Re: How about a proper TEMPORARY TABLESPACE?

On Sun, Jun 29, 2014 at 3:19 AM, Matheus de Oliveira
<matioli(dot)matheus(at)gmail(dot)com> wrote:
> Hi Hackers,
>
> I have worked on that patch a little more. So now I have functional patch
> (although still WIP) attached. The feature works as following:
>
> - Added a boolean parameter "only_temp_files" to pg_tablespace.spcoptions;
> - This parameter can be set to true only during CREATE TABLESPACE, not on
> ALTER TABLESPACE (I have thought of ways of implementing the latter, and I'd
> like to discuss it more latter);
> - On the creation of relations, it is checked if it is a
> temporary-tablespace, and an error occurs when it is and the relation is not
> temporary (temp table or index on a temp table);
> - When a temporary file (either relation file or sort/agg file) is created
> inside a temporary-tablespace, the entire directories structure is created
> on-demand (e.g. if pg_tblspc/<oid>/<TABLESPACE_VERSION_DIRECTORY> is
> missing, it is created on demand) it is done on
> OpenTemporaryFileInTablespace, at fd.c (I wonder if shouldn't we do that for
> any tablespace) and on TablespaceCreateDbspace, at tablespace.c.
>
> I still haven't change documentation, as I think I need some insights about
> the changes. I have some more thoughts about the syntax and I still think
> that "TEMP LOCATION" syntax is better suited for this patch. First because
> of the nature of the changes I made, it seems more suitable to a column on
> pg_tablespace rather than an option. Second because no ALTER is available
> (so far) and I think it is odd to have an option that can't be changed.
> Third, I think "TEMP" keyword is more clear and users can be more used to
> it.
>
> Thoughts?
>
> I'm going to add the CF app entry next. Could I get some review now or after
> discussion about how things are going (remember I'm a newbie on this, so I'm
> a little lost)?

I got the following warning messages at the compilation.

dbcommands.c:420: warning: implicit declaration of function
'is_tablespace_temp_only'
indexcmds.c:437: warning: implicit declaration of function
'is_tablespace_temp_only'
tablecmds.c:527: warning: implicit declaration of function
'is_tablespace_temp_only'

When I created temporary tablespace and executed pg_dumpall,
it generated the SQL "ALTER TABLESPACE hoge SET (only_temp_files=on);".
This is clearly a bug because that SQL is not allowed to be executed.

> ERROR: this tablespace only allows temporary files

I think that this ERROR message can be improved, for example, for the
database creation case, what about something like the following?

ERROR: database cannot be created on temporary tablespace
HINT: temporary tablespace is allowed to store only temporary files.

Regards,

--
Fujii Masao