fix(dbml): resolve commented cross-file // Ref: lines

Commented refs are collected per file and resolved against the combined
model after all inputs are loaded (directory, --from-list, merge, jobs).
Matched refs become FKs and relationships; duplicates of existing FKs are
skipped; missing targets are skipped with a warning; column type
mismatches warn.

Also keep reused index names within a DBML table instead of overwriting,
give a second FK to the same table a distinct relationship name, and make
the pgsql writer match relationships to FKs by name first.

cmd/relspec/convert.go

@@ -229,6 +229,7 @@ func runConvert(cmd *cobra.Command, args []string) error {
 	if err != nil {
 		return fmt.Errorf("failed to read source: %w", err)
 	}
+	finalizeCommentedRefs(db, stderrWarn)
 
 	fmt.Fprintf(os.Stderr, "      ✓ Successfully read database '%s'\n", db.Name)
 	fmt.Fprintf(os.Stderr, "      Found: %d schema(s)\n", len(db.Schemas))
@@ -261,6 +262,18 @@ func runConvert(cmd *cobra.Command, args []string) error {
 	return nil
 }
 
+// finalizeCommentedRefs resolves DBML `// Ref:` comments against the fully
+// loaded model and warns about refs whose target is not loaded.
+func finalizeCommentedRefs(db *models.Database, warn func(string)) {
+	for _, w := range dbml.ResolveCommentedRefs(db, true) {
+		warn(w)
+	}
+}
+
+func stderrWarn(msg string) {
+	fmt.Fprintf(os.Stderr, "      ⚠ %s\n", msg)
+}
+
 func readDatabaseListForConvert(dbType string, files []string) (*models.Database, error) {
 	if len(files) == 0 {
 		return nil, fmt.Errorf("file list is empty")

cmd/relspec/job.go

@@ -578,6 +578,7 @@ func runMergeJob(rj *resolvedJob, lg *jobLogger) error {
 		lg.logf("merging: %s", inputLabel(ri))
 		merge.MergeDatabases(base, db, opts)
 	}
+	finalizeCommentedRefs(base, func(w string) { lg.logf("warning: %s", w) })
 	base.UpdateDate()
 	return writeJobOutput(rj, base, lg)
 }
@@ -814,6 +815,7 @@ func readJobInputs(rj *resolvedJob, lg *jobLogger) (*models.Database, error) {
 	if base == nil {
 		return nil, fmt.Errorf("no inputs produced a database")
 	}
+	finalizeCommentedRefs(base, func(w string) { lg.logf("warning: %s", w) })
 	return base, nil
 }
 

cmd/relspec/merge.go

@@ -248,6 +248,7 @@ func runMerge(cmd *cobra.Command, args []string) error {
 	}
 
 	result := merge.MergeDatabases(targetDB, sourceDB, opts)
+	finalizeCommentedRefs(targetDB, stderrWarn)
 
 	// Update timestamp
 	targetDB.UpdateDate()

cmd/relspec/templ.go

@@ -114,6 +114,7 @@ func runTempl(cmd *cobra.Command, args []string) error {
 	if err != nil {
 		return fmt.Errorf("failed to read source: %w", err)
 	}
+	finalizeCommentedRefs(db, stderrWarn)
 
 	// Print database stats
 	schemaCount := len(db.Schemas)

pkg/merge/merge.go

@@ -91,6 +91,45 @@ func (r *MergeResult) merge(target, source *models.Database, opts *MergeOptions)
 	if !opts.SkipDomains {
 		r.mergeDomains(target, source)
 	}
+
+	mergeDatabaseMetadata(target, source)
+}
+
+// mergeDatabaseMetadata adds missing metadata keys and unions []string values,
+// so per-file reader state (e.g. pending DBML commented refs) survives a merge.
+func mergeDatabaseMetadata(target, source *models.Database) {
+	if len(source.Metadata) == 0 {
+		return
+	}
+	if target.Metadata == nil {
+		target.Metadata = make(map[string]any, len(source.Metadata))
+	}
+	for key, srcVal := range source.Metadata {
+		tgtVal, exists := target.Metadata[key]
+		if !exists {
+			if list, ok := srcVal.([]string); ok {
+				srcVal = append([]string(nil), list...)
+			}
+			target.Metadata[key] = srcVal
+			continue
+		}
+		tgtList, tgtOK := tgtVal.([]string)
+		srcList, srcOK := srcVal.([]string)
+		if !tgtOK || !srcOK {
+			continue
+		}
+		seen := make(map[string]bool, len(tgtList))
+		for _, v := range tgtList {
+			seen[v] = true
+		}
+		for _, v := range srcList {
+			if !seen[v] {
+				tgtList = append(tgtList, v)
+				seen[v] = true
+			}
+		}
+		target.Metadata[key] = tgtList
+	}
 }
 
