I'm trying to alter the type of a column from a table but I also want to know how long it takes to alter the table. I therefore combined:

EXPLAIN ANALYSE

command with:

ALTER TABLE tbl_name ALTER COLUMN col_name TYPE new_type;

So I did:

EXPLAIN ANALYSE ALTER TABLE my_table ALTER COLUMN my_column TYPE text;

But I get the error:

ERROR:  syntax error at or near "ALTER"
LINE 1: EXPLAIN ANALYSE ALTER TABLE my_table ALTER COLUMN my_column...
                        ^

But when I EXPLAIN ANALYSE with a SELECT it has no problem. I.e.:

EXPLAIN ANALYSE SELECT * FROM my_table LIMIT 300;

I must be missing something really simple but I'm not seeing it?

CodePudding user response：

The manual for EXPLAIN:

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

ALTER TABLE is not covered.