| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Mithun Cy <mithun(dot)cy(at)enterprisedb(dot)com>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [HACKERS] Moving relation extension locks out of heavyweight lock manager |
| Date: | 2018-03-01 20:37:17 |
| Message-ID: | CA+TgmoYPdA4jUGgwdBEkFWOivq+Vs47REZ-DRf+H7XOvK8DYDQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Mar 1, 2018 at 2:17 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>> However, if we take the position that no hash collision probability is
>> low enough and that we must eliminate all chance of false collisions,
>> except perhaps when the table is full, then we have to make this
>> locking mechanism a whole lot more complicated. We can no longer
>> compute the location of the lock we need without first taking some
>> other kind of lock that protects the mapping from {db_oid, rel_oid} ->
>> {memory address of the relevant lock}.
>
> Hm, that's not necessarily true, is it? Wile not trivial, it also
> doesn't seem impossible?
You can't both store every lock at a fixed address and at the same
time put locks at a different address if the one they would have used
is already occupied.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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