November 21, 2011 – 17:46
And you should remember that. Here is a nice example how Cost Based Optimizer can miss an obvious option (which is available to human eye and Oracle run-time with a hint) while searching for the best plan. CBO simply doesn’t consider Index Skip Scan with constant ‘in list’ predicates in the query, although it costs [...]
February 28, 2011 – 21:58
As a follow-up to a recent post on different names Oracle can use for the intermediate views, here is a quick example of the technique called distinct placement.
Oracle 11g has introduced a hell lot of new features related to Parallel Execution – like statement queuing, in-memory PX and auto-DOP, to name a few. There are also small bits of enhancements here and there – like default value of the PARALLEL_EXECUTION_MESSAGE_SIZE and an introduction of an easy way to stick PX slaves to [...]
Here is a recent thread from OTN forums. The question raised is WTF? whether a hint in the examples section of DBMS_PARALLEL_EXECUTE documentation have to be used or not and why it is there. What do you think about it? Have a look in the documentation and mark your choice in a poll: PS. In [...]
February 22, 2010 – 19:16
Starting with version 11gR1 Oracle database uses native FULL JOIN implementation based on HASH JOIN whenever possible. It’s good to know that this functionality first appeared in Oracle 10.2.0.3 and could be used to overcome different issues, including performance and bugs. Here is an example appeared on the SQL.ru recently:
There are 19 new hints in Oracle 11.2.0.1: Some of them represents new CBO features (like FACTORIZE_JOIN/NO_FACTORIZE_JOIN). Here I’ll show purpose of COALESCE_SQ hint (NO_COALESCE is it’s inverse).
November 25, 2009 – 00:08
Here’s a question appeared on the oracle-l mailing list recently: Does anyone know if opt_param hint works with optimizer_features_enable in 11.1.0.7?
