vendor/doctrine/lib/Doctrine/ORM/Query/SqlWalker.php
changeset 0 7f95f8617b0b
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/vendor/doctrine/lib/Doctrine/ORM/Query/SqlWalker.php	Sat Sep 24 15:40:41 2011 +0200
@@ -0,0 +1,1976 @@
+<?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 LGPL. For more information, see
+ * <http://www.doctrine-project.org>.
+ */
+
+namespace Doctrine\ORM\Query;
+
+use Doctrine\DBAL\LockMode,
+    Doctrine\ORM\Mapping\ClassMetadata,
+    Doctrine\ORM\Query,
+    Doctrine\ORM\Query\QueryException;
+
+/**
+ * The SqlWalker is a TreeWalker that walks over a DQL AST and constructs
+ * the corresponding SQL.
+ *
+ * @author Roman Borschel <roman@code-factory.org>
+ * @author Benjamin Eberlei <kontakt@beberlei.de>
+ * @since 2.0
+ * @todo Rename: SQLWalker
+ */
+class SqlWalker implements TreeWalker
+{
+    /**
+     * @var ResultSetMapping
+     */
+    private $_rsm;
+
+    /** Counters for generating unique column aliases, table aliases and parameter indexes. */
+    private $_aliasCounter = 0;
+    private $_tableAliasCounter = 0;
+    private $_scalarResultCounter = 1;
+    private $_sqlParamIndex = 0;
+
+    /**
+     * @var ParserResult
+     */
+    private $_parserResult;
+
+    /**
+     * @var EntityManager
+     */
+    private $_em;
+
+    /**
+     * @var Doctrine\DBAL\Connection
+     */
+    private $_conn;
+
+    /**
+     * @var AbstractQuery
+     */
+    private $_query;
+
+    private $_tableAliasMap = array();
+
+    /** Map from result variable names to their SQL column alias names. */
+    private $_scalarResultAliasMap = array();
+
+    /** Map of all components/classes that appear in the DQL query. */
+    private $_queryComponents;
+
+    /** A list of classes that appear in non-scalar SelectExpressions. */
+    private $_selectedClasses = array();
+
+    /**
+     * The DQL alias of the root class of the currently traversed query.
+     */
+    private $_rootAliases = array();
+
+    /**
+     * Flag that indicates whether to generate SQL table aliases in the SQL.
+     * These should only be generated for SELECT queries, not for UPDATE/DELETE.
+     */
+    private $_useSqlTableAliases = true;
+
+    /**
+     * The database platform abstraction.
+     *
+     * @var AbstractPlatform
+     */
+    private $_platform;
+
+    /**
+     * {@inheritDoc}
+     */
+    public function __construct($query, $parserResult, array $queryComponents)
+    {
+        $this->_query = $query;
+        $this->_parserResult = $parserResult;
+        $this->_queryComponents = $queryComponents;
+        $this->_rsm = $parserResult->getResultSetMapping();
+        $this->_em = $query->getEntityManager();
+        $this->_conn = $this->_em->getConnection();
+        $this->_platform = $this->_conn->getDatabasePlatform();
+    }
+
+    /**
+     * Gets the Query instance used by the walker.
+     *
+     * @return Query.
+     */
+    public function getQuery()
+    {
+        return $this->_query;
+    }
+
+    /**
+     * Gets the Connection used by the walker.
+     *
+     * @return Connection
+     */
+    public function getConnection()
+    {
+        return $this->_conn;
+    }
+
+    /**
+     * Gets the EntityManager used by the walker.
+     *
+     * @return EntityManager
+     */
+    public function getEntityManager()
+    {
+        return $this->_em;
+    }
+
+    /**
+     * Gets the information about a single query component.
+     *
+     * @param string $dqlAlias The DQL alias.
+     * @return array
+     */
+    public function getQueryComponent($dqlAlias)
+    {
+        return $this->_queryComponents[$dqlAlias];
+    }
+
+    /**
+     * Gets an executor that can be used to execute the result of this walker.
+     *
+     * @return AbstractExecutor
+     */
+    public function getExecutor($AST)
+    {
+        $isDeleteStatement = $AST instanceof AST\DeleteStatement;
+        $isUpdateStatement = $AST instanceof AST\UpdateStatement;
+
+        if ($isDeleteStatement) {
+            $primaryClass = $this->_em->getClassMetadata(
+                $AST->deleteClause->abstractSchemaName
+            );
+
+            if ($primaryClass->isInheritanceTypeJoined()) {
+                return new Exec\MultiTableDeleteExecutor($AST, $this);
+            } else {
+                return new Exec\SingleTableDeleteUpdateExecutor($AST, $this);
+            }
+        } else if ($isUpdateStatement) {
+            $primaryClass = $this->_em->getClassMetadata(
+                $AST->updateClause->abstractSchemaName
+            );
+
+            if ($primaryClass->isInheritanceTypeJoined()) {
+                return new Exec\MultiTableUpdateExecutor($AST, $this);
+            } else {
+                return new Exec\SingleTableDeleteUpdateExecutor($AST, $this);
+            }
+        }
+
+        return new Exec\SingleSelectExecutor($AST, $this);
+    }
+
+    /**
+     * Generates a unique, short SQL table alias.
+     *
+     * @param string $tableName Table name
+     * @param string $dqlAlias The DQL alias.
+     * @return string Generated table alias.
+     */
+    public function getSQLTableAlias($tableName, $dqlAlias = '')
+    {
+        $tableName .= ($dqlAlias) ? '@[' . $dqlAlias . ']' : '';
+
+        if ( ! isset($this->_tableAliasMap[$tableName])) {
+            $this->_tableAliasMap[$tableName] = strtolower(substr($tableName, 0, 1)) . $this->_tableAliasCounter++ . '_';
+        }
+
+        return $this->_tableAliasMap[$tableName];
+    }
+
+    /**
+     * Forces the SqlWalker to use a specific alias for a table name, rather than
+     * generating an alias on its own.
+     *
+     * @param string $tableName
+     * @param string $alias
+     * @param string $dqlAlias
+     * @return string
+     */
+    public function setSQLTableAlias($tableName, $alias, $dqlAlias = '')
+    {
+        $tableName .= ($dqlAlias) ? '@[' . $dqlAlias . ']' : '';
+
+        $this->_tableAliasMap[$tableName] = $alias;
+
+        return $alias;
+    }
+
+    /**
+     * Gets an SQL column alias for a column name.
+     *
+     * @param string $columnName
+     * @return string
+     */
+    public function getSQLColumnAlias($columnName)
+    {
+        return $columnName . $this->_aliasCounter++;
+    }
+
+    /**
+     * Generates the SQL JOINs that are necessary for Class Table Inheritance
+     * for the given class.
+     *
+     * @param ClassMetadata $class The class for which to generate the joins.
+     * @param string $dqlAlias The DQL alias of the class.
+     * @return string The SQL.
+     */
+    private function _generateClassTableInheritanceJoins($class, $dqlAlias)
+    {
+        $sql = '';
+
+        $baseTableAlias = $this->getSQLTableAlias($class->table['name'], $dqlAlias);
+
+        // INNER JOIN parent class tables
+        foreach ($class->parentClasses as $parentClassName) {
+            $parentClass = $this->_em->getClassMetadata($parentClassName);
+            $tableAlias = $this->getSQLTableAlias($parentClass->table['name'], $dqlAlias);
+            // If this is a joined association we must use left joins to preserve the correct result.
+            $sql .= isset($this->_queryComponents[$dqlAlias]['relation']) ? ' LEFT ' : ' INNER ';
+            $sql .= 'JOIN ' . $parentClass->getQuotedTableName($this->_platform)
+                  . ' ' . $tableAlias . ' ON ';
+            $first = true;
+            foreach ($class->identifier as $idField) {
+                if ($first) $first = false; else $sql .= ' AND ';
+
+                $columnName = $class->getQuotedColumnName($idField, $this->_platform);
+                $sql .= $baseTableAlias . '.' . $columnName
+                      . ' = '
+                      . $tableAlias . '.' . $columnName;
+            }
+        }
+
+        // LEFT JOIN subclass tables, if partial objects disallowed.
+        if ( ! $this->_query->getHint(Query::HINT_FORCE_PARTIAL_LOAD)) {
+            foreach ($class->subClasses as $subClassName) {
+                $subClass = $this->_em->getClassMetadata($subClassName);
+                $tableAlias = $this->getSQLTableAlias($subClass->table['name'], $dqlAlias);
+                $sql .= ' LEFT JOIN ' . $subClass->getQuotedTableName($this->_platform)
+                        . ' ' . $tableAlias . ' ON ';
+                $first = true;
+                foreach ($class->identifier as $idField) {
+                    if ($first) $first = false; else $sql .= ' AND ';
+
+                    $columnName = $class->getQuotedColumnName($idField, $this->_platform);
+                    $sql .= $baseTableAlias . '.' . $columnName
+                            . ' = '
+                            . $tableAlias . '.' . $columnName;
+                }
+            }
+        }
+
+        return $sql;
+    }
+
+    private function _generateOrderedCollectionOrderByItems()
+    {
+        $sql = '';
+        foreach ($this->_selectedClasses AS $dqlAlias => $class) {
+            $qComp = $this->_queryComponents[$dqlAlias];
+            if (isset($qComp['relation']['orderBy'])) {
+                foreach ($qComp['relation']['orderBy'] AS $fieldName => $orientation) {
+                    if ($qComp['metadata']->isInheritanceTypeJoined()) {
+                        $tableName = $this->_em->getUnitOfWork()->getEntityPersister($class->name)->getOwningTable($fieldName);
+                    } else {
+                        $tableName = $qComp['metadata']->table['name'];
+                    }
+
+                    if ($sql != '') {
+                        $sql .= ', ';
+                    }
+                    $sql .= $this->getSQLTableAlias($tableName, $dqlAlias) . '.' .