 func (r *MergeResult) mergeSchemaContents(target, source *models.Schema, opts *MergeOptions) {

pkg/merge/merge_test.go

@@ -721,3 +721,32 @@ func TestComplexMerge(t *testing.T) {
 		t.Error("Expected ukey_users_guid constraint to exist")
 	}
 }
+
+func TestMergeDatabases_Metadata(t *testing.T) {
+	target := &models.Database{Metadata: map[string]any{
+		"refs": []string{"a", "b"},
+		"name": "target",
+	}}
+	source := &models.Database{Metadata: map[string]any{
+		"refs":  []string{"b", "c"},
+		"name":  "source",
+		"extra": []string{"x"},
+	}}
+
+	MergeDatabases(target, source, nil)
+
+	if got := target.Metadata["refs"].([]string); strings.Join(got, ",") != "a,b,c" {
+		t.Errorf("refs = %v, want [a b c]", got)
+	}
+	if got := target.Metadata["name"]; got != "target" {
+		t.Errorf("name = %v, want target (existing scalar keys are kept)", got)
+	}
+	extra := target.Metadata["extra"].([]string)
+	if strings.Join(extra, ",") != "x" {
+		t.Errorf("extra = %v, want [x]", extra)
+	}
+	source.Metadata["extra"].([]string)[0] = "changed"
+	if extra[0] != "x" {
+		t.Error("copied slice must not alias the source")
+	}
+}

pkg/readers/dbml/README.md

@@ -90,11 +90,28 @@ Ref: posts.user_id > users.id [delete: cascade]
 - Default values (`default`)
 - Inline references (`ref`)
 - Standalone `Ref` blocks
+- Commented cross-file refs (`// Ref:` — see below)
 - Indexes and composite indexes
 - Table notes and column notes
 - Enums
 - Dialect directives (`@postgres:` / `@sqlite:` — see below)
 
+## Commented cross-file refs
+
+`// Ref:` / `// ref:` lines (ignored by dbdiagram) become FKs + relationships once both ends are loaded.
+
+| Rule | Behaviour |
+|---|---|
+| When | Single file / directory: end of read. `--from-list`, `merge`, jobs: after all inputs are combined |
+| Match | `schema.table.column` on both sides, case-insensitive |
+| Operators | `>`, `<`, `-` (parsed like `Ref:`) |
+| Duplicate of an FK on the same columns | Skipped silently |
+| Target not loaded | Kept pending; skipped with a warning on the final pass |
+| Column type mismatch | Warning, FK still created (`serial`≈`integer`, `bigserial`≈`bigint`) |
+| Pending state | `Database.Metadata["dbml.commented_refs"]` (`[]string`) |
+
+API: `dbml.ResolveCommentedRefs(db, final bool) []string` returns warnings.
+
 ## Dialect directives
 
