Re: multi-install PostgresNode fails with older postgres versions

> On Mar 30, 2021, at 3:12 PM, Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
> 
> On 2021-Mar-30, Mark Dilger wrote:
> 
>> The problem is clear enough; -N/--nosync was added in 9.3, and
>> PostgresNode::init is passing -N to initdb unconditionally. I wonder
>> if during PostgresNode::new a call should be made to pg_config and the
>> version information grep'd out so that version specific options to
>> various functions (init, backup, etc) could hinge on the version of
>> postgres being used?
> 
> Yeah, I think making it backwards-compatible would be good.  Is running
> pg_config to obtain the version the best way to do it?  I'm not sure --
> what other ways are there?  I can't of anything.  (Asking the user seems
> right out.)

Once you have a node running, you can query the version using safe_psql, but that clearly doesn't work soon enough, since we need the information prior to running initdb.

One of the things I noticed while playing with this new toy (thanks, Andrew!) is that if you pass a completely insane install_path, you don't get any errors.  In fact, you get executables and libraries from whatever PATH="/no/such/postgres:$PATH" gets you, probably the executables and libraries of your latest development branch.  By forcing get_new_node to call the pg_config of the path you pass in, you'd fix that problem.  I didn't do that, mind you, but you could.  I just executed pg_config, which means you'll still get the wrong version owing to the PATH confusion.


—
Mark Dilger
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