Re: [WIP] Keeping track of snapshots

"Alvaro Herrera" <alvherre(at)commandprompt(dot)com> writes:

> The other question is about CommitTransactionCommand. Currently my
> EOXact routine barfs for every snapshot not unregistered on main
> transaction commit -- a leak. I see this as a good thing, however it
> forced me to be more meticulous about not having ActiveSnapshot be set
> in commands that have multiple transactions like VACUUM, multitable
> CLUSTER and CREATE INDEX CONCURRENTLY.

I believe ActiveSnapshot has to be set during CREATE INDEX CONCURRENTLY if
it's an expression index which calls a function which needs a snapshot...

AFAICT VACUUM had better not ever need a snapshot because its xmin isn't
included in other vacuum commands' globalxmin so there's no guarantee that if
it had a snapshot that the tuples visible in that snapshot wouldn't disappear
out from under it.

--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com
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