The Blog

Keeping your logs clean with Apache Tomcat 9, log4j2 and spring-boot

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.

Testing web applications SSO with Keycloak

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.

Oracle VPD as a safeguard for DML

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.

Minimal Oracle

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:

Oracle Index compression for range scan on file names

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.

Oracle LIKE predicate and cardinality estimations

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.

An .rpm to install Oracle Database 18c

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.

Download

In the Oracle Database 18c download page there are two files for 18.3. One is a zip of the Oracle Home that we have to unzip and run the setup (named runInstaller but different than the one we had in pre-18c releases). The other file is an RPM: oracle-database-ee-18c-1.0-1.x86_64.rpm

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