fix(db diff): filter inherited constraints for partitioned tables

when a foreign key references a partitioned table, postgresql automatically
creates inherited constraints with numeric suffixes (fkey1, fkey2, etc.) for
each partition. migra treats these as independent constraints and generates
drop/add statements for them, which fails because postgresql forbids dropping
inherited constraints directly.

this change filters out alter table statements that operate on constraints
matching the pattern fkey followed by digits, as these are always postgresql
auto-generated inherited constraints. legitimate user-defined constraints
(like users_id_fkey without numeric suffix) are preserved.

the fix is applied to both the migra and pgadmin diff paths to ensure
consistent behavior across all diff methods.

closes #4562

Author: 7ttp

internal/db/diff/diff.go

@@ -35,6 +35,7 @@ func Run(ctx context.Context, schema []string, file string, config pgconn.Config
 	if err != nil {
 		return err
 	}
+	out = filterInheritedConstraints(out)
 	branch := keys.GetGitBranch(fsys)
 	fmt.Fprintln(os.Stderr, "Finished "+utils.Aqua("supabase db diff")+" on branch "+utils.Aqua(branch)+".\n")
 	if err := SaveDiff(out, file, fsys); err != nil {
@@ -89,6 +90,29 @@ func findDropStatements(out string) []string {
 	return drops
 }
 
+var inheritedConstraintPattern = regexp.MustCompile(`(?i)alter\s+table\s+[^;]+\s+(drop|add)\s+constraint\s+"[^"]*fkey\d+"`)
+
+func filterInheritedConstraints(out string) string {
+	lines, err := parser.SplitAndTrim(strings.NewReader(out))
+	if err != nil {
+		return out
+	}
+	var filtered []string
+	for _, line := range lines {
+		if !inheritedConstraintPattern.MatchString(line) {
+			filtered = append(filtered, line)
+		}
+	}
+	if len(filtered) == 0 {
+		return ""
+	}
+	result := strings.Join(filtered, ";\n\n") + ";"
+	if strings.HasSuffix(out, "\n") {
+		result += "\n"
+	}
+	return result
+}
+
 func CreateShadowDatabase(ctx context.Context, port uint16) (string, error) {
 	// Disable background workers in shadow database
 	config := start.NewContainerConfig("-c", "max_worker_processes=0")

internal/db/diff/diff_test.go

@@ -345,6 +345,68 @@ func TestDropStatements(t *testing.T) {
 	assert.Equal(t, []string{"drop table t", "alter table t drop column c"}, drops)
 }
 
+func TestFilterInheritedConstraints(t *testing.T) {
+	t.Run("filters inherited fkey constraints", func(t *testing.T) {
+		input := `alter table "public"."users" drop constraint "users_avatar_id_fkey1";
+alter table "public"."users" drop constraint "users_avatar_id_fkey2";
+alter table "public"."users" add constraint "users_avatar_id_fkey1" FOREIGN KEY (avatar_id) REFERENCES photos_avatars(id);
+create table test();`
+		result := filterInheritedConstraints(input)
+		assert.Equal(t, "create table test();", result)
+	})
+
+	t.Run("preserves non-inherited constraints", func(t *testing.T) {
+		input := `alter table "public"."users" drop constraint "users_avatar_id_fkey";
+alter table "public"."users" add constraint "users_avatar_id_fkey" FOREIGN KEY (avatar_id) REFERENCES photos(id);`
+		result := filterInheritedConstraints(input)
+		assert.Contains(t, result, `alter table "public"."users" drop constraint "users_avatar_id_fkey"`)
+		assert.Contains(t, result, `alter table "public"."users" add constraint "users_avatar_id_fkey" FOREIGN KEY (avatar_id) REFERENCES photos(id)`)
+	})
+
+	t.Run("returns empty string when all statements filtered", func(t *testing.T) {
+		input := `alter table "public"."users" drop constraint "users_fkey1";
+alter table "public"."users" drop constraint "users_fkey2";`
+		result := filterInheritedConstraints(input)
+		assert.Equal(t, "", result)
+	})
+
+	t.Run("handles empty input", func(t *testing.T) {
+		result := filterInheritedConstraints("")
+		assert.Equal(t, "", result)
+	})
+
+	t.Run("handles mixed statements with partitioned table constraints", func(t *testing.T) {
+		input := `create table accounts(id text primary key);
+alter table "public"."users" drop constraint "users_avatar_id_avatar_bucket_fkey1";
+alter table "public"."users" drop constraint "users_avatar_id_avatar_bucket_fkey14";
+alter table "public"."companies" drop constraint "companies_logo_id_fkey1";
+create index idx_test on test(id);`
+		result := filterInheritedConstraints(input)
+		assert.Contains(t, result, "create table accounts(id text primary key)")
+		assert.Contains(t, result, "create index idx_test on test(id)")
+		assert.NotContains(t, result, "fkey1")
+		assert.NotContains(t, result, "fkey14")
+	})
+
+	t.Run("filters exact bug report pattern", func(t *testing.T) {
+		input := `alter table "public"."users" drop constraint "users_avatar_id_avatar_bucket_fkey1";
+alter table "public"."users" drop constraint "users_avatar_id_avatar_bucket_fkey2";
+alter table "public"."users" drop constraint "users_avatar_id_avatar_bucket_fkey3";
+alter table "public"."users" add constraint "users_avatar_id_avatar_bucket_fkey1" FOREIGN KEY (avatar_id, avatar_bucket) REFERENCES photos_avatars(id, bucket) ON DELETE SET NULL;
+alter table "public"."users" add constraint "users_avatar_id_avatar_bucket_fkey2" FOREIGN KEY (avatar_id, avatar_bucket) REFERENCES photos_brands(id, bucket) ON DELETE SET NULL;`
+		result := filterInheritedConstraints(input)
+		assert.Equal(t, "", result)
+	})
+
+	t.Run("preserves legitimate constraint operations", func(t *testing.T) {
+		input := `alter table "public"."users" drop constraint "users_avatar_id_avatar_bucket_fkey";
+alter table "public"."users" add constraint "users_avatar_id_avatar_bucket_fkey" FOREIGN KEY (avatar_id, avatar_bucket) REFERENCES photos(id, bucket) ON DELETE SET NULL;`
+		result := filterInheritedConstraints(input)
+		assert.Contains(t, result, "users_avatar_id_avatar_bucket_fkey")
+		assert.NotContains(t, result, "fkey1")
+	})
+}
+
 func TestLoadSchemas(t *testing.T) {
 	expected := []string{
 		filepath.Join(utils.SchemasDir, "comment", "model.sql"),

internal/db/diff/pgadmin.go

@@ -44,7 +44,7 @@ func RunPgAdmin(ctx context.Context, schema []string, file string, config pgconn
 		return err
 	}
 
-	return SaveDiff(output, file, fsys)
+	return SaveDiff(filterInheritedConstraints(output), file, fsys)
 }
 
 var output string