B-Trees

PostgreSQL implements several types of indexes, such as btree, hash, gist, spgist. The default and most common type of index is btree. A btree (balanced tree) allows for easier and faster searching. This can be seen in the image above where we search for the key with the value of 53. 

Btrees speed up searches because: 

• They sort the values (known as keys) inside of each node.
• They are balanced: B-Trees evenly distribute the keys among the nodes, minimizing the number of times we have to follow a pointer from one node to another.