# 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 API

- 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>4.3.0</version>
    </dependency>

- Gradle (in your `build.gradle` file):

    dependencies {
     compile 'io.vertx:vertx-pg-client:4.3.0'
    }

## 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
    SqlClient client = PgPool.client(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
    SqlClient client = PgPool.client(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
    SqlClient client = PgPool.client(vertx, connectOptions, poolOptions);

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

    client.close();

When you need to execute several operations on the same connection, you need to acquire a `connection` from a pool.

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 pool = PgPool.pool(vertx, connectOptions, poolOptions);

    // Get a connection from the pool
    pool.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.

## Command pipelining

In some use cases, command pipelining can improve database access performance.

You can configure the client to use pipelining

    PgPool pool = PgPool.pool(vertx, connectOptions.setPipeliningLimit(16), poolOptions);

The default pipelining limit is `256`.

You can set this value to `1` to disable pipelining.

## Pool versus pooled client

The `PgPool` allows you to create a pool or a pooled client

    SqlClient client = PgPool.client(vertx, connectOptions, poolOptions);

    // Pipelined
    Future<RowSet<Row>> res1 = client.query(sql).execute();

    // Connection pool
    PgPool pool = PgPool.pool(vertx, connectOptions, poolOptions);

    // Not pipelined
    Future<RowSet<Row>> res2 = pool.query(sql).execute();

- pool operations are not pipelined, only connections acquired from the pool are pipelined

- pooled client operations are pipelined, you cannot acquire a connection from a pooled client

## Pool sharing

You can share an pool between multiple verticles or instances of the same verticle. Such pool should be created outside a verticle otherwise it will be closed when the verticle that created it is undeployed

    PgPool pool = PgPool.pool(database, new PoolOptions().setMaxSize(maxSize));
    vertx.deployVerticle(() -> new AbstractVerticle() {
      @Override
      public void start() throws Exception {
        // Use the pool
      }
    }, new DeploymentOptions().setInstances(4));

You can also create a shared pool in each verticle:

    vertx.deployVerticle(() -> new AbstractVerticle() {
      PgPool pool;
      @Override
      public void start() {
        // Get or create a shared pool
        // this actually creates a lease to the pool
        // when the verticle is undeployed, the lease will be released automaticaly
        pool = PgPool.pool(database, new PoolOptions()
          .setMaxSize(maxSize)
          .setShared(true)
          .setName("my-pool"));
      }
    }, new DeploymentOptions().setInstances(4));

The first time a shared pool is created it will create the resources for the pool. Subsequent calls will reuse this pool and create a lease to this pool. The resources are disposed after all leases have been closed.

By default, a pool reuses the current event-loop when it needs to create a TCP connection. The shared pool will therefore randomly use event-loops of verticles using it.

You can assign a number of event loop a pool will use independently of the context using it

    PgPool pool = PgPool.pool(database, new PoolOptions()
      .setMaxSize(maxSize)
      .setShared(true)
      .setName("my-pool")
      .setEventLoopSize(4));

## Unix domain sockets

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.

## Connect retries

You can configure the client to retry when a connection fails to be established.

    options
      .setReconnectAttempts(2)
      .setReconnectInterval(1000);

## 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
    Map<String, String> props = new HashMap<>();
    props.put("search_path", "myschema");
    connectOptions.setProperties(props);

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

## 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'")
      .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());
      }
    });

### Prepared queries

You can do the same with prepared queries.

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

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

Query methods provides an asynchronous `RowSet` instance that works for SELECT queries

    client
      .preparedQuery("SELECT first_name, last_name FROM users")
      .execute(ar -> {
      if (ar.succeeded()) {
        RowSet<Row> rows = ar.result();
        for (Row row : rows) {
          System.out.println("User " + row.getString(0) + " " + row.getString(1));
        }
      } else {
        System.out.println("Failure: " + ar.cause().getMessage());
      }
    });

or UPDATE/INSERT queries:

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

The `Row` gives you access to your data by index

    System.out.println("User " + row.getString(0) + " " + row.getString(1));

or by name

    System.out.println("User " + row.getString("first_name") + " " + row.getString("last_name"));

The client will not do any magic here and the column name is identified with the name in the table regardless of how your SQL text is.

