Ignore nulls in Postgres

Despite the lack of ignore nulls syntax in postgres, we can mimic the required behavior by defining custom aggregates. Albeit being simple, it has several advantages.

[My] Top 7 JPA and SQL performance pitfalls [EN]

Some time ago I had a pleasure to speak at Wrocław JUG about performance issues I have faced when working with persistence layer. These are not the most frequent ones, but rather the most tricky – not visible at the first sight and causing quite a lot of trouble in production.

Poor man’s fuzzy search

0. The problem When I hear the term fuzzy searching, I think of high computation cost, but this is not always the case. In the great book Art of Computer Programming by D. Knuth, vol. 3, ch. 6: Searching we can read about the soundex algorithm. It was originally used to deal with misspelled English

Java’s type parameter’s and wildcard’s (lack of) equivalence

Yet another post based on an interesting question I have encountered on StackOverflow quite a while ago. But let us start with a slightly different thing. Once upon a time there was a question: what is the difference between ? extends Sometype and T extends Sometype? For example: <? extends Number> and <T extends Number>

Top mistakes when working with JPA (Hibernate) and SQL [PL]

Recently I have given a talk about top (in my opinion) performance issues we are challenged with when working with JPA (Hibernate) and SQL (Postgres, Oracle). The talk is in polish.

Calculating moving median in Postgres

0. The problem Some time ago I’ve stumbled on this interesting question on stackoverflow (as stated in the title). I could not find any satisfactory answer at that time, so I came up with this solution. I think the problem is interesting enough to make it into a blog post. The following table shows the