Re: [HACKERS] Show stopper ? (was: Re: "cruising" or "browsing" through tables using an index / ordering)

  Hey ! You sound like you know exactly what I mean ! ;-)

On Fri, 23 Jan 1998, Bruce Momjian wrote:

> >   Important : I'm not looking for a "pure SQL" solution. I'm writing a C
> > emulation library, so if it can be achieved via a call to a C Postgres
> > function, it would be great.
>
> You can put an index on the table, and embed a function inside the
> engine to spin through the index, getting valid rows.

  Aha, this implies that in the index there are valid and non-valid rows.
I guess those that are to be "valid" (no current transactions on that
row) and the non-valid "those that are subject to an update lock /
transaction".

>  The code is
> already there to spin through the index, so you could just hook on to
> the index, get the 'tid' and use that to get data from the physical
> table.

    This sounds like what I meant. Would you have any pointers (to source
files / functions I should read / understand / call ) ?


>  No locking, but you may get in trouble if other people are
> reading the index.

  I don't see what trouble I could get into. Any hints appreciated.


> Maybe a quick lock-unlock would do it for you.

   Do you mean lock-unlock on the table or on the index ?


> Not easy, because the engine really doesn't provide a user-friendly C
> interface for this, but it could be done.

   Can you point me to some of the user-nonfriendly files / functions I
should use then ?

      Thanx a bunch (I have to have the implementation by tomorrow 10am),

           Jan

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