presto-hive/src/main/java/io/prestosql/plugin/hive/metastore/thrift/BridgingHiveMetastore.java/BridgingHiveMetastore/addColumn
class BridgingHiveMetastore:    @Override
    public void addColumn(HiveIdentity identity, String databaseName, String tableName, String columnName, HiveType columnType, String columnComment)
    {
        Optional<org.apache.hadoop.hive.metastore.api.Table> source = delegate.getTable(identity, databaseName, tableName);
        if (!source.isPresent()) {
            throw new TableNotFoundException(new SchemaTableName(databaseName, tableName));
        }
        org.apache.hadoop.hive.metastore.api.Table table = source.get();
        table.getSd().getCols().add(
                new FieldSchema(columnName, columnType.getHiveTypeName().toString(), columnComment));
        alterTable(identity, databaseName, tableName, table);
    }