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pgclient.adoc

Reactive PostgreSQL Client

The Reactive PostgreSQL Client is a client for PostgreSQL with a straightforward API focusing on scalability and low overhead.

The client is reactive and non blocking, allowing to handle many database connections with a single thread.

  • Event driven

  • Lightweight

  • Built-in connection pooling

  • Prepared queries caching

  • Publish / subscribe using PostgreSQL NOTIFY/LISTEN

  • Batch and cursor

  • Row streaming

  • Command pipeling

  • RxJava 1 and RxJava 2

  • Direct memory to object without unnecessary copies

  • Java 8 Date and Time

  • SSL/TLS

  • Unix domain socket

  • HTTP/1.x CONNECT, SOCKS4a or SOCKS5 proxy support

Usage

To use the Reactive PostgreSQL Client add the following dependency to the dependencies section of your build descriptor:

  • Maven (in your pom.xml):

<dependency>
 <groupId>io.vertx</groupId>
 <artifactId>vertx-pg-client</artifactId>
 <version>4.0.0-SNAPSHOT</version>
</dependency>

  • Gradle (in your build.gradle file):

dependencies {
 compile 'io.vertx:vertx-pg-client:4.0.0-SNAPSHOT'
}

Getting started

Here is the simplest way to connect, query and disconnect

PgConnectOptions connectOptions = new PgConnectOptions()
  .setPort(5432)
  .setHost("the-host")
  .setDatabase("the-db")
  .setUser("user")
  .setPassword("secret");

// Pool options
PoolOptions poolOptions = new PoolOptions()
  .setMaxSize(5);

// Create the client pool
PgPool client = PgPool.pool(connectOptions, poolOptions);

// A simple query
client
  .query("SELECT * FROM users WHERE id='julien'")
  .execute(ar -> {
  if (ar.succeeded()) {
    RowSet<Row> result = ar.result();
    System.out.println("Got " + result.size() + " rows ");
  } else {
    System.out.println("Failure: " + ar.cause().getMessage());
  }

  // Now close the pool
  client.close();
});

Connecting to PostgreSQL

Most of the time you will use a pool to connect to PostgreSQL:

PgConnectOptions connectOptions = new PgConnectOptions()
  .setPort(5432)
  .setHost("the-host")
  .setDatabase("the-db")
  .setUser("user")
  .setPassword("secret");

// Pool options
PoolOptions poolOptions = new PoolOptions()
  .setMaxSize(5);

// Create the pooled client
PgPool client = PgPool.pool(connectOptions, poolOptions);

The pooled client uses a connection pool and any operation will borrow a connection from the pool to execute the operation and release it to the pool.

If you are running with Vert.x you can pass it your Vertx instance:

PgConnectOptions connectOptions = new PgConnectOptions()
  .setPort(5432)
  .setHost("the-host")
  .setDatabase("the-db")
  .setUser("user")
  .setPassword("secret");

// Pool options
PoolOptions poolOptions = new PoolOptions()
  .setMaxSize(5);

// Create the pooled client
PgPool client = PgPool.pool(vertx, connectOptions, poolOptions);

You need to release the pool when you don’t need it anymore:

pool.close();

When you need to execute several operations on the same connection, you need to use a client connection.

You can easily get one from the pool:

PgConnectOptions connectOptions = new PgConnectOptions()
  .setPort(5432)
  .setHost("the-host")
  .setDatabase("the-db")
  .setUser("user")
  .setPassword("secret");

// Pool options
PoolOptions poolOptions = new PoolOptions()
  .setMaxSize(5);

// Create the pooled client
PgPool client = PgPool.pool(vertx, connectOptions, poolOptions);

// Get a connection from the pool
client.getConnection().compose(conn -> {
  System.out.println("Got a connection from the pool");

  // All operations execute on the same connection
  return conn
    .query("SELECT * FROM users WHERE id='julien'")
    .execute()
    .compose(res -> conn
      .query("SELECT * FROM users WHERE id='emad'")
      .execute())
    .onComplete(ar -> {
      // Release the connection to the pool
      conn.close();
    });
}).onComplete(ar -> {
  if (ar.succeeded()) {

    System.out.println("Done");
  } else {
    System.out.println("Something went wrong " + ar.cause().getMessage());
  }
});

Once you are done with the connection you must close it to release it to the pool, so it can be reused.

