Analyzing objects invalidates all execution plans which are dependent on
those objects ( unless you set no_invalidate=>true in oracle 9 ) forcing
the statement to go through the full parse again with the possibility of e
different execution plan as a result of the new statistics.
At 12:45 PM 3/4/2004, you wrote:
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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