From 667a94531c0dc6eaca95612e09d9e803affe064a Mon Sep 17 00:00:00 2001
From: Aaron Piotrowski <aaron@trowski.com>
Date: Thu, 5 Jul 2018 00:11:37 -0500
Subject: [PATCH] Use decorators instead of Operation

---
 src/Connection.php            |  14 +-
 src/ConnectionListener.php    |  91 +++++++++
 src/ConnectionTransaction.php | 334 +++++++++++++++++++++++++++++++++
 src/Handle.php                |  24 +--
 src/Listener.php              |  84 +--------
 src/PgSqlHandle.php           |   4 +-
 src/PgSqlStatement.php        |  11 +-
 src/Pool.php                  |  31 +++-
 src/PooledListener.php        |  66 +++++++
 src/PooledResultSet.php       |  40 ++++
 src/PooledStatement.php       |  51 ++++++
 src/PooledTransaction.php     | 198 ++++++++++++++++++++
 src/PqHandle.php              |   5 +-
 src/PqStatement.php           |  16 +-
 src/PqUnbufferedResultSet.php |  18 +-
 src/Quoter.php                |  29 +++
 src/StatementPool.php         |  15 ++
 src/Transaction.php           | 335 +---------------------------------
 test/PoolTest.php             |  55 ------
 test/PooledStatementTest.php  |  80 --------
 20 files changed, 874 insertions(+), 627 deletions(-)
 create mode 100644 src/ConnectionListener.php
 create mode 100644 src/ConnectionTransaction.php
 create mode 100644 src/PooledListener.php
 create mode 100644 src/PooledResultSet.php
 create mode 100644 src/PooledStatement.php
 create mode 100644 src/PooledTransaction.php
 create mode 100644 src/Quoter.php
 create mode 100644 src/StatementPool.php
 delete mode 100644 test/PoolTest.php
 delete mode 100644 test/PooledStatementTest.php

diff --git a/src/Connection.php b/src/Connection.php
index 4aaa06f..3f26476 100644
--- a/src/Connection.php
+++ b/src/Connection.php
@@ -182,7 +182,7 @@ abstract class Connection implements Link, Handle
      *
      * @throws FailureException
      */
-    final public function transaction(int $isolation = Transaction::ISOLATION_COMMITTED): Promise
+    final public function transaction(int $isolation = ConnectionTransaction::ISOLATION_COMMITTED): Promise
     {
         if (! $this->handle) {
             throw new FailureException('Not connected');
@@ -190,19 +190,19 @@ abstract class Connection implements Link, Handle
 
         return call(function () use ($isolation) {
             switch ($isolation) {
-                case Transaction::ISOLATION_UNCOMMITTED:
+                case ConnectionTransaction::ISOLATION_UNCOMMITTED:
                     yield $this->handle->query("BEGIN TRANSACTION ISOLATION LEVEL READ UNCOMMITTED");
                     break;
 
-                case Transaction::ISOLATION_COMMITTED:
+                case ConnectionTransaction::ISOLATION_COMMITTED:
                     yield $this->handle->query("BEGIN TRANSACTION ISOLATION LEVEL READ COMMITTED");
                     break;
 
-                case Transaction::ISOLATION_REPEATABLE:
+                case ConnectionTransaction::ISOLATION_REPEATABLE:
                     yield $this->handle->query("BEGIN TRANSACTION ISOLATION LEVEL REPEATABLE READ");
                     break;
 
-                case Transaction::ISOLATION_SERIALIZABLE:
+                case ConnectionTransaction::ISOLATION_SERIALIZABLE:
                     yield $this->handle->query("BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE");
                     break;
 
@@ -212,9 +212,7 @@ abstract class Connection implements Link, Handle
 
             $this->busy = new Deferred;
 
-            $transaction = new Transaction($this->handle, $isolation);
-            $transaction->onDestruct($this->release);
-            return $transaction;
+            return new ConnectionTransaction($this->handle, $isolation, $this->release);
         });
     }
 
