diff --git a/composer.json b/composer.json
index f8d3f27..4538b66 100644
--- a/composer.json
+++ b/composer.json
@@ -19,6 +19,7 @@
         }
     ],
     "require": {
+        "php": "^7.0",
         "amphp/amp": "^2",
         "amphp/sql": "dev-master"
     },
diff --git a/src/Connection.php b/src/Connection.php
index f8cf662..f1b4b76 100644
--- a/src/Connection.php
+++ b/src/Connection.php
@@ -55,13 +55,13 @@ final public function isAlive(): bool
      *
      * @throws FailureException
      */
-    final public function lastUsedAt(): int
+    final public function getLastUsedAt(): int
     {
         if (! $this->handle) {
             throw new FailureException('Not connected');
         }
 
-        return $this->handle->lastUsedAt();
+        return $this->handle->getLastUsedAt();
     }
 
     /**
@@ -183,7 +183,7 @@ final public function listen(string $channel): Promise
      *
      * @throws FailureException
      */
-    final public function transaction(int $isolation = Transaction::ISOLATION_COMMITTED): Promise
+    final public function beginTransaction(int $isolation = Transaction::ISOLATION_COMMITTED): Promise
     {
         if (! $this->handle) {
             throw new FailureException('Not connected');
@@ -213,7 +213,7 @@ final public function transaction(int $isolation = Transaction::ISOLATION_COMMIT
 
             $this->busy = new Deferred;
 
-            return new ConnectionTransaction($this->handle, $isolation, $this->release);
+            return new ConnectionTransaction($this->handle, $this->release, $isolation);
         });
     }
 
diff --git a/src/ConnectionTransaction.php b/src/ConnectionTransaction.php
index 3171ebc..1558e1b 100644
--- a/src/ConnectionTransaction.php
+++ b/src/ConnectionTransaction.php
@@ -23,12 +23,12 @@ final class ConnectionTransaction implements Transaction
 
     /**
      * @param Handle $handle
-     * @param int $isolation
      * @param callable $release
+     * @param int $isolation
      *
      * @throws \Error If the isolation level is invalid.
      */
-    public function __construct(Handle $handle, int $isolation = SqlTransaction::ISOLATION_COMMITTED, callable $release)
+    public function __construct(Handle $handle, callable $release, int $isolation = SqlTransaction::ISOLATION_COMMITTED)
     {
         switch ($isolation) {
             case SqlTransaction::ISOLATION_UNCOMMITTED:
@@ -62,9 +62,9 @@ public function __destruct()
     /**
      * {@inheritdoc}
      */
-    public function lastUsedAt(): int
+    public function getLastUsedAt(): int
     {
-        return $this->handle->lastUsedAt();
+        return $this->handle->getLastUsedAt();
     }
 
     /**
diff --git a/src/PgSqlCommandResult.php b/src/PgSqlCommandResult.php
index 909c852..5b23c08 100644
--- a/src/PgSqlCommandResult.php
+++ b/src/PgSqlCommandResult.php
@@ -28,7 +28,7 @@ public function __destruct()
     /**
      * @return int Number of rows affected by the INSERT, UPDATE, or DELETE query.
      */
-    public function affectedRows(): int
+    public function getAffectedRowCount(): int
     {
         return \pg_affected_rows($this->handle);
     }
@@ -36,7 +36,7 @@ public function affectedRows(): int
     /**
      * @return string
      */
-    public function lastOid(): string
+    public function getLastOid(): string
     {
         return (string) \pg_last_oid($this->handle);
     }
diff --git a/src/PgSqlHandle.php b/src/PgSqlHandle.php
index 9ae779d..32e8f5d 100644
--- a/src/PgSqlHandle.php
+++ b/src/PgSqlHandle.php
@@ -195,7 +195,7 @@ public function isAlive(): bool
     /**
      * {@inheritdoc}
      */
-    public function lastUsedAt(): int
+    public function getLastUsedAt(): int
     {
         return $this->lastUsedAt;
     }
diff --git a/src/PgSqlResultSet.php b/src/PgSqlResultSet.php
index 594a398..46944ec 100644
--- a/src/PgSqlResultSet.php
+++ b/src/PgSqlResultSet.php
@@ -17,9 +17,6 @@ final class PgSqlResultSet implements ResultSet
     /** @var mixed Last row emitted. */
     private $currentRow;
 
