Quoting Pete Sharman's signature from my memory:
Controlling developers is harder then herding cats.
Tell your developers that there exists a thing called "CBO" which has
something called "hints" that can alleviate the need for such ridiculous
WHERE clauses.
On 2003.10.21 07:44, "Hately, Mike (LogicaCMG)" wrote:
> Morning folks,
>
> the developers here are looking at a view with a where clause which
> specifies :
>
> WHERE 1=1 AND
> ............... AND
> ............... etc.
>
> I'd seen this used before as a way of tweaking the RBO into certain
> behaviours but it was years ago and my recollection is very hazy.
> The only explanation I've found so far is :
>
> "the 1=1 is in there to avoid doing repetitive index scans for single
> rowids, when the app "knows" the result set is going to be manipulated
> rowid's for a large subset of the table. I would guess your DUAL/CBO example
> had some similar effect."
>
> Is anyone familiar enough with this tweak to explain it ?
>
> Cheers,
> Mike
>
> PS Maybe it'll head off some replies if I make it clear that this view
> hasn't been generated by code so the "1=1" isn't an accidental artifact It
> was custom written and is definitely supposed to have exactly this
> structure.
>
>
>
>
>
>
>
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> --
> Author: Hately, Mike (LogicaCMG)
> INET: mike.hately_at_nedl.co.uk
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--
Mladen Gogala
Oracle DBA
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Received on Tue Oct 21 2003 - 07:05:27 CDT
