feat(pgsql): enhance data type mapping to support serial types

pkg/readers/pgsql/queries.go

@@ -231,14 +231,13 @@ func (r *Reader) queryColumns(schemaName string) (map[string]map[string]*models.
 		}
 
 		column := models.InitColumn(columnName, tableName, schema)
-		column.Type = r.mapDataType(dataType, udtName)
-		column.NotNull = (isNullable == "NO")
-		column.Sequence = uint(ordinalPosition)
 
+		// Check if this is a serial type (has nextval default)
+		hasNextval := false
 		if columnDefault != nil {
-			// Parse default value - remove nextval for sequences
 			defaultVal := *columnDefault
 			if strings.HasPrefix(defaultVal, "nextval") {
+				hasNextval = true
 				column.AutoIncrement = true
 				column.Default = defaultVal
 			} else {
@@ -246,6 +245,11 @@ func (r *Reader) queryColumns(schemaName string) (map[string]map[string]*models.
 			}
 		}
 
+		// Map data type, preserving serial types when detected
+		column.Type = r.mapDataType(dataType, udtName, hasNextval)
+		column.NotNull = (isNullable == "NO")
+		column.Sequence = uint(ordinalPosition)
+
 		if description != nil {
 			column.Description = *description
 		}