Thanks for the clarification Craig. On Mon, Oct 29, 2012 at 8:46 AM, Craig Ringer <ring...@ringerc.id.au> wrote:
> On 10/29/2012 04:07 PM, Seref Arikan wrote: > > Greetings, > > I keep seeing statements like "Postgresql optimizer rewrites this query > > as...." What I'm curious about is, is there a way to obtain SQL form of > > the re-written queries somewhere in the chain of query evaluation? It > > does not make a lot sense to generate sql again, but it would help a lot > > to see the queries in their rewritten form. > > I've never seen such a tool, and I'm not sure one is possible, though I > agree it'd be interesting. > > The same SQL can result in many different query plans, and there are > many different SQL statements that can all result in the same query > plan. How would you unambiguously show what plan the SQL represented? > > It's not so much that Pg's planner "rewrites" one SQL statement to > another. Usually, it's that two or more different SQL statements > optimize down to the same query plan. > > EXPLAIN and EXPLAIN ANALYZE show the query plans, and I'm not really > sure you can go backwards from there to SQL in any consistent and > logical way. > > -- > Craig Ringer > >