+                            $qComp['metadata']->getQuotedColumnName($fieldName, $this->_platform) . " $orientation";
+                }
+            }
+        }
+        return $sql;
+    }
+
+    /**
+     * Generates a discriminator column SQL condition for the class with the given DQL alias.
+     *
+     * @param array $dqlAliases List of root DQL aliases to inspect for discriminator restrictions.
+     * @return string
+     */
+    private function _generateDiscriminatorColumnConditionSQL(array $dqlAliases)
+    {
+        $encapsulate = false;
+        $sql = '';
+
+        foreach ($dqlAliases as $dqlAlias) {
+            $class = $this->_queryComponents[$dqlAlias]['metadata'];
+
+            if ($class->isInheritanceTypeSingleTable()) {
+                $conn = $this->_em->getConnection();
+                $values = array();
+                if ($class->discriminatorValue !== null) { // discrimnators can be 0
+                    $values[] = $conn->quote($class->discriminatorValue);
+                }
+
+                foreach ($class->subClasses as $subclassName) {
+                    $values[] = $conn->quote($this->_em->getClassMetadata($subclassName)->discriminatorValue);
+                }
+
+                if ($sql != '') {
+                    $sql .= ' AND ';
+                    $encapsulate = true;
+                }
+
+                $sql .= ($sql != '' ? ' AND ' : '')
+                      . (($this->_useSqlTableAliases) ? $this->getSQLTableAlias($class->table['name'], $dqlAlias) . '.' : '')
+                      . $class->discriminatorColumn['name'] . ' IN (' . implode(', ', $values) . ')';
+            }
+        }
+
+        return ($encapsulate) ? '(' . $sql . ')' : $sql;
+    }
+
+    /**
+     * Walks down a SelectStatement AST node, thereby generating the appropriate SQL.
+     *
+     * @return string The SQL.
+     */
+    public function walkSelectStatement(AST\SelectStatement $AST)
+    {
+        $sql = $this->walkSelectClause($AST->selectClause);
+        $sql .= $this->walkFromClause($AST->fromClause);
+
+        if (($whereClause = $AST->whereClause) !== null) {
+            $sql .= $this->walkWhereClause($whereClause);
+        } else if (($discSql = $this->_generateDiscriminatorColumnConditionSQL($this->_rootAliases)) !== '') {
+            $sql .= ' WHERE ' . $discSql;
+        }
+
+        $sql .= $AST->groupByClause ? $this->walkGroupByClause($AST->groupByClause) : '';
+        $sql .= $AST->havingClause ? $this->walkHavingClause($AST->havingClause) : '';
+
+        if (($orderByClause = $AST->orderByClause) !== null) {
+            $sql .= $AST->orderByClause ? $this->walkOrderByClause($AST->orderByClause) : '';
+        } else if (($orderBySql = $this->_generateOrderedCollectionOrderByItems()) !== '') {
+            $sql .= ' ORDER BY '.$orderBySql;
+        }
+
+
+        $sql = $this->_platform->modifyLimitQuery(
+            $sql, $this->_query->getMaxResults(), $this->_query->getFirstResult()
+        );
+
+        if (($lockMode = $this->_query->getHint(Query::HINT_LOCK_MODE)) !== false) {
+            if ($lockMode == LockMode::PESSIMISTIC_READ) {
+                $sql .= " " . $this->_platform->getReadLockSQL();
+            } else if ($lockMode == LockMode::PESSIMISTIC_WRITE) {
+                $sql .= " " . $this->_platform->getWriteLockSQL();
+            } else if ($lockMode == LockMode::OPTIMISTIC) {
+                foreach ($this->_selectedClasses AS $class) {
+                    if ( ! $class->isVersioned) {
+                        throw \Doctrine\ORM\OptimisticLockException::lockFailed();
+                    }
+                }
+            }
+        }
+
+        return $sql;
+    }
+
+    /**
+     * Walks down an UpdateStatement AST node, thereby generating the appropriate SQL.
+     *
+     * @param UpdateStatement
+     * @return string The SQL.
+     */
+    public function walkUpdateStatement(AST\UpdateStatement $AST)
+    {
+        $this->_useSqlTableAliases = false;
+        $sql = $this->walkUpdateClause($AST->updateClause);
+
+        if (($whereClause = $AST->whereClause) !== null) {
+            $sql .= $this->walkWhereClause($whereClause);
+        } else if (($discSql = $this->_generateDiscriminatorColumnConditionSQL($this->_rootAliases)) !== '') {
+            $sql .= ' WHERE ' . $discSql;
+        }
+
+        return $sql;
+    }
+
+    /**
+     * Walks down a DeleteStatement AST node, thereby generating the appropriate SQL.
+     *
+     * @param DeleteStatement
+     * @return string The SQL.
+     */
+    public function walkDeleteStatement(AST\DeleteStatement $AST)
+    {
+        $this->_useSqlTableAliases = false;
+        $sql = $this->walkDeleteClause($AST->deleteClause);
+
+        if (($whereClause = $AST->whereClause) !== null) {
+            $sql .= $this->walkWhereClause($whereClause);
+        } else if (($discSql = $this->_generateDiscriminatorColumnConditionSQL($this->_rootAliases)) !== '') {
+            $sql .= ' WHERE ' . $discSql;
+        }
+
+        return $sql;
+    }
+
+
+    /**
+     * Walks down an IdentificationVariable (no AST node associated), thereby generating the SQL.
+     *
+     * @param string $identificationVariable
+     * @param string $fieldName
+     * @return string The SQL.
+     */
+    public function walkIdentificationVariable($identificationVariable, $fieldName = null)
+    {
+        $class = $this->_queryComponents[$identificationVariable]['metadata'];
+
+        if (
+            $fieldName !== null && $class->isInheritanceTypeJoined() &&
+            isset($class->fieldMappings[$fieldName]['inherited'])
+        ) {
+            $class = $this->_em->getClassMetadata($class->fieldMappings[$fieldName]['inherited']);
+        }
+
+        return $this->getSQLTableAlias($class->table['name'], $identificationVariable);
+    }
+
+    /**
+     * Walks down a PathExpression AST node, thereby generating the appropriate SQL.
+     *
+     * @param mixed
+     * @return string The SQL.
+     */
+    public function walkPathExpression($pathExpr)
+    {
+        $sql = '';
+
+        switch ($pathExpr->type) {
+            case AST\PathExpression::TYPE_STATE_FIELD:
+                $fieldName = $pathExpr->field;
+                $dqlAlias = $pathExpr->identificationVariable;
+                $class = $this->_queryComponents[$dqlAlias]['metadata'];
+
+                if ($this->_useSqlTableAliases) {
+                    $sql .= $this->walkIdentificationVariable($dqlAlias, $fieldName) . '.';
+                }
+
+                $sql .= $class->getQuotedColumnName($fieldName, $this->_platform);
+                break;
+
+            case AST\PathExpression::TYPE_SINGLE_VALUED_ASSOCIATION:
+                // 1- the owning side:
+                //    Just use the foreign key, i.e. u.group_id
+                $fieldName = $pathExpr->field;
+                $dqlAlias = $pathExpr->identificationVariable;
+                $class = $this->_queryComponents[$dqlAlias]['metadata'];
+
+                if (isset($class->associationMappings[$fieldName]['inherited'])) {
+                    $class = $this->_em->getClassMetadata($class->associationMappings[$fieldName]['inherited']);
+                }
+
+                $assoc = $class->associationMappings[$fieldName];
+
+                if ($assoc['isOwningSide']) {
+                    // COMPOSITE KEYS NOT (YET?) SUPPORTED
+                    if (count($assoc['sourceToTargetKeyColumns']) > 1) {
+                        throw QueryException::associationPathCompositeKeyNotSupported();
+                    }
+
+                    if ($this->_useSqlTableAliases) {
+                        $sql .= $this->getSQLTableAlias($class->table['name'], $dqlAlias) . '.';
+                    }
+
+                    $sql .= reset($assoc['targetToSourceKeyColumns']);
+                } else {
+                    throw QueryException::associationPathInverseSideNotSupported();
+                }
+                break;
+                
+            default:
+                throw QueryException::invalidPathExpression($pathExpr);
+        }
+
+        return $sql;
+    }
+
+    /**
+     * Walks down a SelectClause AST node, thereby generating the appropriate SQL.
+     *
+     * @param $selectClause
+     * @return string The SQL.
+     */
+    public function walkSelectClause($selectClause)
+    {
+        $sql = 'SELECT ' . (($selectClause->isDistinct) ? 'DISTINCT ' : '') . implode(
+            ', ', array_filter(array_map(array($this, 'walkSelectExpression'), $selectClause->selectExpressions))
+        );
+
+        $addMetaColumns = ! $this->_query->getHint(Query::HINT_FORCE_PARTIAL_LOAD) &&
+                $this->_query->getHydrationMode() == Query::HYDRATE_OBJECT
+                ||
+                $this->_query->getHydrationMode() != Query::HYDRATE_OBJECT &&
+                $this->_query->getHint(Query::HINT_INCLUDE_META_COLUMNS);
+
+        foreach ($this->_selectedClasses as $dqlAlias => $class) {
+            // Register as entity or joined entity result
+            if ($this->_queryComponents[$dqlAlias]['relation'] === null) {
+                $this->_rsm->addEntityResult($class->name, $dqlAlias);
+            } else {
+                $this->_rsm->addJoinedEntityResult(
+                    $class->name, $dqlAlias,
+                    $this->_queryComponents[$dqlAlias]['parent'],
+                    $this->_queryComponents[$dqlAlias]['relation']['fieldName']
+                );
+            }
+
+            if ($class->isInheritanceTypeSingleTable() || $class->isInheritanceTypeJoined()) {
+                // Add discriminator columns to SQL
+                $rootClass = $this->_em->getClassMetadata($class->rootEntityName);
+                $tblAlias = $this->getSQLTableAlias($rootClass->table['name'], $dqlAlias);
+                $discrColumn = $rootClass->discriminatorColumn;
+                $columnAlias = $this->getSQLColumnAlias($discrColumn['name']);
+                $sql .= ", $tblAlias." . $discrColumn['name'] . ' AS ' . $columnAlias;
+
+                $columnAlias = $this->_platform->getSQLResultCasing($columnAlias);
+                $this->_rsm->setDiscriminatorColumn($dqlAlias, $columnAlias);
+                $this->_rsm->addMetaResult($dqlAlias, $columnAlias, $discrColumn['fieldName']);
+
+                // Add foreign key columns to SQL, if necessary
+                if ($addMetaColumns) {
+                    //FIXME: Include foreign key columns of child classes also!!??
