Re: [HACKERS] WARM and indirect indexes

On 1/11/17 8:09 PM, Pavan Deolasee wrote:
> The other thing the patch changes is how update-chain is maintained. In
> order to quickly find the root offset while updating a tuple, we now
> store the root offset in the t_ctid field of the last tuple in the chain
> and use a separate bit to mark end-of-the-chain (instead of relying of
> t_ctid = t_self check). That can lead to problems if chains are not
> maintained or followed correctly. These changes are in the first patch
> of the patch series and if you've any suggestions on how to improve that
> or solidify chain following, please let me know. I was looking for some
> way to hide t_ctid field to ensure that the links are only accessed via
> some standard API.

AIUI, that's going to affect every method of heap access except for 
index scans that can skip the heap due to being all-visible. That means 
the risk here is comparable to the MXID changes.
-- 
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
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