Horton

Re: PROC_IN_ANALYZE stillborn 13 years ago

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Alvaro Herrera <alvherre@2ndquadrant.com>, James Coleman <jtc331@gmail.com>, pgsql-hackers <pgsql-hackers@lists.postgresql.org>, Simon Riggs <simon@2ndquadrant.com>
Date: 2020-08-06T21:26:32Z
Lists: pgsql-hackers 
Hi,

On 2020-08-06 14:48:52 -0400, Robert Haas wrote:
> On Thu, Aug 6, 2020 at 2:37 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> > +1 for removal.  It's not clear to me that we'd ever put it back.
> > Long-running ANALYZE snapshots are indeed a problem, but Simon's proposal
> > upthread to just take a new one every so often seems like a much cleaner
> > and simpler answer than having onlookers assume that it's safe to ignore
> > ANALYZE processes.  (Given that ANALYZE can invoke user-defined functions,
> > and can be invoked from inside user transactions, any such assumption
> > seems horribly dangerous.
> 
> Not to get too far from the proposal on the table of just removing
> something that's been unused for a really long time, which stands on
> its own merits, but if a particular ANALYZE doesn't invoke any
> user-defined functions and isn't run inside a transaction, could we
> skip acquiring a snapshot altogether? That's an extremely common case,
> though by no means universal.

I don't think so, at least not in very common situations. E.g. as long
as there's a toast table we need to hold a snapshot to ensure that we
don't get failures looking up toasted datums. IIRC there were some other
similar issues that I can't quite recall right now.

Greetings,

Andres Freund

Commits

  1. Call out vacuum considerations in create index docs

  2. Document concurrent indexes waiting on each other

  3. snapshot scalability: Don't compute global horizons while building snapshots.

  4. Remove PROC_IN_ANALYZE and derived flags

  5. Improve performance of get_actual_variable_range with recently-dead tuples.