Sometimes you want to improve performance via Unix domain socket connection, we achieve this with Vert.x Native transports.

Make sure you have added the required netty-transport-native dependency in your classpath and enabled the Unix domain socket option.

PgConnectOptions connectOptions = new PgConnectOptions()
  .setHost("/var/run/postgresql")
  .setPort(5432)
  .setDatabase("the-db");

// Pool options
PoolOptions poolOptions = new PoolOptions()
  .setMaxSize(5);

// Create the pooled client
PgPool client = PgPool.pool(connectOptions, poolOptions);

// Create the pooled client with a vertx instance
// Make sure the vertx instance has enabled native transports
PgPool client2 = PgPool.pool(vertx, connectOptions, poolOptions);

More information can be found in the [Vert.x documentation](https://vertx.io/docs/vertx-core/java/#_native_transports).

Configuration

There are several alternatives for you to configure the client.

data object

A simple way to configure the client is to specify a PgConnectOptions data object.

PgConnectOptions connectOptions = new PgConnectOptions()
  .setPort(5432)
  .setHost("the-host")
  .setDatabase("the-db")
  .setUser("user")
  .setPassword("secret");

// Pool Options
PoolOptions poolOptions = new PoolOptions().setMaxSize(5);

// Create the pool from the data object
PgPool pool = PgPool.pool(vertx, connectOptions, poolOptions);

pool.getConnection(ar -> {
  // Handling your connection
});

You can also configure the generic properties with the setProperties or addProperty methods. Note setProperties will override the default client properties.

For example, you can set a default schema for the connection with adding a search_path property.

PgConnectOptions connectOptions = new PgConnectOptions();

// Set the default schema
connectOptions.addProperty("search_path", "myschema");

More information about the available properties can be found in the PostgreSQL Manuals.

connection uri

Apart from configuring with a PgConnectOptions data object, We also provide you an alternative way to connect when you want to configure with a connection URI:

String connectionUri = "postgresql://dbuser:secretpassword@database.server.com:3211/mydb";

// Create the pool from the connection URI
PgPool pool = PgPool.pool(connectionUri);

// Create the connection from the connection URI
PgConnection.connect(vertx, connectionUri, res -> {
  // Handling your connection
});

More information about connection string formats can be found in the PostgreSQL Manuals.

Currently the client supports the following parameter key words in connection uri

  • host

  • hostaddr

  • port

  • user

  • password

  • dbname

  • sslmode

  • properties including(application_name, fallback_application_name, search_path)

Note: configuring properties in connection URI will override the default properties.

environment variables

You can also use environment variables to set default connection setting values, this is useful when you want to avoid hard-coding database connection information. You can refer to the official documentation for more details. The following parameters are supported:

  • PGHOST

  • PGHOSTADDR

  • PGPORT

  • PGDATABASE

  • PGUSER

  • PGPASSWORD

  • PGSSLMODE

If you don’t specify a data object or a connection URI string to connect, environment variables will take precedence over them.

$ PGUSER=user \
 PGHOST=the-host \
 PGPASSWORD=secret \
 PGDATABASE=the-db \
 PGPORT=5432 \
 PGSSLMODE=DISABLE
PgPool pool = PgPool.pool();

// Create the connection from the environment variables
PgConnection.connect(vertx, res -> {
  // Handling your connection
});

SASL SCRAM-SHA-256 authentication mechanism.

