Postgres（DBeaver）报告ST_Transform后0行已更改

Question

When I execute:

ALTER TABLE london_all_nodes ALTER COLUMN geom TYPE geometry(Point, 27700) USING ST_TRANSFORM(geom, 27700);

the Dbeaver statistics window reports Updated Rows = 0

When I check the data with

SELECT * FROM london_all_nodes LIMIT 5;

the geom column looks transformed as expected but it seems like updated rows should be equal to the number of rows in the table no?

Answer 1

per @a_horse_with_no_name's comment, and confirmed by the documentation "ALTER TABLE changes the definition of an existing table." ALTER TABLE acts on a column, not any individual rows.

Thus every cell in the column is changed but it considers the rows to be unchanged.