diff --git a/src/ConnectionListener.php b/src/ConnectionListener.php
new file mode 100644
index 0000000..9f16281
--- /dev/null
+++ b/src/ConnectionListener.php
@@ -0,0 +1,91 @@
+<?php
+
+namespace Amp\Postgres;
+
+use Amp\Iterator;
+use Amp\Promise;
+
+final class ConnectionListener implements Listener
+{
+    /** @var \Amp\Iterator */
+    private $iterator;
+
+    /** @var string */
+    private $channel;
+
+    /** @var callable|null */
+    private $unlisten;
+
+    /**
+     * @param \Amp\Iterator $iterator Iterator emitting notificatons on the channel.
+     * @param string $channel Channel name.
+     * @param callable(string $channel):  $unlisten Function invoked to unlisten from the channel.
+     */
+    public function __construct(Iterator $iterator, string $channel, callable $unlisten)
+    {
+        $this->iterator = $iterator;
+        $this->channel = $channel;
+        $this->unlisten = $unlisten;
+    }
+
+    public function __destruct()
+    {
+        if ($this->unlisten) {
+            $this->unlisten(); // Invokes $this->queue->complete().
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function advance(): Promise
+    {
+        return $this->iterator->advance();
+    }
+
+    /**
+     * {@inheritdoc}
+     *
+     * @return Notification
+     */
+    public function getCurrent(): Notification
+    {
+        return $this->iterator->getCurrent();
+    }
+
+    /**
+     * @return string Channel name.
+     */
+    public function getChannel(): string
+    {
+        return $this->channel;
+    }
+
+    /**
+     * @return bool
+     */
+    public function isListening(): bool
+    {
+        return $this->unlisten !== null;
+    }
+
+    /**
+     * Unlistens from the channel. No more values will be emitted from this listener.
+     *
+     * @return Promise<\Amp\Sql\CommandResult>
+     *
+     * @throws \Error If this method was previously invoked.
+     */
+    public function unlisten(): Promise
+    {
+        if (!$this->unlisten) {
+            throw new \Error("Already unlistened on this channel");
+        }
+
+        /** @var Promise $promise */
+        $promise = ($this->unlisten)($this->channel);
+        $this->unlisten = null;
+
+        return $promise;
+    }
+}
diff --git a/src/ConnectionTransaction.php b/src/ConnectionTransaction.php
new file mode 100644
index 0000000..fb635a7
--- /dev/null
+++ b/src/ConnectionTransaction.php
@@ -0,0 +1,334 @@
+<?php
+
+namespace Amp\Postgres;
+
+use Amp\Promise;
+use Amp\Sql\Transaction as SqlTransaction;
+use Amp\Sql\TransactionError;
+use function Amp\call;
+
+final class ConnectionTransaction implements Handle, Transaction
+{
+    /** @var Handle|null */
+    private $handle;
+
+    /** @var int */
+    private $isolation;
+
+    /** @var Internal\ReferenceQueue */
+    private $queue;
+
+    /** @var ConnectionListener[] */
+    private $listeners = [];
+
+    /**
+     * @param Handle $handle
+     * @param int $isolation
+     * @param callable $release
+     *
+     * @throws \Error If the isolation level is invalid.
+     */
+    public function __construct(Handle $handle, int $isolation = SqlTransaction::ISOLATION_COMMITTED, callable $release)
+    {
+        switch ($isolation) {
+            case SqlTransaction::ISOLATION_UNCOMMITTED:
+            case SqlTransaction::ISOLATION_COMMITTED:
+            case SqlTransaction::ISOLATION_REPEATABLE:
+            case SqlTransaction::ISOLATION_SERIALIZABLE:
+                $this->isolation = $isolation;
+                break;
+
+            default:
+                throw new \Error("Isolation must be a valid transaction isolation level");
+        }
+
+        $this->handle = $handle;
+        $this->queue = new Internal\ReferenceQueue;
+
+        $listeners =& $this->listeners;
+        $this->queue->onDestruct(static function () use (&$listeners) {
+            foreach ($listeners as $listener) {
+                if ($listener->isListening()) {
+                    $listener->unlisten();
+                }
+            }
+        });
+    }
+
+    public function __destruct()
+    {
+        if ($this->handle && $this->handle->isAlive()) {
+            $this->rollback(); // Invokes $this->queue->complete().
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function lastUsedAt(): int
+    {
+        return $this->handle->lastUsedAt();
+    }
+
+    /**
+     * {@inheritdoc}
+     *
+     * Closes and commits all changes in the transaction.
+     */
+    public function close()
+    {
+        if ($this->handle) {
+            $this->commit(); // Invokes $this->queue->unreference().
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function isAlive(): bool
+    {
+        return $this->handle && $this->handle->isAlive();
+    }
+
+    /**
+     * @return bool True if the transaction is active, false if it has been committed or rolled back.
+     */
+    public function isActive(): bool
+    {
+        return $this->handle !== null;
+    }
+
+    /**
+     * @return int
+     */
+    public function getIsolationLevel(): int
+    {
+        return $this->isolation;
+    }
+
+    /**
+     * {@inheritdoc}
+     *
+     * @throws TransactionError If the transaction has been committed or rolled back.
+     */
+    public function query(string $sql): Promise
+    {
+        if ($this->handle === null) {
+            throw new TransactionError("The transaction has been committed or rolled back");
+        }
+
+        $this->queue->reference();
+
+        $promise = $this->handle->query($sql);
+
+        $promise->onResolve(function ($exception, $result) {
+            if ($result instanceof Operation) {
+                $result->onDestruct([$this->queue, "unreference"]);
+                return;
+            }
+
+            $this->queue->unreference();
+        });
+
+        return $promise;
+    }
+
+    /**
+     * {@inheritdoc}
+     *
+     * @throws TransactionError If the transaction has been committed or rolled back.
+     */
+    public function prepare(string $sql): Promise
+    {
+        if ($this->handle === null) {
+            throw new TransactionError("The transaction has been committed or rolled back");
+        }
+
+        $this->queue->reference();
+
+        $promise = $this->handle->prepare($sql);
+
+        $promise->onResolve(function ($exception, $statement) {
+            if ($statement instanceof Operation) {
+                $statement->onDestruct([$this->queue, "unreference"]);
+                return;
+            }
+
+            $this->queue->unreference();
+        });
+
+        return $promise;
+    }
+
+    /**
+     * {@inheritdoc}
+     *
+     * @throws TransactionError If the transaction has been committed or rolled back.
+     */
+    public function execute(string $sql, array $params = []): Promise
+    {
+        if ($this->handle === null) {
+            throw new TransactionError("The transaction has been committed or rolled back");
+        }
+
+        $this->queue->reference();
+
+        $promise = $this->handle->execute($sql, $params);
+
+        $promise->onResolve(function ($exception, $result) {
+            if ($result instanceof Operation) {
+                $result->onDestruct([$this->queue, "unreference"]);
+                return;
+            }
+
+            $this->queue->unreference();
+        });
+
+        return $promise;
+    }
+
+
+    /**
+     * {@inheritdoc}
+     *
+     * @throws TransactionError If the transaction has been committed or rolled back.
+     */
+    public function notify(string $channel, string $payload = ""): Promise
+    {
+        if ($this->handle === null) {
+            throw new TransactionError("The transaction has been committed or rolled back");
+        }
+
+        return $this->handle->notify($channel, $payload);
+    }
+
+    /**
+     * Commits the transaction and makes it inactive.
+     *
+     * @return Promise<\Amp\Sql\CommandResult>
+     *
+     * @throws TransactionError If the transaction has been committed or rolled back.
+     */
+    public function commit(): Promise
+    {
+        if ($this->handle === null) {
+            throw new TransactionError("The transaction has been committed or rolled back");
+        }
+
+        $promise = $this->handle->query("COMMIT");
+        $this->handle = null;
+        $promise->onResolve([$this->queue, "unreference"]);
+
+        return $promise;
+    }
+
+    /**
+     * Rolls back the transaction and makes it inactive.
+     *
+     * @return Promise<\Amp\Sql\CommandResult>
+     *
+     * @throws TransactionError If the transaction has been committed or rolled back.
+     */
+    public function rollback(): Promise
+    {
+        if ($this->handle === null) {
+            throw new TransactionError("The transaction has been committed or rolled back");
+        }
+
+        $promise = $this->handle->query("ROLLBACK");
+        $this->handle = null;
+        $promise->onResolve([$this->queue, "unreference"]);
+
+        return $promise;
+    }
+
+    /**
+     * Creates a savepoint with the given identifier.
+     *
+     * @param string $identifier Savepoint identifier.
+     *
+     * @return Promise<\Amp\Sql\CommandResult>
+     *
+     * @throws TransactionError If the transaction has been committed or rolled back.
+     */
+    public function createSavepoint(string $identifier): Promise
+    {
+        return $this->query("SAVEPOINT " . $this->quoteName($identifier));
+    }
+
+    /**
+     * Rolls back to the savepoint with the given identifier.
+     *
+     * @param string $identifier Savepoint identifier.
+     *
+     * @return Promise<\Amp\Sql\CommandResult>
+     *
+     * @throws TransactionError If the transaction has been committed or rolled back.
+     */
+    public function rollbackTo(string $identifier): Promise
+    {
+        return $this->query("ROLLBACK TO " . $this->quoteName($identifier));
+    }
+
+    /**
+     * Releases the savepoint with the given identifier.
+     *
+     * @param string $identifier Savepoint identifier.
+     *
+     * @return Promise<\Amp\Sql\CommandResult>
+     *
+     * @throws TransactionError If the transaction has been committed or rolled back.
+     */
+    public function releaseSavepoint(string $identifier): Promise
+    {
+        return $this->query("RELEASE SAVEPOINT " . $this->quoteName($identifier));
+    }
+
+    /**
+     * {@inheritdoc}
+     *
+     * Listeners automatically unlisten when the transaction is committed or rolled back.
+     *
+     * @throws TransactionError If the transaction has been committed or rolled back.
+     */
+    public function listen(string $channel): Promise
+    {
+        if ($this->handle === null) {
+            throw new TransactionError("The transaction has been committed or rolled back");
+        }
+
+        return call(function () use ($channel) {
+            $listener = yield $this->handle->listen($channel);
+            $this->listeners[] = $listener;
+            return $listener;
+        });
+    }
+
+    /**
+     * {@inheritdoc}
+     *
+     * @throws TransactionError If the transaction has been committed or rolled back.
+     */
+    public function quoteString(string $data): string
+    {
+        if ($this->handle === null) {
+            throw new TransactionError("The transaction has been committed or rolled back");
+        }
+
+        return $this->handle->quoteString($data);
+    }
+
+    /**
+     * {@inheritdoc}
+     *
+     * @throws TransactionError If the transaction has been committed or rolled back.
+     */
+    public function quoteName(string $name): string
+    {
+        if ($this->handle === null) {
+            throw new TransactionError("The transaction has been committed or rolled back");
+        }
+
+        return $this->handle->quoteName($name);
+    }
+}
diff --git a/src/Handle.php b/src/Handle.php
index b393511..ad17d6f 100644
--- a/src/Handle.php
+++ b/src/Handle.php
@@ -2,28 +2,6 @@
 
