pathological LDM regular-expressions

• To: ldm-users@xxxxxxxxxxxxxxxx
• Subject: pathological LDM regular-expressions
• From: Steve Emmerson <steve@xxxxxxxxxxxxxxxx>
• Date: Fri, 14 Feb 2003 10:12:41 -0700

Hi,

In getting the latest LDM ready for release, we've learned that certain,
seemingly inocent regular-expressions (RE-s) can cause the upstream LDM
to spend over 99% of its user-time executing the RE -- leaving little
time for sending you the data. This email is to let you know about these
RE-s and to ask you to replace them in your LDM configuration-file.

The pathological RE-s have the form

    .*<rest of RE>

i.e., they have "dot-star" as a prefix. The ".*" adds nothing to the
meaning of the RE but, on a Solaris system at least, it's execution is
about 1300 times slower than the corresponding unprefixed RE.

I'm not making this up.

Would you please go through your LDM configuration file and replace all
RE-s of the above form with the unprefixed version.  For example, the
entry

    request HDS  ".*foo/bar" ...

should become

    request HDS  "foo/bar" ...

i.e., remove the ".*" prefix.  Note that this is only applicable to RE-s
with ".*" AS A PREFIX.  RE-s that consist solely of ".*" (as many, if
not most, due) should be left unaltered.

Then, restart your LDM if you made any changes.

Email me or this list if you have any questions.

Regards,
Steve Emmerson