 Lines of the form `@<namespace>[(<column>)]: <args>` embed database-specific

pkg/readers/dbml/commented_refs.go

@@ -0,0 +1,218 @@
+package dbml
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+
+	"git.warky.dev/wdevs/relspecgo/pkg/models"
+)
+
+// CommentedRefsMetadataKey is the Database.Metadata key holding commented
+// `// Ref:` lines not yet resolved against the model ([]string).
+const CommentedRefsMetadataKey = "dbml.commented_refs"
+
+// commentedRefRegex matches `// Ref: ...` and `// ref: ...`.
+var commentedRefRegex = regexp.MustCompile(`^//\s*[Rr]ef\s*:\s*(.+)$`)
+
+// commentedRef returns the ref body of a trimmed `// Ref:` comment line.
+func commentedRef(line string) (string, bool) {
+	m := commentedRefRegex.FindStringSubmatch(line)
+	if m == nil {
+		return "", false
+	}
+	ref := strings.TrimSpace(m[1])
+	return ref, ref != ""
+}
+
+// PendingCommentedRefs returns the commented refs not yet resolved.
+func PendingCommentedRefs(db *models.Database) []string {
+	if db == nil || db.Metadata == nil {
+		return nil
+	}
+	refs, _ := db.Metadata[CommentedRefsMetadataKey].([]string)
+	return refs
+}
+
+func setPendingCommentedRefs(db *models.Database, refs []string) {
+	if len(refs) == 0 {
+		if db.Metadata != nil {
+			delete(db.Metadata, CommentedRefsMetadataKey)
+		}
+		return
+	}
+	if db.Metadata == nil {
+		db.Metadata = make(map[string]any)
+	}
+	db.Metadata[CommentedRefsMetadataKey] = refs
+}
+
+// addPendingCommentedRef queues a ref, skipping exact repeats.
+func addPendingCommentedRef(db *models.Database, ref string) {
+	refs := PendingCommentedRefs(db)
+	for _, existing := range refs {
+		if existing == ref {
+			return
+		}
+	}
+	setPendingCommentedRefs(db, append(refs, ref))
+}
+
+// ResolveCommentedRefs turns pending commented refs into foreign keys and
+// relationships when both ends (schema.table.column) exist in db. A ref that
+// matches an existing FK on the same columns is dropped as a duplicate.
+// Unmatched refs stay pending unless final is set, in which case they are
+// dropped with a warning. Returns human-readable warnings.
+func ResolveCommentedRefs(db *models.Database, final bool) []string {
+	refs := PendingCommentedRefs(db)
+	if len(refs) == 0 {
+		return nil
+	}
+
+	var warnings []string
+	var pending []string
+	parser := &Reader{}
+
+	for _, ref := range refs {
+		fk := parser.parseRef(ref)
+		if fk == nil || len(fk.Columns) == 0 || len(fk.Columns) != len(fk.ReferencedColumns) {
+			warnings = append(warnings, fmt.Sprintf("skipping commented ref %q: cannot parse", ref))
+			continue
+		}
+
+		srcTable, srcCols, srcMissing := lookupColumns(db, fk.Schema, fk.Table, fk.Columns)
+		dstTable, dstCols, dstMissing := lookupColumns(db, fk.ReferencedSchema, fk.ReferencedTable, fk.ReferencedColumns)
+		if srcMissing != "" || dstMissing != "" {
+			if final {
+				missing := srcMissing
+				if missing == "" {
+					missing = dstMissing
+				}
+				warnings = append(warnings, fmt.Sprintf("skipping commented ref %q: %s not found", ref, missing))
+			} else {
+				pending = append(pending, ref)
+			}
+			continue
+		}
+
+		fk.Schema, fk.Table, fk.Columns = srcTable.Schema, srcTable.Name, columnNames(srcCols)
+		fk.ReferencedSchema, fk.ReferencedTable, fk.ReferencedColumns = dstTable.Schema, dstTable.Name, columnNames(dstCols)
+
+		if hasFKOnColumns(srcTable, fk.Columns) {
+			continue // already declared by an uncommented Ref or inline ref
+		}
+		if _, taken := srcTable.Constraints[fk.Name]; taken {
+			warnings = append(warnings, fmt.Sprintf("skipping commented ref %q: constraint %s already exists", ref, fk.Name))
+			continue
+		}
+
+		for i := range srcCols {
+			if !compatibleFKTypes(srcCols[i].Type, dstCols[i].Type) {
+				warnings = append(warnings, fmt.Sprintf("commented ref %q: type mismatch %s.%s.%s (%s) -> %s.%s.%s (%s)",
+					ref, srcTable.Schema, srcTable.Name, srcCols[i].Name, srcCols[i].Type,
+					dstTable.Schema, dstTable.Name, dstCols[i].Name, dstCols[i].Type))
+			}
+		}
+
+		if srcTable.Constraints == nil {
+			srcTable.Constraints = make(map[string]*models.Constraint)
+		}
+		srcTable.Constraints[fk.Name] = fk
+		addFKRelationship(srcTable, fk)
+	}
+
+	setPendingCommentedRefs(db, pending)
+	return warnings
+}
+
+// lookupColumns finds a table and its columns, case-insensitively. missing
+// names the first object not found, or is empty.
+func lookupColumns(db *models.Database, schemaName, tableName string, cols []string) (*models.Table, []*models.Column, string) {
+	qualified := schemaName + "." + tableName
+	var table *models.Table
+	for _, schema := range db.Schemas {
+		if !strings.EqualFold(schema.Name, schemaName) {
+			continue
+		}
+		for _, t := range schema.Tables {
+			if strings.EqualFold(t.Name, tableName) {
+				table = t
+				break
+			}
+		}
+	}
+	if table == nil {
+		return nil, nil, "table " + qualified
+	}
+
+	found := make([]*models.Column, 0, len(cols))
+	for _, name := range cols {
+		col := table.Columns[name]
+		if col == nil {
+			for _, c := range table.Columns {
+				if strings.EqualFold(c.Name, name) {
+					col = c
+					break
+				}
+			}
+		}
+		if col == nil {
+			return nil, nil, "column " + qualified + "." + name
+		}
+		found = append(found, col)
+	}
+	return table, found, ""
+}
+
+func columnNames(cols []*models.Column) []string {
+	names := make([]string, len(cols))
+	for i, c := range cols {
+		names[i] = c.Name
+	}
+	return names
+}
+
+// hasFKOnColumns reports whether table already has a foreign key over cols.
+func hasFKOnColumns(table *models.Table, cols []string) bool {
+	for _, c := range table.Constraints {
+		if c.Type != models.ForeignKeyConstraint || len(c.Columns) != len(cols) {
+			continue
+		}
+		same := true
+		for i := range cols {
+			if !strings.EqualFold(c.Columns[i], cols[i]) {
+				same = false
+				break
+			}
+		}
+		if same {
+			return true
+		}
+	}
+	return false
+}
+
+// fkTypeAliases maps serial and alias spellings to their storage type.
+var fkTypeAliases = map[string]string{
+	"smallserial": "smallint", "serial2": "smallint", "int2": "smallint",
+	"serial": "integer", "serial4": "integer", "int": "integer", "int4": "integer",
+	"bigserial": "bigint", "serial8": "bigint", "int8": "bigint",
+}
+
+// compatibleFKTypes compares column types ignoring case, length and serial
+// vs. integer spelling. Unknown (empty) types are treated as compatible.
+func compatibleFKTypes(a, b string) bool {
+	na, nb := normalizeFKType(a), normalizeFKType(b)
+	return na == "" || nb == "" || na == nb
+}
+
+func normalizeFKType(t string) string {
+	t = strings.ToLower(strings.TrimSpace(t))
+	if i := strings.Index(t, "("); i >= 0 {
+		t = strings.TrimSpace(t[:i])
+	}
+	if alias, ok := fkTypeAliases[t]; ok {
+		return alias
+	}
+	return t
+}

