PostgreSQL: Using EXPLAIN ANALYZE, Know your Query Execution Plan

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Like any other RDBMS, PostgreSQL generates a Query Execution Plan for each query that it receives.

It is also used Genetic Query Optimizer (GEQO) that does query planning for heuristic search and It reduce query planning time for large and complex queries.

An Optimizer always tries to choose a good Query Execution Plan.

The structure of Query Execution Plan is like a Tree and It contains different information like: type of scan details, join details, sorting details, aggregation details, Estimated rows details, Estimated start-up cost, Estimated total cost and others.

To know about the Query Execution Plan, is very important for all Database Professionals because It helps us to improve the Query Performance.

With the help of Query Execution Plan, We can make our decisions on Index tuning, Join tuning and other.

In PostgreSQL, we have EXPLAIN and EXPLAIN ANALYZE command to know about the Query Execution Plan.

Here, I have used one table tbl_itemtransactions which you can create using below post.

Example of EXPLAIN: It generates the Estimated Query Execution Plan with out executing an actual SQL Query.

Example of EXPLAIN ANALYZE: It first executes the SQL Query and than It generates the actual Query Execution Plan.