Parsing question
- From: "Koivu, Lisa" <Lisa.Koivu@xxxxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Thu, 4 Mar 2004 14:45:12 -0500
Hello my learned friends,
I read Bjorn Engsig's paper over a huge plate of sushi for lunch.
Refreshing memory and opening your sinuses never hurts. However, I have
a question about this statement:
"During the first execute of a SQL statement, the optimization takes
place, i.e. Oracle finds the best path to access data. The access plan,
along with the SQL statement and it's parse tree is stored in the
library cache. Finally, the SQL statement is executed, and for queries,
the resulting rows are then fetched. Once a statement is parsed and
executed, it can efficiently be executed again, completely avoiding the
parse and optimization steps."
My question is: If a statement is stored with the execution plan, then
if the statement is still in cache when the stats change, doesn't the
plan change? I deal with changing execution plans daily, and my first
response is "how fresh are the stats". 95% of the time, an analyze
fixes the problem and the plan changes for the exact same statement.
What am I missing? Thanks everyone
Lisa Koivu
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