-    /** @var int Next row fetch type. */
-    private $type = self::FETCH_ASSOC;
-
     /** @var int[] */
     private $fieldTypes = [];
 
@@ -56,10 +53,9 @@ public function __destruct()
     /**
      * {@inheritdoc}
      */
-    public function advance(int $type = self::FETCH_ASSOC): Promise
+    public function advance(): Promise
     {
         $this->currentRow = null;
-        $this->type = $type;
 
         if (++$this->position > \pg_num_rows($this->handle)) {
             return new Success(false);
@@ -71,7 +67,7 @@ public function advance(int $type = self::FETCH_ASSOC): Promise
     /**
      * {@inheritdoc}
      */
-    public function getCurrent()
+    public function getCurrent(int $type = self::FETCH_ASSOC)
     {
         if ($this->currentRow !== null) {
             return $this->currentRow;
@@ -98,7 +94,7 @@ public function getCurrent()
             $result[$column] = $this->cast($column, $result[$column]);
         }
 
-        if ($this->type === self::FETCH_ARRAY) {
+        if ($type === self::FETCH_ARRAY) {
             return $this->currentRow = $result;
         }
 
@@ -107,11 +103,11 @@ public function getCurrent()
             $assoc[$name] = $result[$index];
         }
 
-        if ($this->type === self::FETCH_ASSOC) {
+        if ($type === self::FETCH_ASSOC) {
             return $this->currentRow = $assoc;
         }
 
-        if ($this->type === self::FETCH_OBJECT) {
+        if ($type === self::FETCH_OBJECT) {
             return $this->currentRow = (object) $assoc;
         }
 
@@ -243,7 +239,7 @@ public function numRows(): int
     /**
      * @return int Number of fields in each row.
      */
-    public function numFields(): int
+    public function getFieldCount(): int
     {
         return \pg_num_fields($this->handle);
     }
@@ -255,9 +251,9 @@ public function numFields(): int
      *
      * @throws \Error If the field number does not exist in the result.
      */
-    public function fieldName(int $fieldNum): string
+    public function getFieldName(int $fieldNum): string
     {
-        if (0 > $fieldNum || $this->numFields() <= $fieldNum) {
+        if (0 > $fieldNum || $this->getFieldCount() <= $fieldNum) {
             throw new \Error(\sprintf('No field with index %d in result', $fieldNum));
         }
 
@@ -271,7 +267,7 @@ public function fieldName(int $fieldNum): string
      *
      * @throws \Error If the field name does not exist in the result.
      */
-    public function fieldNum(string $fieldName): int
+    public function getFieldIndex(string $fieldName): int
     {
         $result = \pg_field_num($this->handle, $fieldName);
 
diff --git a/src/PgSqlStatement.php b/src/PgSqlStatement.php
index 3d6790e..b440c6f 100644
--- a/src/PgSqlStatement.php
+++ b/src/PgSqlStatement.php
@@ -16,9 +16,6 @@ final class PgSqlStatement implements Statement
     /** @var string */
     private $sql;
 
-    /** @var Internal\ReferenceQueue */
-    private $queue;
-
     /** @var string[] */
     private $params;
 
@@ -58,7 +55,7 @@ public function getQuery(): string
     }
 
     /** {@inheritdoc} */
-    public function lastUsedAt(): int
+    public function getLastUsedAt(): int
     {
         return $this->lastUsedAt;
     }
diff --git a/src/PooledResultSet.php b/src/PooledResultSet.php
index 4c04853..fcf88f3 100644
--- a/src/PooledResultSet.php
+++ b/src/PooledResultSet.php
@@ -19,8 +19,8 @@ public function __construct(ResultSet $result, callable $release)
         $this->result = $result;
     }
 
