On Wed, 2003-09-03 at 17:28, Martijn van Oosterhout wrote:
> If you know the OID of a row, PostgreSQL doesn't have a special lookup table
> to find it. That's also why they're not unique; the backend would have to
> scan through every table to find out if the next one is available.
Ahh, thats not nice, hav'nt checked that, yet.
> So, unless you specifically add an index to the table, looking up by OID
> will always trigger a sequential scan.
I thought it was much more easy for PG to find these, but I quess ctid
are the one that is fast to find.
> That said, there is no reason why someone couldn't create a last_sequence()
> function so you could say SELECT currval( last_sequence() ). Ofcourse, if
> your table has no SERIAL field, you're stuffed either way.
Not as nice as oid's.
/BL
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TIP 9: the planner will ignore your desire to choose an index scan if your
joining column's datatypes do not match