You can access a wide variety of of types

    String firstName = row.getString("first_name");
    Boolean male = row.getBoolean("male");
    Integer age = row.getInteger("age");

You can use cached prepared statements to execute one-shot prepared queries:

    connectOptions.setCachePreparedStatements(true);
    client
      .preparedQuery("SELECT * FROM users WHERE id = $1")
      .execute(Tuple.of("julien"), ar -> {
        if (ar.succeeded()) {
          RowSet<Row> rows = ar.result();
          System.out.println("Got " + rows.size() + " rows ");
        } else {
          System.out.println("Failure: " + ar.cause().getMessage());
        }
      });

You can create a `PreparedStatement` and manage the lifecycle by yourself.

    sqlConnection
      .prepare("SELECT * FROM users WHERE id = $1", ar -> {
        if (ar.succeeded()) {
          PreparedStatement preparedStatement = ar.result();
          preparedStatement.query()
            .execute(Tuple.of("julien"), ar2 -> {
              if (ar2.succeeded()) {
                RowSet<Row> rows = ar2.result();
                System.out.println("Got " + rows.size() + " rows ");
                preparedStatement.close();
              } else {
                System.out.println("Failure: " + ar2.cause().getMessage());
              }
            });
        } else {
          System.out.println("Failure: " + ar.cause().getMessage());
        }
      });

### Batches

You can execute prepared batch

    List<Tuple> batch = new ArrayList<>();
    batch.add(Tuple.of("julien", "Julien Viet"));
    batch.add(Tuple.of("emad", "Emad Alblueshi"));

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

        // Process rows
        RowSet<Row> rows = res.result();
      } else {
        System.out.println("Batch failed " + res.cause());
      }
    });

## Returning clauses

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"))
      .onSuccess(rows -> {
        for (Row row : rows) {
          System.out.println("generated key: " + row.getInteger("color_id"));
        }
    });

This works with any SQL as long as there is a `RETURNING` clause:

    client
      .query("DELETE FROM color RETURNING color_name")
      .execute()
      .onSuccess(rows -> {
        for (Row row : rows) {
          System.out.println("deleted color: " + row.getString("color_name"));
        }
      });

A batch query with a `RETURNING` clause creates a `RowSet` containing a single for each element of the batch:

    client
      .preparedQuery("INSERT INTO color (color_name) VALUES ($1) RETURNING color_id")
      .executeBatch(Arrays.asList(Tuple.of("white"), Tuple.of("red"), Tuple.of("blue")))
      .onSuccess(res -> {
        for (RowSet<Row> rows = res;rows.next() != null;rows = rows.next()) {
          Integer colorId = rows.iterator().next().getInteger("color_id");
          System.out.println("generated key: " + colorId);
        }
      });

## Using connections

### Getting a connection

When you need to execute sequential queries (without a transaction), you can create a new connection or borrow one from the pool. Remember that between acquiring the connection from the pool and returning it to the pool, you should take care of the connection because it might be closed by the server for some reason such as an idle time out.

    pool
      .getConnection()
      .compose(connection ->
        connection
          .preparedQuery("INSERT INTO Users (first_name,last_name) VALUES ($1, $2)")
          .executeBatch(Arrays.asList(
            Tuple.of("Julien", "Viet"),
            Tuple.of("Emad", "Alblueshi")
          ))
          .compose(res -> connection
            // Do something with rows
            .query("SELECT COUNT(*) FROM Users")
            .execute()
            .map(rows -> rows.iterator().next().getInteger(0)))
          // Return the connection to the pool
          .eventually(v -> connection.close())
      ).onSuccess(count -> {
      System.out.println("Insert users, now the number of users is " + count);
    });

Prepared queries can be created:

    connection
      .prepare("SELECT * FROM users WHERE first_name LIKE $1")
      .compose(pq ->
        pq.query()
          .execute(Tuple.of("Julien"))
          .eventually(v -> pq.close())
      ).onSuccess(rows -> {
      // All rows
    });

### Simplified connection API

When you use a pool, you can call `withConnection` to pass it a function executed within a connection.

It borrows a connection from the pool and calls the function with this connection.

The function must return a future of an arbitrary result.

After the future completes, the connection is returned to the pool and the overall result is provided.

    pool.withConnection(connection ->
      connection
        .preparedQuery("INSERT INTO Users (first_name,last_name) VALUES ($1, $2)")
        .executeBatch(Arrays.asList(
          Tuple.of("Julien", "Viet"),
          Tuple.of("Emad", "Alblueshi")
        ))
        .compose(res -> connection
          // Do something with rows
          .query("SELECT COUNT(*) FROM Users")
          .execute()
          .map(rows -> rows.iterator().next().getInteger(0)))
    ).onSuccess(count -> {
      System.out.println("Insert users, now the number of users is " + count);
    });

