Horton

Re: COPY FREEZE and setting PD_ALL_VISIBLE/visibility map bits

Pavan Deolasee <pavan.deolasee@gmail.com>

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From: Pavan Deolasee <pavan.deolasee@gmail.com>
To: Masahiko Sawada <sawada.mshk@gmail.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>, Jeff Janes <jeff.janes@gmail.com>, Simon Riggs <simon@2ndquadrant.com>
Date: 2019-03-12T07:54:16Z
Lists: pgsql-hackers 
On Mon, Mar 11, 2019 at 1:37 PM Masahiko Sawada <sawada.mshk@gmail.com>
wrote:

>
>
> I might be missing something but why do we need to recheck whether
> each pages is all-frozen after insertion? I wonder if we can set
> all-frozen without checking all tuples again in this case.
>

It's possible that the user may have inserted unfrozen rows (via regular
INSERT or COPY without FREEZE option) before inserting frozen rows. So we
can't set the all-visible/all-frozen flag unconditionally. I also find it
safer to do an explicit check to ensure we never accidentally mark a page
as all-frozen. Since the check is performed immediately after the page
becomes full and only once per page, there shouldn't be any additional IO
cost and the check should be quite fast.

Thanks,
Pavan
-- 
 Pavan Deolasee                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

Commits

  1. Fix COPY FREEZE with CLOBBER_CACHE_ALWAYS

  2. Set PD_ALL_VISIBLE and visibility map bits in COPY FREEZE

  3. docs: client certificates are always sent to the server

  4. Mark commit and abort WAL records with XLR_SPECIAL_REL_UPDATE.

  5. docs: land height is "elevation", not "altitude"

  6. Improve the internal implementation of ereport().