PostgreSQL B-Tree Indexing and Database Query Acceleration — Interactive System Model
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Once a database holds hundreds of thousands of records, every SELECT query on a table without an index triggers a full table scan (Seq Scan). This sends disk I/O load through the roof and can lock up the entire system.
How Does the B-Tree (Balanced Tree) Architecture Work?
PostgreSQL uses B-Tree indexing by default. A B-Tree keeps data in a sorted, balanced tree structure, reducing search complexity from O(N) to O(log N). A single record among millions of rows is located with just 3-4 disk reads.
Column Order in Composite Indexes
In composite indexes that span multiple columns, the order in which the columns are written is vital. Columns with equality conditions should come first, while range or ordering (order by) conditions should come after.
Reading Execution Plans with EXPLAIN ANALYZE
When optimizing queries, look not at guesses but at the real timings and index scan types in the EXPLAIN ANALYZE output. With the right index, a heavy reporting query that takes 1200ms can be brought down to around 4ms.