Blog: Jonathan Lewis

219 blogs updated: 64 min. ago
DML Tablescans
This note is a follow-up to a recent comment a blog note about Row Migration: So I wonder what is the difference between the two, parallel d...
18-01-2019 14:55:18 Jonathan Lewis Oracle
Hint Reports
Nigel Bayliss has posted a note about a frequently requested feature that has now appeared in Oracle 19c a mechanism to help people understa...
17-01-2019 11:45:38 Jonathan Lewis Oracle
QC vs. PX
One last post before closing down for the Christmas break. Here's a little puzzle with a remarkably easy and obvious solution that Ivica Ars...
21-12-2018 14:33:01 Jonathan Lewis Oracle
Transitive Closure
This is a follow-up to a note I wrote nearly 12 years ago, looking at the problems of transitive closure (or absence thereof) from the oppos...
20-12-2018 14:29:59 Jonathan Lewis Oracle
NULL predicate
People ask me from time to time if I'm going to write another book on the Cost Based Optimizer and I think the answer has to be no because t...
18-12-2018 14:27:14 Jonathan Lewis Oracle
Extreme Nulls
This note is a variant of a note that I wrote a few months ago about the impact of nulls on column groups. The effect showed up recently on ...
14-12-2018 20:21:39 Jonathan Lewis Oracle
Case Study
A recent thread on the ODC database forum highlighted a case where the optimizer was estimating 83,000 for a particular index full scan when...
10-12-2018 15:08:36 Jonathan Lewis Oracle
Plans and Trees
Prompted by a question on the ODC database forum and also because I failed to get to the "Bonus slides" on my presentation on basic executio...
07-12-2018 20:50:02 Jonathan Lewis Oracle
A recent post on the ODC database forum prompted me to write a short note about a trap that catches everyone from time to time. The trap is ...
07-12-2018 14:03:52 Jonathan Lewis Oracle
Row Migration
There's a little detail of row migration that's been bugging me for a long time and I've finally found a comment on MoS explaining why it ha...
03-12-2018 18:40:48 Jonathan Lewis Oracle

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