## Using transactions

### Transactions with connections

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

Or you can use the transaction API of `SqlConnection`:

    pool.getConnection()
      // Transaction must use a connection
      .onSuccess(conn -> {
      // Begin the transaction
      conn.begin()
        .compose(tx -> conn
          // Various statements
          .query("INSERT INTO Users (first_name,last_name) VALUES ('Julien','Viet')")
          .execute()
          .compose(res2 -> conn
            .query("INSERT INTO Users (first_name,last_name) VALUES ('Emad','Alblueshi')")
            .execute())
          // Commit the transaction
          .compose(res3 -> tx.commit()))
        // Return the connection to the pool
        .eventually(v -> conn.close())
        .onSuccess(v -> System.out.println("Transaction succeeded"))
        .onFailure(err -> System.out.println("Transaction failed: " + err.getMessage()));
    });

When the database server 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 `completion` future is failed with a `TransactionRollbackException`:

    tx.completion()
      .onFailure(err -> {
      System.out.println("Transaction failed => rolled back");
    });

### Simplified transaction API

When you use a pool, you can call `withTransaction` to pass it a function executed within a transaction.

It borrows a connection from the pool, begins the transaction and calls the function with a client executing all operations in the scope of this transaction.

The function must return a future of an arbitrary result:

- when the future succeeds the client will commit the transaction

- when the future fails the client will rollback the transaction

After the transaction completes, the connection is returned to the pool and the overall result is provided.

    pool.withTransaction(client -> client
      .query("INSERT INTO Users (first_name,last_name) VALUES ('Julien','Viet')")
      .execute()
      .flatMap(res -> client
        .query("INSERT INTO Users (first_name,last_name) VALUES ('Emad','Alblueshi')")
        .execute()
        // Map to a message result
        .map("Users inserted")))
      .onSuccess(v -> System.out.println("Transaction succeeded"))
      .onFailure(err -> System.out.println("Transaction failed: " + err.getMessage()));

## Cursors and streaming

By default prepared query execution fetches all rows, you can use a `Cursor` to control the amount of rows you want to read:

    connection.prepare("SELECT * FROM users WHERE first_name LIKE $1", ar0 -> {
      if (ar0.succeeded()) {
        PreparedStatement pq = ar0.result();

        // Cursors require to run within a transaction
        connection.begin(ar1 -> {
          if (ar1.succeeded()) {
            Transaction tx = ar1.result();

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

            // Read 50 rows
            cursor.read(50, ar2 -> {
              if (ar2.succeeded()) {
                RowSet<Row> rows = ar2.result();

                // Check for more ?
                if (cursor.hasMore()) {
                  // Repeat the process...
                } else {
                  // No more rows - commit the transaction
                  tx.commit();
                }
              }
            });
          }
        });
      }
    });

Cursors shall be closed when they are released prematurely:

    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", ar0 -> {
      if (ar0.succeeded()) {
        PreparedStatement pq = ar0.result();

        // Streams require to run within a transaction
        connection.begin(ar1 -> {
          if (ar1.succeeded()) {
            Transaction tx = ar1.result();

            // Fetch 50 rows at a time
            RowStream<Row> stream = pq.createStream(50, Tuple.of("julien"));

            // Use the stream
            stream.exceptionHandler(err -> {
              System.out.println("Error: " + err.getMessage());
            });
            stream.endHandler(v -> {
              // Close the stream to release the resources in the database
              stream.close(closed -> {
                tx.commit(committed -> {
                  System.out.println("End of stream");
                });
              });
            });
            stream.handler(row -> {
              System.out.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.

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.

## Tracing queries

The SQL client can trace query execution when Vert.x has tracing enabled.

The client reports the following client spans:

- `Query` operation name

- tags

- `db.user`: the database username

- `db.instance`: the database instance

- `db.statement`: the SQL query

- `db.type`: sql

The default tracing policy is `PROPAGATE`, the client will only create a span when involved in an active trace.

You can change the client policy with `setTracingPolicy`, e.g you can set `ALWAYS` to always report a span:

    options.setTracingPolicy(TracingPolicy.ALWAYS);

## 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`)

- INET (`io.vertx.pgclient.data.Inet`)

- MONEY (`io.vertx.pgclient.data.Money`)

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.addArrayOfString(new String[]{"another", "array"});

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

## Handling Date/Time infinity

PostgreSQL defines special values to represent infinity.

The max/min constants of the corresponding type represents special value.

