Date: Tue, 31 Mar 2020 17:27:47 -0400
From: Bruce Momjian <bruce@momjian.us>
To: me@sillymon.ch, pgsql-docs@lists.postgresql.org
Subject: Re: Move description of general lock behaviour out of the "13.3.1.
 Table-level Locks section"
Message-ID: <20200331212747.GE17676@momjian.us>
References: <158074944048.1095.4309647363871637715@wrigleys.postgresql.org>
 <20200312203420.GA2309@momjian.us>
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Patch applied through 9.5.

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On Thu, Mar 12, 2020 at 04:34:20PM -0400, Bruce Momjian wrote:
> On Mon, Feb  3, 2020 at 05:04:00PM +0000, PG Doc comments form wrote:
> > The following documentation comment has been logged on the website:
> > 
> > Page: https://www.postgresql.org/docs/9.4/explicit-locking.html
> > Description:
> > 
> > Hi
> > 
> > The "13.3.1. Table-level Locks" subsection mentions the following: "Once
> > acquired, a lock is normally held till end of transaction." (maybe we should
> > also squeeze a "...till the end of a transaction" in there) According to a
> 
> Sorry for the delay in replying.  Yes, this wording needs improvement,
> which I have done in the attached patch.
> 
> > helpful stranger on IRC, this behavior is also true for row-level locks.
> > 
> > Since this sentence also applies to the row-level locks described in the
> > following subsection 13.3.2 I think it would be more fitting to move the
> > paragraph containing this sentence to the introduction of the topic in
> > section "13.3. Explicit Locking". This would then read something like:
> 
> Uh, we can't move that paragraph up because Page-Level Locks and
> Advisory Locks aren't always released on transaction end or rollback. 
> What I did do was to mention that row-level locks are released in a
> similar way to table-level locks.
> 
> Patch attached.
> 
> -- 
>   Bruce Momjian  <bruce@momjian.us>        https://momjian.us
>   EnterpriseDB                             https://enterprisedb.com
> 
> + As you are, so once was I.  As I am, so you will be. +
> +                      Ancient Roman grave inscription +

> diff --git a/doc/src/sgml/mvcc.sgml b/doc/src/sgml/mvcc.sgml
> index f8c9655111..95465d581b 100644
> --- a/doc/src/sgml/mvcc.sgml
> +++ b/doc/src/sgml/mvcc.sgml
> @@ -1039,9 +1039,9 @@ ERROR:  could not serialize access due to read/write dependencies among transact
>       </tip>
>  
>     <para>
> -    Once acquired, a lock is normally held till end of transaction.  But if a
> +    Once acquired, a lock is normally held until the end of the transaction.  But if a
>      lock is acquired after establishing a savepoint, the lock is released
> -    immediately if the savepoint is rolled back to.  This is consistent with
> +    immediately if the savepoint is rolled back.  This is consistent with
>      the principle that <command>ROLLBACK</command> cancels all effects of the
>      commands since the savepoint.  The same holds for locks acquired within a
>      <application>PL/pgSQL</application> exception block: an error escape from the block
> @@ -1178,7 +1178,10 @@ ERROR:  could not serialize access due to read/write dependencies among transact
>       conflicting locks on the same row, even in different subtransactions;
>       but other than that, two transactions can never hold conflicting locks
>       on the same row.  Row-level locks do not affect data querying; they
> -     block only <emphasis>writers and lockers</emphasis> to the same row.
> +     block only <emphasis>writers and lockers</emphasis> to the same
> +     row.  Row-level locks are released at transaction end or during
> +     savepoint rollback, just like table-level locks.
> +
>      </para>
>  
>       <variablelist>


-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EnterpriseDB                             https://enterprisedb.com

+ As you are, so once was I.  As I am, so you will be. +
+                      Ancient Roman grave inscription +