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Drupal example source code file (query.inc)

This example Drupal source code file (query.inc) is included in the DevDaily.com "Drupal Source Code Warehouse" project. The intent of this project is to help you "Learn Drupal by Example".

PHP - Drupal tags/keywords

array, connection, field, fields, function, if, null, operator, php, protected, public, return, this, value

The query.inc Drupal example source code

<?php
// $Id: query.inc,v 1.60 2010/12/31 20:43:43 webchick Exp $

/**
 * @ingroup database
 * @{
 */

/**
 * @file
 * Non-specific Database query code. Used by all engines.
 */

/**
 * Interface for a conditional clause in a query.
 */
interface QueryConditionInterface {

  /**
   * Helper function: builds the most common conditional clauses.
   *
   * This method can take a variable number of parameters. If called with two
   * parameters, they are taken as $field and $value with $operator having a
   * value of IN if $value is an array and = otherwise.
   *
   * @param $field
   *   The name of the field to check. If you would like to add a more complex
   *   condition involving operators or functions, use where().
   * @param $value
   *   The value to test the field against. In most cases, this is a scalar.
   *   For more complex options, it is an array. The meaning of each element in
   *   the array is dependent on the $operator.
   * @param $operator
   *   The comparison operator, such as =, <, or >=. It also accepts more
   *   complex options such as IN, LIKE, or BETWEEN. Defaults to IN if $value is
   *   an array, and = otherwise.
   *
   * @return QueryConditionInterface
   *   The called object.
   */
  public function condition($field, $value = NULL, $operator = NULL);

  /**
   * Adds an arbitrary WHERE clause to the query.
   *
   * @param $snippet
   *   A portion of a WHERE clause as a prepared statement. It must use named
   *   placeholders, not ? placeholders.
   * @param $args
   *   An associative array of arguments.
   *
   * @return QueryConditionInterface
   *   The called object.
   */
  public function where($snippet, $args = array());

  /**
   * Sets a condition that the specified field be NULL.
   *
   * @param $field
   *   The name of the field to check.
   *
   * @return QueryConditionInterface
   *   The called object.
   */
  public function isNull($field);

  /**
   * Sets a condition that the specified field be NOT NULL.
   *
   * @param $field
   *   The name of the field to check.
   *
   * @return QueryConditionInterface
   *   The called object.
   */
  public function isNotNull($field);

  /**
   * Sets a condition that the specified subquery returns values.
   * 
   * @param SelectQueryInterface $select
   *   The subquery that must contain results.
   *
   * @return QueryConditionInterface
   *   The called object.
   */
  public function exists(SelectQueryInterface $select);
  
  /**
   * Sets a condition that the specified subquery returns no values.
   * 
   * @param SelectQueryInterface $select
   *   The subquery that must not contain results.
   *
   * @return QueryConditionInterface
   *   The called object.
   */
  public function notExists(SelectQueryInterface $select);
  
  /**
   * Gets a complete list of all conditions in this conditional clause.
   *
   * This method returns by reference. That allows alter hooks to access the
   * data structure directly and manipulate it before it gets compiled.
   *
   * The data structure that is returned is an indexed array of entries, where
   * each entry looks like the following:
   * @code
   * array(
   *   'field' => $field,
   *   'value' => $value,
   *   'operator' => $operator,
   * );
   * @endcode
   *
   * In the special case that $operator is NULL, the $field is taken as a raw
   * SQL snippet (possibly containing a function) and $value is an associative
   * array of placeholders for the snippet.
   *
   * There will also be a single array entry of #conjunction, which is the
   * conjunction that will be applied to the array, such as AND.
   */
  public function &conditions();

  /**
   * Gets a complete list of all values to insert into the prepared statement.
   *
   * @return
   *   An associative array of placeholders and values.
   */
  public function arguments();

  /**
   * Compiles the saved conditions for later retrieval.
   *
   * This method does not return anything, but simply prepares data to be
   * retrieved via __toString() and arguments().
   *
   * @param $connection
   *   The database connection for which to compile the conditionals.
   * @param $queryPlaceholder
   *   The query this condition belongs to. If not given, the current query is
   *   used.
   */
  public function compile(DatabaseConnection $connection, QueryPlaceholderInterface $queryPlaceholder = NULL);
}


/**
 * Interface for a query that can be manipulated via an alter hook.
 */
interface QueryAlterableInterface {

  /**
   * Adds a tag to a query.
   *
   * Tags are strings that identify a query. A query may have any number of
   * tags. Tags are used to mark a query so that alter hooks may decide if they
   * wish to take action. Tags should be all lower-case and contain only
   * letters, numbers, and underscore, and start with a letter. That is, they
   * should follow the same rules as PHP identifiers in general.
   *
   * @param $tag
   *   The tag to add.
   *
   * @return QueryAlterableInterface
   *   The called object.
   */
  public function addTag($tag);

  /**
   * Determines if a given query has a given tag.
   *
   * @param $tag
   *   The tag to check.
   *
   * @return
   *   TRUE if this query has been marked with this tag, FALSE otherwise.
   */
  public function hasTag($tag);