To use the sasl SCRAM-SHA-256 authentication add the following dependency to the dependencies section of your build descriptor:

  • Maven (in your pom.xml):

<dependency>
 <groupId>com.ongres.scram</groupId>
 <artifactId>client</artifactId>
 <version>2.1</version>
</dependency>

  • Gradle (in your build.gradle file):

dependencies {
 compile 'com.ongres.scram:client:2.1'
}

Note that SCRAM-SHA-256-PLUS (added in Postgresql 11) is not supported.

You can fetch generated keys with a 'RETURNING' clause in your query:

client
  .preparedQuery("INSERT INTO color (color_name) VALUES ($1), ($2), ($3) RETURNING color_id")
  .execute(Tuple.of("white", "red", "blue"), ar -> {
  if (ar.succeeded()) {
    RowSet<Row> rows = ar.result();
    System.out.println(rows.rowCount());
    for (Row row : rows) {
      System.out.println("generated key: " + row.getInteger("color_id"));
    }
  } else {
    System.out.println("Failure: " + ar.cause().getMessage());
  }
});

Note: PostreSQL destroys cursors at the end of a transaction, so the cursor API shall be used within a transaction, otherwise you will likely get the 34000 PostgreSQL error.

PostgreSQL type mapping

Currently the client supports the following PostgreSQL types

  • BOOLEAN (java.lang.Boolean)

  • INT2 (java.lang.Short)

  • INT4 (java.lang.Integer)

  • INT8 (java.lang.Long)

  • FLOAT4 (java.lang.Float)

  • FLOAT8 (java.lang.Double)

  • CHAR (java.lang.String)

  • VARCHAR (java.lang.String)

  • TEXT (java.lang.String)

  • ENUM (java.lang.String)

  • NAME (java.lang.String)

  • SERIAL2 (java.lang.Short)

  • SERIAL4 (java.lang.Integer)

  • SERIAL8 (java.lang.Long)

  • NUMERIC (io.vertx.sqlclient.data.Numeric)

  • UUID (java.util.UUID)

  • DATE (java.time.LocalDate)

  • TIME (java.time.LocalTime)

  • TIMETZ (java.time.OffsetTime)

  • TIMESTAMP (java.time.LocalDateTime)

  • TIMESTAMPTZ (java.time.OffsetDateTime)

  • INTERVAL (io.vertx.pgclient.data.Interval)

  • BYTEA (io.vertx.core.buffer.Buffer)

  • JSON (io.vertx.core.json.JsonObject, io.vertx.core.json.JsonArray, Number, Boolean, String, io.vertx.sqlclient.Tuple#JSON_NULL)

  • JSONB (io.vertx.core.json.JsonObject, io.vertx.core.json.JsonArray, Number, Boolean, String, io.vertx.sqlclient.Tuple#JSON_NULL)

  • POINT (io.vertx.pgclient.data.Point)

  • LINE (io.vertx.pgclient.data.Line)

  • LSEG (io.vertx.pgclient.data.LineSegment)

  • BOX (io.vertx.pgclient.data.Box)

  • PATH (io.vertx.pgclient.data.Path)

  • POLYGON (io.vertx.pgclient.data.Polygon)

  • CIRCLE (io.vertx.pgclient.data.Circle)

  • TSVECTOR (java.lang.String)

  • TSQUERY (java.lang.String)

Tuple decoding uses the above types when storing values, it also performs on the flu conversion the actual value when possible:

pool
  .query("SELECT 1::BIGINT \"VAL\"")
  .execute(ar -> {
  RowSet<Row> rowSet = ar.result();
  Row row = rowSet.iterator().next();

  // Stored as java.lang.Long
  Object value = row.getValue(0);

  // Convert to java.lang.Integer
  Integer intValue = row.getInteger(0);
});

Tuple encoding uses the above type mapping for encoding, unless the type is numeric in which case java.lang.Number is used instead:

pool
  .query("SELECT 1::BIGINT \"VAL\"")
  .execute(ar -> {
  RowSet<Row> rowSet = ar.result();
  Row row = rowSet.iterator().next();

  // Stored as java.lang.Long
  Object value = row.getValue(0);

  // Convert to java.lang.Integer
  Integer intValue = row.getInteger(0);
});

Arrays of these types are supported.