pkg/readers/dbml/commented_refs_test.go

@@ -0,0 +1,260 @@
+package dbml
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"git.warky.dev/wdevs/relspecgo/pkg/models"
+	"git.warky.dev/wdevs/relspecgo/pkg/readers"
+)
+
+func readDBMLString(t *testing.T, content string) *models.Database {
+	t.Helper()
+	path := filepath.Join(t.TempDir(), "in.dbml")
+	if err := os.WriteFile(path, []byte(content), 0o644); err != nil {
+		t.Fatalf("write fixture: %v", err)
+	}
+	db, err := NewReader(&readers.ReaderOptions{FilePath: path}).ReadDatabase()
+	if err != nil {
+		t.Fatalf("ReadDatabase() error = %v", err)
+	}
+	return db
+}
+
+func findTable(db *models.Database, schema, table string) *models.Table {
+	for _, s := range db.Schemas {
+		if s.Name != schema {
+			continue
+		}
+		for _, t := range s.Tables {
+			if t.Name == table {
+				return t
+			}
+		}
+	}
+	return nil
+}
+
+func fkOn(table *models.Table, col string) *models.Constraint {
+	for _, c := range table.Constraints {
+		if c.Type == models.ForeignKeyConstraint && len(c.Columns) == 1 && c.Columns[0] == col {
+			return c
+		}
+	}
+	return nil
+}
+
+func relFor(table *models.Table, fkName string) *models.Relationship {
+	for _, r := range table.Relationships {
+		if r.ForeignKey == fkName {
+			return r
+		}
+	}
+	return nil
+}
+
+func TestCommentedRef(t *testing.T) {
+	tests := []struct {
+		line string
+		want string
+		ok   bool
+	}{
+		{`// Ref: a.b.c > d.e.f`, `a.b.c > d.e.f`, true},
+		{`// ref: a.b.c - d.e.f`, `a.b.c - d.e.f`, true},
+		{`//Ref:a.b.c > d.e.f`, `a.b.c > d.e.f`, true},
+		{`// Reference notes`, "", false},
+		{`// see Ref: a.b.c > d.e.f`, "", false},
+		{`// Ref:`, "", false},
+	}
+	for _, tt := range tests {
+		got, ok := commentedRef(tt.line)
+		if ok != tt.ok || got != tt.want {
+			t.Errorf("commentedRef(%q) = (%q, %v), want (%q, %v)", tt.line, got, ok, tt.want, tt.ok)
+		}
+	}
+}
+
+// A commented ref whose tables are in the same file resolves on read.
+func TestReader_CommentedRefSameFile(t *testing.T) {
+	db := readDBMLString(t, `Table "org"."department" {
+  "id_department" bigserial [pk]
+}
+Table "entity"."employee" {
+  "id_employee" bigserial [pk]
+  "rid_department" bigint
+}
+// Ref: "entity"."employee"."rid_department" > "org"."department"."id_department" [delete: restrict, update: restrict]
+`)
+	emp := findTable(db, "entity", "employee")
+	fk := fkOn(emp, "rid_department")
+	if fk == nil {
+		t.Fatal("expected FK on rid_department")
+	}
+	if fk.ReferencedSchema != "org" || fk.ReferencedTable != "department" || fk.ReferencedColumns[0] != "id_department" {
+		t.Errorf("FK target = %s.%s.%v", fk.ReferencedSchema, fk.ReferencedTable, fk.ReferencedColumns)
+	}
+	if fk.OnDelete != "restrict" || fk.OnUpdate != "restrict" {
+		t.Errorf("FK actions = %q/%q, want restrict/restrict", fk.OnDelete, fk.OnUpdate)
+	}
+	if relFor(emp, fk.Name) == nil {
+		t.Error("expected relationship for FK")
+	}
+	if refs := PendingCommentedRefs(db); len(refs) != 0 {
+		t.Errorf("pending = %v, want none", refs)
+	}
+}
+
+// A cross-file commented ref stays pending after a single-file read.
+func TestReader_CommentedRefCrossFilePending(t *testing.T) {
+	db := readDBMLString(t, `Table "entity"."employee" {
+  "id_employee" bigserial [pk]
+  "rid_department" bigint
+}
+// Ref: "entity"."employee"."rid_department" > "org"."department"."id_department"
+`)
+	if fk := fkOn(findTable(db, "entity", "employee"), "rid_department"); fk != nil {
+		t.Fatal("FK must not resolve without the target table")
+	}
+	if refs := PendingCommentedRefs(db); len(refs) != 1 {
+		t.Fatalf("pending = %v, want 1", refs)
+	}
+}
+
+// Directory reads resolve commented refs after all files are merged.
+func TestReader_CommentedRefDirectory(t *testing.T) {
+	db, err := NewReader(&readers.ReaderOptions{
+		FilePath: filepath.Join("..", "..", "..", "tests", "assets", "dbml", "multifile"),
+	}).ReadDatabase()
+	if err != nil {
+		t.Fatalf("ReadDatabase() error = %v", err)
+	}
+	fk := fkOn(findTable(db, "public", "posts"), "user_id")
+	if fk == nil {
