query-optimization

Query debugging identifies performance and correctness issues. I use EXPLAIN ANALYZE to understand execution plans. Slow query logs reveal problematic queries. pgstatstatements tracks query statistics. Understanding sequential scans vs index scans hel

SQL joins combine data from multiple tables. INNER JOIN returns matching rows only. LEFT/RIGHT JOIN includes all rows from one table, nulls for non-matches. FULL OUTER JOIN combines both. I use CROSS JOIN for Cartesian products sparingly—performance k

Understanding query execution plans is essential for optimizing slow queries. Rails provides explain method on ActiveRecord relations to show PostgreSQL's query planner output. I look for sequential scans on large tables (indicating missing indexes),

EXPLAIN reveals database execution plans. I use EXPLAIN ANALYZE for actual runtime statistics. Understanding plan nodes—Seq Scan, Index Scan, Nested Loop, Hash Join—guides optimization. Cost estimates predict query expense. Rows estimates show expecte