One of things people learn is that adding indexes isn't free. All write operations (insert, update, delete) will be slower – well, they have to update index.
But realistically – how much slower?
Full tests should involve lots of operations, on realistic data, but I just wanted to see some basic info. So I figured I'll just look at speed of inserting data (well, COPYing data), and will try to extract some knowledge from it…
Today, I'd like to show you how you can use the same index for two different types of conditions. One that is using normal BTree indexing ( equal, less than, greater than ), and one that is using GIN/GiST index, for full text searching.
Today, Mattias|farm on IRC asked how to create primary key using HASH index. After some talk, he said that in some books it said that for “=" (equality) hash indexes are better.
So, I digged a bit deeper.