Merge pull request #2546 from morozov/close-cursor-frees-statement

Prepared statements become unusable after calling closeCursor() on IBM DB2, Oracle and MS SQL Server.

lib/Doctrine/DBAL/Driver/IBMDB2/DB2Statement.php

@@ -48,6 +48,13 @@ class DB2Statement implements \IteratorAggregate, Statement
      */
     private $_defaultFetchMode = \PDO::FETCH_BOTH;
 
+    /**
+     * Indicates whether the statement is in the state when fetching results is possible
+     *
+     * @var bool
+     */
+    private $result = false;
+
     /**
      * DB2_BINARY, DB2_CHAR, DB2_DOUBLE, or DB2_LONG
      *
@@ -104,11 +111,14 @@ class DB2Statement implements \IteratorAggregate, Statement
         }
 
         $this->_bindParam = array();
-        db2_free_result($this->_stmt);
-        $ret = db2_free_stmt($this->_stmt);
-        $this->_stmt = false;
 
-        return $ret;
+        if (!db2_free_result($this->_stmt)) {
+            return false;
+        }
+
+        $this->result = false;
+
+        return true;
     }
 
     /**
@@ -151,22 +161,24 @@ class DB2Statement implements \IteratorAggregate, Statement
             return false;
         }
 
-        /*$retval = true;
-        if ($params !== null) {
-            $retval = @db2_execute($this->_stmt, $params);
-        } else {
-            $retval = @db2_execute($this->_stmt);
-        }*/
         if ($params === null) {
             ksort($this->_bindParam);
-            $params = array_values($this->_bindParam);
+
+            $params = array();
+
+            foreach ($this->_bindParam as $column => $value) {
+                $params[] = $value;
+            }
         }
+
         $retval = @db2_execute($this->_stmt, $params);
 
         if ($retval === false) {
             throw new DB2Exception(db2_stmt_errormsg());
         }
 
+        $this->result = true;
+
         return $retval;
     }
 
@@ -197,6 +209,12 @@ class DB2Statement implements \IteratorAggregate, Statement
      */
     public function fetch($fetchMode = null)
     {
+        // do not try fetching from the statement if it's not expected to contain result
+        // in order to prevent exceptional situation
+        if (!$this->result) {
+            return false;
+        }
+
         $fetchMode = $fetchMode ?: $this->_defaultFetchMode;
         switch ($fetchMode) {
             case \PDO::FETCH_BOTH:

lib/Doctrine/DBAL/Driver/Mysqli/MysqliStatement.php

@@ -80,6 +80,13 @@ class MysqliStatement implements \IteratorAggregate, Statement
      */
     protected $_defaultFetchMode = PDO::FETCH_BOTH;
 
+    /**
+     * Indicates whether the statement is in the state when fetching results is possible
+     *
+     * @var bool
+     */
+    private $result = false;
+
     /**
      * @param \mysqli $conn
      * @param string  $prepareString
@@ -168,9 +175,6 @@ class MysqliStatement implements \IteratorAggregate, Statement
         if (null === $this->_columnNames) {
             $meta = $this->_stmt->result_metadata();
             if (false !== $meta) {
-                // We have a result.
-                $this->_stmt->store_result();
-
                 $columnNames = array();
                 foreach ($meta->fetch_fields() as $col) {
                     $columnNames[] = $col->name;
@@ -178,21 +182,42 @@ class MysqliStatement implements \IteratorAggregate, Statement
                 $meta->free();
 
                 $this->_columnNames = $columnNames;
-                $this->_rowBindedValues = array_fill(0, count($columnNames), null);
-
-                $refs = array();
-                foreach ($this->_rowBindedValues as $key => &$value) {
-                    $refs[$key] =& $value;
-                }
-
-                if (!call_user_func_array(array($this->_stmt, 'bind_result'), $refs)) {
-                    throw new MysqliException($this->_stmt->error, $this->_stmt->sqlstate, $this->_stmt->errno);
-                }
             } else {
                 $this->_columnNames = false;
             }
         }
 
