Re: What is an item pointer, anyway? - Mailing list pgsql-hackers

From Peter Geoghegan
Subject Re: What is an item pointer, anyway?
Date
Msg-id CAH2-Wz=yYwrjb41e=1tMbSUoEcj85MFKcGOC0QhrdJP+S17LNQ@mail.gmail.com
Whole thread Raw
In response to Re: What is an item pointer, anyway?  (Ashwin Agrawal <aagrawal@pivotal.io>)
List pgsql-hackers
On Fri, Apr 26, 2019 at 4:23 PM Ashwin Agrawal <aagrawal@pivotal.io> wrote:
> How about we rename ItemPointerData to TupleIdentifier or ItemIdentifier instead and leave ItemPointer or Item
confinedto AM term, where item can be tuple, datum or anything else ?
 

I'm not a fan of that idea, because the reality is that an
ItemPointerData is quite explicitly supposed to be a physiological
identifier (TID) used by heapam, or a similar heap-like access method
such as zheap. This is baked into a number of things.

The limitation that pluggable storage engines have to work in terms of
item pointers is certainly a problem, especially for things like the
Zedstore column store project you're working on. However, I suspect
that that problem is best solved by accommodating other types of
identifiers that don't work like TIDs.

I understand why you've adopted ItemPointerData as a fully-logical
identifier in your prototype, but it's not a great long term solution.

-- 
Peter Geoghegan



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