reactive-pg-client

High performance reactive Postgres Client written in Java

View the Project on GitHub reactiverse/reactive-pg-client

Reactive Postgres Client

The Reactive Postgres Client is a client for Postgres 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.

Usage

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

[source,xml,subs#”+attributes”]

<dependency>
 <groupId>io.reactiverse</groupId>
 <artifactId>reactive-pg-client</artifactId>
 <version>0.10.6</version>
</dependency>
dependencies {
 compile 'io.reactiverse:reactive-pg-client:0.10.6'
}

Getting started

Here is the simplest way to connect, query and disconnect


// Pool options
def options = [
  port:5432,
  host:"the-host",
  database:"the-db",
  user:"user",
  password:"secret",
  maxSize:5
]

// Create the client pool
def client = PgClient.pool(options)

// A simple query
client.query("SELECT * FROM users WHERE id='julien'", { ar ->
  if (ar.succeeded()) {
    def result = ar.result()
    println("Got ${result.size()} rows ")
  } else {
    println("Failure: ${ar.cause().getMessage()}")
  }

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

Connecting to Postgres

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


// Pool options
def options = [
  port:5432,
  host:"the-host",
  database:"the-db",
  user:"user",
  password:"secret",
  maxSize:5
]

// Create the pooled client
def client = PgClient.pool(options)

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:


// Pool options
def options = [
  port:5432,
  host:"the-host",
  database:"the-db",
  user:"user",
  password:"secret",
  maxSize:5
]

// Create the pooled client
def client = PgClient.pool(vertx, options)

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


// Close the pool and all the associated resources
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:


// Pool options
def options = [
  port:5432,
  host:"the-host",
  database:"the-db",
  user:"user",
  password:"secret",
  maxSize:5
]

// Create the pooled client
def client = PgClient.pool(vertx, options)

// Get a connection from the pool
client.getConnection({ ar1 ->

  if (ar1.succeeded()) {

    println("Connected")

    // Obtain our connection
    def conn = ar1.result()

    // All operations execute on the same connection
    conn.query("SELECT * FROM users WHERE id='julien'", { ar2 ->
      if (ar2.succeeded()) {
        conn.query("SELECT * FROM users WHERE id='emad'", { ar3 ->
          // Release the connection to the pool
          conn.close()
        })
      } else {
        // Release the connection to the pool
        conn.close()
      }
    })
  } else {
    println("Could not connect: ${ar1.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.


// Pool Options
// Socket file name will be /var/run/postgresql/.s.PGSQL.5432
def options = [
  host:"/var/run/postgresql",
  port:5432,
  database:"the-db"
]

// Create the pooled client
def client = PgClient.pool(options)

// Create the pooled client with a vertx instance
// Make sure the vertx instance has enabled native transports
def client2 = PgClient.pool(vertx, options)

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

Configuration

There are several options for you to configure the client.

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


// Connection URI
def connectionUri = "postgresql://dbuser:[email protected]:3211/mydb"

// Create the pool from the connection URI
def pool = PgClient.pool(connectionUri)

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

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

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:

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

// Create the pool from the environment variables
def pool = PgClient.pool()

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

Running queries

When you don’t need a transaction or run single queries, you can run queries directly on the pool; the pool will use one of its connection to run the query and return the result to you.

Here is how to run simple queries:

client.query("SELECT * FROM users WHERE id='julien'", { ar ->
  if (ar.succeeded()) {
    def result = ar.result()
    println("Got ${result.size()} rows ")
  } else {
    println("Failure: ${ar.cause().getMessage()}")
  }
})

You can do the same with prepared queries.

The SQL string can refer to parameters by position, using $1, $2, etc…​

client.preparedQuery("SELECT * FROM users WHERE id=$1", Tuple.of("julien"), { ar ->
  if (ar.succeeded()) {
    def rows = ar.result()
    println("Got ${rows.size()} rows ")
  } else {
    println("Failure: ${ar.cause().getMessage()}")
  }
})

Query methods provides an asynchronous PgRowSet instance that works for SELECT queries

client.preparedQuery("SELECT first_name, last_name FROM users", { ar ->
  if (ar.succeeded()) {
    def rows = ar.result()
    rows.each { row ->
      println("User ${row.getString(0)} ${row.getString(1)}")
    }
  } else {
    println("Failure: ${ar.cause().getMessage()}")
  }
})

or UPDATE/INSERT queries:

client.preparedQuery("INSERT INTO users (first_name, last_name) VALUES ($1, $2)", Tuple.of("Julien", "Viet"), { ar ->
  if (ar.succeeded()) {
    def rows = ar.result()
    println(rows.rowCount())
  } else {
    println("Failure: ${ar.cause().getMessage()}")
  }
})

The Row gives you access to your data by index

println("User ${row.getString(0)} ${row.getString(1)}")

or by name

println("User ${row.getString("first_name")} ${row.getString("last_name")}")

You can access a wide variety of of types


def firstName = row.getString("first_name")
def male = row.getBoolean("male")
def age = row.getInteger("age")

// ...


