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

From Ashwin Agrawal
Subject Re: What is an item pointer, anyway?
Date
Msg-id CALfoeivDtaQPn8tfb48q1LJ1m1g6AKsgZ5Ws7OQZFBDHOUjnDQ@mail.gmail.com
Whole thread Raw
In response to What is an item pointer, anyway?  (Peter Geoghegan <pg@bowt.ie>)
Responses Re: What is an item pointer, anyway?
Re: What is an item pointer, anyway?
List pgsql-hackers

On Fri, Apr 26, 2019 at 2:19 PM Peter Geoghegan <pg@bowt.ie> wrote:
itemid.h introduces the struct ItemIdData as follows:

/*
 * An item pointer (also called line pointer) on a buffer page

Meanwhile, itemptr.h introduces the struct ItemPointerData as follows:

/*
 * ItemPointer:
 *
 * This is a pointer to an item within a disk page of a known file
 * (for example, a cross-link from an index to its parent table).

It doesn't seem reasonable to assume that you should know the
difference based on context. The two concepts are closely related. An
ItemPointerData points to a block, as well as the, uh, item pointer
within that block.

This ambiguity is avoidable, and should be avoided.

Agree.
 
ISTM that the
least confusing way of removing the ambiguity would be to no longer
refer to ItemIds as item pointers, without changing anything else.

How about we rename ItemPointerData to TupleIdentifier or ItemIdentifier instead and leave ItemPointer or Item confined to AM term, where item can be tuple, datum or anything else ?

pgsql-hackers by date:

Previous
From: Peter Geoghegan
Date:
Subject: What is an item pointer, anyway?
Next
From: Bruce Momjian
Date:
Subject: Re: Optimizer items in the release notes