Re: Tablespace growing at enormous rate

Joe wrote:

> Thank you, Patrick, Alun,
>
> We pinpointed the source of problem, but not the cause.
> It seems that Oracle JOIN is broken.
>
> We have two tables, T with columns ID, A, B, and table
> U, with columns ID, A.
>
> The source of the problem is the following join:
>
> INSERT INTO T_TEMP
> SELECT
> T.ID,
> T.A,
> T.B
> FROM
> T,
> U
> WHERE
> T.ID = U.ID AND
> T.A = U.A
>
> Table T has 15,000,000 rows of daily historical data (for
> the past 100 days, that means 150,000 rows per day), and
> U has 6,000 rows only (this is data for yesterday only).
>
> Every row in U has 10 matching rows in T, so in theory
> the join above should produce 6000 * 10 = 60,000 rows
> only, but instead the join above produces millions (!) of
> rows being inserted into T_TEMP.

If the source is a broken join the cause should be obvious ... Cartesian Product

Daniel Morgan Received on Mon May 27 2002 - 10:54:09 CDT