You can execute prepared batch


// Add commands to the batch
def batch = []
batch.add(Tuple.of("julien", "Julien Viet"))
batch.add(Tuple.of("emad", "Emad Alblueshi"))

// Execute the prepared batch
client.preparedBatch("INSERT INTO USERS (id, name) VALUES ($1, $2)", batch, { res ->
  if (res.succeeded()) {

    // Process rows
    def rows = res.result()
  } else {
    println("Batch failed ${res.cause()}")
  }
})

You can cache prepared queries:


// Enable prepare statements
options.cachePreparedStatements = true

def client = PgClient.pool(vertx, options)

Using connections

When you need to execute sequential queries (without a transaction), you can create a new connection or borrow one from the pool:

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Prepared queries can be created:

connection.prepare("SELECT * FROM users WHERE first_name LIKE $1", { ar1 ->
  if (ar1.succeeded()) {
    def pq = ar1.result()
    pq.execute(Tuple.of("julien"), { ar2 ->
      if (ar2.succeeded()) {
        // All rows
        def rows = ar2.result()
      }
    })
  }
})

NOTE: prepared query caching depends on the setCachePreparedStatements and does not depend on whether you are creating prepared queries or use direct prepared queries

By default prepared query executions fetch all rows, you can use a PgCursor to control the amount of rows you want to read:

connection.prepare("SELECT * FROM users WHERE first_name LIKE $1", { ar1 ->
  if (ar1.succeeded()) {
    def pq = ar1.result()

    // Create a cursor
    def cursor = pq.cursor(Tuple.of("julien"))

    // Read 50 rows
    cursor.read(50, { ar2 ->
      if (ar2.succeeded()) {
        def rows = ar2.result()

        // Check for more ?
        if (cursor.hasMore()) {

          // Read the next 50
          cursor.read(50, { ar3 ->
            // More rows, and so on...
          })
        } else {
          // No more rows
        }
      }
    })
  }
})

Cursors shall be closed when they are released prematurely:

connection.prepare("SELECT * FROM users WHERE first_name LIKE $1", { ar1 ->
  if (ar1.succeeded()) {
    def pq = ar1.result()
    def cursor = pq.cursor(Tuple.of("julien"))
    cursor.read(50, { ar2 ->
      if (ar2.succeeded()) {
        // Close the cursor
        cursor.close()
      }
    })
  }
})

A stream API is also available for cursors, which can be more convenient, specially with the Rxified version.

connection.prepare("SELECT * FROM users WHERE first_name LIKE $1", { ar1 ->
  if (ar1.succeeded()) {
    def pq = ar1.result()

    // Fetch 50 rows at a time
    def stream = pq.createStream(50, Tuple.of("julien"))

    // Use the stream
    stream.exceptionHandler({ err ->
      println("Error: ${err.getMessage()}")
    })
    stream.endHandler({ v ->
      println("End of stream")
    })
    stream.handler({ row ->
      println("User: ${row.getString("last_name")}")
    })
  }
})

The stream read the rows by batch of 50 and stream them, when the rows have been passed to the handler, a new batch of 50 is read and so on.

The stream can be resumed or paused, the loaded rows will remain in memory until they are delivered and the cursor will stop iterating.

PgPreparedQuerycan perform efficient batching:

connection.prepare("INSERT INTO USERS (id, name) VALUES ($1, $2)", { ar1 ->
  if (ar1.succeeded()) {
    def prepared = ar1.result()

    // Create a query : bind parameters
    def batch = []

    // Add commands to the createBatch
    batch.add(Tuple.of("julien", "Julien Viet"))
    batch.add(Tuple.of("emad", "Emad Alblueshi"))

    prepared.batch(batch, { res ->
      if (res.succeeded()) {

        // Process rows
        def rows = res.result()
      } else {
        println("Batch failed ${res.cause()}")
      }
    })
  }
})

Using transactions

Transactions with connections

You can execute transaction using SQL BEGIN/COMMIT/ROLLBACK, if you do so you must use a PgConnection and manage it yourself.

