What are arrays in a category?
A category might seem complicated due to the rather complex category theory. As the matter of fact, category is very simple – it’s a collection of objects and arrays (also called morphisms) connecting these objects. The arrays are composable and for every object an identity arrow exists. The existence of morphisms might impose an intuition,…
It doesn’t matter how much you earn for your financial independence
A simple model of a savings plan to achieve FIRE (financial independence, retire early) in numbers and graphs.
Why I stopped contributing to Stackoverflow
0. Introduction Probably every person who has anything to do with programming knows what Stackoverflow is. This post is not intended against the website itself, on the contrary – there is very much value there. It’s a criticism of the reputation system. Let’s keep in mind that according to Stackoverflow’s Help Center reputation is a…
We need more libraries!
Is it worth taking part in this race of projects proliferation or would you rather improve an existing product and provide more and more value?
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.
Oracle SQL certificate – is it worth it?
Some time ago I have passed an exam 1Z0-071 Oracle Database SQL and received the certificate. I have stumbled across many problems, majority of them being of organizational nature. Here is a wrap up of how it looks like and what to expect. Note: I am not going to address the content of the exam, particular…
[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.
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