+		t.Fatal("expected FK posts.user_id from 9_refs.dbml commented ref")
+	}
+	if fk.ReferencedTable != "users" || fk.OnDelete != "CASCADE" {
+		t.Errorf("FK = %s ondelete %s, want users ondelete CASCADE", fk.ReferencedTable, fk.OnDelete)
+	}
+}
+
+func crossFileDB(t *testing.T, refs ...string) *models.Database {
+	t.Helper()
+	db := readDBMLString(t, `Table "org"."department" {
+  "id_department" bigserial [pk]
+}
+Table "entity"."employee" {
+  "id_employee" bigserial [pk]
+  "rid_department" bigint
+  "rid_manager" integer
+  "rid_team" bigint
+}
+`)
+	setPendingCommentedRefs(db, refs)
+	return db
+}
+
+func TestResolveCommentedRefs(t *testing.T) {
+	t.Run("lowercase ref and one-to-one", func(t *testing.T) {
+		db := crossFileDB(t,
+			`"entity"."employee"."rid_department" > "org"."department"."id_department"`,
+			`entity.employee.rid_team - org.department.id_department`,
+		)
+		if w := ResolveCommentedRefs(db, true); len(w) != 0 {
+			t.Errorf("warnings = %v, want none", w)
+		}
+		emp := findTable(db, "entity", "employee")
+		for _, col := range []string{"rid_department", "rid_team"} {
+			fk := fkOn(emp, col)
+			if fk == nil {
+				t.Fatalf("expected FK on %s", col)
+			}
+			if relFor(emp, fk.Name) == nil {
+				t.Errorf("expected relationship for %s", fk.Name)
+			}
+		}
+		if len(emp.Relationships) != 2 {
+			t.Errorf("relationships = %d, want 2 (same target must not overwrite)", len(emp.Relationships))
+		}
+	})
+
+	t.Run("type mismatch warns but resolves", func(t *testing.T) {
+		db := crossFileDB(t, `entity.employee.rid_manager > org.department.id_department`)
+		w := ResolveCommentedRefs(db, true)
+		if len(w) != 1 || !strings.Contains(w[0], "type mismatch") {
+			t.Errorf("warnings = %v, want one type mismatch", w)
+		}
+		if fkOn(findTable(db, "entity", "employee"), "rid_manager") == nil {
+			t.Error("expected FK on rid_manager")
+		}
+	})
+
+	t.Run("missing target stays pending until final", func(t *testing.T) {
+		db := crossFileDB(t, `entity.employee.rid_team > hr.team.id_team`)
+		if w := ResolveCommentedRefs(db, false); len(w) != 0 {
+			t.Errorf("non-final warnings = %v, want none", w)
+		}
+		if len(PendingCommentedRefs(db)) != 1 {
+			t.Fatal("ref should stay pending")
+		}
+		w := ResolveCommentedRefs(db, true)
+		if len(w) != 1 || !strings.Contains(w[0], "table hr.team not found") {
+			t.Errorf("final warnings = %v, want missing table", w)
+		}
+		if len(PendingCommentedRefs(db)) != 0 {
+			t.Error("final pass must clear pending refs")
+		}
+	})
+
+	t.Run("missing column", func(t *testing.T) {
+		db := crossFileDB(t, `entity.employee.rid_nope > org.department.id_department`)
+		w := ResolveCommentedRefs(db, true)
+		if len(w) != 1 || !strings.Contains(w[0], "column entity.employee.rid_nope not found") {
+			t.Errorf("warnings = %v, want missing column", w)
+		}
+	})
+
+	t.Run("deduplicates against uncommented ref", func(t *testing.T) {
+		db := readDBMLString(t, `Table "org"."department" {
+  "id_department" bigserial [pk]
+}
+Table "entity"."employee" {
+  "id_employee" bigserial [pk]
+  "rid_department" bigint
+}
+Ref: "entity"."employee"."rid_department" > "org"."department"."id_department"
+// Ref: "entity"."employee"."rid_department" > "org"."department"."id_department"
+`)
+		emp := findTable(db, "entity", "employee")
+		count := 0
+		for _, c := range emp.Constraints {
+			if c.Type == models.ForeignKeyConstraint {
+				count++
+			}
+		}
+		if count != 1 || len(emp.Relationships) != 1 {
+			t.Errorf("FKs = %d, relationships = %d, want 1 and 1", count, len(emp.Relationships))
+		}
+	})
+}
+
+func TestCompatibleFKTypes(t *testing.T) {
+	tests := []struct {
+		a, b string
+		want bool
+	}{
+		{"bigint", "bigserial", true},
+		{"integer", "serial", true},
+		{"INT4", "integer", true},
+		{"varchar(10)", "varchar(20)", true},
+		{"bigint", "serial", false},
+		{"uuid", "bigint", false},
+		{"", "bigint", true},
+	}
+	for _, tt := range tests {
+		if got := compatibleFKTypes(tt.a, tt.b); got != tt.want {
+			t.Errorf("compatibleFKTypes(%q, %q) = %v, want %v", tt.a, tt.b, got, tt.want)
+		}
+	}
+}

