| From: | Stephen Frost <sfrost(at)snowman(dot)net> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Simon Riggs <simon(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Turning off HOT/Cleanup sometimes |
| Date: | 2014-01-09 18:28:11 |
| Message-ID: | 20140109182811.GO2686@tamriel.snowman.net |
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| Lists: | pgsql-hackers |
* Alvaro Herrera (alvherre(at)2ndquadrant(dot)com) wrote:
> But in a
> SELECT, the effect is only that you will have to skip less dead tuples,
> which is not as exciting.
Agreed. There's also the option to have it be done based on some
expectation of future work- that is, if we have to traverse X number of
dead tuples during a select, then don't bother with HOT pruning, but if
we get up to X+Y dead tuples, then do HOT pruning.
That said, I'm not entirely convinced that traversing these dead tuples
is all *that* painful during SELECT. If there's that many levels then
hopefully it's not long til an UPDATE comes along and cleans them up.
Thanks,
Stephen
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