Re: [HACKERS] Make subquery alias optional in FROM clause

On Thu, Feb 23, 2017 at 10:37:16AM +0100, Bernd Helmle wrote:
> Am Mittwoch, den 22.02.2017, 22:17 -0500 schrieb Tom Lane:
> > [ shrug... ]  Well, I won't resist this hard as long as it's done
> > competently, which to me means "the subquery name doesn't conflict
> > with
> > anything else".  Not "it doesn't conflict unless you're unlucky
> > enough
> > to have used the same name elsewhere".  There are a couple ways we
> > could
> > achieve that result, but the submitted patch fails to.
> 
> Right, i'm going to give it a try then. Currently i see these options:
> 
> * Validate any generated alias against a list of explicit alias names.
> 
> This means we have to collect explicit alias names in, say a hashtable,
> and validate a generated name against potential collisions and retry.
> Or better, generate the name in a way that doesn't produce a collision
> with this list.

There's another option:
* Gensym an alias name, and if the compilation fails with that alias  name as a conflict, try again with a new gensym'ed name.

> * Don't force/generate an alias at all.

That seems like a lot of work.

Nico
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