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September 2020

Oracle ADB from a Jupyter Notebook

By Franck Pachot

My first attempt to connect to an Oracle database from a Jupyter Notebook on Google Colab was about one year ago:

Serial Bloom

Following the recent note I wrote about an enhancement to the optimizer’s use of Bloom filters, I received a question by email asking about the use of Bloom filters in serial execution plans:

I’m having difficulty understanding the point of a Bloom filter when used in conjunction with a hash join where everything happens within the same process.

I believe you mentioned in your book (Cost Based Oracle) that hash joins have a mechanism similar to a Bloom filter where a row from the probe table is checked against a bitmap, where each hash table bucket is indicated by a single bit. (You have a picture on page 327 of the hash join and bitmap, etc).

UUID performance with CockroachDB

Recently, I have been working with customers that have been concerned about the performance of various UUID formats. Other products have various performance characteristics for inserting, generating and presenting UUID data.

For this blog, I ran a quick series of tests using jmeter insert data along with some simple SQL tests to generate UUID values. Hopefully, this will be helpful to better your understanding of UUID with CockroachDB.

UUID formats

Cockroach DB has four different ways data can be formatted for use with the UUID data type.

String format

Curly Brace format

Oracle REST Data Services (ORDS) : Database APIs – First Steps 258w" sizes="(max-width: 223px) 85vw, 223px" />

In my never ending quest for automation, I finally got round to looking at the Oracle REST Data Services (ORDS) Database APIs.

Video : Multitenant : Memory Resource Management for Pluggable Databases (PDBs)

In today’s video we’ll discuss how Resource Manager allows us to manage the memory usage in PDBs. This can be useful to stop a small number of PDBs using all memory assigned to the instance.

This video was based on this article.

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Oracle 19c Automatic Indexing: Data Skew Fixed By Baselines Part II (Sound And Vision)

  In my previous post, I discussed how the Automatic Indexing task by using Dynamic Sampling Level=11 can correctly determine the correct query cardinality estimates and assume the CBO will likewise determine the correct cardinality estimate and NOT use an index if it would cause performance to regress. However, if other database sessions DON’T use […]

Oracle MAA reference architecture and HA, DR, RTO, RPO

By Franck Pachot

I may have mentioned in some previous blog post that, in my opinion, the names of Oracle Database features make sense on the vendor product management context more than in a user context. I’m not saying that it is good or bad. There are so many features, that can be combined, and that evolved for many years. The possible use cases is unlimited. What I see customers doing in Europe is very different from what I have seen in US companies or in Africa for example. What I’m saying is that most of the time you need a vendor-to-user dictionary when reading Oracle documentation and presentations. I’ll focus here on the MAA reference architecture. Yes, acronyms add to the complexity. MAA means Maximum Availability Architecture. Because when you have High Availability features for decades, you need another name when you bring an “higher” High Availability.

Oracle 19c Automatic Indexing: Data Skew Fixed By Baselines Part I (The Prettiest Star))

In my previous few blog posts, I’ve been discussing some issues in relation to how Automatic Indexes handle SQL statements that accesses skewed data. In this post, I’m going to setup the scenario in which Automatic Indexing can potentially use Baselines to help address some of these issues. BUT, as we’ll see, I’m having to […]

Packer by HashiCorp : Second Steps?

In a previous post I mentioned my first steps with Packer by HashiCorp. This is a brief update to that post. 300w" sizes="(max-width: 584px) 85vw, 584px" />

I’ve created a new box called “oracle-7” for Oracle Linux 7 + UEK. This will track the latest OL7 spin. You can find it on Vagrant Cloud here.

BARC Survey confirms: #Exasol dominates Analytical Database Peers

Exasol leads the categories Performance, Platform Reliability and Support Quality for Analytical Database products. And we get a 100% recommendation score from the 782 customers in the survey.