Postgresql explain alter table add column doesn't work

Question

I'm using Postgresql 12 (AWS RDS) and pgAdmin4.

While the following statement works

explain select * from table "Commands";

The next one

explain alter table "Commands" drop column "test";

gives this error

LINE 1: explain alter table "Commands" drop column "test";
                ^
SQL state: 42601
Character: 9

I made sure the statement alter table "Commands" drop column "test" itself can be run successfully so this cannot be an issue with that statement.

Does explain not work with alter or am I missing anything?

Answer 1

From the documentation: https://www.postgresql.org/docs/9.1/sql-explain.html, there is no EXPLAIN for ALTER command.

Important: Keep in mind that the statement is actually executed when the ANALYZE option is used. Although EXPLAIN will discard any output that a SELECT would return, other side effects of the statement will happen as usual. If you wish to use EXPLAIN ANALYZE on an INSERT, UPDATE, DELETE, CREATE TABLE AS, or EXECUTE statement without letting the command affect your data, use this approach:

statement

Any SELECT, INSERT, UPDATE, DELETE, VALUES, EXECUTE, DECLARE, or CREATE TABLE AS statement, whose execution plan you wish to see.

BEGIN;
EXPLAIN ANALYZE statement;
ROLLBACK;

Answer 2

The documentation clearly stats:

statement

Any SELECT, INSERT, UPDATE, DELETE, VALUES, EXECUTE, DECLARE, CREATE TABLE AS, or CREATE MATERIALIZED VIEW AS statement, whose execution plan you wish to see.

Other statements are not supported.