+                    foreach ($class->associationMappings as $assoc) {
+                        if ($assoc['isOwningSide'] && $assoc['type'] & ClassMetadata::TO_ONE) {
+                            if (isset($assoc['inherited'])) {
+                                $owningClass = $this->_em->getClassMetadata($assoc['inherited']);
+                                $sqlTableAlias = $this->getSQLTableAlias($owningClass->table['name'], $dqlAlias);
+                            } else {
+                                $sqlTableAlias = $this->getSQLTableAlias($class->table['name'], $dqlAlias);
+                            }
+                            
+                            foreach ($assoc['targetToSourceKeyColumns'] as $srcColumn) {
+                                $columnAlias = $this->getSQLColumnAlias($srcColumn);
+                                $sql .= ", $sqlTableAlias." . $srcColumn . ' AS ' . $columnAlias;
+                                $columnAlias = $this->_platform->getSQLResultCasing($columnAlias);
+                                $this->_rsm->addMetaResult($dqlAlias, $this->_platform->getSQLResultCasing($columnAlias), $srcColumn, (isset($assoc['id']) && $assoc['id'] === true));
+                            }
+                        }
+                    }
+                }
+            } else {
+                // Add foreign key columns to SQL, if necessary
+                if ($addMetaColumns) {
+                    $sqlTableAlias = $this->getSQLTableAlias($class->table['name'], $dqlAlias);
+                    foreach ($class->associationMappings as $assoc) {
+                        if ($assoc['isOwningSide'] && $assoc['type'] & ClassMetadata::TO_ONE) {
+                            foreach ($assoc['targetToSourceKeyColumns'] as $srcColumn) {
+                                $columnAlias = $this->getSQLColumnAlias($srcColumn);
+                                $sql .= ', ' . $sqlTableAlias . '.' . $srcColumn . ' AS ' . $columnAlias;
+                                $columnAlias = $this->_platform->getSQLResultCasing($columnAlias);
+                                $this->_rsm->addMetaResult($dqlAlias, $this->_platform->getSQLResultCasing($columnAlias), $srcColumn, (isset($assoc['id']) && $assoc['id'] === true));
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+        return $sql;
+    }
+
+    /**
+     * Walks down a FromClause AST node, thereby generating the appropriate SQL.
+     *
+     * @return string The SQL.
+     */
+    public function walkFromClause($fromClause)
+    {
+        $identificationVarDecls = $fromClause->identificationVariableDeclarations;
+        $sqlParts = array();
+
+        foreach ($identificationVarDecls as $identificationVariableDecl) {
+            $sql = '';
+
+            $rangeDecl = $identificationVariableDecl->rangeVariableDeclaration;
+            $dqlAlias = $rangeDecl->aliasIdentificationVariable;
+        
+            $this->_rootAliases[] = $dqlAlias;
+
+            $class = $this->_em->getClassMetadata($rangeDecl->abstractSchemaName);
+            $sql .= $class->getQuotedTableName($this->_platform) . ' '
+                  . $this->getSQLTableAlias($class->table['name'], $dqlAlias);
+
+            if ($class->isInheritanceTypeJoined()) {
+                $sql .= $this->_generateClassTableInheritanceJoins($class, $dqlAlias);
+            }
+
+            foreach ($identificationVariableDecl->joinVariableDeclarations as $joinVarDecl) {
+                $sql .= $this->walkJoinVariableDeclaration($joinVarDecl);
+            }
+
+            if ($identificationVariableDecl->indexBy) {
+                $this->_rsm->addIndexBy(
+                    $identificationVariableDecl->indexBy->simpleStateFieldPathExpression->identificationVariable,
+                    $identificationVariableDecl->indexBy->simpleStateFieldPathExpression->field
+                );
+            }
+
+            $sqlParts[] = $this->_platform->appendLockHint($sql, $this->_query->getHint(Query::HINT_LOCK_MODE));
+        }
+
+        return ' FROM ' . implode(', ', $sqlParts);
+    }
+
+    /**
+     * Walks down a FunctionNode AST node, thereby generating the appropriate SQL.
+     *
+     * @return string The SQL.
+     */
+    public function walkFunction($function)
+    {
+        return $function->getSql($this);
+    }
+
+    /**
+     * Walks down an OrderByClause AST node, thereby generating the appropriate SQL.
+     *
+     * @param OrderByClause
+     * @return string The SQL.
+     */
+    public function walkOrderByClause($orderByClause)
+    {
+        $colSql = $this->_generateOrderedCollectionOrderByItems();
+        if ($colSql != '') {
+            $colSql = ", ".$colSql;
+        }
+
+        // OrderByClause ::= "ORDER" "BY" OrderByItem {"," OrderByItem}*
+        return ' ORDER BY ' . implode(
+            ', ', array_map(array($this, 'walkOrderByItem'), $orderByClause->orderByItems)
+        )  . $colSql;
+    }
+
+    /**
+     * Walks down an OrderByItem AST node, thereby generating the appropriate SQL.
+     *
+     * @param OrderByItem
+     * @return string The SQL.
+     */
+    public function walkOrderByItem($orderByItem)
+    {
+        $sql = '';
+        $expr = $orderByItem->expression;
+
+        if ($expr instanceof AST\PathExpression) {
+            $sql = $this->walkPathExpression($expr);
+        } else {
+            $columnName = $this->_queryComponents[$expr]['token']['value'];
+
+            $sql = $this->_scalarResultAliasMap[$columnName];
+        }
+
+        return $sql . ' ' . strtoupper($orderByItem->type);
+    }
+
+    /**
+     * Walks down a HavingClause AST node, thereby generating the appropriate SQL.
+     *
+     * @param HavingClause
+     * @return string The SQL.
+     */
+    public function walkHavingClause($havingClause)
+    {
+        return ' HAVING ' . $this->walkConditionalExpression($havingClause->conditionalExpression);
+    }
+
+    /**
+     * Walks down a JoinVariableDeclaration AST node and creates the corresponding SQL.
+     *
+     * @param JoinVariableDeclaration $joinVarDecl
+     * @return string The SQL.
+     */
+    public function walkJoinVariableDeclaration($joinVarDecl)
+    {
+        $join = $joinVarDecl->join;
+        $joinType = $join->joinType;
+
+        if ($joinVarDecl->indexBy) {
+            // For Many-To-One or One-To-One associations this obviously makes no sense, but is ignored silently.
+            $this->_rsm->addIndexBy(
+                $joinVarDecl->indexBy->simpleStateFieldPathExpression->identificationVariable,
+                $joinVarDecl->indexBy->simpleStateFieldPathExpression->field
+            );
+        }
+
+        if ($joinType == AST\Join::JOIN_TYPE_LEFT || $joinType == AST\Join::JOIN_TYPE_LEFTOUTER) {
+            $sql = ' LEFT JOIN ';
+        } else {
+            $sql = ' INNER JOIN ';
+        }
+
+        $joinAssocPathExpr = $join->joinAssociationPathExpression;
+        $joinedDqlAlias = $join->aliasIdentificationVariable;
+        $relation = $this->_queryComponents[$joinedDqlAlias]['relation'];
+        $targetClass = $this->_em->getClassMetadata($relation['targetEntity']);
+        $sourceClass = $this->_em->getClassMetadata($relation['sourceEntity']);
+        $targetTableName = $targetClass->getQuotedTableName($this->_platform);
+        $targetTableAlias = $this->getSQLTableAlias($targetClass->table['name'], $joinedDqlAlias);
+        $sourceTableAlias = $this->getSQLTableAlias($sourceClass->table['name'], $joinAssocPathExpr->identificationVariable);
+
+        // Ensure we got the owning side, since it has all mapping info
+        $assoc = ( ! $relation['isOwningSide']) ? $targetClass->associationMappings[$relation['mappedBy']] : $relation;
+
+        if ($this->_query->getHint(Query::HINT_INTERNAL_ITERATION) == true) {
+            if ($relation['type'] == ClassMetadata::ONE_TO_MANY || $relation['type'] == ClassMetadata::MANY_TO_MANY) {
+                throw QueryException::iterateWithFetchJoinNotAllowed($assoc);
+            }
+        }
+
+        if ($joinVarDecl->indexBy) {
+            // For Many-To-One or One-To-One associations this obviously makes no sense, but is ignored silently.
+            $this->_rsm->addIndexBy(
+                $joinVarDecl->indexBy->simpleStateFieldPathExpression->identificationVariable,
+                $joinVarDecl->indexBy->simpleStateFieldPathExpression->field
+            );
+        } else if (isset($relation['indexBy'])) {
+            $this->_rsm->addIndexBy($joinedDqlAlias, $relation['indexBy']);
+        }
+
+        // This condition is not checking ClassMetadata::MANY_TO_ONE, because by definition it cannot
+        // be the owning side and previously we ensured that $assoc is always the owning side of the associations.
+        // The owning side is necessary at this point because only it contains the JoinColumn information.
+        if ($assoc['type'] & ClassMetadata::TO_ONE) {
+
+            $sql .= $targetTableName . ' ' . $targetTableAlias . ' ON ';
+            $first = true;
+
+            foreach ($assoc['sourceToTargetKeyColumns'] as $sourceColumn => $targetColumn) {
+                if ( ! $first) $sql .= ' AND '; else $first = false;
+
+                if ($relation['isOwningSide']) {
+                    if ($targetClass->containsForeignIdentifier && !isset($targetClass->fieldNames[$targetColumn])) {
+                        $quotedTargetColumn = $targetColumn; // Join columns cannot be quoted.
