On Mon, Feb 8, 2010 at 6:07 PM, David E. Wheeler wrote:
> On Feb 8, 2010, at 5:15 AM, Magnus Hagander wrote:
>
>> The text is about 180Kb. PostgreSQL takes ~40 seconds without the
>> patch, ~36 seconds with it, to extract the match from it. Perl takes
>> 0.016 seconds.
>
> Obviously we need to sup
On Feb 8, 2010, at 5:15 AM, Magnus Hagander wrote:
> The text is about 180Kb. PostgreSQL takes ~40 seconds without the
> patch, ~36 seconds with it, to extract the match from it. Perl takes
> 0.016 seconds.
Obviously we need to support Perl regular expressions in core. Not PCRE, but
Perl. ;-P
B
2010/2/1 Michael Glaesemann :
>
> On Jan 31, 2010, at 22:14 , Tom Lane wrote:
>
>> The Tcl folk accepted that patch, so I went ahead and applied it to
>> our code. It would still be a good idea for us to do any testing we
>> can on it, though.
>
> I applied the patch and ran both the test query I
On Jan 31, 2010, at 22:14 , Tom Lane wrote:
The Tcl folk accepted that patch, so I went ahead and applied it to
our code. It would still be a good idea for us to do any testing we
can on it, though.
I applied the patch and ran both the test query I submitted as well as
original problematic
I wrote:
> I found a possible patch that seems to improve matters: AFAICS the DFA
> matching is independent of the checking that cdissect() and friends do,
> so we can apply that check first instead of second. This brings the
> runtime down from minutes to sub-second on my machine. However I don'
On Sat, Jan 30, 2010 at 08:07, Tom Lane wrote:
> Michael Glaesemann writes:
>> We came across a regexp that takes very much longer than expected.
>
> I poked into this a little bit. What seems to be happening is that the
> use of non-greedy quantifiers plus backreferences turns off most of the
>
Michael Glaesemann writes:
> We came across a regexp that takes very much longer than expected.
I poked into this a little bit. What seems to be happening is that the
use of non-greedy quantifiers plus backreferences turns off most of the
optimization that the regexp engine usually does, leaving
Magnus Hagander wrote:
> 2010/1/29 Alvaro Herrera :
> > (There's a badly needed CHECK_FOR_INTERRUPTS in this code BTW)
>
> Incidentally, I ran across the exact same issue with a non-greedy
> regexp with a client earlier this week, and put on my TODO to figure
> out a good place to stick a check fo
2010/1/29 Alvaro Herrera :
> Hi Michael,
>
> Michael Glaesemann wrote:
>> We came across a regexp that takes very much longer than expected.
>>
>> PostgreSQL 8.4.1 on x86_64-unknown-linux-gnu, compiled by GCC gcc (GCC)
>> 4.1.2 20080704 (Red Hat 4.1.2-44), 64-bit
>>
>> SELECT 'ooo...' ~ $r$Z(Q)[^Q
On Jan 28, 2010, at 23:21 , Alvaro Herrera wrote:
I think the reason for this is that the first * is greedy and thus the
entire expression is considered greedy. The fact that you've made the
second * non-greedy does not ungreedify the RE ... Note the docs say:
The above rules associat
Michael Glaesemann wrote:
> However, as you point out, Postgres doesn't appear to take this into
> account:
>
> postgres=# select regexp_replace('oooZQoooAoooQooQooQooo', $r$(Z(Q)
> [^Q]*A.*(\2))$r$, $s$X$s$);
> regexp_replace
>
> oooXooo
> (1 row)
>
> postgres=# select regexp
Michael Glaesemann wrote:
>
> On Jan 28, 2010, at 21:59 , Alvaro Herrera wrote:
>
> >Hi Michael,
> >
> >Michael Glaesemann wrote:
> >>We came across a regexp that takes very much longer than expected.
> >>
> >>PostgreSQL 8.4.1 on x86_64-unknown-linux-gnu, compiled by GCC
> >>gcc (GCC) 4.1.2 20080
On Jan 28, 2010, at 21:59 , Alvaro Herrera wrote:
Hi Michael,
Michael Glaesemann wrote:
We came across a regexp that takes very much longer than expected.
PostgreSQL 8.4.1 on x86_64-unknown-linux-gnu, compiled by GCC gcc
(GCC) 4.1.2 20080704 (Red Hat 4.1.2-44), 64-bit
SELECT 'ooo...' ~ $
Hi Michael,
Michael Glaesemann wrote:
> We came across a regexp that takes very much longer than expected.
>
> PostgreSQL 8.4.1 on x86_64-unknown-linux-gnu, compiled by GCC gcc (GCC) 4.1.2
> 20080704 (Red Hat 4.1.2-44), 64-bit
>
> SELECT 'ooo...' ~ $r$Z(Q)[^Q]*A.*?(\1)$r$; -- omitted for email
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