Re: [HACKERS] regex (from TODO)

>  In the PostgreSQL TODO is "Get faster regex() code from Henry Spencer..".
> 
>  I look at current available regex used (a example) in apache, php, .etc. But
> if I look at changes (via diff) between PostgreSQL's regex and more new
> regex in PHP4 it is very same. A differentions are that in new regex code
> are all values marks as 'register' and this new regex not support MULTIBYTE.

Actually Henry has never supported MULTIBYTE:-) We modified his code
so that we could support it.

> It is without any relevant changes (or 'register' is really fastly?).

I vaguely recall that we decided that 'register' did nothing good with
modern compilers, and it'd be better to let the optimizer determine
what variables should be assigned to registers.

>  What means TODO? 

That means "get faster code from Henry and modify it if it does not
support MULTIBYTE" -- I guess.

>  The PG's regex use malloc -- why not MemoryContext?

Probably because the regex caches the results of regcomp in a static
area which points to a malloced memory allocated while compiling a
regular expression. However, for the regexec stage we might be able to
use palloc instead of malloc. I'm not sure if this would result in a
any better performance, though.
--
Tatsuo Ishii