EXPLAIN ​

EXPLAIN describes how CoordinatorDB will execute a statement. Use EXPLAIN QUERY PLAN for an access-plan tree, or EXPLAIN ANALYZE to execute the statement and collect runtime measurements.

Forms ​

• EXPLAIN QUERY PLAN returns the selected access plan without executing the statement.
• Plain EXPLAIN returns explain_key/explain_value rows describing the plan and does not run the statement.
• EXPLAIN ANALYZE executes a SELECT or data-changing statement once and returns an analyzed plan. It does not return the underlying query's result rows.

For analyzed writes, the changes take effect. Use ordinary transaction controls when a write should be rolled back after measurement.

CoordinatorDB does not support ClickHouse EXPLAIN PIPELINE or EXPLAIN AST syntax.

Syntax ​

EXPLAIN QUERY PLAN statement
EXPLAIN statement
EXPLAIN ANALYZE statement

Example ​

Looking up a row by primary key ​

CREATE TABLE lookup(id INTEGER PRIMARY KEY,v TEXT);
EXPLAIN QUERY PLAN SELECT v FROM lookup WHERE id=1;

OK
┌─id─┬─parent─┬─notused─┬─detail────────────────────────────────────────────────────┐
│  1 │      0 │       0 │ PROJECTION v                                              │
│  2 │      1 │       0 │ ROWID_SCAN Table: lookup; Lookup: Eq(Literal(Integer(1))) │
└────┴────────┴─────────┴───────────────────────────────────────────────────────────┘
(2 rows)