 namespace Amp\Postgres;
 
-interface Handle extends Executor
+interface Handle extends Executor, Quoter
 {
-    /**
-     * Quotes (escapes) the given string for use as a string literal or identifier in a query. This method wraps the
-     * string in single quotes, so additional quotes should not be added in the query.
-     *
-     * @param string $data Unquoted data.
-     *
-     * @return string Quoted string wrapped in single quotes.
-     *
-     * @throws \Error If the connection to the database has been closed.
-     */
-    public function quoteString(string $data): string;
-
-    /**
-     * Quotes (escapes) the given string for use as a name or identifier in a query.
-     *
-     * @param string $name Unquoted identifier.
-     *
-     * @return string Quoted identifier.
-     *
-     * @throws \Error If the connection to the database has been closed.
-     */
-    public function quoteName(string $name): string;
 }
diff --git a/src/Listener.php b/src/Listener.php
index 8f15665..3006791 100644
--- a/src/Listener.php
+++ b/src/Listener.php
@@ -4,83 +4,18 @@ namespace Amp\Postgres;
 
 use Amp\Iterator;
 use Amp\Promise;
-use Amp\Sql\Operation;
 
-final class Listener implements Iterator, Operation
+interface Listener extends Iterator
 {
-    /** @var \Amp\Iterator */
-    private $iterator;
-
-    /** @var string */
-    private $channel;
-
-    /** @var callable|null */
-    private $unlisten;
-
-    /** @var Internal\ReferenceQueue */
-    private $queue;
-
-    /**
-     * @param \Amp\Iterator $iterator Iterator emitting notificatons on the channel.
-     * @param string $channel Channel name.
-     * @param callable(string $channel):  $unlisten Function invoked to unlisten from the channel.
-     */
-    public function __construct(Iterator $iterator, string $channel, callable $unlisten)
-    {
-        $this->iterator = $iterator;
-        $this->channel = $channel;
-        $this->unlisten = $unlisten;
-        $this->queue = new Internal\ReferenceQueue;
-    }
-
-    public function __destruct()
-    {
-        if ($this->unlisten) {
-            $this->unlisten(); // Invokes $this->queue->complete().
-        }
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function onDestruct(callable $onComplete)
-    {
-        $this->queue->onDestruct($onComplete);
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function advance(): Promise
-    {
-        return $this->iterator->advance();
-    }
-
-    /**
-     * {@inheritdoc}
-     *
-     * @return Notification
-     */
-    public function getCurrent(): Notification
-    {
-        return $this->iterator->getCurrent();
-    }
-
     /**
      * @return string Channel name.
      */
-    public function getChannel(): string
-    {
-        return $this->channel;
-    }
+    public function getChannel(): string;
 
     /**
      * @return bool
      */
-    public function isListening(): bool
-    {
-        return $this->unlisten !== null;
-    }
+    public function isListening(): bool;
 
     /**
      * Unlistens from the channel. No more values will be emitted from this listener.
@@ -89,16 +24,5 @@ final class Listener implements Iterator, Operation
      *
      * @throws \Error If this method was previously invoked.
      */
-    public function unlisten(): Promise
-    {
-        if (!$this->unlisten) {
-            throw new \Error("Already unlistened on this channel");
-        }
-
-        /** @var Promise $promise */
-        $promise = ($this->unlisten)($this->channel);
-        $this->unlisten = null;
-        $promise->onResolve([$this->queue, "unreference"]);
-        return $promise;
-    }
+    public function unlisten(): Promise;
 }
diff --git a/src/PgSqlHandle.php b/src/PgSqlHandle.php
index 061c4b5..35b5551 100644
--- a/src/PgSqlHandle.php
+++ b/src/PgSqlHandle.php
@@ -189,7 +189,7 @@ final class PgSqlHandle implements Handle
      */
     public function isAlive(): bool
     {
-        return $this->handle !== null;
+        return \is_resource($this->handle);
     }
 
