Re: Optimizing Multiply Joins ???

From: Meszaros Attila <tilla(at)draconis(dot)elte(dot)hu>
To: pgsql-sql(at)hub(dot)org
Subject: Re: Optimizing Multiply Joins ???
Date: 2000-09-14 15:46:48
Message-ID: Pine.LNX.3.96.1000914151743.2542A-100000@draconis.csoma.elte.hu
Views: Raw Message | Whole Thread | Download mbox | Resend email
Thread:
Lists: pgsql-sql

Hi,

> Actually, as the 7.1 code currently stands, a query that uses explicit
> JOIN operators like yours does will always be implemented in exactly
> the given join order, with no searching. I haven't quite decided if
> that's a bug or a feature ...

Do you mean a "linear binary tree" like this is executed?

/\
/\ f
/\ e
/\ d
/\ c
a b

Or can we have some variations on the graph (with the same
preorder run: a,b,c,d,e,f) like this:

/\
/ \
/ /\
/\ d /\
a /\ e f
b c

We could give hints on the joins with brackets this way:
((a,(b,c)),(d,(e,f)))

I'm not sure which version of standards allows to bracket joins,
but I know sybase accepts the above form.

How difficult it looks to hack the parser to accept this form,
and pass the meaning to the planner?

Attila

In response to

Responses

Browse pgsql-sql by date

  From Date Subject
Next Message Tom Lane 2000-09-14 16:21:47 Re: Optimizing Multiply Joins ???
Previous Message Tim Quinlan 2000-09-14 04:57:04 Web Hosts (off-topic)