feat(writer): 🎉 Enhance PostgreSQL writer, fixed bugs found using origin

pkg/readers/dbml/reader.go

@@ -587,10 +587,10 @@ func (r *Reader) parseColumn(line, tableName, schemaName string) (*models.Column
 					refOp := strings.TrimSpace(refStr)
 					var isReverse bool
 					if strings.HasPrefix(refOp, "<") {
-						isReverse = column.IsPrimaryKey // < on PK means "is referenced by" (reverse)
-					} else if strings.HasPrefix(refOp, ">") {
-						isReverse = !column.IsPrimaryKey // > on FK means reverse
+						// < means "is referenced by" - only makes sense on PK columns
+						isReverse = column.IsPrimaryKey
 					}
+					// > means "references" - always a forward FK, never reverse
 
 					constraint = r.parseRef(refStr)
 					if constraint != nil {

pkg/readers/pgsql/reader.go

@@ -329,10 +329,10 @@ func (r *Reader) deriveRelationship(table *models.Table, fk *models.Constraint)
 	relationshipName := fmt.Sprintf("%s_to_%s", table.Name, fk.ReferencedTable)
 
 	relationship := models.InitRelationship(relationshipName, models.OneToMany)
-	relationship.FromTable = fk.ReferencedTable
-	relationship.FromSchema = fk.ReferencedSchema
-	relationship.ToTable = table.Name
-	relationship.ToSchema = table.Schema
+	relationship.FromTable = table.Name
+	relationship.FromSchema = table.Schema
+	relationship.ToTable = fk.ReferencedTable
+	relationship.ToSchema = fk.ReferencedSchema
 	relationship.ForeignKey = fk.Name
 
 	// Store constraint actions in properties

pkg/readers/pgsql/reader_test.go

@@ -328,12 +328,12 @@ func TestDeriveRelationship(t *testing.T) {
 		t.Errorf("Expected relationship type %s, got %s", models.OneToMany, rel.Type)
 	}
 
-	if rel.FromTable != "users" {
-		t.Errorf("Expected FromTable 'users', got '%s'", rel.FromTable)
+	if rel.FromTable != "orders" {
+		t.Errorf("Expected FromTable 'orders', got '%s'", rel.FromTable)
 	}
 
-	if rel.ToTable != "orders" {
-		t.Errorf("Expected ToTable 'orders', got '%s'", rel.ToTable)
+	if rel.ToTable != "users" {
+		t.Errorf("Expected ToTable 'users', got '%s'", rel.ToTable)
 	}
 
 	if rel.ForeignKey != "fk_orders_user_id" {

pkg/writers/pgsql/writer.go

@@ -155,13 +155,30 @@ func (w *Writer) GenerateSchemaStatements(schema *models.Schema) ([]string, erro
 				indexType = "btree"
 			}
 
+			// Build column expressions with operator class support for GIN indexes
+			columnExprs := make([]string, 0, len(index.Columns))
+			for _, colName := range index.Columns {
+				colExpr := colName
+				if col, ok := table.Columns[colName]; ok {
+					// For GIN indexes on text columns, add operator class
+					if strings.EqualFold(indexType, "gin") && isTextType(col.Type) {
+						opClass := extractOperatorClass(index.Comment)
+						if opClass == "" {
+							opClass = "gin_trgm_ops"
+						}
+						colExpr = fmt.Sprintf("%s %s", colName, opClass)
+					}
+				}
+				columnExprs = append(columnExprs, colExpr)
+			}
+
 			whereClause := ""
 			if index.Where != "" {
 				whereClause = fmt.Sprintf(" WHERE %s", index.Where)
 			}
 
 			stmt := fmt.Sprintf("CREATE %sINDEX IF NOT EXISTS %s ON %s.%s USING %s (%s)%s",
-				uniqueStr, index.Name, schema.SQLName(), table.SQLName(), indexType, strings.Join(index.Columns, ", "), whereClause)
+				uniqueStr, index.Name, schema.SQLName(), table.SQLName(), indexType, strings.Join(columnExprs, ", "), whereClause)
 			statements = append(statements, stmt)
 		}
 	}
@@ -273,12 +290,14 @@ func (w *Writer) generateColumnDefinition(col *models.Column) string {
 	if col.Default != nil {
 		switch v := col.Default.(type) {
 		case string:
-			if strings.HasPrefix(v, "nextval") || strings.HasPrefix(v, "CURRENT_") || strings.Contains(v, "()") {
-				parts = append(parts, fmt.Sprintf("DEFAULT %s", v))
-			} else if v == "true" || v == "false" {
-				parts = append(parts, fmt.Sprintf("DEFAULT %s", v))
+			// Strip backticks - DBML uses them for SQL expressions but PostgreSQL doesn't
+			cleanDefault := stripBackticks(v)
+			if strings.HasPrefix(cleanDefault, "nextval") || strings.HasPrefix(cleanDefault, "CURRENT_") || strings.Contains(cleanDefault, "()") {
+				parts = append(parts, fmt.Sprintf("DEFAULT %s", cleanDefault))
+			} else if cleanDefault == "true" || cleanDefault == "false" {
+				parts = append(parts, fmt.Sprintf("DEFAULT %s", cleanDefault))
 			} else {
-				parts = append(parts, fmt.Sprintf("DEFAULT '%s'", escapeQuote(v)))
+				parts = append(parts, fmt.Sprintf("DEFAULT '%s'", escapeQuote(cleanDefault)))
 			}
 		case bool:
 			parts = append(parts, fmt.Sprintf("DEFAULT %v", v))
@@ -408,8 +427,10 @@ func (w *Writer) writeCreateTables(schema *models.Schema) error {
 			colDef := fmt.Sprintf("  %s %s", col.SQLName(), col.Type)
 