+        if (false !== $this->_columnNames) {
+            // Store result of every execution which has it. Otherwise it will be impossible
+            // to execute a new statement in case if the previous one has non-fetched rows
+            // @link http://dev.mysql.com/doc/refman/5.7/en/commands-out-of-sync.html
+            $this->_stmt->store_result();
+
+            // Bind row values _after_ storing the result. Otherwise, if mysqli is compiled with libmysql,
+            // it will have to allocate as much memory as it may be needed for the given column type
+            // (e.g. for a LONGBLOB field it's 4 gigabytes)
+            // @link https://bugs.php.net/bug.php?id=51386#1270673122
+            //
+            // Make sure that the values are bound after each execution. Otherwise, if closeCursor() has been
+            // previously called on the statement, the values are unbound making the statement unusable.
+            //
+            // It's also important that row values are bound after _each_ call to store_result(). Otherwise,
+            // if mysqli is compiled with libmysql, subsequently fetched string values will get truncated
+            // to the length of the ones fetched during the previous execution.
+            $this->_rowBindedValues = array_fill(0, count($this->_columnNames), null);
+
+            $refs = array();
+            foreach ($this->_rowBindedValues as $key => &$value) {
+                $refs[$key] =& $value;
+            }
+
+            if (!call_user_func_array(array($this->_stmt, 'bind_result'), $refs)) {
+                throw new MysqliException($this->_stmt->error, $this->_stmt->sqlstate, $this->_stmt->errno);
+            }
+        }
+
+        $this->result = true;
+
         return true;
     }
 
@@ -240,6 +265,12 @@ class MysqliStatement implements \IteratorAggregate, Statement
      */
     public function fetch($fetchMode = null)
     {
+        // do not try fetching from the statement if it's not expected to contain result
+        // in order to prevent exceptional situation
+        if (!$this->result) {
+            return false;
+        }
+
         $values = $this->_fetch();
         if (null === $values) {
             return false;
@@ -335,6 +366,7 @@ class MysqliStatement implements \IteratorAggregate, Statement
     public function closeCursor()
     {
         $this->_stmt->free_result();
+        $this->result = false;
 
         return true;
     }

lib/Doctrine/DBAL/Driver/OCI8/OCI8Statement.php

@@ -80,6 +80,13 @@ class OCI8Statement implements \IteratorAggregate, Statement
      */
     private $boundValues = array();
 
+    /**
+     * Indicates whether the statement is in the state when fetching results is possible
+     *
+     * @var bool
+     */
+    private $result = false;
+
     /**
      * Creates a new OCI8Statement that uses the given connection handle and SQL statement.
      *
@@ -176,7 +183,20 @@ class OCI8Statement implements \IteratorAggregate, Statement
      */
     public function closeCursor()
     {
-        return oci_free_statement($this->_sth);
+        // not having the result means there's nothing to close
+        if (!$this->result) {
+            return true;
+        }
+
+        // emulate it by fetching and discarding rows, similarly to what PDO does in this case
+        // @link http://php.net/manual/en/pdostatement.closecursor.php
+        // @link https://github.com/php/php-src/blob/php-7.0.11/ext/pdo/pdo_stmt.c#L2075
+        // deliberately do not consider multiple result sets, since doctrine/dbal doesn't support them
+        while (oci_fetch($this->_sth));
+
+        $this->result = false;
+
+        return true;
     }
 
     /**
@@ -229,6 +249,8 @@ class OCI8Statement implements \IteratorAggregate, Statement
             throw OCI8Exception::fromErrorInfo($this->errorInfo());
         }
 
+        $this->result = true;
+
         return $ret;
     }
 
@@ -257,6 +279,12 @@ class OCI8Statement implements \IteratorAggregate, Statement
      */
     public function fetch($fetchMode = null)
     {
+        // do not try fetching from the statement if it's not expected to contain result
+        // in order to prevent exceptional situation
+        if (!$this->result) {
+            return false;
+        }
+
         $fetchMode = $fetchMode ?: $this->_defaultFetchMode;
 
         if (PDO::FETCH_OBJ == $fetchMode) {
@@ -304,6 +332,12 @@ class OCI8Statement implements \IteratorAggregate, Statement
                 $fetchStructure = OCI_FETCHSTATEMENT_BY_COLUMN;
             }
 
+            // do not try fetching from the statement if it's not expected to contain result
+            // in order to prevent exceptional situation
+            if (!$this->result) {
+                return array();
+            }
+
             oci_fetch_all($this->_sth, $result, 0, -1,
                 self::$fetchModeMap[$fetchMode] | OCI_RETURN_NULLS | $fetchStructure | OCI_RETURN_LOBS);
 
