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

Interesting.  I see what you mean.  We have a pyrotechnic API already
installed.


> Bruce,
>     I think that an index interface would be simpler than you think. 
> The index does not need any disk storage which takes out virtually all
> the complexity in implementation.  All that you really need to implement
> is the scan interface, and the only state that the scan needs is a
> single flag that indicates when getnext has already been called once.
> All that getnext need do is return the ctid, and flip the flag so that
> it knows to return null on the next call.  You also need to ensure that
> the access method functions used by the optimizer return appropriate
> values to ensure that the cost of an index search is always zero.  I
> have some suitable functions for that.
> 
> 
> With all due respect to people who I am sure know a lot more about this
> than I do, it seems to me that extensive use of TIDs in user code might
> place an unwelcome restraint on the internal database design.  If you
> follow the arguments of the reiserfs people, the whole idea of a
> buffered cache with fix size blocks is a necessary hack to cope with a
> less than optimal underlying filesystem.  In the ideal world that
> reiserfs promises (:-)) disk access efficiency would be independent of
> file-size, and it would be feasible to construct the buffered cache from
> raw tuples of variable size.  The files on disk would be identified by
> OID.  reiserfs uses a B-tree varient to cope with very large name
> spaces.
> 
> Similar considerations would seem to apply if the storage layer of the
> database is separated from the rest of the backend by a high-speed
> qnetwork interface on something like a hard-disk farm.  ( See for
> example some of the Mariposa work ).
> 
> Until things like that actually happen (Version 10.* perhaps) I can see
> that TIDs are a useful addition, but you might want to fasten them in
> with a pyrotechnic interface so that you can blow them away if need be.
> 
> I have a URL for the reiserfs stuff at home, if anyone is interested
> email me and I will dig it up and post it.
> 
> Bernie Frankpitt
> 


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