 			// Add default value if present
-			if col.Default != "" {
-				colDef += fmt.Sprintf(" DEFAULT %s", col.Default)
+			if col.Default != nil && col.Default != "" {
+				// Strip backticks - DBML uses them for SQL expressions but PostgreSQL doesn't
+				defaultVal := fmt.Sprintf("%v", col.Default)
+				colDef += fmt.Sprintf(" DEFAULT %s", stripBackticks(defaultVal))
 			}
 
 			columnDefs = append(columnDefs, colDef)
@@ -503,15 +524,24 @@ func (w *Writer) writeIndexes(schema *models.Schema) error {
 				indexName = fmt.Sprintf("%s_%s_%s", indexType, schema.SQLName(), table.SQLName())
 			}
 
-			// Build column list
-			columnNames := make([]string, 0, len(index.Columns))
+			// Build column list with operator class support for GIN indexes
+			columnExprs := make([]string, 0, len(index.Columns))
 			for _, colName := range index.Columns {
 				if col, ok := table.Columns[colName]; ok {
-					columnNames = append(columnNames, col.SQLName())
+					colExpr := col.SQLName()
+					// For GIN indexes on text columns, add operator class
+					if strings.EqualFold(index.Type, "gin") && isTextType(col.Type) {
+						opClass := extractOperatorClass(index.Comment)
+						if opClass == "" {
+							opClass = "gin_trgm_ops"
+						}
+						colExpr = fmt.Sprintf("%s %s", col.SQLName(), opClass)
+					}
+					columnExprs = append(columnExprs, colExpr)
 				}
 			}
 
-			if len(columnNames) == 0 {
+			if len(columnExprs) == 0 {
 				continue
 			}
 
@@ -520,10 +550,20 @@ func (w *Writer) writeIndexes(schema *models.Schema) error {
 				unique = "UNIQUE "
 			}
 
+			indexType := index.Type
+			if indexType == "" {
+				indexType = "btree"
+			}
+
+			whereClause := ""
+			if index.Where != "" {
+				whereClause = fmt.Sprintf(" WHERE %s", index.Where)
+			}
+
 			fmt.Fprintf(w.writer, "CREATE %sINDEX IF NOT EXISTS %s\n",
 				unique, indexName)
-			fmt.Fprintf(w.writer, "  ON %s.%s USING btree (%s);\n\n",
-				schema.SQLName(), table.SQLName(), strings.Join(columnNames, ", "))
+			fmt.Fprintf(w.writer, "  ON %s.%s USING %s (%s)%s;\n\n",
+				schema.SQLName(), table.SQLName(), indexType, strings.Join(columnExprs, ", "), whereClause)
 		}
 	}
 
@@ -718,11 +758,46 @@ func isIntegerType(colType string) bool {
 	return false
 }
 
+// isTextType checks if a column type is a text type (for GIN index operator class)
+func isTextType(colType string) bool {
+	textTypes := []string{"text", "varchar", "character varying", "char", "character", "string"}
+	lowerType := strings.ToLower(colType)
+	for _, t := range textTypes {
+		if strings.HasPrefix(lowerType, t) {
+			return true
+		}
+	}
+	return false
+}
+
+// extractOperatorClass extracts operator class from index comment/note
+// Looks for common operator classes like gin_trgm_ops, gist_trgm_ops, etc.
+func extractOperatorClass(comment string) string {
+	if comment == "" {
+		return ""
+	}
+	lowerComment := strings.ToLower(comment)
+	// Common GIN/GiST operator classes
+	opClasses := []string{"gin_trgm_ops", "gist_trgm_ops", "gin_bigm_ops", "jsonb_ops", "jsonb_path_ops", "array_ops"}
+	for _, op := range opClasses {
+		if strings.Contains(lowerComment, op) {
+			return op
+		}
+	}
+	return ""
+}
+
 // escapeQuote escapes single quotes in strings for SQL
 func escapeQuote(s string) string {
 	return strings.ReplaceAll(s, "'", "''")
 }
 
+// stripBackticks removes backticks from SQL expressions
+// DBML uses backticks for SQL expressions like `now()`, but PostgreSQL doesn't use backticks
+func stripBackticks(s string) string {
+	return strings.ReplaceAll(s, "`", "")
+}
+
 // extractSequenceName extracts sequence name from nextval() expression
 // Example: "nextval('public.users_id_seq'::regclass)" returns "users_id_seq"
 func extractSequenceName(defaultExpr string) string {