On Mon, Jul 13, 2009 at 07:06:40PM +0100, Simon Riggs wrote:
> On Mon, 2009-07-13 at 13:33 -0400, Tom Lane wrote:
> > It's hard to believe
> > this sort of case comes up often enough to justify the cycles that would
> > be expended (on *every* join query) to try to recognize it.
>
> Yeh, damn ORMs
On Mon, Jul 13, 2009 at 3:48 PM, decibel wrote:
> On Jul 13, 2009, at 1:06 PM, Simon Riggs wrote:
>>
>> Not just because of this but I wonder if we might benefit from an
>> optimizer setting specifically aimed at the foolishnesses of
>> automatically generated SQL.
>
>
> +1. And it's not just ORMs
On Jul 13, 2009, at 1:06 PM, Simon Riggs wrote:
Not just because of this but I wonder if we might benefit from an
optimizer setting specifically aimed at the foolishnesses of
automatically generated SQL.
+1. And it's not just ORMs that do stupid things, I've seen crap like
this come out of u
Tom Lane wrote:
> Writing a join for a single-table query? Why, in heavens name?
> (Or have you mercifully blotted the details from your memory?)
Actually, I had only the vaguest recollection of why, but I found an
email where I was explaining the problem to Sybase. Basically, it
boiled down
On Mon, Jul 13, 2009 at 1:33 PM, Tom Lane wrote:
> Simon Riggs writes:
>> In some cases, we have SQL being submitted that has superfluous
>> self-joins. An example would be
>
>> select count(*)
>> from foo1 a, foo1 b
>> where a.c1 = b.c1 /* PK join */
>> and a.c2 = 5
>> and b.c2 = 10;
>
>> You may
On Mon, 2009-07-13 at 13:33 -0400, Tom Lane wrote:
> Simon Riggs writes:
> > In some cases, we have SQL being submitted that has superfluous
> > self-joins. An example would be
>
> > select count(*)
> > from foo1 a, foo1 b
> > where a.c1 = b.c1 /* PK join */
> > and a.c2 = 5
> > and b.c2 = 10
"Kevin Grittner" writes:
> Simon Riggs wrote:
>> select count(*)
>> from foo1 a, foo1 b
>> where a.c1 = b.c1 /* PK join */
> We had to do something like that to get acceptable performance from
> Sybase ASE.
Writing a join for a single-table query? Why, in heavens name?
(Or have you merciful
Simon Riggs writes:
> In some cases, we have SQL being submitted that has superfluous
> self-joins. An example would be
> select count(*)
> from foo1 a, foo1 b
> where a.c1 = b.c1 /* PK join */
> and a.c2 = 5
> and b.c2 = 10;
> You may well ask who would be stupid enough to write SQL like tha
Simon Riggs wrote:
> select count(*)
> from foo1 a, foo1 b
> where a.c1 = b.c1 /* PK join */
> You may well ask who would be stupid enough to write SQL like that.
> The answer is of course that it is automatically generated by an
> ORM.
We had to do something like that to get acceptable pe
In some cases, we have SQL being submitted that has superfluous
self-joins. An example would be
select count(*)
from foo1 a, foo1 b
where a.c1 = b.c1 /* PK join */
and a.c2 = 5
and b.c2 = 10;
We can recognise that and are the same table because they are
joined on the PK. PK is never NULL, s
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