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December 2018

Understanding Partitioning in #Exasol

Exasol introduced Partitioning in version 6.1. This feature helps to improve the performance of statements accessing large tables. As an example, let’s take these two tables:

Say t2 is too large to fit in memory and may get partitioned therefore.

In contrast to distribution, partitioning should be done on columns that are used for filtering:


Now without taking distribution into account (on a one-node cluster), the table t2 looks like this:

Notice that partitioning changes the way the table is physically ordered on disk.

A statement like

CLI for Amazon RDS Performance Insights

Installing CLI on LINUX

1. install PIP

curl -O
python --user

2. install AWS CLI

pip install awscli --upgrade --user

3. configure

aws configure

For “aws configure” you will need

  • AWS Access Key ID:
  • AWS Secret Access Key:

Which you can get by going to the AWS console, going to IMS and creating access key.

Running example

Once “aws” is configured you can run the CLI like

Accelerate your #BI Performance with #Exasol

Your BI users complain about slow performance of their analytical queries? Is this your Status Quo?

Minimal Oracle installation (and Docker image)

A new blog post on the Databases at CERN blog about some research on the minimal Oracle Database installation:

And a bonus here: the Dockerfile which builds this minimal image. You need to build the Oracle XE image (oracle/database:18.4.0-xe) with the buildfiles provided by Oracle ( and this Dockerfile will copy only the necessary:

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 the SQL Monitor output for the operation showed that it was returning 11,000,000 rows.

Apart from the minor detail that the OP didn’t specifically ask a question, the information supplied was pretty good. The OP had given us a list of bind variables, with values, and the SQL statement, followed by the text output of the Monitor’ed SQL and, to get the predicate section of the plan, the output from a call to dbms_xplan. This was followed by the DDL for the critical index and a list of the stats for all the columns in the index.

Sangam 18: Presentations, Scripts and More

Many, many thanks to those who came to my three sessions at Sangam 18, the largest meeting of Oracle technologists in South Asia.

As I promised, you can download the presentations and scripts for all my sessions here. As always, your feedback will be highly appreciated.

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 execution plans at both the DOAG and UKOUG conferences, here’s a small of slides demonstrating how to convert a text execution plan into a tree that you can read using the mechanism described in Oracle’s white paper by the phrase: “start from the bottom left and work across and then up”.

The file is a Microsoft Powerpoint file (early version).


Installing Ansible on Oracle Linux 7 for test and development use

There are a few alternative ways of installing Ansible on Linux, and the install guide for Ansible 2.7 (the current version at the time of writing) does a great job in explaining them all in detail.  There is a potentially easier way to get to a current Ansible version if you are using Oracle Linux 7, but it comes with a very important limitation. Let’s get that out of the way first.

See you in OBUG Tech Days Belgium

Antwerp, February 7, 2019 — February 8, 2019

I’ll demo join methods in slow motion, but look at the full Agenda:

And it’s not only about sessions: all speakers are well known in the community for their will to discuss and share knowledge, opinions… and beers.

Registration opened

Tickets! " Techdays Belgium

OBUG Tech Days Belgium 2019 – Antwerp – 7/8-FEB-2019


Dates: February 7 and 8, 2019

Location: in Antwerp, Belgium

More information soon.

For people from the netherlands: this is easy reachable by car or by train! This is a chance to attend a conference and meet up with a lot of well-known speakers in the Oracle database area without too extensive travelling.