+                    } else {
+                        $quotedTargetColumn = $targetClass->getQuotedColumnName($targetClass->fieldNames[$targetColumn], $this->_platform);
+                    }
+                    $sql .= $sourceTableAlias . '.' . $sourceColumn . ' = ' . $targetTableAlias . '.' . $quotedTargetColumn;
+                } else {
+                    if ($sourceClass->containsForeignIdentifier && !isset($sourceClass->fieldNames[$targetColumn])) {
+                        $quotedTargetColumn = $targetColumn; // Join columns cannot be quoted.
+                    } else {
+                        $quotedTargetColumn = $sourceClass->getQuotedColumnName($sourceClass->fieldNames[$targetColumn], $this->_platform);
+                    }
+                    $sql .= $sourceTableAlias . '.' . $quotedTargetColumn . ' = ' . $targetTableAlias . '.' . $sourceColumn;
+                }
+            }
+        } else if ($assoc['type'] == ClassMetadata::MANY_TO_MANY) {
+            // Join relation table
+            $joinTable = $assoc['joinTable'];
+            $joinTableAlias = $this->getSQLTableAlias($joinTable['name'], $joinedDqlAlias);
+            $sql .= $sourceClass->getQuotedJoinTableName($assoc, $this->_platform) . ' ' . $joinTableAlias . ' ON ';
+
+            $first = true;
+            if ($relation['isOwningSide']) {
+                foreach ($assoc['relationToSourceKeyColumns'] as $relationColumn => $sourceColumn) {
+                    if ( ! $first) $sql .= ' AND '; else $first = false;
+
+                    if ($sourceClass->containsForeignIdentifier && !isset($sourceClass->fieldNames[$sourceColumn])) {
+                        $quotedTargetColumn = $sourceColumn; // Join columns cannot be quoted.
+                    } else {
+                        $quotedTargetColumn = $sourceClass->getQuotedColumnName($sourceClass->fieldNames[$sourceColumn], $this->_platform);
+                    }
+
+                    $sql .= $sourceTableAlias . '.' . $quotedTargetColumn . ' = ' . $joinTableAlias . '.' . $relationColumn;
+                }
+            } else {
+                foreach ($assoc['relationToTargetKeyColumns'] as $relationColumn => $targetColumn) {
+                    if ( ! $first) $sql .= ' AND '; else $first = false;
+
+                    if ($sourceClass->containsForeignIdentifier && !isset($sourceClass->fieldNames[$targetColumn])) {
+                        $quotedTargetColumn = $targetColumn; // Join columns cannot be quoted.
+                    } else {
+                        $quotedTargetColumn = $sourceClass->getQuotedColumnName($sourceClass->fieldNames[$targetColumn], $this->_platform);
+                    }
+
+                    $sql .= $sourceTableAlias . '.' . $quotedTargetColumn . ' = ' . $joinTableAlias . '.' . $relationColumn;
+                }
+            }
+
+            // Join target table
+            $sql .= ($joinType == AST\Join::JOIN_TYPE_LEFT || $joinType == AST\Join::JOIN_TYPE_LEFTOUTER)
+            	? ' LEFT JOIN ' : ' INNER JOIN ';
+            $sql .= $targetTableName . ' ' . $targetTableAlias . ' ON ';
+
+            $first = true;
+            if ($relation['isOwningSide']) {
+                foreach ($assoc['relationToTargetKeyColumns'] as $relationColumn => $targetColumn) {
+                    if ( ! $first) $sql .= ' AND '; else $first = false;
+
+                    if ($targetClass->containsForeignIdentifier && !isset($targetClass->fieldNames[$targetColumn])) {
+                        $quotedTargetColumn = $targetColumn; // Join columns cannot be quoted.
+                    } else {
+                        $quotedTargetColumn = $targetClass->getQuotedColumnName($targetClass->fieldNames[$targetColumn], $this->_platform);
+                    }
+
+                    $sql .= $targetTableAlias . '.' . $quotedTargetColumn . ' = ' . $joinTableAlias . '.' . $relationColumn;
+                }
+            } else {
+                foreach ($assoc['relationToSourceKeyColumns'] as $relationColumn => $sourceColumn) {
+                    if ( ! $first) $sql .= ' AND '; else $first = false;
+
+                    if ($targetClass->containsForeignIdentifier && !isset($targetClass->fieldNames[$sourceColumn])) {
+                        $quotedTargetColumn = $sourceColumn; // Join columns cannot be quoted.
+                    } else {
+                        $quotedTargetColumn = $targetClass->getQuotedColumnName($targetClass->fieldNames[$sourceColumn], $this->_platform);
+                    }
+
+                    $sql .= $targetTableAlias . '.' . $quotedTargetColumn . ' = ' . $joinTableAlias . '.' . $relationColumn;
+                }
+            }
+        }
+
+        // Handle WITH clause
+        if (($condExpr = $join->conditionalExpression) !== null) {
+            // Phase 2 AST optimization: Skip processment of ConditionalExpression
+            // if only one ConditionalTerm is defined
+            $sql .= ' AND (' . $this->walkConditionalExpression($condExpr) . ')';
+        }
+
+        $discrSql = $this->_generateDiscriminatorColumnConditionSQL(array($joinedDqlAlias));
+
+        if ($discrSql) {
+            $sql .= ' AND ' . $discrSql;
+        }
+
+        // FIXME: these should either be nested or all forced to be left joins (DDC-XXX)
+        if ($targetClass->isInheritanceTypeJoined()) {
+            $sql .= $this->_generateClassTableInheritanceJoins($targetClass, $joinedDqlAlias);
+        }
+
+        return $sql;
+    }
+    
+    /**
+     * Walks down a CoalesceExpression AST node and generates the corresponding SQL.
+     *
+     * @param CoalesceExpression $coalesceExpression
+     * @return string The SQL.
+     */
+    public function walkCoalesceExpression($coalesceExpression)
+    {
+        $sql = 'COALESCE(';
+        
+        $scalarExpressions = array();
+        
+        foreach ($coalesceExpression->scalarExpressions as $scalarExpression) {
+            $scalarExpressions[] = $this->walkSimpleArithmeticExpression($scalarExpression);
+        }
+        
+        $sql .= implode(', ', $scalarExpressions) . ')';
+        
+        return $sql;
+    }
+    
+    public function walkCaseExpression($expression)
+    {
+        switch (true) {
+            case ($expression instanceof AST\CoalesceExpression):
+                return $this->walkCoalesceExpression($expression);
+                
+            case ($expression instanceof AST\NullIfExpression):
+                return $this->walkNullIfExpression($expression);
+                
+            default:
+                return '';
+        }
+    }
+    
+    /**
+     * Walks down a NullIfExpression AST node and generates the corresponding SQL.
+     *
+     * @param NullIfExpression $nullIfExpression
+     * @return string The SQL.
+     */
+    public function walkNullIfExpression($nullIfExpression)
+    {
+        $firstExpression = is_string($nullIfExpression->firstExpression) 
+            ? $this->_conn->quote($nullIfExpression->firstExpression)
+            : $this->walkSimpleArithmeticExpression($nullIfExpression->firstExpression);
+        
+        $secondExpression = is_string($nullIfExpression->secondExpression) 
+            ? $this->_conn->quote($nullIfExpression->secondExpression)
+            : $this->walkSimpleArithmeticExpression($nullIfExpression->secondExpression);
+        
+        return 'NULLIF(' . $firstExpression . ', ' . $secondExpression . ')';
+    }
+
+    /**
+     * Walks down a SelectExpression AST node and generates the corresponding SQL.
+     *
+     * @param SelectExpression $selectExpression
+     * @return string The SQL.
