[IMPALA-5298] Investigate and fix from_unixtime() slowness, currently 100x slower than scanning Bigint

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Impala 2.6.0
• Fix Version/s: Impala 2.9.0
• Component/s: Backend
• Labels: newbie performance
• Epic Color: ghx-label-4
• Assignee: Unassigned
• Reporter: Mostafa Mokhtar
• Created: 10/May/17 00:28
• Updated: 26/Nov/17 20:46
• Resolved: 24/Nov/17 05:23

Description

Noticed that applying from_unixtime against a Bigint results in ~100x slowdown compared to just scanning the Bigint column

select max(from_unixtime (l_orderkey)) from lineitem where l_shipdate < "1993-01-01"
Fetched 1 row(s) in 75.67s

select max (l_orderkey) from lineitem where l_shipdate < "1993-01-01"
Fetched 1 row(s) in 0.87s

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%

Issue Links

• relates to: IMPALA-4055 Investigate and fix to_date() slowness