Horton

Re: [HACKERS] [COMMITTERS] pgsql: Fix freezing of a dead HOT-updated tuple

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: "Wood, Dan" <hexpert@amazon.com>, Peter Geoghegan <pg@bowt.ie>, pgsql-committers@postgresql.org, "Wong, Yi Wen" <yiwong@amazon.com>, Michael Paquier <michael.paquier@gmail.com>, Robert Haas <robertmhaas@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, pgsql-hackers@postgresql.org
Date: 2017-12-15T01:00:29Z
Lists: pgsql-hackers 
Hi,

On 2017-11-13 19:03:41 -0800, Andres Freund wrote:
> diff --git a/src/backend/access/heap/rewriteheap.c b/src/backend/access/heap/rewriteheap.c
> index f93c194e182..7d163c91379 100644
> --- a/src/backend/access/heap/rewriteheap.c
> +++ b/src/backend/access/heap/rewriteheap.c
> @@ -407,7 +407,10 @@ rewrite_heap_tuple(RewriteState state,
>  	 * While we have our hands on the tuple, we may as well freeze any
>  	 * eligible xmin or xmax, so that future VACUUM effort can be saved.
>  	 */
> -	heap_freeze_tuple(new_tuple->t_data, state->rs_freeze_xid,
> +	heap_freeze_tuple(new_tuple->t_data,
> +					  state->rs_old_rel->rd_rel->relfrozenxid,
> +					  state->rs_old_rel->rd_rel->relminmxid,
> +					  state->rs_freeze_xid,
>  					  state->rs_cutoff_multi);

Hm. So this requires backpatching the introduction of
RewriteStateData->rs_old_rel into 9.3, which in turn requires a new
argument to begin_heap_rewrite().  It originally was added in the
logical decoding commit (i.e. 9.4).

I'm fine with that, but it could theoretically cause issues for somebody
with an extension that calls begin_heap_rewrite() - which seems unlikely
and I couldn't find any that does so.

Does anybody have a problem with that?

Regards,

Andres

Commits

  1. Backport addition of rs_old_rel to rewriteheap's state.

  2. Perform a lot more sanity checks when freezing tuples.

  3. Revert bogus fixes of HOT-freezing bug

  4. Fix traversal of half-frozen update chains

  5. Fix freezing of a dead HOT-updated tuple

  6. During index build, check and elog (not just Assert) for broken HOT chain.

  7. Fix WAL replay of locking an updated tuple

  8. Change the way we mark tuples as frozen.