Robert Haas <robertmh...@gmail.com> writes: > On Thu, Aug 25, 2011 at 12:47 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: >> 1. Somebody broke the no-backtracking property back in 9.0 while adding >> quoted variable substitution. According to the flex manual, use of >> backtracking creates a performance penalty. We once measured the >> backend's lexer as being about a third faster with backtrack avoidance, >> and presumably it's about the same for psql's. This is not hard to fix, >> but should I consider it a bug fix and back-patch? We've not had >> complaints about psql getting slower as of 9.0.
> That may well have been me. [ checks "git blame" ] Well, you commmitted the patch anyway: d0cfc018. > How would I have known that I broke it? Per the header comments in the backend lexer, you should run flex with "-b" switch and verify that the resulting lex.backup file says "no backing up". I've occasionally thought about automating that, but I'm not sure if the output is entirely locale- and flex-version-independent. > Also, how invasive is the fix? We need to add a couple more rules that will match an unterminated quoted variable and do something reasonable (probably just throw back everything but the colon with yyless). I've not coded it but I think it can't be more than a dozen lines or so. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers