Обсуждение: OID vs overall system performances on high load

От:
"Eric Lauzon"
Дата:

I am still in the dark due to my lack of knowledge on internal OID management,but
i would presume that a table with OID enable and that has high load would require
some more work from pgsql internal to maintain the OID index for the database.

So OID can be beneficial on static tables, or tables that you want to be able to manipulate
with pgadmin X , but can a table without OID increase performances on insert,delete,update,COPY?

I am not really worried about disk space that an OID collumn can take, but i was wandering if an
insert in a table of 20 millions and more that has oid would slow the insert process. Since OID seem
to act as a global index mabey maintaning that index can become costy over high table load by postgresql
backend.

-Eric Lauzon







От:
Andrew McMillan
Дата:

On Sun, 2005-05-29 at 16:17 -0400, Eric Lauzon wrote:
> I am still in the dark due to my lack of knowledge on internal OID management,but
> i would presume that a table with OID enable and that has high load would require
> some more work from pgsql internal to maintain the OID index for the database.
>
> So OID can be beneficial on static tables, or tables that you want to be able to manipulate
> with pgadmin X , but can a table without OID increase performances on insert,delete,update,COPY?
>
> I am not really worried about disk space that an OID collumn can take, but i was wandering if an
> insert in a table of 20 millions and more that has oid would slow the insert process. Since OID seem
> to act as a global index mabey maintaning that index can become costy over high table load by postgresql
> backend.

There is no OID index, unless you create one.

The disk space that an OID column can take has an effect on performance:
reducing the amount of physical disk reads will mean that more of your
real data is cached, and so forth.  How much effect it will have will
depend on the relative size of the OID column and the other columns in
your data.

Regards,
                    Andrew McMillan.

-------------------------------------------------------------------------
Andrew @ Catalyst .Net .NZ  Ltd,  PO Box 11-053, Manners St,  Wellington
WEB: http://catalyst.net.nz/            PHYS: Level 2, 150-154 Willis St
DDI: +64(4)803-2201      MOB: +64(272)DEBIAN      OFFICE: +64(4)499-2267
               http://survey.net.nz/ - any more questions?
-------------------------------------------------------------------------


От:
Tom Lane
Дата:

"Eric Lauzon" <> writes:
> I am still in the dark due to my lack of knowledge on internal OID management,but
> i would presume that a table with OID enable and that has high load would require
> some more work from pgsql internal to maintain the OID index for the database.

There is no "OID index"; at least not unless you choose to create one
for a given table.  The only thing particularly special about OID is
that there is an internal database-wide sequence generator for assigning
new values.  Otherwise it works a whole lot like a serial column.

            regards, tom lane

От:
Neil Conway
Дата:

On Sun, 2005-05-29 at 16:17 -0400, Eric Lauzon wrote:
> So OID can be beneficial on static tables

OIDs aren't beneficial on "static tables"; unless you have unusual
requirements[1], there is no benefit to having OIDs on user-created
tables (see the default_with_oids GUC var, which will default to "false"
in 8.1)

-Neil

[1] Such as a column that references a column in the system catalogs.