     /**
@@ -448,7 +448,7 @@ final class PgSqlHandle implements Handle
             }
 
             Loop::enable($this->poll);
-            return new Listener($emitter->iterate(), $channel, $this->unlisten);
+            return new ConnectionListener($emitter->iterate(), $channel, $this->unlisten);
         });
     }
 
diff --git a/src/PgSqlStatement.php b/src/PgSqlStatement.php
index aa9fdf3..3d6790e 100644
--- a/src/PgSqlStatement.php
+++ b/src/PgSqlStatement.php
@@ -3,10 +3,9 @@
 namespace Amp\Postgres;
 
 use Amp\Promise;
-use Amp\Sql\Operation;
 use Amp\Sql\Statement;
 
-final class PgSqlStatement implements Statement, Operation
+final class PgSqlStatement implements Statement
 {
     /** @var PgSqlHandle */
     private $handle;
@@ -38,14 +37,12 @@ final class PgSqlStatement implements Statement, Operation
         $this->name = $name;
         $this->sql = $sql;
         $this->params = $params;
-        $this->queue = new Internal\ReferenceQueue;
         $this->lastUsedAt = \time();
     }
 
     public function __destruct()
     {
         $this->handle->statementDeallocate($this->name);
-        $this->queue->unreference();
     }
 
     /** {@inheritdoc} */
@@ -71,10 +68,4 @@ final class PgSqlStatement implements Statement, Operation
     {
         return $this->handle->statementExecute($this->name, Internal\replaceNamedParams($params, $this->params));
     }
-
-    /** {@inheritdoc} */
-    public function onDestruct(callable $onDestruct)
-    {
-        $this->queue->onDestruct($onDestruct);
-    }
 }
diff --git a/src/Pool.php b/src/Pool.php
index 9640874..1cbac83 100644
--- a/src/Pool.php
+++ b/src/Pool.php
@@ -6,6 +6,11 @@ use Amp\Coroutine;
 use Amp\Promise;
 use Amp\Sql\AbstractPool;
 use Amp\Sql\Connector;
+use Amp\Sql\Pool as SqlPool;
+use Amp\Sql\ResultSet as SqlResultSet;
+use Amp\Sql\Statement as SqlStatement;
+use Amp\Sql\StatementPool as SqlStatementPool;
+use Amp\Sql\Transaction as SqlTransaction;
 use function Amp\call;
 
 final class Pool extends AbstractPool implements Link
@@ -27,6 +32,28 @@ final class Pool extends AbstractPool implements Link
         return connector();
     }
 
+    protected function createStatement(SqlStatement $statement, callable $release): SqlStatement
+    {
+        return new PooledStatement($statement, $release);
+    }
+
+    protected function createStatementPool(SqlPool $pool, SqlStatement $statement, callable $prepare): SqlStatementPool
+    {
+        return new StatementPool($pool, $statement, $prepare);
+    }
+
+    protected function createTransaction(SqlTransaction $transaction, callable $release): SqlTransaction
+    {
+        \assert($transaction instanceof Transaction);
+        return new PooledTransaction($transaction, $release);
+    }
+
+    protected function createResultSet(SqlResultSet $resultSet, callable $release): SqlResultSet
+    {
+        \assert($resultSet instanceof ResultSet);
+        return new PooledResultSet($resultSet, $release);
+    }
+
     /**
      * @param bool $reset True to automatically execute RESET ALL on a connection before it is used by the pool.
      */
@@ -94,15 +121,13 @@ final class Pool extends AbstractPool implements Link
                 throw $exception;
             }
 
