::ios_base 1.50%
> impala::TimestampValue::DebugString 1.40%
> impala::Tuple::IsNull 1.30%
> [Import thunk std::basic_streambuf<char, std::char_traits<char>>::xsputn]
> 0.90%
> std::locale::classic 0.90%
> boost::detail::lexical_converter_impl<std::string,
> impala::TimestampValue>::try_convert 0.80%
> {code}
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