  /**
   * Determines if a given query has all specified tags.
   *
   * @param $tags
   *   A variable number of arguments, one for each tag to check.
   *
   * @return
   *   TRUE if this query has been marked with all specified tags, FALSE
   *   otherwise.
   */
  public function hasAllTags();

  /**
   * Determines if a given query has any specified tag.
   *
   * @param $tags
   *   A variable number of arguments, one for each tag to check.
   *
   * @return
   *   TRUE if this query has been marked with at least one of the specified
   *   tags, FALSE otherwise.
   */
  public function hasAnyTag();

  /**
   * Adds additional metadata to the query.
   *
   * Often, a query may need to provide additional contextual data to alter
   * hooks. Alter hooks may then use that information to decide if and how
   * to take action.
   *
   * @param $key
   *   The unique identifier for this piece of metadata. Must be a string that
   *   follows the same rules as any other PHP identifier.
   * @param $object
   *   The additional data to add to the query. May be any valid PHP variable.
   *
   * @return QueryAlterableInterface
   *   The called object.
   */
  public function addMetaData($key, $object);

  /**
   * Retrieves a given piece of metadata.
   *
   * @param $key
   *   The unique identifier for the piece of metadata to retrieve.
   *
   * @return
   *   The previously attached metadata object, or NULL if one doesn't exist.
   */
  public function getMetaData($key);
}

/**
 * Interface for a query that accepts placeholders.
 */
interface QueryPlaceholderInterface {

  /**
   * Returns the next placeholder ID for the query.
   *
   * @return
   *   The next available placeholder ID as an integer.
   */
  function nextPlaceholder();
}

/**
 * Base class for query builders.
 *
 * Note that query builders use PHP's magic __toString() method to compile the
 * query object into a prepared statement.
 */
abstract class Query implements QueryPlaceholderInterface {

  /**
   * The connection object on which to run this query.
   *
   * @var DatabaseConnection
   */
  protected $connection;

  /**
   * The target of the connection object.
   * 
   * @var string
   */
  protected $connectionTarget;

  /**
   * The key of the connection object.
   * 
   * @var string
   */
  protected $connectionKey;

  /**
   * The query options to pass on to the connection object.
   *
   * @var array
   */
  protected $queryOptions;

  /**
   * The placeholder counter.
   */
  protected $nextPlaceholder = 0;

  /**
   * An array of comments that can be prepended to a query.
   *
   * @var array
   */
  protected $comments = array();

  /**
   * Constructs a Query object.
   *
   * @param DatabaseConnection $connection
   *   Database connection object.
   * @param array $options
   *   Array of query options.
   */
  public function __construct(DatabaseConnection $connection, $options) {
    $this->connection = $connection;
    $this->connectionKey = $this->connection->getKey();
    $this->connectionTarget = $this->connection->getTarget();

    $this->queryOptions = $options;
  }

  /**
   * Implements the magic __sleep function to disconnect from the database.
   */
  public function __sleep() {
    $keys = get_object_vars($this);
    unset($keys['connection']);
    return array_keys($keys);
  }

  /**
  * Implements the magic __wakeup function to reconnect to the database.
   */
  public function __wakeup() {
    $this->connection = Database::getConnection($this->connectionTarget, $this->connectionKey);
  }

  /**
   * Runs the query against the database.
   */
  abstract protected function execute();

  /**
   * Implements PHP magic __toString method to convert the query to a string.
   *
   * The toString operation is how we compile a query object to a prepared
   * statement.
   *
   * @return
   *   A prepared statement query string for this object.
   */
  abstract public function __toString();

  /**
   * Gets the next placeholder value for this query object.
   *
   * @return int
   *   Next placeholder value.
   */
  public function nextPlaceholder() {
    return $this->nextPlaceholder++;
  }

  /**
   * Adds a comment to the query.
   *
   * By adding a comment to a query, you can more easily find it in your
   * query log or the list of active queries on an SQL server. This allows
   * for easier debugging and allows you to more easily find where a query
   * with a performance problem is being generated.
   *
   * @param $comment
   *   The comment string to be inserted into the query.
   *
   * @return Query
   *   The called object.
   */
  public function comment($comment) {
    $this->comments[] = $comment;
    return $this;
  }

  /**
   * Returns a reference to the comments array for the query.
   *
   * Because this method returns by reference, alter hooks may edit the comments
   * array directly to make their changes. If just adding comments, however, the
   * use of comment() is preferred.
   *
   * Note that this method must be called by reference as well:
   * @code
   * $comments =& $query->getComments();
   * @endcode
   *
   * @return
   *   A reference to the comments array structure.
   */
  public function &getComments() {
    return $this->comments;
  }
}

/**
 * General class for an abstracted INSERT query.
 */
class InsertQuery extends Query {

  /**
   * The table on which to insert.
   *
   * @var string
   */
  protected $table;

  /**
   * An array of fields on which to insert.
   *
   * @var array
   */
  protected $insertFields = array();

  /**
   * An array of fields that should be set to their database-defined defaults.
   *
   * @var array
   */
  protected $defaultFields = array();