-            $listener->onDestruct(function () {
+            return new PooledListener($listener, function () {
                 if (--$this->listenerCount === 0) {
                     $connection = $this->listeningConnection;
                     $this->listeningConnection = null;
                     $this->push($connection);
                 }
             });
-
-            return $listener;
         });
     }
 }
diff --git a/src/PooledListener.php b/src/PooledListener.php
new file mode 100644
index 0000000..5fdd2cc
--- /dev/null
+++ b/src/PooledListener.php
@@ -0,0 +1,66 @@
+<?php
+
+namespace Amp\Postgres;
+
+use Amp\Promise;
+
+class PooledListener implements Listener
+{
+    /** @var Listener */
+    private $listener;
+
+    /** @var callable|null */
+    private $release;
+
+    public function __construct(Listener $listener, callable $release)
+    {
+        $this->listener = $listener;
+        $this->release = $release;
+
+        if (!$this->listener->isListening()) {
+            ($this->release)();
+            $this->release = null;
+        }
+    }
+
+    public function __destruct()
+    {
+        if ($this->listener->isListening()) {
+            $this->unlisten(); // Invokes $this->release callback.
+        }
+    }
+
+    public function advance(): Promise
+    {
+        return $this->listener->advance();
+    }
+
+    public function getCurrent()
+    {
+        return $this->listener->getCurrent();
+    }
+
+    public function getChannel(): string
+    {
+        return $this->listener->getChannel();
+    }
+
+    public function isListening(): bool
+    {
+        return $this->listener->isListening();
+    }
+
+    public function unlisten(): Promise
+    {
+        if (!$this->release) {
+            throw new \Error("Already unlistened on this channel");
+        }
+
+        $promise = $this->listener->unlisten();
+        $promise->onResolve($this->release);
+
+        $this->release = null;
+
+        return $promise;
+    }
+}
diff --git a/src/PooledResultSet.php b/src/PooledResultSet.php
new file mode 100644
index 0000000..465d40b
--- /dev/null
+++ b/src/PooledResultSet.php
@@ -0,0 +1,40 @@
+<?php
+
+namespace Amp\Postgres;
+
+use Amp\Promise;
+
+class PooledResultSet implements ResultSet
+{
+    /** @var ResultSet */
+    private $result;
+
+    /** @var callable|null */
+    private $release;
+
+    public function __construct(ResultSet $result, callable $release)
+    {
+        $this->result = $result;
+        $this->release = $release;
+    }
+
+    public function __destruct()
+    {
+        ($this->release)();
+    }
+
+    public function advance(int $type = self::FETCH_ASSOC): Promise
+    {
+        return $this->result->advance($type);
+    }
+
+    public function getCurrent()
+    {
+        return $this->result->getCurrent();
+    }
+
+    public function numFields(): int
+    {
+        return $this->result->numFields();
+    }
+}
diff --git a/src/PooledStatement.php b/src/PooledStatement.php
new file mode 100644
index 0000000..0e482b3
--- /dev/null
+++ b/src/PooledStatement.php
@@ -0,0 +1,51 @@
+<?php
+
+namespace Amp\Postgres;
+
+use Amp\Promise;
+use Amp\Sql\Statement;
+
+class PooledStatement implements Statement
+{
+    /** @var Statement */
+    private $statement;
+
+    /** @var callable|null */
+    private $release;
+
+    public function __construct(Statement $statement, callable $release)
+    {
+        $this->statement = $statement;
+        $this->release = $release;
+
+        if (!$this->statement->isAlive()) {
+            ($this->release)();
+            $this->release = null;
+        }
+    }
+
+    public function __destruct()
+    {
+        ($this->release)();
+    }
+
+    public function execute(array $params = []): Promise
+    {
+        return $this->statement->execute($params);
+    }
+
+    public function isAlive(): bool
+    {
+        return $this->statement->isAlive();
+    }
+
+    public function getQuery(): string
+    {
+        return $this->statement->getQuery();
+    }
+
+    public function lastUsedAt(): int
+    {
+        return $this->statement->lastUsedAt();
+    }
+}
diff --git a/src/PooledTransaction.php b/src/PooledTransaction.php
new file mode 100644
index 0000000..f6699b6
--- /dev/null
+++ b/src/PooledTransaction.php
@@ -0,0 +1,198 @@
+<?php
+
+namespace Amp\Postgres;
+
+use Amp\Promise;
+use Amp\Sql\TransactionError;
+
+class PooledTransaction implements Transaction
+{
+    /** @var Transaction|null */
+    private $transaction;
+
+    /** @var callable|null */
+    private $release;
+
+    /**
+     * PooledTransaction constructor.
+     *
+     * @param Transaction $transaction
+     * @param callable    $release
+     */
+    public function __construct(Transaction $transaction, callable $release)
+    {
+        $this->transaction = $transaction;
+        $this->release = $release;
+
+        if (!$this->transaction->isActive()) {
+            ($this->release)();
+            $this->transaction = null;
+            $this->release = null;
+        }
+    }
+
+    public function __destruct()
+    {
+        if ($this->transaction && $this->transaction->isActive()) {
+            $this->close(); // Invokes $this->release callback.
+        }
+    }
+
+    public function query(string $sql): Promise
+    {
+        if (!$this->transaction) {
+            throw new TransactionError("The transaction has been committed or rolled back");
+        }
+
+        return $this->transaction->query($sql);
+    }
+
+    public function prepare(string $sql): Promise
+    {
+        if (!$this->transaction) {
+            throw new TransactionError("The transaction has been committed or rolled back");
+        }
+
+        return $this->transaction->prepare($sql);
+    }
+
+    public function execute(string $sql, array $params = []): Promise
+    {
+        if (!$this->transaction) {
+            throw new TransactionError("The transaction has been committed or rolled back");
+        }
+
+        return $this->transaction->execute($sql, $params);
+    }
+
+    public function notify(string $channel, string $payload = ""): Promise
+    {
+        if (!$this->transaction) {
+            throw new TransactionError("The transaction has been committed or rolled back");
+        }
+
+        return $this->transaction->notify($channel, $payload);
+    }
+
+    public function listen(string $channel): Promise
+    {
+        if (!$this->transaction) {
+            throw new TransactionError("The transaction has been committed or rolled back");
+        }
+
+        return $this->transaction->listen($channel);
+    }
+
+    public function isAlive(): bool
+    {
+        return $this->transaction && $this->transaction->isAlive();
+    }
+
+    public function lastUsedAt(): int
+    {
+        if (!$this->transaction) {
+            throw new TransactionError("The transaction has been committed or rolled back");
+        }
+
+        return $this->transaction->lastUsedAt();
+    }
+
+    public function close()
+    {
+        if (!$this->transaction) {
+            return;
+        }
+
+        $promise = $this->transaction->commit();
+        $promise->onResolve($this->release);
+
+        $this->transaction = null;
+    }
+
+    public function quoteString(string $data): string
+    {
+        if (!$this->transaction) {
+            throw new TransactionError("The transaction has been committed or rolled back");
+        }
+
+        return $this->transaction->quoteString($data);
+    }
+
+    public function quoteName(string $name): string
+    {
+        if (!$this->transaction) {
+            throw new TransactionError("The transaction has been committed or rolled back");
+        }
+
+        return $this->transaction->quoteName($name);
+    }
+
+    public function getIsolationLevel(): int
+    {
+        if (!$this->transaction) {
+            throw new TransactionError("The transaction has been committed or rolled back");
+        }
+
+        return $this->transaction->getIsolationLevel();
+    }
+
+    public function isActive(): bool
+    {
+        return $this->transaction && $this->transaction->isActive();
+    }
+
+    public function commit(): Promise
+    {
+        if (!$this->transaction) {
+            throw new TransactionError("The transaction has been committed or rolled back");
+        }
+
+        $promise = $this->transaction->commit();
+        $promise->onResolve($this->release);
+
+        $this->transaction = null;
+
+        return $promise;
+    }
+
+    public function rollback(): Promise
+    {
+        if (!$this->transaction) {
+            throw new TransactionError("The transaction has been committed or rolled back");
+        }
+
+        $promise = $this->transaction->rollback();
+        $promise->onResolve($this->release);
+
+        $this->transaction = null;
+
+        return $promise;
+    }
+
+    public function createSavepoint(string $identifier): Promise
+    {
+        if (!$this->transaction) {
+            throw new TransactionError("The transaction has been committed or rolled back");
+        }
+
+        return $this->transaction->createSavepoint($identifier);
+    }
+
+    public function rollbackTo(string $identifier): Promise
+    {
+        if (!$this->transaction) {
+            throw new TransactionError("The transaction has been committed or rolled back");
+        }
+
+        return $this->transaction->rollbackTo($identifier);
+    }
+
+    public function releaseSavepoint(string $identifier): Promise
+    {
+        if (!$this->transaction) {
+            throw new TransactionError("The transaction has been committed or rolled back");
+        }
+
+        return $this->transaction->releaseSavepoint($identifier);
+    }
+}
diff --git a/src/PqHandle.php b/src/PqHandle.php
index 74cc27b..087c905 100644
--- a/src/PqHandle.php
+++ b/src/PqHandle.php
@@ -238,8 +238,7 @@ final class PqHandle implements Handle
 
             case pq\Result::SINGLE_TUPLE:
                 $this->busy = new Deferred;
-                $result = new PqUnbufferedResultSet($this->fetch, $result);
-                $result->onDestruct($this->release);
+                $result = new PqUnbufferedResultSet($this->fetch, $result, $this->release);
                 return $result;
 
             case pq\Result::NONFATAL_ERROR:
@@ -452,7 +451,7 @@ final class PqHandle implements Handle
             }
 
