In previous chapters, we talked about query optimization and indexing. When we talked about indexing, we learned how to make our queries faster through the use of indices. However, B-tree indices do not index all types of operations. Now let's consider textual data types (char, varchar, or text). We have seen that the B-tree, using the varchar_pattern_ops opclass, is able to index like operations only as regards the 'search%' type queries, but it is not able to index queries with a where condition of the '%search' or 'search%' type:
- Before diving into our example, let's do set enable_seqscan to 'off' in order to force PostgreSQL to use any index if it exists. We need to do this because, in our example case, PostgreSQL would always use sequential scanning, because we have less data in our table and all data that is present in the table is stored on a single page:
db_source=# set enable_seqscan to &apos...