pkg/readers/dbml/reader.go

@@ -48,7 +48,22 @@ func (r *Reader) ReadDatabase() (*models.Database, error) {
 		return nil, fmt.Errorf("failed to read file: %w", err)
 	}
 
-	return r.parseDBML(string(content))
+	db, err := r.parseDBML(string(content))
+	if err != nil {
+		return nil, err
+	}
+	r.resolveCommentedRefs(db)
+	return db, nil
+}
+
+// resolveCommentedRefs resolves the commented refs whose tables are loaded.
+// Unmatched refs stay pending for a later pass over a combined model.
+func (r *Reader) resolveCommentedRefs(db *models.Database) {
+	for _, w := range ResolveCommentedRefs(db, false) {
+		if r.options.Progress != nil {
+			r.options.Progress("warning: " + w)
+		}
+	}
 }
 
 // ReadSchema reads and parses DBML input, returning a Schema model
@@ -125,6 +140,7 @@ func (r *Reader) readDirectoryDBML(dirPath string) (*models.Database, error) {
 		}
 	}
 
+	r.resolveCommentedRefs(db)
 	return db, nil
 }
 
@@ -440,6 +456,10 @@ func mergeDatabase(baseDB, fileDB *models.Database) {
 	// Merge domains
 	baseDB.Domains = append(baseDB.Domains, fileDB.Domains...)
 
