Are you fed up with slow PostgreSQL queries that search for case-insensitive matches? Look no farther than indexes based on functions!
An index that is constructed based on the result of a function or expression is known as a function-based index. This means that it can be used to accelerate searches that repeatedly evaluate the same function or expression.
For example, let's say you have a table called employees that contains a column called first_name. You frequently run queries that search for employees with a given first name, but you want the search to be case-insensitive. One way to achieve this is to create a function-based index on the lower() function of the first_name column:
CREATE INDEX lower_first_name_idx ON employees (lower(first_name));
Now, when you run a query like the following:
SELECT * FROM employees WHERE lower(first_name) = 'john';
PostgreSQL will use the lower_first_name_idx index to search for rows that match the condition, which should be faster than a full table scan.
It's important to remember that function-based indexes can only be used if the indexed expression is in the WHERE clause of a query and is used in an exact match (i.e., = or IN) or a range condition (i.e., BETWEEN). If the expression is used in a SELECT list or an ORDER BY clause, they can't be used.
So, if you want to make your queries run faster, think about using function-based indexes in PostgreSQL the next time you want to do that. Your database will thank you, as will your users.
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