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From "Antonio Gallardo" <agalla...@agsoftware.dnsalias.com>
Subject RE: [ESQL] Improvement....
Date Mon, 27 Jan 2003 17:29:18 GMT
Hunsberger, Peter dijo:
>> This is the example I tried to explain:
>>
>> I have a table that store the status of some tickets. You always know
>> how
> many status there can be. > If you said:
>>
>> 1-Open
>> 2-Close
>> 3-Invalid
>>
>> Then if you want to show the history, you will ask for LIMIT 3, but
>> the
> database will try to find
>> the 4th row after finding the only 3 that can exist.
>>
>> This is why I told this is a performance issue. Not an error.
>
> I sure hope you've normalized your database so that "status" is stored
> in a separate table from the rest of the history? If so, you should
> have a proper primary key in the history table that you can index on and
> the search will stop after looking at 4 records; the three that match
> and first one that doesn't match (at which point it will know the search
> is done.)
>

I think this is not a issue of how I build my database or not. This is
more general. Maybe this improvement will does not help nothing in some
Database constructions and give too much in performance.

My point of view is: "If a user dont want to know if there are or not more
results. We must almost build the correct SQL clausule". In this case the
correct clausule is:

LIMIT X

and not LIMIT X+1

Of course if you need to know if there are more rows, then the correct SQL
clausule is:

LIMIT X+1

This is without thinking if you use Oracle, PotgreSQL or any other DB
Engine. I think that the improvement will always helps.

At the end, how much time take for a processor decide to use X or X+1 vrs.
how much time will have to search the X+1 row in a big table? I think the
second one will be always slower regarless if you index or not. Then lets
help the database Engine with better SQL clausules. Tha will helps to
build a faster Database interface for Cocoon. ;-)

Best Regards,

Antonio Gallardo.




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