Re: pg_upgrade if 'postgres' database is dropped

On Sat, Oct 29, 2011 at 4:07 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Fri, Oct 28, 2011 at 9:22 PM, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
>> OK, the attached, applied patch removes the pg_upgrade dependency on the
>> 'postgres' database existing in the new cluster.  However, vacuumdb,
>> used by pg_upgrade, still has this dependency:
>>
>>            conn = connectDatabase("postgres", host, port, username,
>>                prompt_password, progname);
>>
>> In fact, all the /scripts binaries use the postgres database, except for
>> createdb/dropdb, which has this heuristic:
>>
>>    /*
>>     * Connect to the 'postgres' database by default, except have the
>>     * 'postgres' user use 'template1' so he can create the 'postgres'
>>     * database.
>>     */
>>    conn = connectDatabase(strcmp(dbname, "postgres") == 0 ? "template1" : "postgres",
>>                           host, port, username, prompt_password, progname);
>>
>> This makes sense because you might be creating or dropping the postgres
>> database.  Do we want these to have smarter database selection code?
>
> Well, I suppose as long as we're cleaning this up, we might as well be
> thorough, so, sure, why not?  I think the algorithm pg_dumpall uses is
> pretty sensible: let the user specify the database to use if they so
> desire; if not, try postgres first and then template1.  I think we
> could stick some logic for that in common.c which could be shared by
> clusterdb, createdb, dropdb, dropuser, reindexdb, and vacuumdb.
>
> However, we need to rethink the flag to be used for this: pg_dumpall
> uses -l, but many of the other utilities already use that for some
> other purpose, and it's not exactly mnemonic anyway.  "-d" for
> database could work, but that's also in use in some places, and
> furthermore somewhat confusing since many if not all of these
> utilities have an option to operate on a single database only, and you
> might think that -d would specify the database to operate on, rather
> than the one to be used to get the list of databases.  pgAdmin uses
> the term "maintenance database" to refer to a database to be used when
> none is explicitly specified, and I think that's fairly clear
> terminology.  So I propose that we add a --maintenance-db option (with
> no short form, since this is a relatively obscure need) to the tools
> listed above.  The tools will pass the associated value (or NULL if
> the option is not specified) to the above-mentioned routine in
> common.c, which will do the rest.
>
> If nobody objects, I'll go do that.  Hopefully that should be enough
> to put this problem to bed more or less permanently.

All right, I've worked up a (rather boring and tedious) patch to do
this, which is attached.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company