+     */
+    public function walkSelectExpression($selectExpression)
+    {
+        $sql = '';
+        $expr = $selectExpression->expression;
+
+        if ($expr instanceof AST\PathExpression) {
+            if ($expr->type == AST\PathExpression::TYPE_STATE_FIELD) {
+                $fieldName = $expr->field;
+                $dqlAlias = $expr->identificationVariable;
+                $qComp = $this->_queryComponents[$dqlAlias];
+                $class = $qComp['metadata'];
+
+                if ( ! $selectExpression->fieldIdentificationVariable) {
+                    $resultAlias = $fieldName;
+                } else {
+                    $resultAlias = $selectExpression->fieldIdentificationVariable;
+                }
+
+                if ($class->isInheritanceTypeJoined()) {
+                    $tableName = $this->_em->getUnitOfWork()->getEntityPersister($class->name)->getOwningTable($fieldName);
+                } else {
+                    $tableName = $class->getTableName();
+                }
+
+                $sqlTableAlias = $this->getSQLTableAlias($tableName, $dqlAlias);
+                $columnName = $class->getQuotedColumnName($fieldName, $this->_platform);
+
+                $columnAlias = $this->getSQLColumnAlias($columnName);
+                $sql .= $sqlTableAlias . '.' . $columnName . ' AS ' . $columnAlias;
+                $columnAlias = $this->_platform->getSQLResultCasing($columnAlias);
+                $this->_rsm->addScalarResult($columnAlias, $resultAlias);
+            } else {
+                throw QueryException::invalidPathExpression($expr->type);
+            }
+        }
+        else if ($expr instanceof AST\AggregateExpression) {
+            if ( ! $selectExpression->fieldIdentificationVariable) {
+                $resultAlias = $this->_scalarResultCounter++;
+            } else {
+                $resultAlias = $selectExpression->fieldIdentificationVariable;
+            }
+
+            $columnAlias = 'sclr' . $this->_aliasCounter++;
+            $sql .= $this->walkAggregateExpression($expr) . ' AS ' . $columnAlias;
+            $this->_scalarResultAliasMap[$resultAlias] = $columnAlias;
+
+            $columnAlias = $this->_platform->getSQLResultCasing($columnAlias);
+            $this->_rsm->addScalarResult($columnAlias, $resultAlias);
+        }
+        else if ($expr instanceof AST\Subselect) {
+            if ( ! $selectExpression->fieldIdentificationVariable) {
+                $resultAlias = $this->_scalarResultCounter++;
+            } else {
+                $resultAlias = $selectExpression->fieldIdentificationVariable;
+            }
+
+            $columnAlias = 'sclr' . $this->_aliasCounter++;
+            $sql .= '(' . $this->walkSubselect($expr) . ') AS '.$columnAlias;
+            $this->_scalarResultAliasMap[$resultAlias] = $columnAlias;
+
+            $columnAlias = $this->_platform->getSQLResultCasing($columnAlias);
+            $this->_rsm->addScalarResult($columnAlias, $resultAlias);
+        }
+        else if ($expr instanceof AST\Functions\FunctionNode) {
+            if ( ! $selectExpression->fieldIdentificationVariable) {
+                $resultAlias = $this->_scalarResultCounter++;
+            } else {
+                $resultAlias = $selectExpression->fieldIdentificationVariable;
+            }
+
+            $columnAlias = 'sclr' . $this->_aliasCounter++;
+            $sql .= $this->walkFunction($expr) . ' AS ' . $columnAlias;
+            $this->_scalarResultAliasMap[$resultAlias] = $columnAlias;
+
+            $columnAlias = $this->_platform->getSQLResultCasing($columnAlias);
+            $this->_rsm->addScalarResult($columnAlias, $resultAlias);
+        } else if (
+            $expr instanceof AST\SimpleArithmeticExpression ||
+            $expr instanceof AST\ArithmeticTerm ||
+            $expr instanceof AST\ArithmeticFactor ||
+            $expr instanceof AST\ArithmeticPrimary ||
+            $expr instanceof AST\Literal
+        ) {
+            if ( ! $selectExpression->fieldIdentificationVariable) {
+                $resultAlias = $this->_scalarResultCounter++;
+            } else {
+                $resultAlias = $selectExpression->fieldIdentificationVariable;
+            }
+
+            $columnAlias = 'sclr' . $this->_aliasCounter++;
+            
+            if ($expr instanceof AST\Literal) {
+                $sql .= $this->walkLiteral($expr) . ' AS ' .$columnAlias;
+            } else {
+                $sql .= $this->walkSimpleArithmeticExpression($expr) . ' AS ' . $columnAlias;
+            }
+            
+            $this->_scalarResultAliasMap[$resultAlias] = $columnAlias;
+
+            $columnAlias = $this->_platform->getSQLResultCasing($columnAlias);
+            $this->_rsm->addScalarResult($columnAlias, $resultAlias);
+        } else if (
+            $expr instanceof AST\NullIfExpression ||
+            $expr instanceof AST\CoalesceExpression ||
+            $expr instanceof AST\CaseExpression
+        ) {
+            if ( ! $selectExpression->fieldIdentificationVariable) {
+                $resultAlias = $this->_scalarResultCounter++;
+            } else {
+                $resultAlias = $selectExpression->fieldIdentificationVariable;
+            }
+
+            $columnAlias = 'sclr' . $this->_aliasCounter++;
+            
+            $sql .= $this->walkCaseExpression($expr) . ' AS ' . $columnAlias;
+            
+            $this->_scalarResultAliasMap[$resultAlias] = $columnAlias;
+
+            $columnAlias = $this->_platform->getSQLResultCasing($columnAlias);
+            $this->_rsm->addScalarResult($columnAlias, $resultAlias);
+        } else {
+            // IdentificationVariable or PartialObjectExpression
+            if ($expr instanceof AST\PartialObjectExpression) {
+                $dqlAlias = $expr->identificationVariable;
+                $partialFieldSet = $expr->partialFieldSet;
+            } else {
+                $dqlAlias = $expr;
+                $partialFieldSet = array();
+            }
+
+            $queryComp = $this->_queryComponents[$dqlAlias];
+            $class = $queryComp['metadata'];
+
+            if ( ! isset($this->_selectedClasses[$dqlAlias])) {
+                $this->_selectedClasses[$dqlAlias] = $class;
+            }
+
+            $beginning = true;
+            // Select all fields from the queried class
+            foreach ($class->fieldMappings as $fieldName => $mapping) {
+                if ($partialFieldSet && !in_array($fieldName, $partialFieldSet)) {
+                    continue;
+                }
+
+                if (isset($mapping['inherited'])) {
+                    $tableName = $this->_em->getClassMetadata($mapping['inherited'])->table['name'];
+                } else {
+                    $tableName = $class->table['name'];
+                }
+
+                if ($beginning) $beginning = false; else $sql .= ', ';
+
+                $sqlTableAlias = $this->getSQLTableAlias($tableName, $dqlAlias);
+                $columnAlias = $this->getSQLColumnAlias($mapping['columnName']);
+                $sql .= $sqlTableAlias . '.' . $class->getQuotedColumnName($fieldName, $this->_platform)
+                      . ' AS ' . $columnAlias;
+
+                $columnAlias = $this->_platform->getSQLResultCasing($columnAlias);
+                $this->_rsm->addFieldResult($dqlAlias, $columnAlias, $fieldName, $class->name);
+            }
+
+            // Add any additional fields of subclasses (excluding inherited fields)
+            // 1) on Single Table Inheritance: always, since its marginal overhead
+            // 2) on Class Table Inheritance only if partial objects are disallowed,
+            //    since it requires outer joining subtables.
+            if ($class->isInheritanceTypeSingleTable() || ! $this->_query->getHint(Query::HINT_FORCE_PARTIAL_LOAD)) {
+                foreach ($class->subClasses as $subClassName) {
+                    $subClass = $this->_em->getClassMetadata($subClassName);
+                    $sqlTableAlias = $this->getSQLTableAlias($subClass->table['name'], $dqlAlias);
+                    foreach ($subClass->fieldMappings as $fieldName => $mapping) {
+                        if (isset($mapping['inherited']) || $partialFieldSet && !in_array($fieldName, $partialFieldSet)) {
+                            continue;
+                        }
+
+                        if ($beginning) $beginning = false; else $sql .= ', ';
+
+                        $columnAlias = $this->getSQLColumnAlias($mapping['columnName']);
+                        $sql .= $sqlTableAlias . '.' . $subClass->getQuotedColumnName($fieldName, $this->_platform)
+                                . ' AS ' . $columnAlias;
+
+                        $columnAlias = $this->_platform->getSQLResultCasing($columnAlias);
+                        $this->_rsm->addFieldResult($dqlAlias, $columnAlias, $fieldName, $subClassName);
+                    }
+
+                    // Add join columns (foreign keys) of the subclass
+                    //TODO: Probably better do this in walkSelectClause to honor the INCLUDE_META_COLUMNS hint
+                    foreach ($subClass->associationMappings as $fieldName => $assoc) {
+                        if ($assoc['isOwningSide'] && $assoc['type'] & ClassMetadata::TO_ONE && ! isset($assoc['inherited'])) {
+                            foreach ($assoc['targetToSourceKeyColumns'] as $srcColumn) {
+                                if ($beginning) $beginning = false; else $sql .= ', ';
+                                $columnAlias = $this->getSQLColumnAlias($srcColumn);
+                                $sql .= $sqlTableAlias . '.' . $srcColumn . ' AS ' . $columnAlias;
+                                $this->_rsm->addMetaResult($dqlAlias, $this->_platform->getSQLResultCasing($columnAlias), $srcColumn);
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+        return $sql;
+    }
+
+    /**
+     * Walks down a QuantifiedExpression AST node, thereby generating the appropriate SQL.
+     *
+     * @param QuantifiedExpression
+     * @return string The SQL.
+     */
+    public function walkQuantifiedExpression($qExpr)
+    {
+        return ' ' . strtoupper($qExpr->type)
+             . '(' . $this->walkSubselect($qExpr->subselect) . ')';
+    }
+
+    /**
+     * Walks down a Subselect AST node, thereby generating the appropriate SQL.
+     *
+     * @param Subselect
+     * @return string The SQL.
+     */
+    public function walkSubselect($subselect)
+    {
+        $useAliasesBefore = $this->_useSqlTableAliases;
+        $this->_useSqlTableAliases = true;
+
+        $sql = $this->walkSimpleSelectClause($subselect->simpleSelectClause);
+        $sql .= $this->walkSubselectFromClause($subselect->subselectFromClause);
+        $sql .= $subselect->whereClause ? $this->walkWhereClause($subselect->whereClause) : '';
+        $sql .= $subselect->groupByClause ? $this->walkGroupByClause($subselect->groupByClause) : '';
+        $sql .= $subselect->havingClause ? $this->walkHavingClause($subselect->havingClause) : '';
+        $sql .= $subselect->orderByClause ? $this->walkOrderByClause($subselect->orderByClause) : '';
+
+        $this->_useSqlTableAliases = $useAliasesBefore;
+
+        return $sql;
+    }
+
+    /**
+     * Walks down a SubselectFromClause AST node, thereby generating the appropriate SQL.
+     *
+     * @param SubselectFromClause
+     * @return string The SQL.
