Can you explain what the use of conditional indexes in a database means?

Partial indexes in a database are indexes that are created not on the entire table, but only on a subset of rows that satisfy a certain condition. This allows optimizing the performance of queries that frequently filter data based on this condition and reduces the size of the index.

For example, if you have an orders table and often query only for orders with the status "active," you can create an index specifically for such records:

CREATE INDEX idx_active_orders ON orders(order_date) WHERE status = 'active';

This index will be used only for queries where the condition includes status = 'active', speeding up their execution, while it does not interfere with other queries.

This is especially useful when most of the data is not needed for certain queries, and a full index would be too large and slow.