Or you can use the transaction API of PgConnection:

Code not translatable

When Postgres reports the current transaction is failed (e.g the infamous current transaction is aborted, commands ignored until end of transaction block), the transaction is rollbacked and the abortHandler is called:

pool.getConnection({ res ->
  if (res.succeeded()) {

    // Transaction must use a connection
    def conn = res.result()

    // Begin the transaction
    def tx = conn.begin().abortHandler({ v ->
      println("Transaction failed => rollbacked")
    })

    conn.query("INSERT INTO Users (first_name,last_name) VALUES ('Julien','Viet')", { ar ->
      // Works fine of course
      if (ar.succeeded()) {

      } else {
        tx.rollback()
        conn.close()
      }
    })
    conn.query("INSERT INTO Users (first_name,last_name) VALUES ('Julien','Viet')", { ar ->
      // Fails and triggers transaction aborts
    })

    // Attempt to commit the transaction
    tx.commit({ ar ->
      // But transaction abortion fails it

      // Return the connection to the pool
      conn.close()
    })
  }
})

Simplified transaction API

When you use a pool, you can start a transaction directly on the pool.

It borrows a connection from the pool, begins the transaction and releases the connection to the pool when the transaction ends.

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Postgres type mapping

Currently the client supports the following Postgres types

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\"", { ar ->
  def rowSet = ar.result()
  def row = rowSet.iterator().next()

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

  // Convert to java.lang.Integer
  def 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\"", { ar ->
  def rowSet = ar.result()
  def row = rowSet.iterator().next()

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

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


Arrays of these types are supported.

Handling JSON

The Json Java type is used to represent the Postgres JSON and JSONB type.

The main reason of this type is handling null JSON values.


// Create a tuple
def tuple = Tuple.of(Json.create(Json.create(null)), Json.create(Json.create([
  foo:"bar"
])), Json.create(Json.create(null)))

// Retrieving json
def value = tuple.getJson(0).value()

//
value = tuple.getJson(1).value()

//
value = tuple.getJson(3).value()

Handling NUMERIC

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

def numeric = row.getNumeric("value")
if (numeric.isNaN()) {
  // Handle NaN
} else {
  def value = numeric.bigDecimalValue()
}

Handling arrays

Arrays are available on Tuple and Row:

Code not translatable

Handling custom types

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

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

client.preparedQuery("SELECT address, (address).city FROM address_book WHERE id=$1", Tuple.of(3), { ar ->
  if (ar.succeeded()) {
    def rows = ar.result()
    rows.each { row ->
      println("Full Address ${row.getString(0)}, City ${row.getString(1)}")
    }
  } else {
    println("Failure: ${ar.cause().getMessage()}")
  }
})

You can also write to Postgres by providing a string

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

Collector queries

You can use Java collectors with the query API:

Code not translatable

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:

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RxJava support

The rxified API supports RxJava 1 and RxJava 2, the following examples use RxJava 2.

Most asynchronous constructs are available as methods prefixed by rx:

Code not translatable

Streaming

RxJava 2 supports Observable and Flowable types, these are exposed using the PgStream that you can get from a PgPreparedQuery:

Code not translatable

The same example using Flowable:

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Transaction

The simplified transaction API allows to easily write transactional asynchronous flows:

Code not translatable

Pub/sub

Postgres supports pub/sub communication channels.

You can set a notificationHandler to receive Postgres notifications:


connection.notificationHandler({ notification ->
  println("Received ${notification.payload} on channel ${notification.channel}")
})

connection.query("LISTEN some-channel", { ar ->
  println("Subscribed to channel")
})

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


def subscriber = PgSubscriber.subscriber(vertx, [
  port:5432,
  host:"the-host",
  database:"the-db",
  user:"user",
  password:"secret"
])

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

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

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

The channel name that is given to the channel method will be the exact name of the channel as held by Postgres 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:


def subscriber = PgSubscriber.subscriber(vertx, [
  port:5432,
  host:"the-host",
  database:"the-db",
  user:"user",
  password:"secret"
])

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

    // PostgreSQL simple ID's are forced lower-case
    subscriber.channel("simple_channel").handler({ payload ->
      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'", { notified ->
        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 ->
      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:


def subscriber = PgSubscriber.subscriber(vertx, [
  port:5432,
  host:"the-host",
  database:"the-db",
  user:"user",
  password:"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.

Using SSL/TLS

To configure the client to use SSL connection, you can configure the PgConnectOptions like a Vert.x NetClient.


def options = [
  port:5432,
  host:"the-host",
  database:"the-db",
  user:"user",
  password:"secret",
  ssl:true,
  pemTrustOptions:[
    certPaths:[
      "/path/to/cert.pem"
    ]
  ]
]

PgClient.connect(vertx, options, { res ->
  if (res.succeeded()) {
    // Connected with SSL
  } else {
    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.