  /**
   * A nested array of values to insert.
   *
   * $insertValues is an array of arrays. Each sub-array is either an
   * associative array whose keys are field names and whose values are field
   * values to insert, or a non-associative array of values in the same order
   * as $insertFields.
   *
   * Whether multiple insert sets will be run in a single query or multiple
   * queries is left to individual drivers to implement in whatever manner is
   * most appropriate. The order of values in each sub-array must match the
   * order of fields in $insertFields.
   *
   * @var array
   */
  protected $insertValues = array();

  /**
   * A SelectQuery object to fetch the rows that should be inserted.
   *
   * @var SelectQueryInterface
   */
  protected $fromQuery;

  /**
   * Constructs an InsertQuery object.
   *
   * @param DatabaseConnection $connection
   *   A DatabaseConnection object.
   * @param string $table
   *   Name of the table to associate with this query.
   * @param array $options
   *   Array of database options.
   */
  public function __construct($connection, $table, array $options = array()) {
    if (!isset($options['return'])) {
      $options['return'] = Database::RETURN_INSERT_ID;
    }
    parent::__construct($connection, $options);
    $this->table = $table;
  }

  /**
   * Adds a set of field->value pairs to be inserted.
   *
   * This method may only be called once. Calling it a second time will be
   * ignored. To queue up multiple sets of values to be inserted at once,
   * use the values() method.
   *
   * @param $fields
   *   An array of fields on which to insert. This array may be indexed or
   *   associative. If indexed, the array is taken to be the list of fields.
   *   If associative, the keys of the array are taken to be the fields and
   *   the values are taken to be corresponding values to insert. If a
   *   $values argument is provided, $fields must be indexed.
   * @param $values
   *   An array of fields to insert into the database. The values must be
   *   specified in the same order as the $fields array.
   *
   * @return InsertQuery
   *   The called object.
   */
  public function fields(array $fields, array $values = array()) {
    if (empty($this->insertFields)) {
      if (empty($values)) {
        if (!is_numeric(key($fields))) {
          $values = array_values($fields);
          $fields = array_keys($fields);
        }
      }
      $this->insertFields = $fields;
      if (!empty($values)) {
        $this->insertValues[] = $values;
      }
    }

    return $this;
  }

  /**
   * Adds another set of values to the query to be inserted.
   *
   * If $values is a numeric-keyed array, it will be assumed to be in the same
   * order as the original fields() call. If it is associative, it may be
   * in any order as long as the keys of the array match the names of the
   * fields.
   *
   * @param $values
   *   An array of values to add to the query.
   *
   * @return InsertQuery
   *   The called object.
   */
  public function values(array $values) {
    if (is_numeric(key($values))) {
      $this->insertValues[] = $values;
    }
    else {
      // Reorder the submitted values to match the fields array.
      foreach ($this->insertFields as $key) {
        $insert_values[$key] = $values[$key];
      }
      // For consistency, the values array is always numerically indexed.
      $this->insertValues[] = array_values($insert_values);
    }
    return $this;
  }

  /**
   * Specifies fields for which the database defaults should be used.
   *
   * If you want to force a given field to use the database-defined default,
   * not NULL or undefined, use this method to instruct the database to use
   * default values explicitly. In most cases this will not be necessary
   * unless you are inserting a row that is all default values, as you cannot
   * specify no values in an INSERT query.
   *
   * Specifying a field both in fields() and in useDefaults() is an error
   * and will not execute.
   *
   * @param $fields
   *   An array of values for which to use the default values
   *   specified in the table definition.
   *
   * @return InsertQuery
   *   The called object.
   */
  public function useDefaults(array $fields) {
    $this->defaultFields = $fields;
    return $this;
  }

  /**
   * Sets the fromQuery on this InsertQuery object.
   *
   * @param SelectQueryInterface $query
   *   The query to fetch the rows that should be inserted.
   *
   * @return InsertQuery
   *   The called object.
   */
  public function from(SelectQueryInterface $query) {
    $this->fromQuery = $query;
    return $this;
  }

  /**
   * Executes the insert query.
   *
   * @return
   *   The last insert ID of the query, if one exists. If the query
   *   was given multiple sets of values to insert, the return value is
   *   undefined. If no fields are specified, this method will do nothing and
   *   return NULL. That makes it safe to use in multi-insert loops.
   */
  public function execute() {
    // If validation fails, simply return NULL. Note that validation routines
    // in preExecute() may throw exceptions instead.
    if (!$this->preExecute()) {
      return NULL;
    }

    // If we're selecting from a SelectQuery, finish building the query and
    // pass it back, as any remaining options are irrelevant.
    if (!empty($this->fromQuery)) {
      $sql = (string) $this;
      // The SelectQuery may contain arguments, load and pass them through.
      return $this->connection->query($sql, $this->fromQuery->getArguments(), $this->queryOptions);
    }

    $last_insert_id = 0;

    // Each insert happens in its own query in the degenerate case. However,
    // we wrap it in a transaction so that it is atomic where possible. On many
    // databases, such as SQLite, this is also a notable performance boost.
    $transaction = $this->connection->startTransaction();

    try {
      $sql = (string) $this;
      foreach ($this->insertValues as $insert_values) {
        $last_insert_id = $this->connection->query($sql, $insert_values, $this->queryOptions);
      }
    }
    catch (Exception $e) {
      // One of the INSERTs failed, rollback the whole batch.
      $transaction->rollback();
      // Rethrow the exception for the calling code.
      throw $e;
    }