@@ -320,6 +354,12 @@ class OCI8Statement implements \IteratorAggregate, Statement
      */
     public function fetchColumn($columnIndex = 0)
     {
+        // do not try fetching from the statement if it's not expected to contain result
+        // in order to prevent exceptional situation
+        if (!$this->result) {
+            return false;
+        }
+
         $row = oci_fetch_array($this->_sth, OCI_NUM | OCI_RETURN_NULLS | OCI_RETURN_LOBS);
 
         if (false === $row) {

lib/Doctrine/DBAL/Driver/PDOSqlsrv/Connection.php

@@ -28,6 +28,15 @@ use Doctrine\DBAL\Driver\PDOConnection;
  */
 class Connection extends PDOConnection implements \Doctrine\DBAL\Driver\Connection
 {
+    /**
+     * {@inheritdoc}
+     */
+    public function __construct($dsn, $user = null, $password = null, array $options = null)
+    {
+        parent::__construct($dsn, $user, $password, $options);
+        $this->setAttribute(\PDO::ATTR_STATEMENT_CLASS, array(Statement::class, array()));
+    }
+
     /**
      * {@inheritDoc}
      */

lib/Doctrine/DBAL/Driver/PDOSqlsrv/Statement.php

+<?php
+/*
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * This software consists of voluntary contributions made by many individuals
+ * and is licensed under the MIT license. For more information, see
+ * <http://www.doctrine-project.org>.
+ */
+
+namespace Doctrine\DBAL\Driver\PDOSqlsrv;
+
+use Doctrine\DBAL\Driver\PDOStatement;
+use PDO;
+
+/**
+ * PDO SQL Server Statement
+ */
+class Statement extends PDOStatement
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function bindParam($column, &$variable, $type = PDO::PARAM_STR, $length = null, $driverOptions = null)
+    {
+        if ($type === PDO::PARAM_LOB && $driverOptions === null) {
+            $driverOptions = PDO::SQLSRV_ENCODING_BINARY;
+        }
+
+        return parent::bindParam($column, $variable, $type, $length, $driverOptions);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function bindValue($param, $value, $type = PDO::PARAM_STR)
+    {
+        return $this->bindParam($param, $value, $type);
+    }
+}

lib/Doctrine/DBAL/Driver/SQLAnywhere/SQLAnywhereStatement.php

@@ -131,7 +131,7 @@ class SQLAnywhereStatement implements IteratorAggregate, Statement
      */
     public function closeCursor()
     {
-        if ( ! sasql_stmt_free_result($this->stmt)) {
+        if (!sasql_stmt_reset($this->stmt)) {
             throw SQLAnywhereException::fromSQLAnywhereError($this->conn, $this->stmt);
         }
 

lib/Doctrine/DBAL/Driver/SQLSrv/SQLSrvStatement.php

@@ -53,11 +53,18 @@ class SQLSrvStatement implements IteratorAggregate, Statement
     private $stmt;
 
     /**
-     * Parameters to bind.
+     * References to the variables bound as statement parameters.
      *
      * @var array
      */
-    private $params = array();
+    private $variables = array();
+
+    /**
+     * Bound parameter types.
+     *
+     * @var array
+     */
+    private $types = array();
 
     /**
      * Translations.
@@ -98,6 +105,13 @@ class SQLSrvStatement implements IteratorAggregate, Statement
      */
     private $lastInsertId;
 
+    /**
+     * Indicates whether the statement is in the state when fetching results is possible
+     *
+     * @var bool
+     */
+    private $result = false;
+
     /**
      * Append to any INSERT query to retrieve the last insert id.
      *
@@ -138,11 +152,8 @@ class SQLSrvStatement implements IteratorAggregate, Statement
             throw new SQLSrvException("sqlsrv does not support named parameters to queries, use question mark (?) placeholders instead.");
         }
 
-        if ($type === \PDO::PARAM_LOB) {
-            $this->params[$column-1] = array($variable, SQLSRV_PARAM_IN, SQLSRV_PHPTYPE_STREAM(SQLSRV_ENC_BINARY), SQLSRV_SQLTYPE_VARBINARY('max'));
-        } else {
-            $this->params[$column-1] = $variable;
-        }
+        $this->variables[$column] =& $variable;
+        $this->types[$column] = $type;
     }
 
     /**
@@ -150,9 +161,20 @@ class SQLSrvStatement implements IteratorAggregate, Statement
      */
     public function closeCursor()
     {
-        if ($this->stmt) {
-            sqlsrv_free_stmt($this->stmt);
+        // not having the result means there's nothing to close
+        if (!$this->result) {
+            return true;
         }
+
+        // emulate it by fetching and discarding rows, similarly to what PDO does in this case
+        // @link http://php.net/manual/en/pdostatement.closecursor.php
+        // @link https://github.com/php/php-src/blob/php-7.0.11/ext/pdo/pdo_stmt.c#L2075
+        // deliberately do not consider multiple result sets, since doctrine/dbal doesn't support them
+        while (sqlsrv_fetch($this->stmt));
+
+        $this->result = false;
+
+        return true;
     }
 
