How do I read a PostgreSQL explain plan?

Run EXPLAIN (ANALYZE, FORMAT JSON) and look at the node tree from the inside out. Watch for Seq Scans on large tables, joins where actual rows far exceed the estimate, and nodes with high total cost or time.

What is the difference between a Seq Scan and an Index Scan?

A sequential (full table) scan reads every row; an index scan uses an index to jump to matching rows. On large tables an index scan is usually much faster, so a Seq Scan on a filtered query often signals a missing index.

Which databases does this visualizer support?

PostgreSQL, MySQL and MariaDB, SQL Server, and Oracle. The database is auto-detected from the plan, and you can also pick it explicitly.

SQL Explain Plan Visualizer

Paste any dialect

Works with PostgreSQL, MySQL/MariaDB, SQL Server, and Oracle explain output. The database is auto-detected.

See the costly nodes

Spot sequential scans, expensive joins, and the nodes where rows and time pile up, at a glance.

Stays in your browser

Your query plan is parsed locally and never uploaded anywhere.

More information about SQL explain plans

Every relational database can show you its query execution plan: the tree of operations it uses to run a query, and how expensive each one is. Reading that plan is the core skill for fixing slow SQL, and it's how you decide which indexes to add.

Getting a plan you can paste here

PostgreSQL: EXPLAIN (ANALYZE, FORMAT JSON) SELECT ...

MySQL / MariaDB: EXPLAIN FORMAT=JSON SELECT ...

SQL Server: the JSON/XML showplan output.

Oracle: the plan table / DBMS_XPLAN output.

Reading the tree

Seq Scan / Full Table Scan: the database read the whole table. Often a sign a useful index is missing.

Index Scan / Index Seek: an index was used to find rows. Usually what you want.

Nested Loop / Hash Join / Merge Join: how two inputs are joined; the right choice depends on row counts.

rows estimated vs actual: a big gap means the planner's statistics are off, which leads to bad plans.

Frequently asked questions

Explain and tune SQL queries live in VisuaLeaf

VisuaLeaf runs EXPLAIN for you and visualizes the plan next to your data and query, across PostgreSQL, MySQL, SQL Server, Oracle and more, with a visual query builder, schema diagrams, and charts.

MongoDB & SQL in one client

Visual query & aggregation builders

Live visual schema diagrams

Charts, dashboards & query profiler

Connection manager for local, cloud & teams

Free Community Edition