    // Re-initialize the values array so that we can re-use this query.
    $this->insertValues = array();

    // Transaction commits here where $transaction looses scope.

    return $last_insert_id;
  }

  /**
   * Implements PHP magic __toString method to convert the query to a string.
   *
   * @return string
   *   The prepared statement.
   */
  public function __toString() {

    // Create a comments string to prepend to the query.
    $comments = (!empty($this->comments)) ? '/* ' . implode('; ', $this->comments) . ' */ ' : '';

    // Default fields are always placed first for consistency.
    $insert_fields = array_merge($this->defaultFields, $this->insertFields);

    if (!empty($this->fromQuery)) {
      return $comments . 'INSERT INTO {' . $this->table . '} (' . implode(', ', $insert_fields) . ') ' . $this->fromQuery;
    }

    // For simplicity, we will use the $placeholders array to inject
    // default keywords even though they are not, strictly speaking,
    // placeholders for prepared statements.
    $placeholders = array();
    $placeholders = array_pad($placeholders, count($this->defaultFields), 'default');
    $placeholders = array_pad($placeholders, count($this->insertFields), '?');

    return $comments . 'INSERT INTO {' . $this->table . '} (' . implode(', ', $insert_fields) . ') VALUES (' . implode(', ', $placeholders) . ')';
  }

  /**
   * Preprocesses and validates the query.
   *
   * @return
   *   TRUE if the validation was successful, FALSE if not.
   *
   * @throws FieldsOverlapException
   * @throws NoFieldsException
   */
  public function preExecute() {
    // Confirm that the user did not try to specify an identical
    // field and default field.
    if (array_intersect($this->insertFields, $this->defaultFields)) {
      throw new FieldsOverlapException('You may not specify the same field to have a value and a schema-default value.');
    }

    if (!empty($this->fromQuery)) {
      // We have to assume that the used aliases match the insert fields.
      // Regular fields are added to the query before expressions, maintain the
      // same order for the insert fields.
      // This behavior can be overridden by calling fields() manually as only the
      // first call to fields() does have an effect.
      $this->fields(array_merge(array_keys($this->fromQuery->getFields()), array_keys($this->fromQuery->getExpressions())));
    }

    // Don't execute query without fields.
    if (count($this->insertFields) + count($this->defaultFields) == 0) {
      throw new NoFieldsException('There are no fields available to insert with.');
    }

    // If no values have been added, silently ignore this query. This can happen
    // if values are added conditionally, so we don't want to throw an
    // exception.
    if (!isset($this->insertValues[0]) && count($this->insertFields) > 0 && empty($this->fromQuery)) {
      return FALSE;
    }
    return TRUE;
  }
}

/**
 * General class for an abstracted DELETE operation.
 */
class DeleteQuery extends Query implements QueryConditionInterface {

  /**
   * The table from which to delete.
   *
   * @var string
   */
  protected $table;

  /**
   * The condition object for this query.
   *
   * Condition handling is handled via composition.
   *
   * @var DatabaseCondition
   */
  protected $condition;

  /**
   * Constructs a DeleteQuery object.
   *
   * @param DatabaseConnection $connection
   *   A DatabaseConnection object.
   * @param string $table
   *   Name of the table to associate with this query.
   * @param array $options
   *   Array of database options.
   */
  public function __construct(DatabaseConnection $connection, $table, array $options = array()) {
    $options['return'] = Database::RETURN_AFFECTED;
    parent::__construct($connection, $options);
    $this->table = $table;

    $this->condition = new DatabaseCondition('AND');
  }

  /**
   * Implements QueryConditionInterface::condition().
   */
  public function condition($field, $value = NULL, $operator = NULL) {
    $this->condition->condition($field, $value, $operator);
    return $this;
  }

  /**
   * Implements QueryConditionInterface::isNull().
   */
  public function isNull($field) {
    $this->condition->isNull($field);
    return $this;
  }

  /**
   * Implements QueryConditionInterface::isNotNull().
   */
  public function isNotNull($field) {
    $this->condition->isNotNull($field);
    return $this;
  }

  /**
   * Implements QueryConditionInterface::exists().
   */
  public function exists(SelectQueryInterface $select) {
    $this->condition->exists($select);
    return $this;
  }

  /**
   * Implements QueryConditionInterface::notExists().
   */
  public function notExists(SelectQueryInterface $select) {
    $this->condition->notExists($select);
    return $this;
  }
  
  /**
   * Implements QueryConditionInterface::conditions().
   */
  public function &conditions() {
    return $this->condition->conditions();
  }

  /**
   * Implements QueryConditionInterface::arguments().
   */
  public function arguments() {
    return $this->condition->arguments();
  }

  /**
   * Implements QueryConditionInterface::where().
   */
  public function where($snippet, $args = array()) {
    $this->condition->where($snippet, $args);
    return $this;
  }

  /**
   * Implements QueryConditionInterface::compile().
   */
  public function compile(DatabaseConnection $connection, QueryPlaceholderInterface $queryPlaceholder = NULL) {
    return $this->condition->compile($connection, isset($queryPlaceholder) ? $queryPlaceholder : $this);
  }

