Re: Worthwhile optimisation of position()?

Tom Lane wrote:
> Tim Allen <tim@proximity.com.au> writes:
>   
>> Thomas Hallgren wrote:
>>     
>>> The position function must look for 'ch' everywhere in the string so 
>>> there's no way it can use an index.
>>>       
>
>   
>> I think the '= 0' bit is what Chris was suggesting could be the basis 
>> for an optimisation.
>>     
>
> Yeah.  AFAICS the transformation Chris suggested is valid.  I'm really
> dubious that it's worth expending planner cycles to look for it though.
> LIKE is something that everybody and his brother uses, but who uses this
> position()=0 locution?
>
>             regards, tom lane
>   
The documentation says: position('om' in 'Thomas') == 3 so i assumed 
that the returned index was 1-based and that a zero meant 'not found'. 
If I'm wrong ,perhaps the docs need to be updated?

Regards,
Thomas Hallgren