postgresql

PostgreSQL Aggregation

Understanding HashAggregate and GroupAggregate operations.

SELECT department, COUNT(*) FROM employees GROUP BY department;

HashAggregate is used when grouping unsorted data. It builds a hash table of group keys and updates totals as it scans. GroupAggregate is used if the input is already sorted by the group key.

Interactive Execution Plan

EXPLAIN Output

Run: EXPLAIN (ANALYZE, COSTS, VERBOSE, BUFFERS, FORMAT TEXT) your_query;

Enter SQL EXPLAIN output to visualizeSupports PostgreSQL EXPLAIN ANALYZE, MySQL EXPLAIN, and SQLite EXPLAIN QUERY PLAN formats