+	for _, ref := range PendingCommentedRefs(fileDB) {
+		addPendingCommentedRef(baseDB, ref)
+	}
+
 	// Use first non-empty description
 	if baseDB.Description == "" && fileDB.Description != "" {
 		baseDB.Description = fileDB.Description
@@ -493,8 +513,12 @@ func (r *Reader) parseDBML(content string) (*models.Database, error) {
 			continue
 		}
 
-		// Skip empty lines and comments
+		// Skip empty lines and comments. A commented `// Ref:` is kept as a
+		// pending cross-file ref, resolved once every file is loaded.
 		if line == "" || strings.HasPrefix(line, "//") {
+			if ref, ok := commentedRef(line); ok {
+				addPendingCommentedRef(db, ref)
+			}
 			continue
 		}
 
@@ -581,7 +605,13 @@ func (r *Reader) parseDBML(content string) (*models.Database, error) {
 
 			index := r.parseIndex(line, currentTable.Name, currentSchema)
 			if index != nil {
-				currentTable.Indexes[index.Name] = index
+				// Keep a reused name under a unique map key so the duplicate is
+				// not silently dropped; the inspector reports it.
+				key := index.Name
+				for n := 2; currentTable.Indexes[key] != nil; n++ {
+					key = fmt.Sprintf("%s#%d", index.Name, n)
+				}
+				currentTable.Indexes[key] = index
 				lastIndex = index
 			}
 			continue
@@ -659,20 +689,12 @@ func (r *Reader) parseDBML(content string) (*models.Database, error) {
 	// for DBML refs so diffing equivalent schemas compares the same model.
 	for _, schema := range schemaMap {
 		for _, table := range schema.Tables {
-			for _, constraint := range table.Constraints {
+			for _, name := range sortedConstraintNames(table.Constraints) {
+				constraint := table.Constraints[name]
 				if constraint.Type != models.ForeignKeyConstraint {
 					continue
 				}
-				name := fmt.Sprintf("%s_to_%s", table.Name, constraint.ReferencedTable)
-				relationship := models.InitRelationship(name, models.OneToMany)
-				relationship.FromTable = table.Name
-				relationship.FromSchema = table.Schema
-				relationship.FromColumns = append([]string(nil), constraint.Columns...)
-				relationship.ToTable = constraint.ReferencedTable
-				relationship.ToSchema = constraint.ReferencedSchema
-				relationship.ToColumns = append([]string(nil), constraint.ReferencedColumns...)
-				relationship.ForeignKey = constraint.Name
-				table.Relationships[name] = relationship
+				addFKRelationship(table, constraint)
 			}
 		}
 	}
@@ -685,6 +707,39 @@ func (r *Reader) parseDBML(content string) (*models.Database, error) {
 	return db, nil
 }
 
+// sortedConstraintNames returns constraint keys in sorted order so derived
+// relationship names do not depend on map iteration order.
+func sortedConstraintNames(constraints map[string]*models.Constraint) []string {
+	names := make([]string, 0, len(constraints))
+	for name := range constraints {
+		names = append(names, name)
+	}
+	sort.Strings(names)
+	return names
+}
+
+// addFKRelationship derives the relationship for a foreign key, matching how
+// the PostgreSQL reader models FKs.
+func addFKRelationship(table *models.Table, constraint *models.Constraint) {
+	name := fmt.Sprintf("%s_to_%s", table.Name, constraint.ReferencedTable)
+	if existing, taken := table.Relationships[name]; taken && existing.ForeignKey != constraint.Name {
+		// A second FK to the same table must not overwrite the first.
+		name = fmt.Sprintf("%s_%s", name, strings.Join(constraint.Columns, "_"))
+	}
+	relationship := models.InitRelationship(name, models.OneToMany)
+	relationship.FromTable = table.Name
+	relationship.FromSchema = table.Schema
+	relationship.FromColumns = append([]string(nil), constraint.Columns...)
+	relationship.ToTable = constraint.ReferencedTable
+	relationship.ToSchema = constraint.ReferencedSchema
+	relationship.ToColumns = append([]string(nil), constraint.ReferencedColumns...)
+	relationship.ForeignKey = constraint.Name
+	if table.Relationships == nil {
+		table.Relationships = make(map[string]*models.Relationship)
+	}
+	table.Relationships[name] = relationship
+}
+
 // setTableNote preserves multiple table notes. The first maps to Description
 // and the second to Comment, matching the model fields used by code writers.
 func setTableNote(table *models.Table, note string) {

