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

> > TODO list updated.  Seems the tid could be accessed directly, by
> > checking the page list, and if it is valid, just going to the tid.  I
> > assume you are working on that issue, or do you need assistance?
> >
> 
> Yes,I have done a part of my story.
> I would add new type of path and scan by which we are able to access
> tids directly.
> 
> I don't understand planner/executor stage well.
> So I'm happy if someone could check my story.

My guess is that you are going to have to hard-code something into the
backend to handle non-scan lookup of this type specially.

Normally, either there is an index lookup, or a sequential scan.  In
your case, you "know" the actual location of the row, or at least a
request for a possible valid location.

You could create a fake index that really doesn't exist, but returns a
tid that exactly matches the requested tid, or you could have the code
check for a specific TID type, and heap_fetch the desired row directly,
rather than performing a sequential scan.  See the developers FAQ on how
to do a heap_fetch with a tid.
You can also use <I>heap_fetch()</I> to fetch rows by blocknumber/offset.

The block number/offset is the tid.  Of course, you have to make sure
the tid is valid.

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