ban-alter-generated-expression

problem

Adding a generated column changes the result shape for strict SELECT * decoders and can affect positional inserts. Inserts with explicit column lists do not inherently fail. SET EXPRESSION changes values returned to existing clients. For stored generated columns, PostgreSQL rewrites stored values; assess that rewrite separately as an availability concern. This rule is opt-in because compatibility depends on how clients use the column.

ALTER TABLE t ALTER COLUMN c SET EXPRESSION AS (id + 1);

solution

Check client reads and positional inserts before adding a generated column. Check client reads before changing its expression. The default ban-drop-generated-expression rule checks DROP EXPRESSION.

Enable this rule with --include ban-alter-generated-expression (or add ban-alter-generated-expression to your configured include list).