Introduction

Designing a multi-layer system is not rocket science, the difficulty can lie in selecting the right technologies. The main concept behind the design is to have better control and fine tuning of the components. This blog post will discuss the benefits & limitations of implementing this type of design and our practical experience gained from using it for the Open Days reservation system, which helped to welcome 75.000 people on our site and was hosted on the Oracle cloud using their cloud services.

Oracle REST Data Services running on Tomcat - Basic Authentication using JNDI Realm

What do we want to achieve?

Introduction

International organisations can have multiple official languages, in these cases usually their workflows/processes are designed to support that. CERN is one of those organisations, it's official languages are French and English. Therefore one of our tasks was to make the Open Days reservation system bilingual. In this article you will read about the choices we made to internationalize the system, what obstacles we faced and what solution we went for.

Introduction

Introduction

Authored By: Nazerke Seidan, Emil Kleszcz, Zbigniew Baranowski
Published By: CERN IT-DB-SAS

Authored By: Aman Pratap Singh and Prasanth Kothuri

Published By: CERN IT Hadoop and Spark Service

Topic: This post describes a data pipeline for a machine learning task of interest in high energy physics: building a particle cla

These last days I've been playing with Apache Tomcat 9 and log4j2. You may wonder why I want to change the good an old Tomcat JULI. Well, although I love the simplicity of its configuration and the fact that JULI works, log4j2 offers a big variety of appenders that make it very interesting. Also I prefer the way of how log4j2 rolls the files, keeping the original name un-touched (e.g.

Topic: This post dives into the steps for deploying a performance dashboard for Apache Spark, using S

Usually when you are developing a new feature or fixing an issue, you want to focus in your business logic. If your application delegates the authentication in some SSO system you usually mocks the response from this last one. However for integration tests, it is nice to be able to test your application against the full SSO cycle, specially if you have to use things like the SAML2 Web Profile.

Virtual Private Databases (VPD) is an Enterprise Edition feature related to security. It restricts the scope of Data Manipulation Language to a subset of the table rows by transparently adding a where clause before executing them. It is also called Row-Level Security (RLS). Where the policy is enabled, it is like having the selected DML (SELECT, INSERT, UPDATE, DELETE) operate on a transcient view. And the predicates for this view can be dynamic and even query tables that the user cannot see.

The Oracle Database software is large, several gigabytes in Oracle Home for the part that is deployed on the operating system, and additional megabytes in SYSTEM tablespace for the part that is deployed as stored procedures (mainly the dbms_% packages). And this is not a problem with the traditional deployment methods where you can have a .zip golden image of the Oracle Home, and a database template to start a new DB. But this monolithic approach is not adapted to the current way people want to deploy software:

Do you have tables with a column storing filenames? Long filenames with full path? If this is the case, then you probably realized how an index on this can be large. And when looking at the values sorted, you have seen the inefficiency of it: a big part of the full name is reapeated because it has the same prefix for files in the same (sub)directory. The 12cR2 Advanced Index Compression (COMPRESS ADVANCED LOW) does not help here because it only compresses identical values, like the basic compression of tables. With unique filenames, we cannot expect any benefit.

There are not many ways to access efficiently to table rows. Either you want lot of them, because your predicate is not very selective, and you read the whole table in the fastest you can do. This is Table Full Scan. Or you use a structure that gives you access to the subset of rows you need. There are mostly two structures for that: sort and hash.

It was announced at Oracle Open World 2017 and here it is just before the start of OOW18: an RPM to install the Oracle Database software.

Here is my #ThanksODC post. A long one... There's a point that should always be a major topic for database developer community discussions: where to run the procedural code. The access to data is in the database, for sure, and the language for it is SQL. But very often, the business logic of a transaction cannot be executed in one single SQL statement. Either because it is too complex and requires a procedural language.

In Oracle we need to have a index on the foreign key column as soon as we have the intention to delete from the parent row, or a locking situation may block all transactions around the child table. PostgreSQL has a similar way to manage isolation, with MVCC, then do you think you also need to index the foreign keys? Here is a test that confirms that postgres does need to not lock the tables even without index on the foreign key. 

Here is a quick test I did after encountering an abnormal behavior in write consistency and before finding some references to a bug on StackOverflow (yes, write consistency questions on StackOverflow!) and AskTOM. And a bug opened by Tom Kyte in 2011, that is still there in 18c.