| From: | Josh Berkus <josh(at)agliodbs(dot)com> |
|---|---|
| To: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> |
| Cc: | Simon Riggs <simon(at)2ndQuadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Summary and Plan for Hot Standby |
| Date: | 2009-11-20 02:14:19 |
| Message-ID: | 4B05FB7B.4020407@agliodbs.com |
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| Lists: | pgsql-hackers |
On 11/15/09 11:07 PM, Heikki Linnakangas wrote:
> - When replaying b-tree deletions, we currently wait out/cancel all
> running (read-only) transactions. We take the ultra-conservative stance
> because we don't know how recent the tuples being deleted are. If we
> could store a better estimate for latestRemovedXid in the WAL record, we
> could make that less conservative.
Simon was explaining this issue here at JPUGCon; now that I understand
it, this specific issue seems like the worst usability issue in HS now.
Bad enough to kill its usefulness for users, or even our ability to get
useful testing data; in an OLTP production database with several hundred
inserts per second it would result in pretty much never being able to
get any query which takes longer than a few seconds to complete on the
slave.
--Josh Berkus
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