Getting top-N rows per group

Yesterday on irc someone asked: Hi, how do I get top 5 values from a column group by another column?? From further discussion, I learned that: total rows in table is 2 million. It’ll have unique words of less than 1 million.. (approx count) I didn’t have time yesterday, but decided to write a solution, … Continue reading “Getting top-N rows per group”

Two years of explain.depesz.com

First of all – just today I committed patch for Pg::Explain – which is the workhorse behind explain.depesz.com. This patch fixes calculation of exclusive time for explain nodes, and the best thing about it is – I didn’t write it. It’s full patch provided by someone else – Filip Rembiałkowski – my former colleague, friend, … Continue reading “Two years of explain.depesz.com”

What mistakes you can avoid when looking for help on IRC?

Today, there was this one person on IRC, which asked question and provided some data. While working on helping him (her?), I noticed some things, that bugged me before in other cases, but this time i decided to write about it – it’s kind of rant, and if you (the reader) are the person that … Continue reading “What mistakes you can avoid when looking for help on IRC?”

How to remove backups?

Question from title sounds weird to you? It’s just a ‘rm backup_filename’? Well. I really wish it was so simple in some cases. One of the servers I’m looking into, there is interesting situation: quite busy database server (2k tps is the low point of the day) very beefy hardware daily backups, each sized at … Continue reading “How to remove backups?”