Avatica Overview

Avatica is a framework for building JDBC and ODBC drivers for databases, and an RPC wire protocol.

Avatica Architecture

Avatica’s Java binding has very few dependencies. Even though it is part of Apache Calcite it does not depend on other parts of Calcite. It depends only on JDK 1.7+ and Jackson.

Avatica’s wire protocol is JSON over HTTP. The Java implementation uses Jackson to convert request/response command objects to/from JSON.

Avatica-Server is a Java implementation of Avatica RPC.

Core concepts:

  • Meta is a local API sufficient to implement any Avatica provider
  • Factory creates implementations of the JDBC classes (Driver, Connection, Statement, ResultSet) on top of a Meta
  • Service is an interface that implements the functions of Meta in terms of request and response command objects

JDBC

Avatica implements JDBC by means of Factory. Factory creates implementations of the JDBC classes (Driver, Connection, Statement, PreparedStatement, ResultSet) on top of a Meta.

ODBC

Work has not started on Avatica ODBC.

Avatica ODBC would use the same wire protocol and could use the same server implementation in Java. The ODBC client would be written in C or C++.

Since the Avatica protocol abstracts many of the differences between providers, the same ODBC client could be used for different databases.

HTTP Server

Avatica-server embeds the Jetty HTTP server, providing a class HttpServer that implements the Avatica RPC protocol and can be run as a standalone Java application.

Connectors in HTTP server can be configured if needed by extending HttpServer class and overriding its configureConnector() method. For example, user can set requestHeaderSize to 64K bytes as follows:

HttpServer server = new HttpServer(handler) {
  @Override
  protected ServerConnector configureConnector(
      ServerConnector connector, int port) {
    HttpConnectionFactory factory = (HttpConnectionFactory)
        connector.getDefaultConnectionFactory();
    factory.getHttpConfiguration().setRequestHeaderSize(64 << 10);
    return super.configureConnector(connector, port);
  }
};
server.start();

Project structure

We know that it is important that client libraries have minimal dependencies.

Avatica is currently part of Apache Calcite. It does not depend upon any other part of Calcite. At some point Avatica could become a separate project.

Packages:

Status

Implemented

  • Create connection, create statement, metadata, prepare, bind, execute, fetch
  • RPC using JSON over HTTP
  • Local implementation
  • Implementation over an existing JDBC driver
  • Composite RPCs (combining several requests into one round trip)
    • Execute-Fetch
    • Metadata-Fetch (metadata calls such as getTables return all rows)

Not implemented

  • ODBC
  • RPCs
    • CloseStatement
    • CloseConnection
  • Composite RPCs
    • CreateStatement-Prepare
    • CloseStatement-CloseConnection
    • Prepare-Execute-Fetch (Statement.executeQuery should fetch first N rows)
  • Remove statements from statement table
  • DML (INSERT, UPDATE, DELETE)
  • Statement.execute applied to SELECT statement