Re: Doubts about oid

On Thu, Feb 18, 2010 at 8:46 PM, Jayadevan M
<Jayadevan(dot)Maymala(at)ibsplc(dot)com> wrote:
>
> Hi,
> > The primary question that needs to be asked is what do you want to do with them?
> > It is not so much a performance issue as an admin issue. OIDs where created for
> > Postgres internal system use and leaked out to user space. As a result they
> > have some shortcomings as detailed in the above article. Given that sequences
> > are available as number generators, it was decided to encourage/force OIDs to
> > be for internal system use only. That decision is set and using OIDs on user
> > tables is setting yourself for future problems.
>
> I am an Oracle guy who is learning PostgreSQL. oid sounded a lot like rowid in Oracle. In Oracle, access by rowid is expected to be the fastest way of accessing a record, faster than even an index access followed by table access using the primary key. That was why I have this doubt about usage of oid being deprecated. Even if we use a sequence as PK (which is there in Oracle too), it is not as fast as access by rowid (I don't know if this applies to PostgreSQL's oid too). This is important when we use a cursors in an Oracle procedure (function in PostgreSQL) and loop through it and update specific records, when some conditions are met. Of course, that approach has its drawbacks -as in the case when row movement is enabled some maintenance activity moves the row to another location. Another scenario is when we want to delete duplicate records in a table.

Oracle and postgres are definitely different here. There's really no
equivalent to rowid in pgsql. oid has no special optimizations. An
indexed PK of a serial is about as good as it gets, possibly
clustered.