+     */
+    public function walkSubselectFromClause($subselectFromClause)
+    {
+        $identificationVarDecls = $subselectFromClause->identificationVariableDeclarations;
+        $sqlParts = array ();
+
+        foreach ($identificationVarDecls as $subselectIdVarDecl) {
+            $sql = '';
+
+            $rangeDecl = $subselectIdVarDecl->rangeVariableDeclaration;
+            $dqlAlias = $rangeDecl->aliasIdentificationVariable;
+
+            $class = $this->_em->getClassMetadata($rangeDecl->abstractSchemaName);
+            $sql .= $class->getQuotedTableName($this->_platform) . ' '
+                  . $this->getSQLTableAlias($class->table['name'], $dqlAlias);
+
+            if ($class->isInheritanceTypeJoined()) {
+                $sql .= $this->_generateClassTableInheritanceJoins($class, $dqlAlias);
+            }
+
+            foreach ($subselectIdVarDecl->joinVariableDeclarations as $joinVarDecl) {
+                $sql .= $this->walkJoinVariableDeclaration($joinVarDecl);
+            }
+
+            $sqlParts[] = $this->_platform->appendLockHint($sql, $this->_query->getHint(Query::HINT_LOCK_MODE));
+        }
+
+        return ' FROM ' . implode(', ', $sqlParts);
+    }
+
+    /**
+     * Walks down a SimpleSelectClause AST node, thereby generating the appropriate SQL.
+     *
+     * @param SimpleSelectClause
+     * @return string The SQL.
+     */
+    public function walkSimpleSelectClause($simpleSelectClause)
+    {
+        return 'SELECT' . ($simpleSelectClause->isDistinct ? ' DISTINCT' : '')
+             . $this->walkSimpleSelectExpression($simpleSelectClause->simpleSelectExpression);
+    }
+
+    /**
+     * Walks down a SimpleSelectExpression AST node, thereby generating the appropriate SQL.
+     *
+     * @param SimpleSelectExpression
+     * @return string The SQL.
+     */
+    public function walkSimpleSelectExpression($simpleSelectExpression)
+    {
+        $sql = '';
+        $expr = $simpleSelectExpression->expression;
+
+        if ($expr instanceof AST\PathExpression) {
+            $sql .= $this->walkPathExpression($expr);
+        } else if ($expr instanceof AST\AggregateExpression) {
+            if ( ! $simpleSelectExpression->fieldIdentificationVariable) {
+                $alias = $this->_scalarResultCounter++;
+            } else {
+                $alias = $simpleSelectExpression->fieldIdentificationVariable;
+            }
+
+            $sql .= $this->walkAggregateExpression($expr) . ' AS dctrn__' . $alias;
+        } else if ($expr instanceof AST\Subselect) {
+            if ( ! $simpleSelectExpression->fieldIdentificationVariable) {
+                $alias = $this->_scalarResultCounter++;
+            } else {
+                $alias = $simpleSelectExpression->fieldIdentificationVariable;
+            }
+
+            $columnAlias = 'sclr' . $this->_aliasCounter++;
+            $sql .= '(' . $this->walkSubselect($expr) . ') AS ' . $columnAlias;
+            $this->_scalarResultAliasMap[$alias] = $columnAlias;
+        } else if ($expr instanceof AST\Functions\FunctionNode) {
+            if ( ! $simpleSelectExpression->fieldIdentificationVariable) {
+                $alias = $this->_scalarResultCounter++;
+            } else {
+                $alias = $simpleSelectExpression->fieldIdentificationVariable;
+            }
+
+            $columnAlias = 'sclr' . $this->_aliasCounter++;
+            $sql .= $this->walkFunction($expr) . ' AS ' . $columnAlias;
+            $this->_scalarResultAliasMap[$alias] = $columnAlias;
+        } else if (
+            $expr instanceof AST\SimpleArithmeticExpression ||
+            $expr instanceof AST\ArithmeticTerm ||
+            $expr instanceof AST\ArithmeticFactor ||
+            $expr instanceof AST\ArithmeticPrimary
+        ) {
+            if ( ! $simpleSelectExpression->fieldIdentificationVariable) {
+                $alias = $this->_scalarResultCounter++;
+            } else {
+                $alias = $simpleSelectExpression->fieldIdentificationVariable;
+            }
+
+            $columnAlias = 'sclr' . $this->_aliasCounter++;
+            $sql .= $this->walkSimpleArithmeticExpression($expr) . ' AS ' . $columnAlias;
+            $this->_scalarResultAliasMap[$alias] = $columnAlias;
+        } else {
+            // IdentificationVariable
+            $class = $this->_queryComponents[$expr]['metadata'];
+            $tableAlias = $this->getSQLTableAlias($class->getTableName(), $expr);
+            $first = true;
+
+            foreach ($class->identifier as $identifier) {
+                if ($first) $first = false; else $sql .= ', ';
+                $sql .= $tableAlias . '.' . $class->getQuotedColumnName($identifier, $this->_platform);
+            }
+        }
+
+        return ' ' . $sql;
+    }
+
+    /**
+     * Walks down an AggregateExpression AST node, thereby generating the appropriate SQL.
+     *
+     * @param AggregateExpression
+     * @return string The SQL.
+     */
+    public function walkAggregateExpression($aggExpression)
+    {
+        return $aggExpression->functionName . '(' . ($aggExpression->isDistinct ? 'DISTINCT ' : '')
+             . $this->walkSimpleArithmeticExpression($aggExpression->pathExpression) . ')';
+    }
+
+    /**
+     * Walks down a GroupByClause AST node, thereby generating the appropriate SQL.
+     *
+     * @param GroupByClause
+     * @return string The SQL.
+     */
+    public function walkGroupByClause($groupByClause)
+    {
+        $sql = '';
+        foreach ($groupByClause->groupByItems AS $groupByItem) {
+            if (is_string($groupByItem)) {
+                foreach ($this->_queryComponents[$groupByItem]['metadata']->identifier AS $idField) {
+                    if ($sql != '') {
+                        $sql .= ', ';
+                    }
+                    $groupByItem = new AST\PathExpression(AST\PathExpression::TYPE_STATE_FIELD, $groupByItem, $idField);
+                    $groupByItem->type = AST\PathExpression::TYPE_STATE_FIELD;
+                    $sql .= $this->walkGroupByItem($groupByItem);
+                }
+            } else {
+                if ($sql != '') {
+                    $sql .= ', ';
+                }
+                $sql .= $this->walkGroupByItem($groupByItem);
+            }
+        }
+        return ' GROUP BY ' . $sql;
+    }
+
+    /**
+     * Walks down a GroupByItem AST node, thereby generating the appropriate SQL.
+     *
+     * @param GroupByItem
+     * @return string The SQL.
+     */
+    public function walkGroupByItem(AST\PathExpression $pathExpr)
+    {
+        return $this->walkPathExpression($pathExpr);
+    }
+
+    /**
+     * Walks down a DeleteClause AST node, thereby generating the appropriate SQL.
+     *
+     * @param DeleteClause
+     * @return string The SQL.
+     */
+    public function walkDeleteClause(AST\DeleteClause $deleteClause)
+    {
+        $sql = 'DELETE FROM ';
+        $class = $this->_em->getClassMetadata($deleteClause->abstractSchemaName);
+        $sql .= $class->getQuotedTableName($this->_platform);
+
+        $this->setSQLTableAlias($class->getTableName(), $class->getTableName(), $deleteClause->aliasIdentificationVariable);
+
+        $this->_rootAliases[] = $deleteClause->aliasIdentificationVariable;
+
+        return $sql;
+    }
+
+    /**
+     * Walks down an UpdateClause AST node, thereby generating the appropriate SQL.
+     *
+     * @param UpdateClause
+     * @return string The SQL.
+     */
+    public function walkUpdateClause($updateClause)
+    {
+        $sql = 'UPDATE ';
+        $class = $this->_em->getClassMetadata($updateClause->abstractSchemaName);
+        $sql .= $class->getQuotedTableName($this->_platform);
+
+        $this->setSQLTableAlias($class->getTableName(), $class->getTableName(), $updateClause->aliasIdentificationVariable);
+
+        $this->_rootAliases[] = $updateClause->aliasIdentificationVariable;
+
+        $sql .= ' SET ' . implode(
+            ', ', array_map(array($this, 'walkUpdateItem'), $updateClause->updateItems)
+        );
+
+        return $sql;
+    }
+
+    /**
+     * Walks down an UpdateItem AST node, thereby generating the appropriate SQL.
+     *
+     * @param UpdateItem
+     * @return string The SQL.
+     */
+    public function walkUpdateItem($updateItem)
+    {
+        $useTableAliasesBefore = $this->_useSqlTableAliases;
+        $this->_useSqlTableAliases = false;
+
+        $sql = $this->walkPathExpression($updateItem->pathExpression) . ' = ';
+
+        $newValue = $updateItem->newValue;
+
+        if ($newValue === null) {
+            $sql .= 'NULL';
+        } else if ($newValue instanceof AST\Node) {
+            $sql .= $newValue->dispatch($this);
+        } else {
+            $sql .= $this->_conn->quote($newValue);
+        }
+
+        $this->_useSqlTableAliases = $useTableAliasesBefore;
+
+        return $sql;
+    }
+
+    /**
+     * Walks down a WhereClause AST node, thereby generating the appropriate SQL.
+     *
+     * @param WhereClause
+     * @return string The SQL.
+     */
+    public function walkWhereClause($whereClause)
+    {
+        $discrSql = $this->_generateDiscriminatorColumnConditionSql($this->_rootAliases);
+        $condSql = $this->walkConditionalExpression($whereClause->conditionalExpression);
+
+        return ' WHERE ' . (( ! $discrSql) ? $condSql : '(' . $condSql . ') AND ' . $discrSql);
+    }
+
+    /**
+     * Walk down a ConditionalExpression AST node, thereby generating the appropriate SQL.
+     *
+     * @param ConditionalExpression
+     * @return string The SQL.
+     */
+    public function walkConditionalExpression($condExpr)
+    {
+        // Phase 2 AST optimization: Skip processment of ConditionalExpression
+        // if only one ConditionalTerm is defined
+        return ( ! ($condExpr instanceof AST\ConditionalExpression))
+            ? $this->walkConditionalTerm($condExpr)
+            : implode(
+                ' OR ', array_map(array($this, 'walkConditionalTerm'), $condExpr->conditionalTerms)
+            );
+    }
+
+    /**
+     * Walks down a ConditionalTerm AST node, thereby generating the appropriate SQL.
+     *
+     * @param ConditionalTerm
+     * @return string The SQL.
