SIMILAR TO does not return result when invalid pattern is used (with two
adjacent special characters that should be escaped but aren't)
---------------------------------------------------------------------------------------------------------------------------------------
Key: CORE-5931
URL: http://tracker.firebirdsql.org/browse/CORE-5931
Project: Firebird Core
Issue Type: Bug
Affects Versions: 3.0.3, 2.5.8, 4.0 Alpha 1
Reporter: Pavel Zotov
Attachments: difference-on-patterns-that-leads-to-POOR-SIMILAR-TO.png,
firebird_1820.20181001_012003.stack_trc.txt.7z,
firebird_1820.20181001_012034.stack_trc.txt.7z
(yes, i know about tickets CORE-3858, CORE-4893 & CORE-5664 that also relate to
SIMILAR TO performance; perhaps this new sample can help to solve them so i
decided to create separate ticket).
Consider following command:
set count on;
set list on;
select 1 from rdb$database where
'
group by
f01,
f02,
f03,
f04,
f05,
f06,
f07,
f08,
f09,
f10,
f11,
f12,
f13,
'
similar to
'%group[[:WHITESPACE:]]+by[[:WHITESPACE:]]+([[:ALNUM:]])+([[:WHITESPACE:]]*,[[:WHITESPACE:]]*[[:ALNUM:]]+){12,}[[:WHITESPACE:]]*%'
;
It will issue result instantly:
===
CONSTANT 1
Records affected: 1
===
Now let change pattern by adding characters "|" and "_" (PIPE and UNDERSCORE)
after 1st ALNUM, but with missed escaping (and this means that pattern will be
INVALID):
select 1 from rdb$database where
'
group by
f01,
f02,
f03,
f04,
f05,
f06,
f07,
f08,
f09,
f10,
f11,
f12,
f13
'
similar to
'%group[[:WHITESPACE:]]+by[[:WHITESPACE:]]+([[:ALNUM:]]|_)+([[:WHITESPACE:]]*,[[:WHITESPACE:]]*[[:ALNUM:]]+){12,}[[:WHITESPACE:]]*%'
;
This statement will HANGS on 2.5, 3.0 and 4.0.
Difference between patterns - see in attached .pgn
Two stack traces (for WI-V3.0.4.33054 ) are also attached.
NB: This trouble with SIMILAR TO seems to be CRITICAL: no new attachment can be
established while engine "does something inside itself" while working with
parsing such statement!
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