JIT

Starting with Oracle 11gR1 Oracle JVM includes Just-in-Time compiler. Its goal is to convert JVM bytecode into platform-specific native code based on the performance data gathered in run-time. It is stated in the documentation that JIT “enables much faster execution” – and this is, in general, true. There are ways to control the behavior of [...]

ORDER BY

This is a quick note on the importance of ORDER BY for the order of the result set produced by a SELECT. The mantra is very simple: Without an order_by_clause, no guarantee exists that the same query executed more than once will retrieve rows in the same order. Repeat it as necessary many times everywhere, [...]

Extended statistics and function-based indexes

About a year ago I’ve discovered nice feature of Oracle 10gR2 CBO: to overcome an issue with calculated selectivity for predicates on multiple columns, it can use DISTINCT_KEYS of the available index. Couple of weeks ago the bug fix mentioned in the OTN thread actually helped to solve a performance issue of a query. And [...]

Edition name as a property for JDBC thin client

A question on Edition-Based Redefinition appeared on the OTN forum: The purpose is to try to upgrade an app in production. For most application users they will keep using the pre-upgrade app connecting to the old edition by default, while at the same time some UAT users will test out the post-upgraded app on the [...]

OPT_PARAM and OPTIMIZER_FEATURES_ENABLE

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?