             Loop::enable($this->poll);
-            return new Listener($emitter->iterate(), $channel, $this->unlisten);
+            return new ConnectionListener($emitter->iterate(), $channel, $this->unlisten);
         });
     }
 
diff --git a/src/PqStatement.php b/src/PqStatement.php
index 1788e44..82c410c 100644
--- a/src/PqStatement.php
+++ b/src/PqStatement.php
@@ -3,10 +3,9 @@
 namespace Amp\Postgres;
 
 use Amp\Promise;
-use Amp\Sql\Operation;
 use Amp\Sql\Statement;
 
-final class PqStatement implements Statement, Operation
+final class PqStatement implements Statement
 {
     /** @var @return PromisePqHandle */
     private $handle;
@@ -17,9 +16,6 @@ final class PqStatement implements Statement, Operation
     /** @var string */
     private $sql;
 
-    /** @var @return PromiseInternal\ReferenceQueue */
-    private $queue;
-
     /** @var array */
     private $params;
 
@@ -27,7 +23,7 @@ final class PqStatement implements Statement, Operation
     private $lastUsedAt;
 
     /**
-     * @param @return PromisePqHandle $handle
+     * @param PqHandle $handle
      * @param string $name Statement name.
      * @param string $sql Original prepared SQL query.
      * @param string[] $params Parameter indices to parameter names.
@@ -38,14 +34,12 @@ final class PqStatement implements Statement, Operation
         $this->name = $name;
         $this->params = $params;
         $this->sql = $sql;
-        $this->queue = new Internal\ReferenceQueue;
         $this->lastUsedAt = \time();
     }
 
     public function __destruct()
     {
         $this->handle->statementDeallocate($this->name);
-        $this->queue->unreference();
     }
 
     /** {@inheritdoc} */
@@ -72,10 +66,4 @@ final class PqStatement implements Statement, Operation
         $this->lastUsedAt = \time();
         return $this->handle->statementExecute($this->name, Internal\replaceNamedParams($params, $this->params));
     }
-
-    /** {@inheritdoc} */
-    public function onDestruct(callable $onDestruct)
-    {
-        $this->queue->onDestruct($onDestruct);
-    }
 }
diff --git a/src/PqUnbufferedResultSet.php b/src/PqUnbufferedResultSet.php
index 0794ab0..d6e0fa3 100644
--- a/src/PqUnbufferedResultSet.php
+++ b/src/PqUnbufferedResultSet.php
@@ -20,19 +20,15 @@ final class PqUnbufferedResultSet implements ResultSet
     /** @var int Next row fetch type. */
     private $type = self::FETCH_ASSOC;
 
-    /** @var Internal\ReferenceQueue */
-    private $queue;
-
     /**
      * @param callable():  $fetch Function to fetch next result row.
      * @param \pq\Result $result PostgreSQL result object.
      */
-    public function __construct(callable $fetch, pq\Result $result)
+    public function __construct(callable $fetch, pq\Result $result, callable $release)
     {
         $this->numCols = $result->numCols;
-        $this->queue = $queue = new Internal\ReferenceQueue;
 
-        $this->producer = new Producer(static function (callable $emit) use ($queue, $result, $fetch) {
+        $this->producer = new Producer(static function (callable $emit) use ($release, $result, $fetch) {
             try {
                 do {
                     $result->autoConvert = pq\Result::CONV_SCALAR | pq\Result::CONV_ARRAY;
@@ -40,7 +36,7 @@ final class PqUnbufferedResultSet implements ResultSet
                     $result = yield $fetch();
                 } while ($result instanceof pq\Result);
             } finally {
-                $queue->unreference();
+                $release();
             }
         });
     }
@@ -87,12 +83,4 @@ final class PqUnbufferedResultSet implements ResultSet
     {
         return $this->numCols;
     }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function onDestruct(callable $onComplete)
-    {
-        $this->queue->onDestruct($onComplete);
-    }
 }
diff --git a/src/Quoter.php b/src/Quoter.php
new file mode 100644
index 0000000..43a41dc
--- /dev/null
+++ b/src/Quoter.php
@@ -0,0 +1,29 @@
+<?php
+
+namespace Amp\Postgres;
+
+interface Quoter
+{
+    /**
+     * Quotes (escapes) the given string for use as a string literal or identifier in a query. This method wraps the
+     * string in single quotes, so additional quotes should not be added in the query.
+     *
+     * @param string $data Unquoted data.
+     *
+     * @return string Quoted string wrapped in single quotes.
+     *
+     * @throws \Error If the connection to the database has been closed.
+     */
+    public function quoteString(string $data): string;
+
+    /**
+     * Quotes (escapes) the given string for use as a name or identifier in a query.
+     *
+     * @param string $name Unquoted identifier.
+     *
+     * @return string Quoted identifier.
+     *
+     * @throws \Error If the connection to the database has been closed.
+     */
+    public function quoteName(string $name): string;
+}
diff --git a/src/StatementPool.php b/src/StatementPool.php
new file mode 100644
index 0000000..5774a98
--- /dev/null
+++ b/src/StatementPool.php
@@ -0,0 +1,15 @@
+<?php
+
+namespace Amp\Postgres;
+
+use Amp\Sql\ResultSet as SqlResultSet;
+use Amp\Sql\StatementPool as SqlStatementPool;
+
+class StatementPool extends SqlStatementPool
+{
+    protected function createResultSet(SqlResultSet $resultSet, callable $release): SqlResultSet
+    {
+        \assert($resultSet instanceof ResultSet);
+        return new PooledResultSet($resultSet, $release);
+    }
+}
diff --git a/src/Transaction.php b/src/Transaction.php
index c38e4ae..2ef0299 100644
--- a/src/Transaction.php
+++ b/src/Transaction.php
@@ -2,341 +2,8 @@
 
 namespace Amp\Postgres;
 
-use Amp\Promise;
-use Amp\Sql\Operation;
 use Amp\Sql\Transaction as SqlTransaction;
-use Amp\Sql\TransactionError;
-use function Amp\call;
 
