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From jim gan <sonycf...@yahoo.com>
Subject some typo in Derby Optimizer Design
Date Wed, 18 May 2005 21:56:08 GMT

Thanks for the clear write-up on derby optimizer (

Here are a couple of typo in the article.
table name "t1" should be "t2" in the following
paragraph where I marked [--> t2] :

Let's say this partial plan has an estimated cost of
2000. Now suppose the optimizer considers placing the
table t1 [--> t2] as the next table in the join order:

(outer) t4 - t5 - t2 (inner) 

Note that the query has no direct join clause between
t1 [--> t2] and either t4 or t5. The optimizer would
go through all possible access paths for t2 in this
context, and would see that with no useful
qualification on the table it would have to do a full
scan of t2 for every outer row resulting from the join
of t4 and t5.


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