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What happens to unused common table expressions?
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Roy Hann
Jan 4, 2012, 2:14:24 PM1/4/12
to
I could just try this to see, but I'm feeling lazy and someone probably
knows the answer.
If I write a query with one or more common table expressions to which I
don't actually refer in the query, do they just get pruned off or do
they get executed regardless?
--
Roy
UK Ingres User Association Conference 2012 will be on Tuesday June 19 2012.
The latest information is available from www.uk-iua.org.uk.
knows the answer.
If I write a query with one or more common table expressions to which I
don't actually refer in the query, do they just get pruned off or do
they get executed regardless?
--
Roy
UK Ingres User Association Conference 2012 will be on Tuesday June 19 2012.
The latest information is available from www.uk-iua.org.uk.
Karl Schendel
Jan 4, 2012, 6:07:30 PM1/4/12
to Ingres and related product discussion forum
On Jan 4, 2012, at 2:14 PM, Roy Hann wrote:
> I could just try this to see, but I'm feeling lazy and someone probably
> knows the answer.
>
> If I write a query with one or more common table expressions to which I
> don't actually refer in the query, do they just get pruned off or do
> they get executed regardless?
I'm lazy too.
I trust your holidays were merry ... ours were generally quite nice.
Karl
Martin Bowes
Jan 5, 2012, 3:26:16 AM1/5/12
to Ingres and related product discussion forum
Example query?
Marty
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Roy Hann
Jan 5, 2012, 5:41:49 AM1/5/12
to
Karl Schendel wrote:
> On Jan 4, 2012, at 2:14 PM, Roy Hann wrote:
>
>> I could just try this to see, but I'm feeling lazy and someone probably
>> knows the answer.
>>
>> If I write a query with one or more common table expressions to which I
>> don't actually refer in the query, do they just get pruned off or do
>> they get executed regardless?
>
> I'm guessing they get pruned off, but I'd have to try it to find out.
> I'm lazy too.
I summoned enough energy to do the upgrade I needed to apply before just
> On Jan 4, 2012, at 2:14 PM, Roy Hann wrote:
>
>> I could just try this to see, but I'm feeling lazy and someone probably
>> knows the answer.
>>
>> If I write a query with one or more common table expressions to which I
>> don't actually refer in the query, do they just get pruned off or do
>> they get executed regardless?
>
> I'm guessing they get pruned off, but I'd have to try it to find out.
> I'm lazy too.
trying the query for myself.
I can now tell you that the extraneous CTEs *are* pruned, at least in
this simple test on a toy database:
INGRES TERMINAL MONITOR Copyright 2011 Ingres Corporation
Ingres Microsoft Windows Version II 10.1.0 (int.w32/121) login
Thu Jan 05 10:30:59 2012
Enter \g to execute commands, "help help\g" for help, \q to quit
continue
* set qep;
*
* with smallorders ( ordernr ) as
* (
* select ordernr
* from orderitems
* group by ordernr
* having count(*) < 3
* )
* select count(*) from customers;
* \g
Executing . . .
********************************************************************
QUERY PLAN 1,2, no timeout, of simple aggregate
aggregate expression -> count(*)
Proj-rest
Heap
Pages 36 Tups 10000
D64 C100
/
customers
Hashed(NU)
Pages 514 Tups 10000
********************************************************************
+-------------+
|col1 |
+-------------+
| 10000|
+-------------+
(1 row)
continue
*
> I trust your holidays were merry ... ours were generally quite nice.
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