  /**
   * Executes the DELETE query.
   *
   * @return
   *   The return value is dependant on the database connection.
   */
  public function execute() {
    $values = array();
    if (count($this->condition)) {
      $this->condition->compile($this->connection, $this);
      $values = $this->condition->arguments();
    }

    return $this->connection->query((string) $this, $values, $this->queryOptions);
  }

  /**
   * Implements PHP magic __toString method to convert the query to a string.
   *
   * @return string
   *   The prepared statement.
   */
  public function __toString() {

    // Create a comments string to prepend to the query.
    $comments = (!empty($this->comments)) ? '/* ' . implode('; ', $this->comments) . ' */ ' : '';

    $query = $comments . 'DELETE FROM {' . $this->connection->escapeTable($this->table) . '} ';

    if (count($this->condition)) {

      $this->condition->compile($this->connection, $this);
      $query .= "\nWHERE " . $this->condition;
    }

    return $query;
  }
}


/**
 * General class for an abstracted TRUNCATE operation.
 */
class TruncateQuery extends Query {

  /**
   * The table to truncate.
   *
   * @var string
   */
  protected $table;

  /**
   * Constructs a TruncateQuery object.
   *
   * @param DatabaseConnection $connection
   *   A DatabaseConnection object.
   * @param string $table
   *   Name of the table to associate with this query.
   * @param array $options
   *   Array of database options.
   */
  public function __construct(DatabaseConnection $connection, $table, array $options = array()) {
    $options['return'] = Database::RETURN_AFFECTED;
    parent::__construct($connection, $options);
    $this->table = $table;
  }

  /**
   * Implements QueryConditionInterface::compile().
   */
  public function compile(DatabaseConnection $connection, QueryPlaceholderInterface $queryPlaceholder = NULL) {
    return $this->condition->compile($connection, isset($queryPlaceholder) ? $queryPlaceholder : $this);
  }

  /**
   * Executes the TRUNCATE query.
   *
   * @return
   *   Return value is dependent on the database type.
   */
  public function execute() {
    return $this->connection->query((string) $this, array(), $this->queryOptions);
  }

  /**
   * Implements PHP magic __toString method to convert the query to a string.
   *
   * @return string
   *   The prepared statement.
   */
  public function __toString() {
    // Create a comments string to prepend to the query.
    $comments = (!empty($this->comments)) ? '/* ' . implode('; ', $this->comments) . ' */ ' : '';

    return $comments . 'TRUNCATE {' . $this->connection->escapeTable($this->table) . '} ';
  }
}

/**
 * General class for an abstracted UPDATE operation.
 */
class UpdateQuery extends Query implements QueryConditionInterface {

  /**
   * The table to update.
   *
   * @var string
   */
  protected $table;

  /**
   * An array of fields that will be updated.
   *
   * @var array
   */
  protected $fields = array();

  /**
   * An array of values to update to.
   *
   * @var array
   */
  protected $arguments = array();

  /**
   * The condition object for this query.
   *
   * Condition handling is handled via composition.
   *
   * @var DatabaseCondition
   */
  protected $condition;

  /**
   * Array of fields to update to an expression in case of a duplicate record.
   *
   * This variable is a nested array in the following format:
   * @code
   * <some field> => array(
   *  'condition' => <condition to execute, as a string>,
   *  'arguments' => <array of arguments for condition, or NULL for none>,
   * );
   * @endcode
   *
   * @var array
   */
  protected $expressionFields = array();

  /**
   * Constructs an UpdateQuery object.
   *
   * @param DatabaseConnection $connection
   *   A DatabaseConnection object.
   * @param string $table
   *   Name of the table to associate with this query.
   * @param array $options
   *   Array of database options.
   */
  public function __construct(DatabaseConnection $connection, $table, array $options = array()) {
    $options['return'] = Database::RETURN_AFFECTED;
    parent::__construct($connection, $options);
    $this->table = $table;

    $this->condition = new DatabaseCondition('AND');
  }

  /**
   * Implements QueryConditionInterface::condition().
   */
  public function condition($field, $value = NULL, $operator = NULL) {
    $this->condition->condition($field, $value, $operator);
    return $this;
  }

  /**
   * Implements QueryConditionInterface::isNull().
   */
  public function isNull($field) {
    $this->condition->isNull($field);
    return $this;
  }

  /**
   * Implements QueryConditionInterface::isNotNull().
   */
  public function isNotNull($field) {
    $this->condition->isNotNull($field);
    return $this;
  }

  /**
   * Implements QueryConditionInterface::exists().
   */
  public function exists(SelectQueryInterface $select) {
    $this->condition->exists($select);
    return $this;
  }

  /**
   * Implements QueryConditionInterface::notExists().
   */
  public function notExists(SelectQueryInterface $select) {
    $this->condition->notExists($select);
    return $this;
  }
  
  /**
   * Implements QueryConditionInterface::conditions().
   */
  public function &conditions() {
    return $this->condition->conditions();
  }

  /**
   * Implements QueryConditionInterface::arguments().
   */
  public function arguments() {
    return $this->condition->arguments();
  }

  /**
   * Implements QueryConditionInterface::where().
   */
  public function where($snippet, $args = array()) {
    $this->condition->where($snippet, $args);
    return $this;
  }

