Re: Psql regex is NFA or DFA?

Alvaro Herrera wrote:
> > I am continuing to talk to Henry about getting a newer version of his
> > regex library. He is working on it but is not yet finished.
>
> Do you have some details about the implementation itself? I would like
> to work on implementing a regex engine using the Shift-And algorithm
> families, and that can probably give a performance improvement over the
> current engine.

[ CC'ing Henry Spencer. ]

No, I don't know any details except that his regex library is in the new
tcl code and has to repackaged as a separate library. Henry, could we
help you finish up your regex stuff?

Henry's regex work is the same code that is in *BSD regex (at least
BSD/OS, FreeBSD, NetBSD), which I have found to be pretty slow in
certain complex cases, so much so that I have moved to super-sed (ssed)
for use on my local machine where I have seen 100x speed improvements
with ssed.

I am not sure how slow our regex really is, but for the sake of
PostgreSQL and of the BSD regex library, I would love to see a newer
version.

In fact, I just had an email exchange with Henry about two weeks ago.

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