Handling JSON

PostgreSQL JSON and JSONB types are represented by the following Java types:

  • String

  • Number

  • Boolean

  • io.vertx.core.json.JsonObject

  • io.vertx.core.json.JsonArray

  • io.vertx.sqlclient.Tuple#JSON_NULL for representing the JSON null literal

Tuple tuple = Tuple.of(
  Tuple.JSON_NULL,
  new JsonObject().put("foo", "bar"),
  3);

// Retrieving json
Object value = tuple.getValue(0); // Expect JSON_NULL

//
value = tuple.get(JsonObject.class, 1); // Expect JSON object

//
value = tuple.get(Integer.class, 2); // Expect 3
value = tuple.getInteger(2); // Expect 3

Handling NUMERIC

The Numeric Java type is used to represent the PostgreSQL NUMERIC type.

Numeric numeric = row.get(Numeric.class, 0);
if (numeric.isNaN()) {
  // Handle NaN
} else {
  BigDecimal value = numeric.bigDecimalValue();
}

Handling arrays

Arrays are available on Tuple and Row:

Tuple tuple = Tuple.of(new String[]{ "a", "tuple", "with", "arrays" });

// Add a string array to the tuple
tuple.addStringArray(new String[]{"another", "array"});

// Get the first array of string
String[] array = tuple.getStringArray(0);

Handling custom types

Strings are used to represent custom types, both sent to and returned from Postgres.

You can read from PostgreSQL and get the custom type as a string

client
  .preparedQuery("SELECT address, (address).city FROM address_book WHERE id=$1")
  .execute(Tuple.of(3),  ar -> {
  if (ar.succeeded()) {
    RowSet<Row> rows = ar.result();
    for (Row row : rows) {
      System.out.println("Full Address " + row.getString(0) + ", City " + row.getString(1));
    }
  } else {
    System.out.println("Failure: " + ar.cause().getMessage());
  }
});

You can also write to PostgreSQL by providing a string

client
  .preparedQuery("INSERT INTO address_book (id, address) VALUES ($1, $2)")
  .execute(Tuple.of(3, "('Anytown', 'Second Ave', false)"),  ar -> {
  if (ar.succeeded()) {
    RowSet<Row> rows = ar.result();
    System.out.println(rows.rowCount());
  } else {
    System.out.println("Failure: " + ar.cause().getMessage());
  }
});

Handling text search

Text search is handling using java String

client
  .preparedQuery("SELECT to_tsvector( $1 ) @@ to_tsquery( $2 )")
  .execute(Tuple.of("fat cats ate fat rats", "fat & rat"),  ar -> {
  if (ar.succeeded()) {
    RowSet<Row> rows = ar.result();
    for (Row row : rows) {
      System.out.println("Match : " + row.getBoolean(0));
    }
  } else {
    System.out.println("Failure: " + ar.cause().getMessage());
  }
});

tsvector and tsquery can be fetched from db using java String

client
  .preparedQuery("SELECT to_tsvector( $1 ), to_tsquery( $2 )")
  .execute(Tuple.of("fat cats ate fat rats", "fat & rat"),  ar -> {
  if (ar.succeeded()) {
    RowSet<Row> rows = ar.result();
    for (Row row : rows) {
      System.out.println("Vector : " + row.getString(0) + ", query : "+row.getString(1));
    }
  } else {
    System.out.println("Failure: " + ar.cause().getMessage());
  }
});

Handling enumerated types

PostgreSQL enumerated types are mapped to java strings.

client
  .preparedQuery("INSERT INTO colors VALUES ($2)")
  .execute(Tuple.of("red"),  res -> {
    // ...
  });

