I am actually not using any indexes, just the raw tables. This may seem strange for working with alot of data but the idea is to try and bring Firebird to it's knees. The time difference seems to be far to much for it to be an issue with indexing( less than 1 second with AND and 12-17 seconds with OR).

----- Original Message ----
From: Svein Erling Tysvær <svein.erling.tysvaer@...>
To: firebird-support@yahoogroups.com
Sent: Tuesday, May 30, 2006 4:16:19 AM
Subject: [firebird-support] Re: Query Times for Firebird. Issue with where claus?

Hmm, you really ought to tell us the respective plans generated by the
optimizer, without them it feels like looking for the needle in the
haystack - without knowing where the haystack is! (ok, I am
exaggerating a bit)

Looking at your query, I notice two things.

You use SQL-89 and not SQL-92.
In your case it doesn't matter much, it is cleaner with SQL-92 and may
make things easier for whichever components you use (my experience is
limited to IBO, and I know that with SQL-89 you often have to specify
one extra attribute called JoinLinks). Though this is not the cause of
your problem.

Parts of your query cannot use indexes: (BERN1.DOB_DAY -
BERN2.DOB_DAY) < 2 cannot possibly use any index (in your original
query, you use the same field twice, but I expect this to just be a
spelling mistake), but it is simple to change to something that may
use an index. This may be the needle if I'm in a haystack, but quite
frankly - it is just guessing without any PLANs and knowledge about
your indexes (normally, the problem is either using too many or too
few indexes, for once I guessed on using too few).

So I suggest you try to change to

select
count(*)
from BERN1
JOIN BERN2 ON BERN1.GENDER = BERN2.GENDER
WHERE
(
(
BERN1.DOB_YEAR = BERN2.DOB_YEAR
AND
(
BERN1.DOB_MO = BERN2.DOB_MO OR
BERN1.DOB_DAY = BERN2.DOB_DAY OR
BERN1.DOB_MO = BERN2.DOB_DAY
)
)
AND /* THIS IS THE PROBLEM LINE *****************/
(
BERN1.DOB_DAY BETWEEN BERN2.DOB_DAY-1 AND BERN2.DOB_DAY+1 AND
BERN1.DOB_MO = BERN2.DOB_MO AND
BERN1.DOB_YEAR = BERN2.DOB_YEAR
)
);

Actually, I'd normally put the DOB_YEAR outside the "problem area",
but if you use combined indexes rather than single field indexes, this
may be a very bad idea - so I didn't change that bit.

I've never done any work on tables with 30 million rows, but I often
join two or three tables with about 1 million rows each. What matters
is how unique indexes you can use for the joining. I would never join
that many records on fields like - say - COUNTRY, whereas joining on
almost unique fields like PERSON is a piece of cake.

HTH,
Set

--- In firebird-support@yahoogroups.com, "lec_sas" wrote:
> Me again,
> I am doing some volume testing and I ran across the following
> issue. The query I have pasted below runs against two tables. Bern1
> having 3730 records, Bern2 having 2987. The query is a bit of a
> dummy query but the idea was to mock some of our old test queries
> for some time comparisons.
>
> This query executes fine in about .2-.5 seconds using the embeded
> version. However, when I alter the identified "AND" condition
> to "OR", the query takes anywhere from 12-17 seconds. I ported the
> syntax and ran it in SQL Server 2005 and my query times were the
> same for both (or very close).
>
> Could this perhaps be an issue with the way FireBird interprets
> the "OR'S" in the where clause?
>
> Is there any possible suggestions to how this can be optimized to
> avoid such results? In our production environments, worst case
> scenario could have a query running against a pair of 30 million
> record tables, so 12-17 seconds with such a small set of data raises
> concerns.
>
> Has there been anyone in the past do some major volume testing whith
> those kinds of numbers before (30 mil). If so, care to share some
> results?
>
> Query:
>
> select
> count(*)
> from
> BERN1,
> BERN2
> where
> (BERN1.GENDER = BERN2.GENDER)
> AND
> (
> (
> BERN1.DOB_YEAR = BERN2.DOB_YEAR
> AND
> (
> BERN1.DOB_MO = BERN2.DOB_MO OR
> BERN1.DOB_DAY = BERN2.DOB_DAY OR
> BERN1.DOB_MO = BERN2.DOB_DAY
> )
> )
> AND /* THIS IS THE PROBLEM LINE *****************/
> (
> (BERN1.DOB_DAY - BERN1.DOB_DAY) < 2 AND
> (BERN2.DOB_DAY - BERN1.DOB_DAY) < 2 AND
> BERN1.DOB_MO = BERN2.DOB_MO AND
> BERN1.DOB_YEAR = BERN2.DOB_YEAR
> )
> );
>
> Thanks
>
> Darin Amos






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