Horton

Re: ATTACH/DETACH PARTITION CONCURRENTLY

Alvaro Herrera <alvherre@2ndquadrant.com>

View thread View on postgr.es
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Michael Paquier <michael@paquier.xyz>, Sergei Kornilov <sk@zsrv.org>, Amit Langote <langote_amit_f8@lab.ntt.co.jp>, David Rowley <david.rowley@2ndquadrant.com>, Andres Freund <andres@anarazel.de>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Simon Riggs <simon@2ndquadrant.com>
Date: 2018-12-20T21:11:47Z
Lists: pgsql-hackers 
On 2018-Dec-20, Robert Haas wrote:

> I didn't handle that.  If partition pruning relies on nothing changing
> between planning and execution, isn't that broken regardless of any of
> this?  It's true that with the simple query protocol we'll hold locks
> continuously from planning into execution, and therefore with the
> current locking regime we couldn't really have a problem.  But unless
> I'm confused, with the extended query protocol it's quite possible to
> generate a plan, release locks, and then reacquire locks at execution
> time.  Unless we have some guarantee that a new plan will always be
> generated if any DDL has happened in the middle, I think we've got
> trouble, and I don't think that is guaranteed in all cases.

Oh, so maybe this case is already handled by plan invalidation -- I
mean, if we run DDL, the stored plan is thrown away and a new one
recomputed.  IOW this was already a solved problem and I didn't need to
spend effort on it. /me slaps own forehead

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Commits

  1. Allow ATTACH PARTITION with only ShareUpdateExclusiveLock.

  2. Change lock acquisition order in expand_inherited_rtentry.

  3. Move code for managing PartitionDescs into a new file, partdesc.c

  4. Remove more redundant relation locking during executor startup.

  5. Add assertions that we hold some relevant lock during relation open.

  6. Try to acquire relation locks in RangeVarGetRelid.