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  1. Doc: Clarify locks taken when using ALTER TABLE ATTACH PARTITION

  2. Doc: Improve description around ALTER TABLE ATTACH PARTITION

  1. update ALTER TABLE with ATTACH PARTITION lock mode

    Justin Pryzby <pryzby@telsasoft.com> — 2019-10-28T00:12:07Z

    commit #898e5e32 (Allow ATTACH PARTITION with only ShareUpdateExclusiveLock)
updates ddl.sgml but not alter_table.sgml, which only says:

https://www.postgresql.org/docs/12/release-12.html
|An ACCESS EXCLUSIVE lock is held unless explicitly noted.

Find attached patch, which also improve language in several related places.

"Without such a constraint": SUCH could refer to either of the constraints..

"because it is no longer necessary.": In our use case, we prefer to keep the
redundant constraint, to avoid having to add it back if we detach/reattach
again in the future..

  2. Re: update ALTER TABLE with ATTACH PARTITION lock mode

    Michael Paquier <michael@paquier.xyz> — 2019-10-28T07:55:46Z

    On Sun, Oct 27, 2019 at 07:12:07PM -0500, Justin Pryzby wrote:
> commit #898e5e32 (Allow ATTACH PARTITION with only ShareUpdateExclusiveLock)
> updates ddl.sgml but not alter_table.sgml, which only says:
> 
> https://www.postgresql.org/docs/12/release-12.html
> |An ACCESS EXCLUSIVE lock is held unless explicitly noted.

+     <para>
+      Attaching a partition acquires a <literal>SHARE UPDATE EXCLUSIVE</literal>
+      lock on the partitioned table, in addition to an
+      <literal>ACCESS EXCLUSIVE</literal> lock on the partition.
+     </para>
Updating the docs of ALTER TABLE sounds like a good idea.  This
sentence looks fine to me.  Perhaps others have suggestions?

> Find attached patch, which also improve language in several related places.

Not sure that these are actually improvements.
--
Michael

  3. Re: update ALTER TABLE with ATTACH PARTITION lock mode

    Alvaro Herrera <alvherre@2ndquadrant.com> — 2019-10-28T15:06:44Z

    On 2019-Oct-28, Michael Paquier wrote:

> On Sun, Oct 27, 2019 at 07:12:07PM -0500, Justin Pryzby wrote:
> > commit #898e5e32 (Allow ATTACH PARTITION with only ShareUpdateExclusiveLock)
> > updates ddl.sgml but not alter_table.sgml, which only says:
> > 
> > https://www.postgresql.org/docs/12/release-12.html
> > |An ACCESS EXCLUSIVE lock is held unless explicitly noted.
> 
> +     <para>
> +      Attaching a partition acquires a <literal>SHARE UPDATE EXCLUSIVE</literal>
> +      lock on the partitioned table, in addition to an
> +      <literal>ACCESS EXCLUSIVE</literal> lock on the partition.
> +     </para>
> Updating the docs of ALTER TABLE sounds like a good idea.  This
> sentence looks fine to me.  Perhaps others have suggestions?

Doesn't the command also acquire a lock on the default partition if
there is one?  It sounds worth noting.

> > Find attached patch, which also improve language in several related places.
> 
> Not sure that these are actually improvements.

I think some of them (most?) are clear improvements.

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

  4. Re: update ALTER TABLE with ATTACH PARTITION lock mode (docs)

    Justin Pryzby <pryzby@telsasoft.com> — 2019-10-29T03:56:33Z

    On Mon, Oct 28, 2019 at 12:06:44PM -0300, Alvaro Herrera wrote:
> On 2019-Oct-28, Michael Paquier wrote:
> 
> > On Sun, Oct 27, 2019 at 07:12:07PM -0500, Justin Pryzby wrote:
> > > commit #898e5e32 (Allow ATTACH PARTITION with only ShareUpdateExclusiveLock)
> > > updates ddl.sgml but not alter_table.sgml, which only says:
> > > 
> > > https://www.postgresql.org/docs/12/release-12.html
> > > |An ACCESS EXCLUSIVE lock is held unless explicitly noted.
> > 
> > +     <para>
> > +      Attaching a partition acquires a <literal>SHARE UPDATE EXCLUSIVE</literal>
> > +      lock on the partitioned table, in addition to an
> > +      <literal>ACCESS EXCLUSIVE</literal> lock on the partition.
> > +     </para>
> > Updating the docs of ALTER TABLE sounds like a good idea.  This
> > sentence looks fine to me.  Perhaps others have suggestions?
> 
> Doesn't the command also acquire a lock on the default partition if
> there is one?  It sounds worth noting.

I suppose it should something other than partition(ed), since partitions can be
partitioned, too...

      Attaching a partition acquires a <literal>SHARE UPDATE EXCLUSIVE</literal>
      lock on the parent table, in addition to
      <literal>ACCESS EXCLUSIVE</literal> locks on the child table and the
      <literal>DEFAULT</literal> partition (if any).

