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From Sunitha Kambhampati <ksunitha...@gmail.com>
Subject Re: Very slow
Date Wed, 01 Jun 2005 16:27:40 GMT
Jack Klebanoff wrote:

> Sunitha Kambhampati wrote:
>> Edson Carlos Ericksson Richter wrote:
>>> I've run with derby.language.logQueryPlan=true and result is that I 
>>> have table scan for only one table, that has actually one record.
>> I am curious as to why a table scan is being picked.  Does this table 
>> have indexes that can be used  for the query in question ?  Also what 
>> isolation level is this query running at.
>> Sunitha.
> If the table only has one row then a table scan is faster than an 
> index scan.
True for one row case.

But lets say the table is modified to have more rows and then it 
probably makes sense to have an index scan ,  but you will be stuck with 
a tablescan for this query till the query gets recompiled as  a result 
of a stale plan check. (right ?).  So it still seems it would be better 
for the optimizer to pick an index scan when it can instead of table 
scan even for a single row.


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