SQL

Oracle 12cR2 SQL new feature: LISTAGG overflow

By Franck Pachot . LISTAGG was a great feature introduced in 11g: put rows into line with a simple aggregate function. 12cR2 adds an overflow clause to it. What happens when you have so many rows that the LISTAGG(…)

Oracle serializable is not serializable

By Franck Pachot . Did you know that when you set isolation level to SERIALIZABLE, it is not serializable but SNAPSHOT? This isolation level is lower than serializable. I've never thought about it until I read Markus Winand(…)

Nulls in composite keys

By Franck Pachot . Comparison of NULL can be misleading and it's even worse for unique constraint validation. Having partial nulls in a composite key can be tricky because the SQL ANSI specification is not very easy to understand, and(…)

SQL Server 2016: new T-SQL commands COMPRESS and DECOMPRESS

In live from the JSS2015 (Journée SQL Server 2015) in Paris, we saw that the CTP3.1 has been available in the night of these 2 days. One new feature available for this release in the T-SQL(…)

Parallel sequential scans are coming to PostgreSQL

It didn’t made it into the upcoming PostgreSQL 9.5 release but it will probably be coming in 9.6: Parallel sequential scans. If you take a look at the development documentation some new parameters showed up: max_parallel_degree: The(…)

Monitoring tools for PostgreSQL – POWA

The last posts introduced the logging system, pg_stat_statements, pg_activity and pgcluu. This post will look at POWA: PostgreSQL Workload Analyzer. For getting the most out of POWA the following extension(…)

Monitoring tools for PostgreSQL – pgcluu

The last posts introduced the logging system, pg_stat_statements and pg_activity. All of these can be used to monitor sql statements the PostgreSQL server is executing. In this post I’ll look into pgcluu:(…)

SQL Monitoring in PostgreSQL (3) – pg_activity

The last posts looked at how the logging system and the pg_stat_statements extension can be used to monitor sql statements in PostgreSQL. This post will introduce pg_activity which is very similar to(…)

SQL Monitoring in PostgreSQL (2) – pg_stat_statements

The last post looked into how you can monitor queries using the logging system. This post will introduce pg_stat_statements. pg_stat_statements is a module that needs to be loaded and is not available in(…)

SQL Monitoring in PostgreSQL (1) – the logging system

When developing an application as well as when the application is in production there is the need to identify long running queries. In Oracle one tool you might use for that is the SQL Monitor. In this post I’ll(…)