The plan summary states "Plan: 2 to drop" which is incorrect. Based on the changes from old.sql to new.sql:

• 1 default privilege needs to be dropped (USAGE on SEQUENCES)
• 1 default privilege needs to be altered (adding INSERT and UPDATE to existing SELECT on TABLES)

The summary should reflect both drop and alter operations, not just "2 to drop".

The schema name and grantee (role name) in these ALTER DEFAULT PRIVILEGES statements are not being quoted using ir.QuoteIdentifier(). This could cause SQL errors if the schema or role name contains uppercase letters, special characters, spaces, or matches PostgreSQL reserved words.

Consider updating the code to use ir.QuoteIdentifier() for both targetSchema and grantee in all statements within this function.

The modifiedDefaultPrivileges slice is not being sorted for deterministic output, unlike addedDefaultPrivileges and droppedDefaultPrivileges which are sorted on lines 954-965. This could lead to non-deterministic diff output when multiple default privileges are modified.

Consider adding a sort for modifiedDefaultPrivileges similar to the other slices, for example after line 965.

The test data files are inconsistent. The diff.sql file shows that a GRANT statement should be generated, but plan.txt states "No changes detected" and plan.json has groups set to null.

These files should be updated to match the expected diff output in diff.sql, indicating that 1 default privilege should be created.

The DDL statement on line 10 is incorrect. It shows:
"ALTER DEFAULT PRIVILEGES IN SCHEMA public REVOKE SELECT ON TABLES FROM app_user;"

However, based on the old.sql and new.sql files, the correct statement should be:
"ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT INSERT, UPDATE ON TABLES TO app_user;"

This is because new.sql adds INSERT and UPDATE privileges while keeping SELECT (it doesn't remove SELECT).

The plan.sql file does not match the expected diff output based on the old.sql and new.sql files.

Looking at the changes:

• old.sql grants SELECT and USAGE privileges
• new.sql grants SELECT, INSERT, UPDATE (no USAGE)

The correct diff should be:

1. REVOKE USAGE ON SEQUENCES FROM app_user (removing USAGE privilege)
2. GRANT INSERT, UPDATE ON TABLES TO app_user (adding INSERT and UPDATE, SELECT already exists)

However, this plan.sql shows:

1. REVOKE USAGE ON SEQUENCES FROM app_user (correct)
2. REVOKE SELECT ON TABLES FROM app_user (incorrect - should be GRANT INSERT, UPDATE)

The diff.sql file has the correct expected output. Please update plan.sql to match diff.sql.

The plan.json does not match the expected diff output. Line 18 shows a REVOKE SELECT statement which is incorrect. Based on old.sql and new.sql, this should be a GRANT statement for INSERT and UPDATE privileges instead.

The correct statement should be:
"ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT INSERT, UPDATE ON TABLES TO app_user;"

This should also have operation "alter" or "create" instead of "drop".

The privileges array should be sorted before being assigned to ensure deterministic output. Currently, the order of privileges within each DefaultPrivilege struct depends on the order they were retrieved from the database and added to the map, which may not be consistent.

Consider adding sort.Strings(privs) before line 1905 to ensure the privileges are always in alphabetical order, matching the behavior in generateGrantDefaultPrivilegeSQL and generateRevokeDefaultPrivilegeSQL which sort privileges before generating SQL.

The test data files are inconsistent. The diff.sql file shows that a GRANT statement should be generated, but:

• plan.txt states "No changes detected" (should indicate 1 change to create/add)
• plan.sql is empty (should contain the GRANT statement from diff.sql)
• plan.json has groups set to null (should have the GRANT operation)

These files should be updated to match the expected diff output in diff.sql.

The test data files are inconsistent. The diff.sql file shows that a GRANT statement should be generated, but plan.txt states "No changes detected" and plan.json has groups set to null.

These files should be updated to match the expected diff output in diff.sql, indicating that 1 default privilege should be created.

The privilege order in the source SQL file does not match the expected output in the plan files. The new.sql specifies "USAGE, SELECT" but plan.sql expects "SELECT, USAGE" (alphabetically sorted). While the code correctly sorts privileges alphabetically at lines 66-68, the test data should be consistent with the expected output to avoid confusion.

The privilege order in the source SQL file does not match the expected output in the plan files. The new.sql specifies "SELECT, INSERT" but plan.sql expects "INSERT, SELECT" (alphabetically sorted). While the code correctly sorts privileges alphabetically, the test data should be consistent with the expected output to avoid confusion.

The privileges array is not sorted when building the DefaultPrivilege objects. While the privileges are sorted later during SQL generation (in generateGrantDefaultPrivilegeSQL), storing them in a deterministic order would improve consistency and make the IR representation more predictable. Consider sorting the privileges array before assigning it to the DefaultPrivilege struct at line 1905.

There is no test case covering the scenario where both privileges and WithGrantOption change simultaneously. This would help validate the fix for the bug in generateAlterDefaultPrivilegeStatements. Consider adding a test case where, for example, old has [SELECT] WITH GRANT OPTION and new has [SELECT, INSERT] WITHOUT GRANT OPTION.

The SQL query includes a mapping for schema object type ('n' -> 'SCHEMAS') but there is no corresponding constant defined in the DefaultPrivilegeObjectType enum. This could cause a type mismatch if PostgreSQL returns default privileges for schemas. Either add a constant for SCHEMAS or filter out schema privileges in the query.

The key used to compare default privileges does not include the schema name, which could cause collisions when default privileges are defined in multiple schemas. If the same ObjectType and Grantee combination exists in different schemas with different privileges, the map will only retain the last one encountered, leading to incorrect diff results. The key should include the schema name to ensure uniqueness across schemas.