EXPLAIN

EXPLAIN statements provide information about how a query will be executed, showing the unoptimized, optimized, and physical plans for the query.

Syntax

EXPLAIN [VERBOSE] [(FORMAT format)] query

Parameters

• VERBOSE: If additional details should be added to the explain.
• format: Format out for the explain.
• query: The query to explain.

Explain output

EXPLAIN displays three forms of a query.

• Unoptimized: The logical plan with no optimizations.
• Optimized: The logical plan after optimizations have be applied, including join reordering and column pruning.
• Physical: The final plan to be executed.

By default, the output is displayed in a text format showing the "base" plan, and any materializations in the plan.

Examples

Simple EXPLAIN:

EXPLAIN SELECT * FROM cities;

EXPLAIN with VERBOSE option:

EXPLAIN VERBOSE SELECT * FROM cities;

EXPLAIN with JSON format:

EXPLAIN (FORMAT JSON) SELECT * FROM cities;