  /**
   * Implements QueryConditionInterface::compile().
   */
  public function compile(DatabaseConnection $connection, QueryPlaceholderInterface $queryPlaceholder = NULL) {
    return $this->condition->compile($connection, isset($queryPlaceholder) ? $queryPlaceholder : $this);
  }

  /**
   * Adds a set of field->value pairs to be updated.
   *
   * @param $fields
   *   An associative array of fields to write into the database. The array keys
   *   are the field names and the values are the values to which to set them.
   *
   * @return UpdateQuery
   *   The called object.
   */
  public function fields(array $fields) {
    $this->fields = $fields;
    return $this;
  }

  /**
   * Specifies fields to be updated as an expression.
   *
   * Expression fields are cases such as counter=counter+1. This method takes
   * precedence over fields().
   *
   * @param $field
   *   The field to set.
   * @param $expression
   *   The field will be set to the value of this expression. This parameter
   *   may include named placeholders.
   * @param $arguments
   *   If specified, this is an array of key/value pairs for named placeholders
   *   corresponding to the expression.
   *
   * @return UpdateQuery
   *   The called object.
   */
  public function expression($field, $expression, array $arguments = NULL) {
    $this->expressionFields[$field] = array(
      'expression' => $expression,
      'arguments' => $arguments,
    );

    return $this;
  }

  /**
   * Executes the UPDATE query.
   *
   * @return
   *   The number of rows affected by the update.
   */
  public function execute() {

    // Expressions take priority over literal fields, so we process those first
    // and remove any literal fields that conflict.
    $fields = $this->fields;
    $update_values = array();
    foreach ($this->expressionFields as $field => $data) {
      if (!empty($data['arguments'])) {
        $update_values += $data['arguments'];
      }
      unset($fields[$field]);
    }

    // Because we filter $fields the same way here and in __toString(), the
    // placeholders will all match up properly.
    $max_placeholder = 0;
    foreach ($fields as $field => $value) {
      $update_values[':db_update_placeholder_' . ($max_placeholder++)] = $value;
    }

    if (count($this->condition)) {
      $this->condition->compile($this->connection, $this);
      $update_values = array_merge($update_values, $this->condition->arguments());
    }

    return $this->connection->query((string) $this, $update_values, $this->queryOptions);
  }

  /**
   * Implements PHP magic __toString method to convert the query to a string.
   *
   * @return string
   *   The prepared statement.
   */
  public function __toString() {

    // Create a comments string to prepend to the query.
    $comments = (!empty($this->comments)) ? '/* ' . implode('; ', $this->comments) . ' */ ' : '';

    // Expressions take priority over literal fields, so we process those first
    // and remove any literal fields that conflict.
    $fields = $this->fields;
    $update_fields = array();
    foreach ($this->expressionFields as $field => $data) {
      $update_fields[] = $field . '=' . $data['expression'];
      unset($fields[$field]);
    }

    $max_placeholder = 0;
    foreach ($fields as $field => $value) {
      $update_fields[] = $field . '=:db_update_placeholder_' . ($max_placeholder++);
    }

    $query = $comments . 'UPDATE {' . $this->connection->escapeTable($this->table) . '} SET ' . implode(', ', $update_fields);

    if (count($this->condition)) {
      $this->condition->compile($this->connection, $this);
      // There is an implicit string cast on $this->condition.
      $query .= "\nWHERE " . $this->condition;
    }

    return $query;
  }

}

/**
 * General class for an abstracted MERGE query operation.
 *
 * An ANSI SQL:2003 compatible database would run the following query:
 *
 * @code
 * MERGE INTO table_name_1 USING table_name_2 ON (condition)
 *   WHEN MATCHED THEN
 *   UPDATE SET column1 = value1 [, column2 = value2 ...]
 *   WHEN NOT MATCHED THEN
 *   INSERT (column1 [, column2 ...]) VALUES (value1 [, value2 ...
 * @endcode
 *
 * Other databases (most notably MySQL, PostgreSQL and SQLite) will emulate
 * this statement by running a SELECT and then INSERT or UPDATE.
 *
 * By default, the two table names are identical and they are passed into the
 * the constructor. table_name_2 can be specified by the
 * MergeQuery::conditionTable() method. It can be either a string or a
 * subquery.
 *
 * The condition is built exactly like SelectQuery or UpdateQuery conditions,
 * the UPDATE query part is built similarly like an UpdateQuery and finally the
 * INSERT query part is built similarly like an InsertQuery. However, both
 * UpdateQuery and InsertQuery has a fields method so
 * MergeQuery::updateFields() and MergeQuery::insertFields() needs to be called
 * instead. MergeQuery::fields() can also be called which calls both of these
 * methods as the common case is to use the same column-value pairs for both
 * INSERT and UPDATE. However, this is not mandatory. Another convinient
 * wrapper is MergeQuery::key() which adds the same column-value pairs to the
 * condition and the INSERT query part.
 *
 * Several methods (key(), fields(), insertFields()) can be called to set a
 * key-value pair for the INSERT query part. Subsequent calls for the same
 * fields override the earlier ones. The same is true for UPDATE and key(),
 * fields() and updateFields().
 */
class MergeQuery extends Query implements QueryConditionInterface {
  /**
   * Returned by execute() if an INSERT query has been executed.
   */
  const STATUS_INSERT = 1;