Thanks,
Justin

  5. Re: update ALTER TABLE with ATTACH PARTITION lock mode

    Amit Langote <amitlangote09@gmail.com> — 2019-10-31T08:00:11Z

    Hello,

On Tue, Oct 29, 2019 at 12:13 AM Alvaro Herrera
<alvherre@2ndquadrant.com> wrote:
> On 2019-Oct-28, Michael Paquier wrote:
> > On Sun, Oct 27, 2019 at 07:12:07PM -0500, Justin Pryzby wrote:
> > > commit #898e5e32 (Allow ATTACH PARTITION with only ShareUpdateExclusiveLock)
> > > updates ddl.sgml but not alter_table.sgml, which only says:
> > >
> > > https://www.postgresql.org/docs/12/release-12.html
> > > |An ACCESS EXCLUSIVE lock is held unless explicitly noted.
> >
> > +     <para>
> > +      Attaching a partition acquires a <literal>SHARE UPDATE EXCLUSIVE</literal>
> > +      lock on the partitioned table, in addition to an
> > +      <literal>ACCESS EXCLUSIVE</literal> lock on the partition.
> > +     </para>
> > Updating the docs of ALTER TABLE sounds like a good idea.  This
> > sentence looks fine to me.  Perhaps others have suggestions?
>
> Doesn't the command also acquire a lock on the default partition if
> there is one?  It sounds worth noting.
>
> > > Find attached patch, which also improve language in several related places.
> >
> > Not sure that these are actually improvements.
>
> I think some of them (most?) are clear improvements.

As someone who has written some of those lines, I agree that Justin's
tweaks make them more readable, so +1 to apply 0002 patch too.

Thanks,
Amit

  6. Re: update ALTER TABLE with ATTACH PARTITION lock mode (docs)

    Michael Paquier <michael@paquier.xyz> — 2019-10-31T09:07:34Z

    On Mon, Oct 28, 2019 at 10:56:33PM -0500, Justin Pryzby wrote:
> I suppose it should something other than partition(ed), since partitions can be
> partitioned, too...
> 
>       Attaching a partition acquires a <literal>SHARE UPDATE EXCLUSIVE</literal>
>       lock on the parent table, in addition to
>       <literal>ACCESS EXCLUSIVE</literal> locks on the child table and the
>       <literal>DEFAULT</literal> partition (if any).

In this context, "on the child table" sounds a bit confusing?  Would
it make more sense to say the "on the table to be attached" instead?
--
Michael

  7. Re: update ALTER TABLE with ATTACH PARTITION lock mode (docs)

    Justin Pryzby <pryzby@telsasoft.com> — 2019-11-01T13:59:48Z

    On Thu, Oct 31, 2019 at 06:07:34PM +0900, Michael Paquier wrote:
> On Mon, Oct 28, 2019 at 10:56:33PM -0500, Justin Pryzby wrote:
> > I suppose it should something other than partition(ed), since partitions can be
> > partitioned, too...
> > 
> >       Attaching a partition acquires a <literal>SHARE UPDATE EXCLUSIVE</literal>
> >       lock on the parent table, in addition to
> >       <literal>ACCESS EXCLUSIVE</literal> locks on the child table and the
> >       <literal>DEFAULT</literal> partition (if any).
> 
> In this context, "on the child table" sounds a bit confusing?  Would
> it make more sense to say the "on the table to be attached" instead?

I guess you mean because it's not a child until after the ALTER.  Yes, that
makes sense.

Thanks,
Justin

  8. Re: update ALTER TABLE with ATTACH PARTITION lock mode (docs)

    Michael Paquier <michael@paquier.xyz> — 2019-11-01T14:01:22Z

    On Fri, Nov 01, 2019 at 08:59:48AM -0500, Justin Pryzby wrote:
> I guess you mean because it's not a child until after the ALTER.  Yes, that
> makes sense.

Yes, perhaps you have another idea than mine on how to shape this
sentence?
--
Michael

  9. Re: update ALTER TABLE with ATTACH PARTITION lock mode (docs)

    Justin Pryzby <pryzby@telsasoft.com> — 2019-11-01T16:58:43Z

    On Fri, Nov 01, 2019 at 11:01:22PM +0900, Michael Paquier wrote:
> On Fri, Nov 01, 2019 at 08:59:48AM -0500, Justin Pryzby wrote:
> > I guess you mean because it's not a child until after the ALTER.  Yes, that
> > makes sense.
> 
> Yes, perhaps you have another idea than mine on how to shape this
> sentence?

I can't think of anything better.

Attaching a partition acquires a <literal>SHARE UPDATE EXCLUSIVE</literal> lock
on the parent table, in addition to <literal>ACCESS EXCLUSIVE</literal> locks
on the table to be attached and the <literal>DEFAULT</literal> partition (if
any).                                                                                                                                 

Justin

  10. Re: update ALTER TABLE with ATTACH PARTITION lock mode (docs)

    Michael Paquier <michael@paquier.xyz> — 2019-11-02T08:19:11Z

    On Fri, Nov 01, 2019 at 11:58:43AM -0500, Justin Pryzby wrote:
> Attaching a partition acquires a <literal>SHARE UPDATE EXCLUSIVE</literal> lock
> on the parent table, in addition to <literal>ACCESS EXCLUSIVE</literal> locks
> on the table to be attached and the <literal>DEFAULT</literal> partition (if
> any).                                                                                                                                 

Sounds fine.  So gathering everything I get the attached.  Any
thoughts from others?
--
Michael

  11. Re: update ALTER TABLE with ATTACH PARTITION lock mode (docs)

    Michael Paquier <michael@paquier.xyz> — 2019-11-05T01:35:47Z

    On Sat, Nov 02, 2019 at 05:19:11PM +0900, Michael Paquier wrote:
> Sounds fine.  So gathering everything I get the attached.  Any
> thoughts from others?

Committed after splitting the changes in two as originally proposed.
--
Michael