     /**
@@ -193,18 +215,13 @@ class SQLSrvStatement implements IteratorAggregate, Statement
             $hasZeroIndex = array_key_exists(0, $params);
             foreach ($params as $key => $val) {
                 $key = ($hasZeroIndex && is_numeric($key)) ? $key + 1 : $key;
-                $this->bindValue($key, $val);
+                $this->variables[$key] = $val;
+                $this->types[$key] = null;
             }
         }
 
         if ( ! $this->stmt) {
-            $stmt = sqlsrv_prepare($this->conn, $this->sql, $this->params);
-
-            if (!$stmt) {
-                throw SQLSrvException::fromSqlSrvErrors();
-            }
-
-            $this->stmt = $stmt;
+            $this->stmt = $this->prepare();
         }
 
         if (!sqlsrv_execute($this->stmt)) {
@@ -216,6 +233,40 @@ class SQLSrvStatement implements IteratorAggregate, Statement
             sqlsrv_fetch($this->stmt);
             $this->lastInsertId->setId(sqlsrv_get_field($this->stmt, 0));
         }
+
+        $this->result = true;
+    }
+
+    /**
+     * Prepares SQL Server statement resource
+     *
+     * @return resource
+     * @throws SQLSrvException
+     */
+    private function prepare()
+    {
+        $params = array();
+
+        foreach ($this->variables as $column => &$variable) {
+            if ($this->types[$column] === \PDO::PARAM_LOB) {
+                $params[$column - 1] = array(
+                    &$variable,
+                    SQLSRV_PARAM_IN,
+                    SQLSRV_PHPTYPE_STREAM(SQLSRV_ENC_BINARY),
+                    SQLSRV_SQLTYPE_VARBINARY('max'),
+                );
+            } else {
+                $params[$column - 1] =& $variable;
+            }
+        }
+
+        $stmt = sqlsrv_prepare($this->conn, $this->sql, $params);
+
+        if (!$stmt) {
+            throw SQLSrvException::fromSqlSrvErrors();
+        }
+
+        return $stmt;
     }
 
     /**
@@ -245,6 +296,12 @@ class SQLSrvStatement implements IteratorAggregate, Statement
      */
     public function fetch($fetchMode = null)
     {
+        // do not try fetching from the statement if it's not expected to contain result
+        // in order to prevent exceptional situation
+        if (!$this->result) {
+            return false;
+        }
+
         $args      = func_get_args();
         $fetchMode = $fetchMode ?: $this->defaultFetchMode;
 

tests/Doctrine/Tests/DBAL/Functional/Driver/PDOConnectionTest.php

@@ -29,6 +29,13 @@ class PDOConnectionTest extends DbalFunctionalTestCase
         }
     }
 
+    protected function tearDown()
+    {
+        $this->resetSharedConn();
+
+        parent::tearDown();
+    }
+
     public function testDoesNotRequireQueryForServerVersion()
     {
         $this->assertFalse($this->driverConnection->requiresQueryForServerVersion());

