Indexing in PostgreSQL: how to create an index for a query with multiple parameters? Why did the index degrade after six months with active updates?

To create an index in PostgreSQL that speeds up queries with multiple parameters (for example, filtering by several columns), a composite index is used. It is created as follows:

CREATE INDEX idx_name ON table_name (column1, column2, column3);

It is important to consider the order of columns in the index: it should match the order used in the WHERE conditions for maximum efficiency.

The reason for index degradation during active updates is fragmentation and the accumulation of "dead" tuples. PostgreSQL uses MVCC, and during updates, old versions of rows are not immediately deleted but remain in the table and index, which reduces performance. To address this, regularly run VACUUM or VACUUM FULL, as well as ANALYZE to update statistics. Automatic autovacuum usually handles this, but in cases of very intensive updates, parameter tuning or manual intervention may be necessary.