| From: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
|---|---|
| To: | "Wood, Dan" <hexpert(at)amazon(dot)com> |
| Cc: | Peter Geoghegan <pg(at)bowt(dot)ie>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, "Wong, Yi Wen" <yiwong(at)amazon(dot)com> |
| Subject: | Re: [COMMITTERS] pgsql: Fix freezing of a dead HOT-updated tuple |
| Date: | 2017-10-04 09:54:29 |
| Message-ID: | 20171004095429.lh37mah23vp3ydau@alvherre.pgsql |
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| Lists: | pgsql-committers pgsql-hackers |
Wood, Dan wrote:
> One minor side note… Is it weird for xmin/xmax to go backwards in a hot row chain?
>
> lp | t_ctid | lp_off | t_infomask | t_infomask2 | t_xmin | t_xmax
> ----+--------+--------+------------+-------------+--------+--------
> 1 | (0,1) | 8152 | 2818 | 3 | 36957 | 0
> 2 | | 5 | | | |
> 3 | | 0 | | | |
> 4 | | 0 | | | |
> 5 | (0,6) | 8112 | 9986 | 49155 | 36962 | 36963
> 6 | (0,7) | 8072 | 9986 | 49155 | 36963 | 36961
> 7 | (0,7) | 8032 | 11010 | 32771 | 36961 | 0
> (7 rows)
No, it just means transaction A got its XID before transaction B, but B
executed the update first and A updated the tuple second.
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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