Using Java enum types

You can map Java enum types to these column types:

  • Strings (VARCHAR, TEXT)

  • PosgreSQL enumerated types

  • Numbers (INT2, INT4, INT8)

client
  .preparedQuery("INSERT INTO colors VALUES ($1)")
  .execute(Tuple.of(Color.red))
  .flatMap(res ->
    client
      .preparedQuery("SELECT color FROM colors")
      .execute()
  ).onComplete(res -> {
    if (res.succeeded()) {
      RowSet<Row> rows = res.result();
      for (Row row : rows) {
        System.out.println(row.get(Color.class, "color"));
      }
    }
});

String and PostgreSQL enumerated types are matched with the Java enum’s name returned by the name() method.

Numbers types are matched with the Java enum’s ordinal returned by the ordinal() method.

Collector queries

You can use Java collectors with the query API:

Collector<Row, ?, Map<Long, String>> collector = Collectors.toMap(
  row -> row.getLong("id"),
  row -> row.getString("last_name"));

// Run the query with the collector
client.query("SELECT * FROM users")
  .collecting(collector)
  .execute(ar -> {
  if (ar.succeeded()) {
    SqlResult<Map<Long, String>> result = ar.result();

    // Get the map created by the collector
    Map<Long, String> map = result.value();
    System.out.println("Got " + map);
  } else {
    System.out.println("Failure: " + ar.cause().getMessage());
  }
});

The collector processing must not keep a reference on the Row as there is a single row used for processing the entire set.

The Java Collectors provides many interesting predefined collectors, for example you can create easily create a string directly from the row set:

Collector<Row, ?, String> collector = Collectors.mapping(
  row -> row.getString("last_name"),
  Collectors.joining(",", "(", ")")
);

// Run the query with the collector
client.query("SELECT * FROM users").collecting(collector).execute(ar -> {
    if (ar.succeeded()) {
      SqlResult<String> result = ar.result();

      // Get the string created by the collector
      String list = result.value();
      System.out.println("Got " + list);
    } else {
      System.out.println("Failure: " + ar.cause().getMessage());
    }
  });

Pub/sub

PostgreSQL supports pub/sub communication channels.

You can set a notificationHandler to receive PostgreSQL notifications:

connection.notificationHandler(notification -> {
  System.out.println("Received " + notification.getPayload() + " on channel " + notification.getChannel());
});

connection
  .query("LISTEN some-channel")
  .execute(ar -> {
  System.out.println("Subscribed to channel");
});

The PgSubscriber is a channel manager managing a single connection that provides per channel subscription:

PgSubscriber subscriber = PgSubscriber.subscriber(vertx, new PgConnectOptions()
  .setPort(5432)
  .setHost("the-host")
  .setDatabase("the-db")
  .setUser("user")
  .setPassword("secret")
);

// You can set the channel before connect
subscriber.channel("channel1").handler(payload -> {
  System.out.println("Received " + payload);
});

subscriber.connect(ar -> {
  if (ar.succeeded()) {

    // Or you can set the channel after connect
    subscriber.channel("channel2").handler(payload -> {
      System.out.println("Received " + payload);
    });
  }
});

The channel name that is given to the channel method will be the exact name of the channel as held by PostgreSQL for sending notifications. Note this is different than the representation of the channel name in SQL, and internally PgSubscriber will prepare the submitted channel name as a quoted identifier:

PgSubscriber subscriber = PgSubscriber.subscriber(vertx, new PgConnectOptions()
  .setPort(5432)
  .setHost("the-host")
  .setDatabase("the-db")
  .setUser("user")
  .setPassword("secret")
);

subscriber.connect(ar -> {
    if (ar.succeeded()) {
      // Complex channel name - name in PostgreSQL requires a quoted ID
      subscriber.channel("Complex.Channel.Name").handler(payload -> {
        System.out.println("Received " + payload);
      });
      subscriber.channel("Complex.Channel.Name").subscribeHandler(subscribed -> {
        subscriber.actualConnection()
          .query("NOTIFY \"Complex.Channel.Name\", 'msg'")
          .execute(notified -> {
            System.out.println("Notified \"Complex.Channel.Name\"");
          });
      });

