Search

Top 60 Oracle Blogs

Recent comments

Non-Unique Indexes

Unique Indexes Force Hints To Be “Ignored” Part I (What’s Really Happening)

As I was compiling my new “Oracle Diagnostics and Performance Tuning” seminar, I realised there were quite a number of indexing performance issues I haven’t discussed here previously. The following is a classic example of what difference a Unique Index can have over a Non-Unique index, while also covering the classic myth that Oracle sometimes […]

So What Is A Good Cardinality Estimate For A Bitmap Index Column ? (Song 2)

As I’ve discussed previously, using a Bitmap index on a unique column makes little sense as the underling index must be larger than a corresponding B-tree index due to the implicit additional overheads associated with Bitmap indexes. As such, Oracle doesn’t permit the use of a Bitmap Index on a declared unique column or to [...]