Re: Scan by TID (was RE: [HACKERS] How to add a new build-in operator)

> > > Looks like a lot of work, and a lot of added code bulk that will
> > > have to be maintained.  I haven't figured out why you think it's
> > > worth it... tids are so transient that I don't see much need for
> > > finding tuples by them...
> > 
> > That's why I just suggested a more short-circuited option of snatching
> > tid oids from expressions, and doing a heap_fetch directly at that point
> > to avoid the index scan.  Seems it could be done in just one file.
> >
> 
> I have thought the way as Tom says and I have a prospect to do it.
> But it would take a lot of work.
> 
> Where to snatch and return to(or exit from) planner/executor 
> in your story ?

Basically, if I remember, in the executor, access to a table either
opens the table for sequential scan, does an index scan, or has the
value it needs already in a result of a previous join result.

If we put something in the executor so when a sequential/index scan is
requested on a table that has a restriction on tid, you could just do a
heap_fetch and return the single row, rather than putting the query
through the whole scan process for every row checking to see if it
matches the WHERE restriction.

Seems like a few lines in the executor could do the entire job of
fetching by tid by short-circuiting the sequential/index scan.

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