      // PostgreSQL simple ID's are forced lower-case
      subscriber.channel("simple_channel").handler(payload -> {
          System.out.println("Received " + payload);
      });
      subscriber.channel("simple_channel").subscribeHandler(subscribed -> {
        // The following simple channel identifier is forced to lower case
        subscriber.actualConnection()
          .query("NOTIFY Simple_CHANNEL, 'msg'")
          .execute(notified -> {
            System.out.println("Notified simple_channel");
          });
      });

      // The following channel name is longer than the current
      // (NAMEDATALEN = 64) - 1 == 63 character limit and will be truncated
      subscriber.channel("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaabbbbb")
        .handler(payload -> {
        System.out.println("Received " + payload);
      });
    }
  });

You can provide a reconnect policy as a function that takes the number of retries as argument and returns an amountOfTime value:

  • when amountOfTime < 0: the subscriber is closed and there is no retry

  • when amountOfTime = 0: the subscriber retries to connect immediately

  • when amountOfTime > 0: the subscriber retries after amountOfTime milliseconds

PgSubscriber subscriber = PgSubscriber.subscriber(vertx, new PgConnectOptions()
  .setPort(5432)
  .setHost("the-host")
  .setDatabase("the-db")
  .setUser("user")
  .setPassword("secret")
);

// Reconnect at most 10 times after 100 ms each
subscriber.reconnectPolicy(retries -> {
  if (retries < 10) {
    return 100L;
  } else {
    return -1L;
  }
});

The default policy is to not reconnect.

Cancelling Request

PostgreSQL supports cancellation of requests in progress. You can cancel inflight requests using cancelRequest. Cancelling a request opens a new connection to the server and cancels the request and then close the connection.

connection
  .query("SELECT pg_sleep(20)")
  .execute(ar -> {
  if (ar.succeeded()) {
    // imagine this is a long query and is still running
    System.out.println("Query success");
  } else {
    // the server will abort the current query after cancelling request
    System.out.println("Failed to query due to " + ar.cause().getMessage());
  }
});
connection.cancelRequest(ar -> {
  if (ar.succeeded()) {
    System.out.println("Cancelling request has been sent");
  } else {
    System.out.println("Failed to send cancelling request");
  }
});

The cancellation signal might or might not have any effect — for example, if it arrives after the backend has finished processing the query, then it will have no effect. If the cancellation is effective, it results in the current command being terminated early with an error message.

More information can be found in the official documentation.

Using SSL/TLS

To configure the client to use SSL connection, you can configure the PgConnectOptions like a Vert.x NetClient. All SSL modes are supported and you are able to configure sslmode. The client is in DISABLE SSL mode by default. ssl parameter is kept as a mere shortcut for setting sslmode. setSsl(true) is equivalent to setSslMode(VERIFY_CA) and setSsl(false) is equivalent to setSslMode(DISABLE).

PgConnectOptions options = new PgConnectOptions()
  .setPort(5432)
  .setHost("the-host")
  .setDatabase("the-db")
  .setUser("user")
  .setPassword("secret")
  .setSslMode(SslMode.VERIFY_CA)
  .setPemTrustOptions(new PemTrustOptions().addCertPath("/path/to/cert.pem"));

PgConnection.connect(vertx, options, res -> {
  if (res.succeeded()) {
    // Connected with SSL
  } else {
    System.out.println("Could not connect " + res.cause());
  }
});

More information can be found in the Vert.x documentation.

Using a proxy

You can also configure the client to use an HTTP/1.x CONNECT, SOCKS4a or SOCKS5 proxy.

More information can be found in the Vert.x documentation.

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