-final class Transaction implements Handle, SqlTransaction
+interface Transaction extends Quoter, SqlTransaction
 {
-    /** @var Handle|null */
-    private $handle;
-
-    /** @var int */
-    private $isolation;
-
-    /** @var Internal\ReferenceQueue */
-    private $queue;
-
-    /** @var Listener[] */
-    private $listeners = [];
-
-    /**
-     * @param Handle $handle
-     * @param int $isolation
-     *
-     * @throws \Error If the isolation level is invalid.
-     */
-    public function __construct(Handle $handle, int $isolation = SqlTransaction::ISOLATION_COMMITTED)
-    {
-        switch ($isolation) {
-            case SqlTransaction::ISOLATION_UNCOMMITTED:
-            case SqlTransaction::ISOLATION_COMMITTED:
-            case SqlTransaction::ISOLATION_REPEATABLE:
-            case SqlTransaction::ISOLATION_SERIALIZABLE:
-                $this->isolation = $isolation;
-                break;
-
-            default:
-                throw new \Error("Isolation must be a valid transaction isolation level");
-        }
-
-        $this->handle = $handle;
-        $this->queue = new Internal\ReferenceQueue;
-
-        $listeners =& $this->listeners;
-        $this->queue->onDestruct(static function () use (&$listeners) {
-            foreach ($listeners as $listener) {
-                if ($listener->isListening()) {
-                    $listener->unlisten();
-                }
-            }
-        });
-    }
-
-    public function __destruct()
-    {
-        if ($this->handle) {
-            $this->rollback(); // Invokes $this->queue->complete().
-        }
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function lastUsedAt(): int
-    {
-        return $this->handle->lastUsedAt();
-    }
-
-    /**
-     * {@inheritdoc}
-     *
-     * Closes and commits all changes in the transaction.
-     */
-    public function close()
-    {
-        if ($this->handle) {
-            $this->commit(); // Invokes $this->queue->unreference().
-        }
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function onDestruct(callable $onComplete)
-    {
-        $this->queue->onDestruct($onComplete);
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function isAlive(): bool
-    {
-        return $this->handle && $this->handle->isAlive();
-    }
-
-    /**
-     * @return bool True if the transaction is active, false if it has been committed or rolled back.
-     */
-    public function isActive(): bool
-    {
-        return $this->handle !== null;
-    }
-
-    /**
-     * @return int
-     */
-    public function getIsolationLevel(): int
-    {
-        return $this->isolation;
-    }
-
-    /**
-     * {@inheritdoc}
-     *
-     * @throws TransactionError If the transaction has been committed or rolled back.
-     */
-    public function query(string $sql): Promise
-    {
-        if ($this->handle === null) {
-            throw new TransactionError("The transaction has been committed or rolled back");
-        }
-
-        $this->queue->reference();
-
-        $promise = $this->handle->query($sql);
-
-        $promise->onResolve(function ($exception, $result) {
-            if ($result instanceof Operation) {
-                $result->onDestruct([$this->queue, "unreference"]);
-                return;
-            }
-
-            $this->queue->unreference();
-        });
-
-        return $promise;
-    }
-
-    /**
-     * {@inheritdoc}
-     *
-     * @throws TransactionError If the transaction has been committed or rolled back.
-     */
-    public function prepare(string $sql): Promise
-    {
-        if ($this->handle === null) {
-            throw new TransactionError("The transaction has been committed or rolled back");
-        }
-
-        $this->queue->reference();
-
-        $promise = $this->handle->prepare($sql);
-
-        $promise->onResolve(function ($exception, $statement) {
-            if ($statement instanceof Operation) {
-                $statement->onDestruct([$this->queue, "unreference"]);
-                return;
-            }
-
-            $this->queue->unreference();
-        });
-
-        return $promise;
-    }
-
-    /**
-     * {@inheritdoc}
-     *
-     * @throws TransactionError If the transaction has been committed or rolled back.
-     */
-    public function execute(string $sql, array $params = []): Promise
-    {
-        if ($this->handle === null) {
-            throw new TransactionError("The transaction has been committed or rolled back");
-        }
-
-        $this->queue->reference();
-
-        $promise = $this->handle->execute($sql, $params);
-
-        $promise->onResolve(function ($exception, $result) {
-            if ($result instanceof Operation) {
-                $result->onDestruct([$this->queue, "unreference"]);
-                return;
-            }
-
-            $this->queue->unreference();
-        });
-
-        return $promise;
-    }
-
-
-    /**
-     * {@inheritdoc}
-     *
-     * @throws TransactionError If the transaction has been committed or rolled back.
-     */
-    public function notify(string $channel, string $payload = ""): Promise
-    {
-        if ($this->handle === null) {
-            throw new TransactionError("The transaction has been committed or rolled back");
-        }
-
-        return $this->handle->notify($channel, $payload);
-    }
-
-    /**
-     * Commits the transaction and makes it inactive.
-     *
-     * @return Promise<\Amp\Sql\CommandResult>
-     *
-     * @throws TransactionError If the transaction has been committed or rolled back.
-     */
-    public function commit(): Promise
-    {
-        if ($this->handle === null) {
-            throw new TransactionError("The transaction has been committed or rolled back");
-        }
-
-        $promise = $this->handle->query("COMMIT");
-        $this->handle = null;
-        $promise->onResolve([$this->queue, "unreference"]);
-
-        return $promise;
-    }
-
-    /**
-     * Rolls back the transaction and makes it inactive.
-     *
-     * @return Promise<\Amp\Sql\CommandResult>
-     *
-     * @throws TransactionError If the transaction has been committed or rolled back.
-     */
-    public function rollback(): Promise
-    {
-        if ($this->handle === null) {
-            throw new TransactionError("The transaction has been committed or rolled back");
-        }
-
-        $promise = $this->handle->query("ROLLBACK");
-        $this->handle = null;
-        $promise->onResolve([$this->queue, "unreference"]);
-
-        return $promise;
-    }
-
-    /**
-     * Creates a savepoint with the given identifier.
-     *
-     * @param string $identifier Savepoint identifier.
-     *
-     * @return Promise<\Amp\Sql\CommandResult>
-     *
-     * @throws TransactionError If the transaction has been committed or rolled back.
-     */
-    public function createSavepoint(string $identifier): Promise
-    {
-        return $this->query("SAVEPOINT " . $this->quoteName($identifier));
-    }
-
-    /**
-     * Rolls back to the savepoint with the given identifier.
