Re: easy way of copying regex_t

On 25.01.2016 13:07, Tomas Vondra wrote:
>
> Right, it's definitely not thread-safe so there'd need to be some lock
> protecting the regex_t copy. I was thinking about either using a group
> of locks, each protecting a small subset of the affixes (thus making it
> possible to work in parallel to some extent), or simply using a single
> lock and each process would make a private copy at the beginning.
>
> In the end, I've decided to do it differently, and simply parse the
> affix list from scratch in each process. The affix list is tiny and
> takes less than a millisecond to parse in most cases, and I don't have
> to care about the regex stuff at all. The main benefit is from sharing
> parsed wordlist anyway.

This is nice decision since the affix list is small. For our task I will 
change shared_ispell to use this solution.

>
> It's an old-school shared segment created by the extension at init time.
> You're right the size is fixed so it's possible to run out of space by
> loading too many dictionaries, but that was not a big deal for the type
> of setups it was designed for - in those cases the list of dictionaries
> is stable, so it's possible to size the segment accordingly in advance.
>
> But I guess we could do better now that we have dynamic shared memory,
> possibly allocating one segment per dictionary as needed, or something
> like that.
>
> regards
>

Yes it would be better as we will not need to define the maximum size of 
the shared segment in postgresql.conf.

-- 
Artur Zakirov
Postgres Professional: http://www.postgrespro.com
Russian Postgres Company