fix(common): skip bun relation fields when building valid columns

Fields tagged rel:, join: or m2m: were registered as columns (e.g. rel:has-many),
which broke the 'all' filter expansion with invalid SQL.

pkg/common/validation.go

@@ -49,6 +49,11 @@ func (v *ColumnValidator) buildValidColumns() {
 			continue
 		}
 
+		// Relation fields are not columns
+		if isBunRelationTag(field.Tag.Get("bun")) {
+			continue
+		}
+
 		// Get column name from bun, gorm, or json tag
 		columnName := v.getColumnName(field)
 		if columnName != "" && columnName != "-" {
@@ -57,6 +62,18 @@ func (v *ColumnValidator) buildValidColumns() {
 	}
 }
 
+// isBunRelationTag reports whether a bun tag describes a relation (rel:, join:, m2m:)
+// rather than a database column.
+func isBunRelationTag(tag string) bool {
+	for _, part := range strings.Split(tag, ",") {
+		part = strings.TrimSpace(part)
+		if strings.HasPrefix(part, "rel:") || strings.HasPrefix(part, "join:") || strings.HasPrefix(part, "m2m:") {
+			return true
+		}
+	}
+	return false
+}
+
 // getColumnName extracts the column name from a struct field's tags
 // Supports both Bun and GORM tags
 func (v *ColumnValidator) getColumnName(field reflect.StructField) string {

pkg/common/validation_test.go

@@ -545,3 +545,29 @@ func TestFilterRequestOptions_PreloadColumnsParentModelFallback(t *testing.T) {
 		t.Errorf("Expected preload column 'id', got '%s'", cols[0])
 	}
 }
+
+type relationTestModel struct {
+	ID       int64              `bun:"id,pk"`
+	Name     string             `bun:"name"`
+	Children []*relationTestKid `bun:"rel:has-many,join:id=parent_id"`
+	Parent   *relationTestKid   `bun:"rel:has-one,join:parent_id=id"`
+	Tags     []*relationTestKid `bun:"m2m:model_tags,join:Model=Tag"`
+}
+
+type relationTestKid struct{}
+
+func TestNewColumnValidator_SkipsRelationFields(t *testing.T) {
+	cols := NewColumnValidator(relationTestModel{}).GetValidColumns()
+	set := map[string]bool{}
+	for _, c := range cols {
+		set[c] = true
+	}
+	if !set["id"] || !set["name"] {
+		t.Errorf("expected id and name columns, got %v", cols)
+	}
+	for _, bad := range []string{"rel:has-many", "rel:has-one", "m2m:model_tags", "children", "parent", "tags"} {
+		if set[bad] {
+			t.Errorf("relation %q must not be a valid column (got %v)", bad, cols)
+		}
+	}
+}