io.cdap.plugin.db.SchemaReader Maven / Gradle / Ivy
/*
* Copyright © 2019 Cask Data, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package io.cdap.plugin.db;
import io.cdap.cdap.api.data.schema.Schema;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.List;
/**
* Main Interface to read db specific types.
*/
public interface SchemaReader {
/**
* Given the result set, get the metadata of the result set and return
* list of {@link io.cdap.cdap.api.data.schema.Schema.Field},
* where name of the field is same as column name and type of the field is obtained using
* {@link SchemaReader#getSchema(ResultSetMetaData, int)}
*
* @param resultSet result set of executed query
* @return list of schema fields
* @throws SQLException
*/
List getSchemaFields(ResultSet resultSet) throws SQLException;
/**
* Given a sql metadata return schema type
* @param metadata resultSet metadata
* @param index column index
* @return CDAP schema
* @throws SQLException
*/
Schema getSchema(ResultSetMetaData metadata, int index) throws SQLException;
/**
* Given a sql metadata indicates if sql column must be ignored and not included in the output schema. Thus we can
* support different data types for Sink and Source plugins.
*
* For example, in MS SQL 'TIMESTAMP' is the synonym for the 'ROWVERSION' data type, values of which are
* automatically generated and can not be inserted or updated. Therefore 'TIMESTAMP' can not be supported by Sink
* plugin. 'TIMESTAMP' reported as non-nullable column by JDBC connector, so inferred schema will be also
* non-nullable for this field, requiring to set a value. By ignoring this column we will avoid schema validation
* failure.
* @param metadata resultSet metadata
* @param index sql column index
* @return 'true' if sql column must not included in the output schema, 'false' otherwise
* @throws SQLException
*/
boolean shouldIgnoreColumn(ResultSetMetaData metadata, int index) throws SQLException;
}