-    public function numFields(): int
+    public function getFieldCount(): int
     {
-        return $this->result->numFields();
+        return $this->result->getFieldCount();
     }
 }
diff --git a/src/PqBufferedResultSet.php b/src/PqBufferedResultSet.php
index 968b879..e0dc232 100644
--- a/src/PqBufferedResultSet.php
+++ b/src/PqBufferedResultSet.php
@@ -17,9 +17,6 @@ final class PqBufferedResultSet implements ResultSet
     /** @var mixed Last row emitted. */
     private $currentRow;
 
-    /** @var int Next row fetch type. */
-    private $type = self::FETCH_ASSOC;
-
     /**
      * @param pq\Result $result PostgreSQL result object.
      */
@@ -32,10 +29,9 @@ public function __construct(pq\Result $result)
     /**
      * {@inheritdoc}
      */
-    public function advance(int $type = self::FETCH_ASSOC): Promise
+    public function advance(): Promise
     {
         $this->currentRow = null;
-        $this->type = $type;
 
         if (++$this->position > $this->result->numRows) {
             return new Success(false);
@@ -47,7 +43,7 @@ public function advance(int $type = self::FETCH_ASSOC): Promise
     /**
      * {@inheritdoc}
      */
-    public function getCurrent()
+    public function getCurrent(int $type = self::FETCH_ASSOC)
     {
         if ($this->currentRow !== null) {
             return $this->currentRow;
@@ -57,7 +53,7 @@ public function getCurrent()
             throw new \Error("No more rows remain in the result set");
         }
 
-        switch ($this->type) {
+        switch ($type) {
             case self::FETCH_ASSOC:
                 return $this->currentRow = $this->result->fetchRow(pq\Result::FETCH_ASSOC);
             case self::FETCH_ARRAY:
@@ -69,12 +65,12 @@ public function getCurrent()
         }
     }
 
-    public function numRows(): int
+    public function getNumRows(): int
     {
         return $this->result->numRows;
     }
 
-    public function numFields(): int
+    public function getFieldCount(): int
     {
         return $this->result->numCols;
     }
diff --git a/src/PqCommandResult.php b/src/PqCommandResult.php
index 43af02d..4972321 100644
--- a/src/PqCommandResult.php
+++ b/src/PqCommandResult.php
@@ -21,7 +21,7 @@ public function __construct(pq\Result $result)
     /**
      * @return int Number of rows affected by the INSERT, UPDATE, or DELETE query.
      */
-    public function affectedRows(): int
+    public function getAffectedRowCount(): int
     {
         return $this->result->affectedRows;
     }
diff --git a/src/PqHandle.php b/src/PqHandle.php
index 73f4cee..121eaa8 100644
--- a/src/PqHandle.php
+++ b/src/PqHandle.php
@@ -150,7 +150,7 @@ public function isAlive(): bool
     /**
      * {@inheritdoc}
      */
-    public function lastUsedAt(): int
+    public function getLastUsedAt(): int
     {
         return $this->lastUsedAt;
     }
diff --git a/src/PqStatement.php b/src/PqStatement.php
index 82c410c..d7fd012 100644
--- a/src/PqStatement.php
+++ b/src/PqStatement.php
@@ -55,7 +55,7 @@ public function getQuery(): string
     }
 
     /** {@inheritdoc} */
-    public function lastUsedAt(): int
+    public function getLastUsedAt(): int
     {
         return $this->lastUsedAt;
     }
diff --git a/src/PqUnbufferedResultSet.php b/src/PqUnbufferedResultSet.php
index d6e0fa3..0f1c9cc 100644
--- a/src/PqUnbufferedResultSet.php
+++ b/src/PqUnbufferedResultSet.php
@@ -17,9 +17,6 @@ final class PqUnbufferedResultSet implements ResultSet
     /** @var array|object Last row emitted. */
     private $currentRow;
 
