(Chris Travers) Arrays in PostgreSQL are relatively well supported by the indexing engines of this RDBMS. There are a fair number of options however to be aware of and an understanding of how arrays are indexed is very helpful. Before going forward, please read my intro on arrays so that you under

(morgan tocker) A friend wrote to me recently with a question. He was working on a method to ship application metrics to statsd on a 1 minute interval. He had three examples of how to estimate the number of rows in a table and he wanted to know the difference between them.

(Chris Travers) This is part of a two part series. The second will discuss indexing arrays which is a complex topic.

(morgan tocker) I find a good interview question for a MySQL DBA position is to ask what the following commands actually do in InnoDB, which has been the default storage engine since MySQL 5.5. From my perspective there is a lot of miss-understanding what still applies.

(depesz) Last time I wrote about what explain output shows. Now I’d like to talk more about various types of “nodes" / operations that you might see in explain plans.

(Sean Hull) We’ve told you all about MySQL mult-master replication’s limitations. If you write to two masters it is bound to fail for myriad reasons.

(Josh Berkus) So a boolean mode() was very simple to construct, partly because booleans have only three potential values (TRUE, FALSE, NULL). However, in many cases we want mode() for, say, integers. Now, there are several constructions of mode() depending on what statistic you really want, but he

(Michael McLaughlin) Somebody asked why you can’t implement MySQL triggers that write information when you want to stop the DML statement, like autonomous procedures in Oracle. The question was a surprise but I didn’t find anything on it, so here’s how you can do it.

(Michael Paquier) Among one of the many new features implemented in 9.3, pg_dump now offers the possibility to perform parallel dumps. This feature has been introduced by the commit below.

(Scott Noyes) From Freenode: how do you generate a five number summary in MySQL? There is no “median” aggregate function built in. You could do some clever things involving self joins or temporary tables, or build an aggregate UDF – see the comments section in the manual for those approaches.