-     *
-     * @param string $identifier Savepoint identifier.
-     *
-     * @return Promise<\Amp\Sql\CommandResult>
-     *
-     * @throws TransactionError If the transaction has been committed or rolled back.
-     */
-    public function rollbackTo(string $identifier): Promise
-    {
-        return $this->query("ROLLBACK TO " . $this->quoteName($identifier));
-    }
-
-    /**
-     * Releases the savepoint with the given identifier.
-     *
-     * @param string $identifier Savepoint identifier.
-     *
-     * @return Promise<\Amp\Sql\CommandResult>
-     *
-     * @throws TransactionError If the transaction has been committed or rolled back.
-     */
-    public function releaseSavepoint(string $identifier): Promise
-    {
-        return $this->query("RELEASE SAVEPOINT " . $this->quoteName($identifier));
-    }
-
-    /**
-     * {@inheritdoc}
-     *
-     * Listeners automatically unlisten when the transaction is committed or rolled back.
-     *
-     * @throws TransactionError If the transaction has been committed or rolled back.
-     */
-    public function listen(string $channel): Promise
-    {
-        if ($this->handle === null) {
-            throw new TransactionError("The transaction has been committed or rolled back");
-        }
-
-        return call(function () use ($channel) {
-            $listener = yield $this->handle->listen($channel);
-            $this->listeners[] = $listener;
-            return $listener;
-        });
-    }
-
-    /**
-     * {@inheritdoc}
-     *
-     * @throws TransactionError If the transaction has been committed or rolled back.
-     */
-    public function quoteString(string $data): string
-    {
-        if ($this->handle === null) {
-            throw new TransactionError("The transaction has been committed or rolled back");
-        }
-
-        return $this->handle->quoteString($data);
-    }
-
-    /**
-     * {@inheritdoc}
-     *
-     * @throws TransactionError If the transaction has been committed or rolled back.
-     */
-    public function quoteName(string $name): string
-    {
-        if ($this->handle === null) {
-            throw new TransactionError("The transaction has been committed or rolled back");
-        }
-
-        return $this->handle->quoteName($name);
-    }
 }
diff --git a/test/PoolTest.php b/test/PoolTest.php
deleted file mode 100644
index 1515809..0000000
--- a/test/PoolTest.php
+++ /dev/null
@@ -1,55 +0,0 @@
-<?php
-
-namespace Amp\Postgres\Test;
-
-use Amp\Delayed;
-use Amp\Loop;
-use Amp\Postgres\ConnectionConfig;
-use Amp\Postgres\Pool;
-use PHPUnit\Framework\TestCase;
-
-class PoolTest extends TestCase
-{
-    /**
-     * @expectedException \Error
-     * @expectedExceptionMessage Pool must contain at least one connection
-     */
-    public function testInvalidMaxConnections()
-    {
-        new Pool(new ConnectionConfig('connection string'), 0);
-    }
-
-    public function testIdleConnectionsRemovedAfterTimeout()
-    {
-        Loop::run(function () {
-            $pool = new Pool(new ConnectionConfig('host=localhost user=postgres'));
-            $pool->setIdleTimeout(2);
-            $count = 3;
-
-            $promises = [];
-            for ($i = 0; $i < $count; ++$i) {
-                $promises[] = $pool->query("SELECT $i");
-            }
-
-            $results = yield $promises;
-
-            /** @var \Amp\Postgres\ResultSet $result */
-            foreach ($results as $result) {
-                while (yield $result->advance()); // Consume results to free connection
-            }
-
-            $this->assertSame($count, $pool->getConnectionCount());
-
-            yield new Delayed(1000);
-
-            $this->assertSame($count, $pool->getConnectionCount());
-
-            $result = yield $pool->query("SELECT $i");
-            while (yield $result->advance()); // Consume results to free connection
-
-            yield new Delayed(1000);
-
-            $this->assertSame(1, $pool->getConnectionCount());
-        });
-    }
-}
diff --git a/test/PooledStatementTest.php b/test/PooledStatementTest.php
deleted file mode 100644
index 0a81ceb..0000000
--- a/test/PooledStatementTest.php
+++ /dev/null
@@ -1,80 +0,0 @@
-<?php
-
-namespace Amp\Postgres\Test;
-
-use Amp\Delayed;
-use Amp\Loop;
-use Amp\PHPUnit\TestCase;
-use Amp\Postgres\ConnectionConfig;
-use Amp\Postgres\Pool;
-use Amp\Postgres\ResultSet;
-use Amp\Sql\PooledStatement;
-use Amp\Sql\Statement;
-use Amp\Success;
-
-class PooledStatementTest extends TestCase
-{
-    public function testActiveStatementsRemainAfterTimeout()
-    {
-        Loop::run(function () {
-            $pool = new Pool(new ConnectionConfig('host=localhost user=postgres'));
-
-            $statement = $this->createMock(Statement::class);
-            $statement->method('getQuery')
-                ->willReturn('SELECT 1');
-            $statement->method('lastUsedAt')
-                ->willReturn(\time());
-            $statement->expects($this->once())
-                ->method('execute');
-
-            $pooledStatement = new PooledStatement($pool, $statement, $this->createCallback(0));
-
-            $this->assertTrue($pooledStatement->isAlive());
-            $this->assertSame(\time(), $pooledStatement->lastUsedAt());
-
-            yield new Delayed(1500); // Give timeout watcher enough time to execute.
-
-            $pooledStatement->execute();
-
-            $this->assertTrue($pooledStatement->isAlive());
-            $this->assertSame(\time(), $pooledStatement->lastUsedAt());
-        });
-    }
-
-    public function testIdleStatementsRemovedAfterTimeout()
-    {
-        Loop::run(function () {
-            $pool = new Pool(new ConnectionConfig('host=localhost user=postgres'));
-
-            $statement = $this->createMock(Statement::class);
-            $statement->method('getQuery')
-                ->willReturn('SELECT 1');
-            $statement->method('lastUsedAt')
-                ->willReturn(0);
-            $statement->expects($this->never())
-                ->method('execute');
-
-            $prepare = function () {
-                $statement = $this->createMock(Statement::class);
-                $statement->expects($this->once())
-                    ->method('execute')
-                    ->willReturn(new Success($this->createMock(ResultSet::class)));
-                return new Success($statement);
-            };
-
-            $pooledStatement = new PooledStatement($pool, $statement, $prepare);
-
-            $this->assertTrue($pooledStatement->isAlive());
-            $this->assertSame(\time(), $pooledStatement->lastUsedAt());
-
-            yield new Delayed(1500); // Give timeout watcher enough time to execute and remove mock statement object.
-
-            $result = yield $pooledStatement->execute();
-
-            $this->assertInstanceOf(ResultSet::class, $result);
-
-            $this->assertTrue($pooledStatement->isAlive());
-            $this->assertSame(\time(), $pooledStatement->lastUsedAt());
-        });
-    }
-}