+     */
+    public function walkConditionalTerm($condTerm)
+    {
+        // Phase 2 AST optimization: Skip processment of ConditionalTerm
+        // if only one ConditionalFactor is defined
+        return ( ! ($condTerm instanceof AST\ConditionalTerm))
+            ? $this->walkConditionalFactor($condTerm)
+            : implode(
+                ' AND ', array_map(array($this, 'walkConditionalFactor'), $condTerm->conditionalFactors)
+            );
+    }
+
+    /**
+     * Walks down a ConditionalFactor AST node, thereby generating the appropriate SQL.
+     *
+     * @param ConditionalFactor
+     * @return string The SQL.
+     */
+    public function walkConditionalFactor($factor)
+    {
+        // Phase 2 AST optimization: Skip processment of ConditionalFactor
+        // if only one ConditionalPrimary is defined
+        return ( ! ($factor instanceof AST\ConditionalFactor))
+            ? $this->walkConditionalPrimary($factor)
+            : ($factor->not ? 'NOT ' : '') . $this->walkConditionalPrimary($factor->conditionalPrimary);
+    }
+
+    /**
+     * Walks down a ConditionalPrimary AST node, thereby generating the appropriate SQL.
+     *
+     * @param ConditionalPrimary
+     * @return string The SQL.
+     */
+    public function walkConditionalPrimary($primary)
+    {
+        if ($primary->isSimpleConditionalExpression()) {
+            return $primary->simpleConditionalExpression->dispatch($this);
+        } else if ($primary->isConditionalExpression()) {
+            $condExpr = $primary->conditionalExpression;
+
+            return '(' . $this->walkConditionalExpression($condExpr) . ')';
+        }
+    }
+
+    /**
+     * Walks down an ExistsExpression AST node, thereby generating the appropriate SQL.
+     *
+     * @param ExistsExpression
+     * @return string The SQL.
+     */
+    public function walkExistsExpression($existsExpr)
+    {
+        $sql = ($existsExpr->not) ? 'NOT ' : '';
+
+        $sql .= 'EXISTS (' . $this->walkSubselect($existsExpr->subselect) . ')';
+
+        return $sql;
+    }
+
+    /**
+     * Walks down a CollectionMemberExpression AST node, thereby generating the appropriate SQL.
+     *
+     * @param CollectionMemberExpression
+     * @return string The SQL.
+     */
+    public function walkCollectionMemberExpression($collMemberExpr)
+    {
+        $sql = $collMemberExpr->not ? 'NOT ' : '';
+        $sql .= 'EXISTS (SELECT 1 FROM ';
+        $entityExpr = $collMemberExpr->entityExpression;
+        $collPathExpr = $collMemberExpr->collectionValuedPathExpression;
+        
+        $fieldName = $collPathExpr->field;
+        $dqlAlias = $collPathExpr->identificationVariable;
+        
+        $class = $this->_queryComponents[$dqlAlias]['metadata'];
+        
+        if ($entityExpr instanceof AST\InputParameter) {
+            $dqlParamKey = $entityExpr->name;
+            $entity = $this->_query->getParameter($dqlParamKey);
+        } else {
+            //TODO
+            throw new \BadMethodCallException("Not implemented");
+        }
+        
+        $assoc = $class->associationMappings[$fieldName];
+        
+        if ($assoc['type'] == ClassMetadata::ONE_TO_MANY) {
+            $targetClass = $this->_em->getClassMetadata($assoc['targetEntity']);
+            $targetTableAlias = $this->getSQLTableAlias($targetClass->table['name']);
+            $sourceTableAlias = $this->getSQLTableAlias($class->table['name'], $dqlAlias);
+            
+            $sql .= $targetClass->getQuotedTableName($this->_platform)
+                  . ' ' . $targetTableAlias . ' WHERE ';
+                    
+            $owningAssoc = $targetClass->associationMappings[$assoc['mappedBy']];
+            
+            $first = true;
+            
+            foreach ($owningAssoc['targetToSourceKeyColumns'] as $targetColumn => $sourceColumn) {
+                if ($first) $first = false; else $sql .= ' AND ';
+                
+                $sql .= $sourceTableAlias . '.' . $class->getQuotedColumnName($class->fieldNames[$targetColumn], $this->_platform) 
+                      . ' = ' 
+                      . $targetTableAlias . '.' . $sourceColumn;
+            }
+            
+            $sql .= ' AND ';
+            $first = true;
+            
+            foreach ($targetClass->identifier as $idField) {
+                if ($first) $first = false; else $sql .= ' AND ';
+                
+                $this->_parserResult->addParameterMapping($dqlParamKey, $this->_sqlParamIndex++);
+                $sql .= $targetTableAlias . '.' 
+                      . $targetClass->getQuotedColumnName($idField, $this->_platform) . ' = ?';
+            }
+        } else { // many-to-many
+            $targetClass = $this->_em->getClassMetadata($assoc['targetEntity']);
+            
+            $owningAssoc = $assoc['isOwningSide'] ? $assoc : $targetClass->associationMappings[$assoc['mappedBy']];
+            $joinTable = $owningAssoc['joinTable'];
+
+            // SQL table aliases
+            $joinTableAlias = $this->getSQLTableAlias($joinTable['name']);
+            $targetTableAlias = $this->getSQLTableAlias($targetClass->table['name']);
+            $sourceTableAlias = $this->getSQLTableAlias($class->table['name'], $dqlAlias);
+            
+            // join to target table
+            $sql .= $targetClass->getQuotedJoinTableName($owningAssoc, $this->_platform)
+                  . ' ' . $joinTableAlias . ' INNER JOIN '
+                  . $targetClass->getQuotedTableName($this->_platform)
+                  . ' ' . $targetTableAlias . ' ON ';
+            
+            // join conditions
+            $joinColumns = $assoc['isOwningSide']
+                ? $joinTable['inverseJoinColumns']
+                : $joinTable['joinColumns'];
+
+            $first = true;
+            foreach ($joinColumns as $joinColumn) {
+                if ($first) $first = false; else $sql .= ' AND ';
+
+                $sql .= $joinTableAlias . '.' . $joinColumn['name'] . ' = '
+                        . $targetTableAlias . '.' . $targetClass->getQuotedColumnName(
+                                $targetClass->fieldNames[$joinColumn['referencedColumnName']],
+                                $this->_platform);
+            }
+
+            $sql .= ' WHERE ';
+
+            $joinColumns = $assoc['isOwningSide']
+                ? $joinTable['joinColumns']
+                : $joinTable['inverseJoinColumns'];
+
+            $first = true;
+            foreach ($joinColumns as $joinColumn) {
+                if ($first) $first = false; else $sql .= ' AND ';
+
+                $sql .= $joinTableAlias . '.' . $joinColumn['name'] . ' = ' 
+                      . $sourceTableAlias . '.' . $class->getQuotedColumnName(
+                              $class->fieldNames[$joinColumn['referencedColumnName']],
+                              $this->_platform);
+            }
+            
+            $sql .= ' AND ';
+            $first = true;
+            
+            foreach ($targetClass->identifier as $idField) {
+                if ($first) $first = false; else $sql .= ' AND ';
+                
+                $this->_parserResult->addParameterMapping($dqlParamKey, $this->_sqlParamIndex++);
+                $sql .= $targetTableAlias . '.' 
+                      . $targetClass->getQuotedColumnName($idField, $this->_platform) . ' = ?';
+            }
+        }
+
+        return $sql . ')';
+    }
+    
+    /**
+     * Walks down an EmptyCollectionComparisonExpression AST node, thereby generating the appropriate SQL.
+     *
+     * @param EmptyCollectionComparisonExpression
+     * @return string The SQL.
+     */
+    public function walkEmptyCollectionComparisonExpression($emptyCollCompExpr)
+    {
+        $sizeFunc = new AST\Functions\SizeFunction('size');
+        $sizeFunc->collectionPathExpression = $emptyCollCompExpr->expression;
+
+        return $sizeFunc->getSql($this) . ($emptyCollCompExpr->not ? ' > 0' : ' = 0');
+    }
+
+    /**
+     * Walks down a NullComparisonExpression AST node, thereby generating the appropriate SQL.
+     *
+     * @param NullComparisonExpression
+     * @return string The SQL.
+     */
+    public function walkNullComparisonExpression($nullCompExpr)
+    {
+        $sql = '';
+        $innerExpr = $nullCompExpr->expression;
+
+        if ($innerExpr instanceof AST\InputParameter) {
+            $dqlParamKey = $innerExpr->name;
+            $this->_parserResult->addParameterMapping($dqlParamKey, $this->_sqlParamIndex++);
+            $sql .= ' ?';
+        } else {
+            $sql .= $this->walkPathExpression($innerExpr);
+        }
+
+        $sql .= ' IS' . ($nullCompExpr->not ? ' NOT' : '') . ' NULL';
+
+        return $sql;
+    }
+
+    /**
+     * Walks down an InExpression AST node, thereby generating the appropriate SQL.
+     *
+     * @param InExpression
+     * @return string The SQL.
+     */
+    public function walkInExpression($inExpr)
+    {
+        $sql = $this->walkPathExpression($inExpr->pathExpression)
+             . ($inExpr->not ? ' NOT' : '') . ' IN (';
+
+        if ($inExpr->subselect) {
+            $sql .= $this->walkSubselect($inExpr->subselect);
+        } else {
+            $sql .= implode(', ', array_map(array($this, 'walkInParameter'), $inExpr->literals));
+        }
+
+        $sql .= ')';
+
+        return $sql;
+    }
+
+    /**
+     * Walks down an InstanceOfExpression AST node, thereby generating the appropriate SQL.
+     *
+     * @param InstanceOfExpression
+     * @return string The SQL.