-    /** @var int Next row fetch type. */
-    private $type = self::FETCH_ASSOC;
-
     /**
      * @param callable():  $fetch Function to fetch next result row.
      * @param \pq\Result $result PostgreSQL result object.
@@ -44,10 +41,9 @@ public function __construct(callable $fetch, pq\Result $result, callable $releas
     /**
      * {@inheritdoc}
      */
-    public function advance(int $type = self::FETCH_ASSOC): Promise
+    public function advance(): Promise
     {
         $this->currentRow = null;
-        $this->type = $type;
 
         return $this->producer->advance();
     }
@@ -55,7 +51,7 @@ public function advance(int $type = self::FETCH_ASSOC): Promise
     /**
      * {@inheritdoc}
      */
-    public function getCurrent()
+    public function getCurrent(int $type = self::FETCH_ASSOC)
     {
         if ($this->currentRow !== null) {
             return $this->currentRow;
@@ -64,7 +60,7 @@ public function getCurrent()
         /** @var \pq\Result $result */
         $result = $this->producer->getCurrent();
 
-        switch ($this->type) {
+        switch ($type) {
             case self::FETCH_ASSOC:
                 return $this->currentRow = $result->fetchRow(pq\Result::FETCH_ASSOC);
             case self::FETCH_ARRAY:
@@ -79,7 +75,7 @@ public function getCurrent()
     /**
      * @return int Number of fields (columns) in each result set.
      */
-    public function numFields(): int
+    public function getFieldCount(): int
     {
         return $this->numCols;
     }
diff --git a/src/ResultSet.php b/src/ResultSet.php
index a7ac24c..3fc03c5 100644
--- a/src/ResultSet.php
+++ b/src/ResultSet.php
@@ -11,5 +11,5 @@ interface ResultSet extends SqlResultSet
      *
      * @return int
      */
-    public function numFields(): int;
+    public function getFieldCount(): int;
 }
diff --git a/test/AbstractLinkTest.php b/test/AbstractLinkTest.php
index a89361c..2939091 100644
--- a/test/AbstractLinkTest.php
+++ b/test/AbstractLinkTest.php
@@ -56,7 +56,7 @@ public function testQueryWithTupleResult()
 
             $this->assertInstanceOf(ResultSet::class, $result);
 
-            $this->assertSame(2, $result->numFields());
+            $this->assertSame(2, $result->getFieldCount());
 
             $data = $this->getData();
 
@@ -83,8 +83,8 @@ public function testQueryWithUnconsumedTupleResult()
 
             $data = $this->getData();
 
-            for ($i = 0; yield $result->advance(SqlResultSet::FETCH_OBJECT); ++$i) {
-                $row = $result->getCurrent();
+            for ($i = 0; yield $result->advance(); ++$i) {
+                $row = $result->getCurrent(SqlResultSet::FETCH_OBJECT);
                 $this->assertSame($data[$i][0], $row->domain);
                 $this->assertSame($data[$i][1], $row->tld);
             }
@@ -98,7 +98,7 @@ public function testQueryWithCommandResult()
             $result = yield $this->connection->query("INSERT INTO test VALUES ('canon', 'jp')");
 
             $this->assertInstanceOf(CommandResult::class, $result);
-            $this->assertSame(1, $result->affectedRows());
+            $this->assertSame(1, $result->getAffectedRowCount());
         });
     }
 
@@ -144,10 +144,10 @@ public function testPrepare()
 
             $this->assertInstanceOf(ResultSet::class, $result);
 
-            $this->assertSame(2, $result->numFields());
+            $this->assertSame(2, $result->getFieldCount());
 
-            while (yield $result->advance(SqlResultSet::FETCH_ARRAY)) {
-                $row = $result->getCurrent();
+            while (yield $result->advance()) {
+                $row = $result->getCurrent(SqlResultSet::FETCH_ARRAY);
                 $this->assertSame($data[0], $row[0]);
                 $this->assertSame($data[1], $row[1]);
             }
@@ -174,10 +174,10 @@ public function testPrepareWithNamedParams()
 
             $this->assertInstanceOf(ResultSet::class, $result);
 
-            $this->assertSame(2, $result->numFields());
+            $this->assertSame(2, $result->getFieldCount());
 
-            while (yield $result->advance(SqlResultSet::FETCH_ARRAY)) {
-                $row = $result->getCurrent();
+            while (yield $result->advance()) {
+                $row = $result->getCurrent(SqlResultSet::FETCH_ARRAY);
                 $this->assertSame($data[0], $row[0]);
                 $this->assertSame($data[1], $row[1]);
             }
@@ -204,10 +204,10 @@ public function testPrepareWithUnnamedParams()
 
