| From: | "Merlin Moncure" <mmoncure(at)gmail(dot)com> |
|---|---|
| To: | josh(at)agliodbs(dot)com |
| Cc: | pgsql-hackers(at)postgresql(dot)org, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Jim C(dot) Nasby" <jimn(at)enterprisedb(dot)com> |
| Subject: | Re: 8.2 beta blockers |
| Date: | 2006-09-18 19:56:57 |
| Message-ID: | b42b73150609181256s3a818e43ydf061ce41c04dc18@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 9/18/06, Josh Berkus <josh(at)agliodbs(dot)com> wrote:
> All,
>
> Is UserLocks a cool enough feature to be worth mentioning in the 8.2 PR?
> If so, can someone explain it to me off-list? I still don't get what it
> does ...
>
yes, i can explain it in detail, and am willing to kick in some
documentation. it is very cool, and relatively undiscovered. email
me for details.
the short answer is you can do long term locking (not scoped to
transaction) using the postgresql high speed internal lock engine.
this allows you to bypass various locking hacks such as keeping
transactions (too) long term, or maintaining a lock flag in a table,
which has cleanup issues.
they are great if you need to emulate pessimistic locking and
transactions is an awkward fit. its up to you, the user to determine
when and what to lock.
i really beat on the user (advisory locks) when doing a cobol/isam
conversion project. they work fabulous.
merlin
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