  /**
   * Returned by execute() if an UPDATE query has been executed.
   */
  const STATUS_UPDATE = 2;

  /**
   * The table to be used for INSERT and UPDATE.
   *
   * @var string
   */
  protected $table;

  /**
   * The table or subquery to be used for the condition.
   */
  protected $conditionTable;

  /**
   * An array of fields on which to insert.
   *
   * @var array
   */
  protected $insertFields = array();

  /**
   * An array of fields which should be set to their database-defined defaults.
   *
   * Used on INSERT.
   *
   * @var array
   */
  protected $defaultFields = array();

  /**
   * An array of values to be inserted.
   *
   * @var string
   */
  protected $insertValues = array();

  /**
   * An array of fields that will be updated.
   *
   * @var array
   */
  protected $updateFields = array();

  /**
   * Array of fields to update to an expression in case of a duplicate record.
   *
   * This variable is a nested array in the following format:
   * @code
   * <some field> => array(
   *  'condition' => <condition to execute, as a string>,
   *  'arguments' => <array of arguments for condition, or NULL for none>,
   * );
   * @endcode
   *
   * @var array
   */
  protected $expressionFields = array();

  /**
   * Flag indicating whether an UPDATE is necessary.
   *
   * @var boolean
   */
  protected $needsUpdate = FALSE;

  /**
  * Constructs a MergeQuery object.
  *
  * @param DatabaseConnection $connection
  *   A DatabaseConnection object.
  * @param string $table
  *   Name of the table to associate with this query.
  * @param array $options
  *   Array of database options.
  */
  public function __construct(DatabaseConnection $connection, $table, array $options = array()) {
    $options['return'] = Database::RETURN_AFFECTED;
    parent::__construct($connection, $options);
    $this->table = $table;
    $this->conditionTable = $table;
    $this->condition = new DatabaseCondition('AND');
  }

  /**
   * Sets the table or subquery to be used for the condition.
   *
   * @param $table
   *   The table name or the subquery to be used. Use a SelectQuery object to
   *   pass in a subquery.
   *
   * @return MergeQuery
   *   The called object.
   */
  protected function conditionTable($table) {
    $this->conditionTable = $table;
    return $this;
  }

  /**
   * Adds a set of field->value pairs to be updated.
   *
   * @param $fields
   *   An associative array of fields to write into the database. The array keys
   *   are the field names and the values are the values to which to set them.
   *
   * @return MergeQuery
   *   The called object.
   */
  public function updateFields(array $fields) {
    $this->updateFields = $fields;
    $this->needsUpdate = TRUE;
    return $this;
  }

  /**
   * Specifies fields to be updated as an expression.
   *
   * Expression fields are cases such as counter = counter + 1. This method
   * takes precedence over MergeQuery::updateFields() and it's wrappers,
   * MergeQuery::key() and MergeQuery::fields().
   *
   * @param $field
   *   The field to set.
   * @param $expression
   *   The field will be set to the value of this expression. This parameter
   *   may include named placeholders.
   * @param $arguments
   *   If specified, this is an array of key/value pairs for named placeholders
   *   corresponding to the expression.
   *
   * @return MergeQuery
   *   The called object.
   */
  public function expression($field, $expression, array $arguments = NULL) {
    $this->expressionFields[$field] = array(
      'expression' => $expression,
      'arguments' => $arguments,
    );
    $this->needsUpdate = TRUE;
    return $this;
  }

  /**
   * Adds a set of field->value pairs to be inserted.
   *
   * @param $fields
   *   An array of fields on which to insert. This array may be indexed or
   *   associative. If indexed, the array is taken to be the list of fields.
   *   If associative, the keys of the array are taken to be the fields and
   *   the values are taken to be corresponding values to insert. If a
   *   $values argument is provided, $fields must be indexed.
   * @param $values
   *   An array of fields to insert into the database. The values must be
   *   specified in the same order as the $fields array.
   *
   * @return MergeQuery
   *   The called object.
   */
  public function insertFields(array $fields, array $values = array()) {
    if ($values) {
      $fields = array_combine($fields, $values);
    }
    $this->insertFields = $fields;
    return $this;
  }

  /**
   * Specifies fields for which the database-defaults should be used.
   *
   * If you want to force a given field to use the database-defined default,
   * not NULL or undefined, use this method to instruct the database to use
   * default values explicitly. In most cases this will not be necessary
   * unless you are inserting a row that is all default values, as you cannot
   * specify no values in an INSERT query.
   *
   * Specifying a field both in fields() and in useDefaults() is an error
   * and will not execute.
   *
   * @param $fields
   *   An array of values for which to use the default values
   *   specified in the table definition.
   *
   * @return MergeQuery
   *   The called object.
   */
  public function useDefaults(array $fields) {
    $this->defaultFields = $fields;
    return $this;
  }

