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.
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