pkg/readers/dbml/reader_test.go

@@ -1085,3 +1085,39 @@ func TestReader_MultilineTableNote(t *testing.T) {
 		t.Errorf("column note = %q, want %q", got, want)
 	}
 }
+
+// A name reused inside one Indexes block must not silently drop the earlier
+// index; both are kept so the inspector can report the duplicate.
+func TestReader_DuplicateIndexNameInTableKept(t *testing.T) {
+	dbmlContent := `Table individual_actor {
+  id bigint [pk]
+  rid_actor bigint
+  kind text
+
+  Indexes {
+    (rid_actor) [name: 'idx_actor', unique]
+    (rid_actor, kind) [name: 'idx_actor']
+  }
+}
+`
+	dir := t.TempDir()
+	path := filepath.Join(dir, "dup_index.dbml")
+	if err := os.WriteFile(path, []byte(dbmlContent), 0o644); err != nil {
+		t.Fatalf("failed to write fixture: %v", err)
+	}
+
+	db, err := NewReader(&readers.ReaderOptions{FilePath: path}).ReadDatabase()
+	if err != nil {
+		t.Fatalf("ReadDatabase() error = %v", err)
+	}
+
+	table := db.Schemas[0].Tables[0]
+	if len(table.Indexes) != 2 {
+		t.Fatalf("expected 2 indexes, got %d: %v", len(table.Indexes), table.Indexes)
+	}
+	for key, idx := range table.Indexes {
+		if idx.Name != "idx_actor" {
+			t.Errorf("index %q: Name = %q, want idx_actor", key, idx.Name)
+		}
+	}
+}

pkg/writers/pgsql/writer.go

@@ -1259,15 +1259,20 @@ func (w *Writer) writeForeignKeys(schema *models.Schema) error {
 				fkName = fmt.Sprintf("fk_%s_%s", table.SQLName(), rel.ToTable)
 			}
 
-			// Find the foreign key constraint that matches this relationship
+			// Find the foreign key constraint that matches this relationship.
+			// Prefer the exact name: with several FKs to the same table, a
+			// referenced-table match alone picks an arbitrary one.
 			var fkConstraint *models.Constraint
-			for _, constraint := range table.Constraints {
-				if constraint.Type == models.ForeignKeyConstraint &&
-					(constraint.Name == fkName || constraint.ReferencedTable == rel.ToTable) {
+			if c, ok := table.Constraints[fkName]; ok && c.Type == models.ForeignKeyConstraint {
+				fkConstraint = c
+			} else {
+				for _, constraint := range sortConstraints(table.Constraints) {
+					if constraint.Type == models.ForeignKeyConstraint && constraint.ReferencedTable == rel.ToTable {
 						fkConstraint = constraint
 						break
 					}
 				}
+			}
 
 			// If no constraint found, skip this relationship
 			if fkConstraint == nil {

pkg/writers/pgsql/writer_test.go

@@ -1549,3 +1549,52 @@ func TestGenerateColumnDefinition_IdentityColumnEmitsIdentityClauseNotDefault(t
 		t.Fatalf("generateColumnDefinition() = %q, want %q", got, want)
 	}
 }
+
+// Two FKs to the same table: each relationship must emit its own FK columns,
+// not whichever FK map iteration returns first.
+func TestWriteDatabase_MultipleForeignKeysToSameTable(t *testing.T) {
+	db := models.InitDatabase("testdb")
+	schema := models.InitSchema("public")
+
+	dept := models.InitTable("department", "public")
+	id := models.InitColumn("id_department", "department", "public")
+	id.Type = "bigint"
+	id.IsPrimaryKey = true
+	dept.Columns["id_department"] = id
+
+	emp := models.InitTable("employee", "public")
+	for _, name := range []string{"rid_department", "rid_manager"} {
+		col := models.InitColumn(name, "employee", "public")
+		col.Type = "bigint"
+		emp.Columns[name] = col
+
+		fkName := "fk_employee_" + name
+		fk := models.InitConstraint(fkName, models.ForeignKeyConstraint)
+		fk.Schema, fk.Table, fk.Columns = "public", "employee", []string{name}
+		fk.ReferencedSchema, fk.ReferencedTable, fk.ReferencedColumns = "public", "department", []string{"id_department"}
+		emp.Constraints[fkName] = fk
+
+		rel := models.InitRelationship("employee_to_department_"+name, models.OneToMany)
+		rel.FromTable, rel.ToTable, rel.ToSchema, rel.ForeignKey = "employee", "department", "public", fkName
+		emp.Relationships[rel.Name] = rel
+	}
+
+	schema.Tables = append(schema.Tables, dept, emp)
+	db.Schemas = append(db.Schemas, schema)
+
+	for i := 0; i < 20; i++ {
+		var buf bytes.Buffer
+		writer := NewWriter(&writers.WriterOptions{})
+		writer.writer = &buf
+		if err := writer.WriteDatabase(db); err != nil {
+			t.Fatalf("WriteDatabase failed: %v", err)
+		}
+		output := buf.String()
+		for _, name := range []string{"rid_department", "rid_manager"} {
+			want := "ADD CONSTRAINT fk_employee_" + name + "\n      FOREIGN KEY (" + name + ")"
+			if !strings.Contains(output, want) {
+				t.Fatalf("run %d: missing %q in output:\n%s", i, want, output)
+			}
+		}
+	}
+}