Hi Dan,
Cartesian join is still a big red flag because it may mean at least one
one full table scan. Cartesian join is a Cartesian product of the row
sources involved. I am not quite certain about the optimization and what
exactly is being optimized by a Cartesian join.
Regards
On 4/3/19 10:25 AM, Daniel Fink (Redacted sender daniel.fink for DMARC)
wrote:
Yes - there is an optimization process that will perform a cartesian join IF one of the row sources will return a single row. I don't recall when it was introduced (11gR2?). Seeing 'CARTESIAN' in the query plan used to be a big ol' red flag...now it is an indication that you should take a closer look at the row sources in the join.
On Tue, Apr 2, 2019 at 2:26 PM Ram Raman <veeeraman@xxxxxxxxx <mailto:veeeraman@xxxxxxxxx>> wrote:
I am not a big expert on joins, but I think Oracle chooses
Cartesian when it thinks one of the row sources is going to return
only one row.
On Sat, Mar 30, 2019 at 3:08 PM Orlando L <oralrnr@xxxxxxxxx
<mailto:oralrnr@xxxxxxxxx>> wrote:
List
When is it OK to do Cartesian joins?
1) It looks like during the star transformation while joining
2 or more small result sets from dimension tables?
2) In an ordinary join, when one of the row sources is
estimated to be 1 row with the other row source be several
thousand? In this case, the Cartesian will be just 1*no of
rows in the other table.
Any explanation is helpful. thanks
Orlando.
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*Daniel Fink*
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