- `OffsetDateTime.MAX`/OffsetDateTime.MIN`

- `LocalDateTime.MAX`/LocalDateTime.MIN`

- `LocalDate.MAX`/LocalDate.MIN`

    client
      .query("SELECT 'infinity'::DATE \"LocalDate\"")
      .execute(ar -> {
        if (ar.succeeded()) {
          Row row = ar.result().iterator().next();
          System.out.println(row.getLocalDate("LocalDate").equals(LocalDate.MAX));
        } else {
          System.out.println("Failure: " + ar.cause().getMessage());
        }
      });

## 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.

## Advanced pool configuration

### Server load balancing

You can configure the pool with a list of servers instead of a single server.

    PgPool pool = PgPool.pool(Arrays.asList(server1, server2, server3), options);

The pool uses a round-robin load balancing when a connection is created to select different servers.

Note | this provides load balancing when the connection is created and not when the connection is borrowed from the pool.

### Pool connection initialization

You can use the `connectHandler` to interact with a connection after it has been created and before it is inserted in the pool.

    pool.connectHandler(conn -> {
      conn.query(sql).execute().onSuccess(res -> {
        // Release the connection to the pool, ready to be used by the application
        conn.close();
      });
    });

Once you are done with the connection, you should simply close it to signal the pool to use it.

## RxJava 3 API

The client provides an Rxified version of the original API. The following examples use RxJava 3.

### Simple query

    Single<RowSet<Row>> single = pool.query("SELECT * FROM users WHERE id='julien'").rxExecute();

    // Execute the query
    single.subscribe(result -> {
      System.out.println("Got " + result.size() + " rows ");
    }, err -> {
      System.out.println("Failure: " + err.getMessage());
    });

### Connection

The simplified connection API allows to easily use a connection, the `withConnection` method borrows a connection from the pool and return it for you:

    Maybe<RowSet<Row>> maybe = pool.withConnection(conn ->
      conn
        .query("INSERT INTO Users (first_name,last_name) VALUES ('Julien','Viet')")
        .rxExecute()
        .flatMap(result -> conn
          .query("SELECT * FROM Users")
          .rxExecute())
        .toMaybe());

    maybe.subscribe(rows -> {
      // Success
    }, err -> {
      // Failed
    });

### Transaction

The simplified transaction API allows to easily write transactional asynchronous flows, The `withTransaction` method start and commit a transaction for you:

    Completable completable = pool.withTransaction(conn ->
      conn
        .query("INSERT INTO Users (first_name,last_name) VALUES ('Julien','Viet')")
        .rxExecute()
        .flatMap(result -> conn
          .query("INSERT INTO Users (first_name,last_name) VALUES ('Emad','Alblueshi')")
          .rxExecute())
        .toMaybe())
      .ignoreElement();

    completable.subscribe(() -> {
      // Transaction succeeded
    }, err -> {
      // Transaction failed
    });

### Streaming

RxJava supports `Observable` and `Flowable` types, these are exposed using the `RowStream` that you can get from a `PreparedQuery`:

    Observable<Row> observable = pool.rxGetConnection().flatMapObservable(conn -> conn
      .rxBegin()
      .flatMapObservable(tx ->
        conn
          .rxPrepare("SELECT * FROM users WHERE first_name LIKE $1")
          .flatMapObservable(preparedQuery -> {
            // Fetch 50 rows at a time
            RowStream<Row> stream = preparedQuery.createStream(50, Tuple.of("julien"));
            return stream.toObservable();
          })
          .doAfterTerminate(tx::commit)));

    // Then subscribe
    observable.subscribe(row -> {
      System.out.println("User: " + row.getString("last_name"));
    }, err -> {
      System.out.println("Error: " + err.getMessage());
    }, () -> {
      System.out.println("End of stream");
    });

The same example using `Flowable`:

    Flowable<Row> flowable = pool.rxGetConnection().flatMapPublisher(conn -> conn
      .rxBegin()
      .flatMapPublisher(tx ->
        conn
          .rxPrepare("SELECT * FROM users WHERE first_name LIKE $1")
          .flatMapPublisher(preparedQuery -> {
            // Fetch 50 rows at a time
            RowStream<Row> stream = preparedQuery.createStream(50, Tuple.of("julien"));
            return stream.toFlowable();
          })
          .doAfterTerminate(tx::commit)));

    // Then subscribe
    flowable.subscribe(new Subscriber<Row>() {

      private Subscription sub;

      @Override
      public void onSubscribe(Subscription subscription) {
        sub = subscription;
        subscription.request(1);
      }

      @Override
      public void onNext(Row row) {
        sub.request(1);
        System.out.println("User: " + row.getString("last_name"));
      }

      @Override
      public void onError(Throwable err) {
        System.out.println("Error: " + err.getMessage());
      }

      @Override
      public void onComplete() {
        System.out.println("End of stream");
      }
    });