tests/Doctrine/Tests/DBAL/Functional/StatementTest.php

+<?php
+
+namespace Doctrine\Tests\DBAL\Functional;
+
+use Doctrine\DBAL\Driver\Statement;
+use Doctrine\DBAL\Schema\Table;
+use Doctrine\DBAL\Types\Type;
+
+class StatementTest extends \Doctrine\Tests\DbalFunctionalTestCase
+{
+    protected function setUp()
+    {
+        parent::setUp();
+
+        $table = new Table('stmt_test');
+        $table->addColumn('id', 'integer');
+        $this->_conn->getSchemaManager()->dropAndCreateTable($table);
+    }
+
+    public function testStatementIsReusableAfterClosingCursor()
+    {
+        $this->_conn->insert('stmt_test', array('id' => 1));
+        $this->_conn->insert('stmt_test', array('id' => 2));
+
+        $stmt = $this->_conn->prepare('SELECT id FROM stmt_test ORDER BY id');
+
+        $stmt->execute();
+
+        $id = $stmt->fetchColumn();
+        $this->assertEquals(1, $id);
+
+        $stmt->closeCursor();
+
+        $stmt->execute();
+        $id = $stmt->fetchColumn();
+        $this->assertEquals(1, $id);
+        $id = $stmt->fetchColumn();
+        $this->assertEquals(2, $id);
+    }
+
+    public function testReuseStatementWithLongerResults()
+    {
+        $sm = $this->_conn->getSchemaManager();
+        $table = new Table('stmt_longer_results');
+        $table->addColumn('param', 'string');
+        $table->addColumn('val', 'text');
+        $sm->createTable($table);
+
+        $row1 = array(
+            'param' => 'param1',
+            'val' => 'X',
+        );
+        $this->_conn->insert('stmt_longer_results', $row1);
+
+        $stmt = $this->_conn->prepare('SELECT param, val FROM stmt_longer_results ORDER BY param');
+        $stmt->execute();
+        $this->assertArraySubset(array(
+            array('param1', 'X'),
+        ), $stmt->fetchAll(\PDO::FETCH_NUM));
+
+        $row2 = array(
+            'param' => 'param2',
+            'val' => 'A bit longer value',
+        );
+        $this->_conn->insert('stmt_longer_results', $row2);
+
+        $stmt->execute();
+        $this->assertArraySubset(array(
+            array('param1', 'X'),
+            array('param2', 'A bit longer value'),
+        ), $stmt->fetchAll(\PDO::FETCH_NUM));
+    }
+
+    public function testFetchLongBlob()
+    {
+        // make sure memory limit is large enough to not cause false positives,
+        // but is still not enough to store a LONGBLOB of the max possible size
+        $this->iniSet('memory_limit', '4G');
+
+        $sm = $this->_conn->getSchemaManager();
+        $table = new Table('stmt_long_blob');
+        $table->addColumn('contents', 'blob', array(
+            'length' => 0xFFFFFFFF,
+        ));
+        $sm->createTable($table);
+
+        $contents = base64_decode(<<<EOF
+H4sICJRACVgCA2RvY3RyaW5lLmljbwDtVNtLFHEU/ia1i9fVzVWxvJSrZmoXS6pd0zK7QhdNc03z
+lrpppq1pWqJCFERZkUFEDybYBQqJhB6iUOqhh+whgl4qkF6MfGh+s87O7GVmO6OlBfUfdIZvznxn
+fpzznW9gAI4unQ50XwirH2AAkEygEuIwU58ODnPBzXGv14sEq4BrwzKKL4sY++SGTz6PodcutN5x
+IPvsFCa+K9CXMfS/cOL5OxesN0Wceygho0WAXVLwcUJBdDVDaqOAij4Rrz640XlXQmAxQ16PHU63
+iqdvXbg4JOHLpILBUSdM7XZEVDDcfuZEbI2ASaYguUGAroSh97GMngcSeFFFerMdI+/dyGy1o+GW
+Ax5FxfAbFwoviajuc+DCIwn+RTwGRmRIThXxdQJyu+z4/NUDYz2DKCsILuERWsoQfoQhqpLhyhMZ
+XfcknBmU0NLvQArpTm0SsI5mqKqKuFoGc8cUcjrtqLohom1AgtujQnapmJJU+BbwCLIwhJXyiKlh
+MB4TkFgvIK3JjrRmAefJm+77Eiqvi+SvCq/qJahQyWuVuEpcIa7QLh7Kbsourb9b66/pZdAd1voz
+fCNfwsp46OnZQPojSX9UFcNy+mYJNDeJPHtJfqeR/nSaPTzmwlXar5dQ1adpd+B//I9/hi0xuCPQ
+Nkvb5um37Wtc+auQXZsVxEVYD5hnCilxTaYYjsuxLlsxXUitzd2hs3GWHLM5UOM7Fy8t3xiat4fb
+sneNxmNb/POO1pRXc7vnF2nc13Rq0cFWiyXkuHmzxuOtzUYfC7fEmK/3mx4QZd5u4E7XJWz6+dey
+Za4tXHUiPyB8Vm781oaT+3fN6Y/eUFDfPkcNWetNxb+tlxEZsPqPdZMOzS4rxwJ8CDC+ABj1+Tu0
+d+N0hqezcjblboJ3Bj8ARJilHX4FAAA=
+EOF
+    );
+
+        $this->_conn->insert('stmt_long_blob', array(
+            'contents' => $contents,
+        ), array(\PDO::PARAM_LOB));
+
+        $stmt = $this->_conn->prepare('SELECT contents FROM stmt_long_blob');
+        $stmt->execute();
+
+        $stream = Type::getType('blob')