             $this->assertInstanceOf(ResultSet::class, $result);
 
-            $this->assertSame(2, $result->numFields());
+            $this->assertSame(2, $result->getFieldCount());
 
-            while (yield $result->advance(SqlResultSet::FETCH_ARRAY)) {
-                $row = $result->getCurrent();
+            while (yield $result->advance()) {
+                $row = $result->getCurrent(SqlResultSet::FETCH_ARRAY);
                 $this->assertSame($data[0], $row[0]);
                 $this->assertSame($data[1], $row[1]);
             }
@@ -234,10 +234,10 @@ public function testPrepareWithNamedParamsWithDataAppearingAsNamedParam()
 
             $this->assertInstanceOf(ResultSet::class, $result);
 
-            $this->assertSame(2, $result->numFields());
+            $this->assertSame(2, $result->getFieldCount());
 
-            while (yield $result->advance(SqlResultSet::FETCH_ARRAY)) {
-                $row = $result->getCurrent();
+            while (yield $result->advance()) {
+                $row = $result->getCurrent(SqlResultSet::FETCH_ARRAY);
                 $this->assertSame($data[0], $row[0]);
                 $this->assertSame($data[1], $row[1]);
             }
@@ -285,7 +285,7 @@ public function testPrepareSameQuery()
 
             $this->assertInstanceOf(ResultSet::class, $result);
 
-            $this->assertSame(2, $result->numFields());
+            $this->assertSame(2, $result->getFieldCount());
 
             while (yield $result->advance()) {
                 $row = $result->getCurrent();
@@ -322,7 +322,7 @@ public function testSimultaneousPrepareSameQuery()
 
             $this->assertInstanceOf(ResultSet::class, $result);
 
-            $this->assertSame(2, $result->numFields());
+            $this->assertSame(2, $result->getFieldCount());
 
             while (yield $result->advance()) {
                 $row = $result->getCurrent();
@@ -337,7 +337,7 @@ public function testSimultaneousPrepareSameQuery()
 
             $this->assertInstanceOf(ResultSet::class, $result);
 
-            $this->assertSame(2, $result->numFields());
+            $this->assertSame(2, $result->getFieldCount());
 
             while (yield $result->advance()) {
                 $row = $result->getCurrent();
@@ -365,8 +365,8 @@ public function testPrepareThenExecuteWithUnconsumedTupleResult()
 
             $data = $this->getData();
 
-            for ($i = 0; yield $result->advance(SqlResultSet::FETCH_OBJECT); ++$i) {
-                $row = $result->getCurrent();
+            for ($i = 0; yield $result->advance(); ++$i) {
+                $row = $result->getCurrent(SqlResultSet::FETCH_OBJECT);
                 $this->assertSame($data[$i][0], $row->domain);
                 $this->assertSame($data[$i][1], $row->tld);
             }
@@ -383,7 +383,7 @@ public function testExecute()
 
             $this->assertInstanceOf(ResultSet::class, $result);
 
-            $this->assertSame(2, $result->numFields());
+            $this->assertSame(2, $result->getFieldCount());
 
             while (yield $result->advance()) {
                 $row = $result->getCurrent();
@@ -409,7 +409,7 @@ public function testExecuteWithNamedParams()
 
             $this->assertInstanceOf(ResultSet::class, $result);
 
-            $this->assertSame(2, $result->numFields());
+            $this->assertSame(2, $result->getFieldCount());
 
             while (yield $result->advance()) {
                 $row = $result->getCurrent();
@@ -581,7 +581,7 @@ public function testTransaction()
             $isolation = SqlTransaction::ISOLATION_COMMITTED;
 
             /** @var \Amp\Postgres\Transaction $transaction */
-            $transaction = yield $this->connection->transaction($isolation);
+            $transaction = yield $this->connection->beginTransaction($isolation);
 
             $this->assertInstanceOf(Transaction::class, $transaction);