+     */
+    public function walkInstanceOfExpression($instanceOfExpr)
+    {
+        $sql = '';
+
+        $dqlAlias = $instanceOfExpr->identificationVariable;
+        $discrClass = $class = $this->_queryComponents[$dqlAlias]['metadata'];
+        $fieldName = null;
+
+        if ($class->discriminatorColumn) {
+            $discrClass = $this->_em->getClassMetadata($class->rootEntityName);
+        }
+
+        if ($this->_useSqlTableAliases) {
+            $sql .= $this->getSQLTableAlias($discrClass->table['name'], $dqlAlias) . '.';
+        }
+
+        $sql .= $class->discriminatorColumn['name'] . ($instanceOfExpr->not ? ' <> ' : ' = ');
+
+        if ($instanceOfExpr->value instanceof AST\InputParameter) {
+            // We need to modify the parameter value to be its correspondent mapped value
+            $dqlParamKey = $instanceOfExpr->value->name;
+            $paramValue  = $this->_query->getParameter($dqlParamKey);
+            
+            if ( ! ($paramValue instanceof \Doctrine\ORM\Mapping\ClassMetadata)) {
+                throw QueryException::invalidParameterType('ClassMetadata', get_class($paramValue));
+            }
+            
+            $entityClassName = $paramValue->name;
+        } else {
+            // Get name from ClassMetadata to resolve aliases.
+            $entityClassName = $this->_em->getClassMetadata($instanceOfExpr->value)->name;
+        }
+
+        if ($entityClassName == $class->name) {
+            $sql .= $this->_conn->quote($class->discriminatorValue);
+        } else {
+            $discrMap = array_flip($class->discriminatorMap);
+            if (!isset($discrMap[$entityClassName])) {
+                throw QueryException::instanceOfUnrelatedClass($entityClassName, $class->rootEntityName);
+            }
+            
+            $sql .= $this->_conn->quote($discrMap[$entityClassName]);
+        }
+
+        return $sql;
+    }
+
+    /**
+     * Walks down an InParameter AST node, thereby generating the appropriate SQL.
+     *
+     * @param InParameter
+     * @return string The SQL.
+     */
+    public function walkInParameter($inParam)
+    {
+        return $inParam instanceof AST\InputParameter ?
+                $this->walkInputParameter($inParam) :
+                $this->walkLiteral($inParam);
+    }
+
+    /**
+     * Walks down a literal that represents an AST node, thereby generating the appropriate SQL.
+     *
+     * @param mixed
+     * @return string The SQL.
+     */
+    public function walkLiteral($literal)
+    {
+        switch ($literal->type) {
+            case AST\Literal::STRING:
+                return $this->_conn->quote($literal->value);
+            case AST\Literal::BOOLEAN:
+                $bool = strtolower($literal->value) == 'true' ? true : false;
+                $boolVal = $this->_conn->getDatabasePlatform()->convertBooleans($bool);
+                return is_string($boolVal) ? $this->_conn->quote($boolVal) : $boolVal;
+            case AST\Literal::NUMERIC:
+                return $literal->value;
+            default:
+                throw QueryException::invalidLiteral($literal);
+        }
+    }
+
+    /**
+     * Walks down a BetweenExpression AST node, thereby generating the appropriate SQL.
+     *
+     * @param BetweenExpression
+     * @return string The SQL.
+     */
+    public function walkBetweenExpression($betweenExpr)
+    {
+        $sql = $this->walkArithmeticExpression($betweenExpr->expression);
+
+        if ($betweenExpr->not) $sql .= ' NOT';
+
+        $sql .= ' BETWEEN ' . $this->walkArithmeticExpression($betweenExpr->leftBetweenExpression)
+              . ' AND ' . $this->walkArithmeticExpression($betweenExpr->rightBetweenExpression);
+
+        return $sql;
+    }
+
+    /**
+     * Walks down a LikeExpression AST node, thereby generating the appropriate SQL.
+     *
+     * @param LikeExpression
+     * @return string The SQL.
+     */
+    public function walkLikeExpression($likeExpr)
+    {
+        $stringExpr = $likeExpr->stringExpression;
+        $sql = $stringExpr->dispatch($this) . ($likeExpr->not ? ' NOT' : '') . ' LIKE ';
+
+        if ($likeExpr->stringPattern instanceof AST\InputParameter) {
+            $inputParam = $likeExpr->stringPattern;
+            $dqlParamKey = $inputParam->name;
+            $this->_parserResult->addParameterMapping($dqlParamKey, $this->_sqlParamIndex++);
+            $sql .= '?';
+        } else {
+            $sql .= $this->_conn->quote($likeExpr->stringPattern);
+        }
+
+        if ($likeExpr->escapeChar) {
+            $sql .= ' ESCAPE ' . $this->_conn->quote($likeExpr->escapeChar);
+        }
+
+        return $sql;
+    }
+
+    /**
+     * Walks down a StateFieldPathExpression AST node, thereby generating the appropriate SQL.
+     *
+     * @param StateFieldPathExpression
+     * @return string The SQL.
+     */
+    public function walkStateFieldPathExpression($stateFieldPathExpression)
+    {
+        return $this->walkPathExpression($stateFieldPathExpression);
+    }
+
+    /**
+     * Walks down a ComparisonExpression AST node, thereby generating the appropriate SQL.
+     *
+     * @param ComparisonExpression
+     * @return string The SQL.
+     */
+    public function walkComparisonExpression($compExpr)
+    {
+        $sql = '';
+        $leftExpr = $compExpr->leftExpression;
+        $rightExpr = $compExpr->rightExpression;
+
+        if ($leftExpr instanceof AST\Node) {
+            $sql .= $leftExpr->dispatch($this);
+        } else {
+            $sql .= is_numeric($leftExpr) ? $leftExpr : $this->_conn->quote($leftExpr);
+        }
+
+        $sql .= ' ' . $compExpr->operator . ' ';
+
+        if ($rightExpr instanceof AST\Node) {
+            $sql .= $rightExpr->dispatch($this);
+        } else {
+            $sql .= is_numeric($rightExpr) ? $rightExpr : $this->_conn->quote($rightExpr);
+        }
+
+        return $sql;
+    }
+
+    /**
+     * Walks down an InputParameter AST node, thereby generating the appropriate SQL.
+     *
+     * @param InputParameter
+     * @return string The SQL.
+     */
+    public function walkInputParameter($inputParam)
+    {
+        $this->_parserResult->addParameterMapping($inputParam->name, $this->_sqlParamIndex++);
+
+        return '?';
+    }
+
+    /**
+     * Walks down an ArithmeticExpression AST node, thereby generating the appropriate SQL.
+     *
+     * @param ArithmeticExpression
+     * @return string The SQL.
+     */
+    public function walkArithmeticExpression($arithmeticExpr)
+    {
+        return ($arithmeticExpr->isSimpleArithmeticExpression())
+        	? $this->walkSimpleArithmeticExpression($arithmeticExpr->simpleArithmeticExpression)
+        	: '(' . $this->walkSubselect($arithmeticExpr->subselect) . ')';
+    }
+
+    /**
+     * Walks down an SimpleArithmeticExpression AST node, thereby generating the appropriate SQL.
+     *
+     * @param SimpleArithmeticExpression
+     * @return string The SQL.
+     */
+    public function walkSimpleArithmeticExpression($simpleArithmeticExpr)
+    {
+        return ( ! ($simpleArithmeticExpr instanceof AST\SimpleArithmeticExpression))
+            ? $this->walkArithmeticTerm($simpleArithmeticExpr)
+            : implode(
+                ' ', array_map(array($this, 'walkArithmeticTerm'), $simpleArithmeticExpr->arithmeticTerms)
+            );
+    }
+
+    /**
+     * Walks down an ArithmeticTerm AST node, thereby generating the appropriate SQL.
+     *
+     * @param mixed
+     * @return string The SQL.
+     */
+    public function walkArithmeticTerm($term)
+    {
+        if (is_string($term)) {
+            return $term;
+        }
+
+        // Phase 2 AST optimization: Skip processment of ArithmeticTerm
+        // if only one ArithmeticFactor is defined
+        return ( ! ($term instanceof AST\ArithmeticTerm))
+            ? $this->walkArithmeticFactor($term)
+            : implode(
+                ' ', array_map(array($this, 'walkArithmeticFactor'), $term->arithmeticFactors)
+            );
+    }
+
+    /**
+     * Walks down an ArithmeticFactor that represents an AST node, thereby generating the appropriate SQL.
+     *
+     * @param mixed
+     * @return string The SQL.
+     */
+    public function walkArithmeticFactor($factor)
+    {
+        if (is_string($factor)) {
+            return $factor;
+        }
+        
+        // Phase 2 AST optimization: Skip processment of ArithmeticFactor
+        // if only one ArithmeticPrimary is defined
+        return ( ! ($factor instanceof AST\ArithmeticFactor))
+            ? $this->walkArithmeticPrimary($factor)
+            : ($factor->isNegativeSigned() ? '-' : ($factor->isPositiveSigned() ? '+' : '')) 
+                . $this->walkArithmeticPrimary($factor->arithmeticPrimary);
+    }
+
+    /**
+     * Walks down an ArithmeticPrimary that represents an AST node, thereby generating the appropriate SQL.
+     *
+     * @param mixed
+     * @return string The SQL.
+     */
+    public function walkArithmeticPrimary($primary)
+    {
+        if ($primary instanceof AST\SimpleArithmeticExpression) {
+            return '(' . $this->walkSimpleArithmeticExpression($primary) . ')';
+        } else if ($primary instanceof AST\Node) {
+            return $primary->dispatch($this);
+        }
+
+        // TODO: We need to deal with IdentificationVariable here
+        return '';
+    }
+
+    /**
+     * Walks down a StringPrimary that represents an AST node, thereby generating the appropriate SQL.
+     *
+     * @param mixed
+     * @return string The SQL.
+     */
+    public function walkStringPrimary($stringPrimary)
+    {
+        return (is_string($stringPrimary))
+            ? $this->_conn->quote($stringPrimary)
+            : $stringPrimary->dispatch($this);
+    }
+}