+            ->convertToPHPValue(
+                $stmt->fetchColumn(),
+                $this->_conn->getDatabasePlatform()
+            );
+
+        if ($this->_conn->getDriver()->getName() === 'pdo_sqlsrv') {
+            $this->markTestSkipped('Skipping on pdo_sqlsrv due to https://github.com/Microsoft/msphpsql/issues/270');
+        }
+
+        $this->assertSame($contents, stream_get_contents($stream));
+    }
+
+    public function testIncompletelyFetchedStatementDoesNotBlockConnection()
+    {
+        $this->_conn->insert('stmt_test', array('id' => 1));
+        $this->_conn->insert('stmt_test', array('id' => 2));
+
+        $stmt1 = $this->_conn->prepare('SELECT id FROM stmt_test');
+        $stmt1->execute();
+        $stmt1->fetch();
+        $stmt1->execute();
+        // fetching only one record out of two
+        $stmt1->fetch();
+
+        $stmt2 = $this->_conn->prepare('SELECT id FROM stmt_test WHERE id = ?');
+        $stmt2->execute(array(1));
+        $this->assertEquals(1, $stmt2->fetchColumn());
+    }
+
+    public function testReuseStatementAfterClosingCursor()
+    {
+        $this->_conn->insert('stmt_test', array('id' => 1));
+        $this->_conn->insert('stmt_test', array('id' => 2));
+
+        $stmt = $this->_conn->prepare('SELECT id FROM stmt_test WHERE id = ?');
+
+        $stmt->execute(array(1));
+        $id = $stmt->fetchColumn();
+        $this->assertEquals(1, $id);
+
+        $stmt->closeCursor();
+
+        $stmt->execute(array(2));
+        $id = $stmt->fetchColumn();
+        $this->assertEquals(2, $id);
+    }
+
+    public function testReuseStatementWithParameterBoundByReference()
+    {
+        $this->_conn->insert('stmt_test', array('id' => 1));
+        $this->_conn->insert('stmt_test', array('id' => 2));
+
+        $stmt = $this->_conn->prepare('SELECT id FROM stmt_test WHERE id = ?');
+        $stmt->bindParam(1, $id);
+
+        $id = 1;
+        $stmt->execute();
+        $this->assertEquals(1, $stmt->fetchColumn());
+
+        $id = 2;
+        $stmt->execute();
+        $this->assertEquals(2, $stmt->fetchColumn());
+    }
+
+    /**
+     * @dataProvider emptyFetchProvider
+     */
+    public function testFetchFromNonExecutedStatement(callable $fetch, $expected)
+    {
+        $stmt = $this->_conn->prepare('SELECT id FROM stmt_test');
+
+        $this->assertSame($expected, $fetch($stmt));
+    }
+
+    public function testCloseCursorOnNonExecutedStatement()
+    {
+        $stmt = $this->_conn->prepare('SELECT id FROM stmt_test');
+
+        $this->assertTrue($stmt->closeCursor());
+    }
+
+    /**
+     * @dataProvider emptyFetchProvider
+     */
+    public function testFetchFromNonExecutedStatementWithClosedCursor(callable $fetch, $expected)
+    {
+        $stmt = $this->_conn->prepare('SELECT id FROM stmt_test');
+        $stmt->closeCursor();
+
+        $this->assertSame($expected, $fetch($stmt));
+    }
+
+    /**
+     * @dataProvider emptyFetchProvider
+     */
+    public function testFetchFromExecutedStatementWithClosedCursor(callable $fetch, $expected)
+    {
+        $this->_conn->insert('stmt_test', array('id' => 1));
+
+        $stmt = $this->_conn->prepare('SELECT id FROM stmt_test');
+        $stmt->execute();
+        $stmt->closeCursor();
+
+        $this->assertSame($expected, $fetch($stmt));
+    }
+
+    public static function emptyFetchProvider()
+    {
+        return array(
+            'fetch' => array(
+                function (Statement $stmt) {
+                    return $stmt->fetch();
+                },
+                false,
+            ),
+            'fetch-column' => array(
+                function (Statement $stmt) {
+                    return $stmt->fetchColumn();
+                },
+                false,
+            ),
+            'fetch-all' => array(
+                function (Statement $stmt) {
+                    return $stmt->fetchAll();
+                },
+                array(),
+            ),
+        );
+    }
+}