  /**
   * Sets common field-value pairs in the INSERT and UPDATE query parts.
   *
   * This method should only be called once. It may be called either
   * with a single associative array or two indexed arrays. If called
   * with an associative array, the keys are taken to be the fields
   * and the values are taken to be the corresponding values to set.
   * If called with two arrays, the first array is taken as the fields
   * and the second array is taken as the corresponding values.
   *
   * @param $fields
   *   An array of fields to insert, or an associative array of fields and
   *   values. The keys of the array are taken to be the fields and the values
   *   are taken to be corresponding values to insert.
   * @param $values
   *   An array of values to set into the database. The values must be
   *   specified in the same order as the $fields array.
   *
   * @return MergeQuery
   *   The called object.
   */
  public function fields(array $fields, array $values = array()) {
    if ($values) {
      $fields = array_combine($fields, $values);
    }
    foreach ($fields as $key => $value) {
      $this->insertFields[$key] = $value;
      $this->updateFields[$key] = $value;
    }
    $this->needsUpdate = TRUE;
    return $this;
  }

  /**
   * Sets the key field(s) to be used as conditions for this query.
   *
   * This method should only be called once. It may be called either
   * with a single associative array or two indexed arrays. If called
   * with an associative array, the keys are taken to be the fields
   * and the values are taken to be the corresponding values to set.
   * If called with two arrays, the first array is taken as the fields
   * and the second array is taken as the corresponding values.
   *
   * The fields are copied to the condition of the query and the INSERT part.
   * If no other method is called, the UPDATE will become a no-op.
   *
   * @param $fields
   *   An array of fields to set, or an associative array of fields and values.
   * @param $values
   *   An array of values to set into the database. The values must be
   *   specified in the same order as the $fields array.
   *
   * @return MergeQuery
   *   The called object.
   */
  public function key(array $fields, array $values = array()) {
    if ($values) {
      $fields = array_combine($fields, $values);
    }
    foreach ($fields as $key => $value) {
      $this->insertFields[$key] = $value;
      $this->condition($key, $value);
    }
    return $this;
  }

  /**
   * Implements QueryConditionInterface::condition().
   */
  public function condition($field, $value = NULL, $operator = NULL) {
    $this->condition->condition($field, $value, $operator);
    return $this;
  }

  /**
   * Implements QueryConditionInterface::isNull().
   */
  public function isNull($field) {
    $this->condition->isNull($field);
    return $this;
  }

  /**
   * Implements QueryConditionInterface::isNotNull().
   */
  public function isNotNull($field) {
    $this->condition->isNotNull($field);
    return $this;
  }

  /**
   * Implements QueryConditionInterface::exists().
   */
  public function exists(SelectQueryInterface $select) {
    $this->condition->exists($select);
    return $this;
  }

  /**
   * Implements QueryConditionInterface::notExists().
   */
  public function notExists(SelectQueryInterface $select) {
    $this->condition->notExists($select);
    return $this;
  }
  
  /**
   * Implements QueryConditionInterface::conditions().
   */
  public function &conditions() {
    return $this->condition->conditions();
  }

  /**
   * Implements QueryConditionInterface::arguments().
   */
  public function arguments() {
    return $this->condition->arguments();
  }

  /**
   * Implements QueryConditionInterface::where().
   */
  public function where($snippet, $args = array()) {
    $this->condition->where($snippet, $args);
    return $this;
  }

  /**
   * Implements QueryConditionInterface::compile().
   */
  public function compile(DatabaseConnection $connection, QueryPlaceholderInterface $queryPlaceholder = NULL) {
    return $this->condition->compile($connection, isset($queryPlaceholder) ? $queryPlaceholder : $this);
  }

  /**
   * Implements PHP magic __toString method to convert the query to a string.
   *
   * In the degenerate case, there is no string-able query as this operation
   * is potentially two queries.
   *
   * @return string
   *   The prepared query statement.
   */
  public function __toString() {
  }

  public function execute() {
    // Wrap multiple queries in a transaction, if the database supports it.
    $transaction = $this->connection->startTransaction();
    try {
      if (!count($this->condition)) {
        throw new InvalidMergeQueryException(t('Invalid merge query: no conditions'));
      }
      $select = $this->connection->select($this->conditionTable)
        ->condition($this->condition)
        ->forUpdate();
      $select->addExpression('1');
      if (!$select->execute()->fetchField()) {
        try {
          $insert = $this->connection->insert($this->table)->fields($this->insertFields);
          if ($this->defaultFields) {
            $insert->useDefaults($this->defaultFields);
          }
          $insert->execute();
          return MergeQuery::STATUS_INSERT;
        }
        catch (Exception $e) {
          // The insert query failed, maybe it's because a racing insert query
          // beat us in inserting the same row. Retry the select query, if it
          // returns a row, ignore the error and continue with the update
          // query below.
          if (!$select->execute()->fetchField()) {
            throw $e;
          }
        }
      }
      if ($this->needsUpdate) {
        $update = $this->connection->update($this->table)
          ->fields($this->updateFields)
          ->condition($this->condition);
        if ($this->expressionFields) {
          foreach ($this->expressionFields as $field => $data) {
            $update->expression($field, $data['expression'], $data['arguments']);
          }
        }
        $update->execute();
        return MergeQuery::STATUS_UPDATE;
      }
    }
    catch (Exception $e) {
      // Something really wrong happened here, bubble up the exception to the
      // caller.
      $transaction->rollback();
      throw $e;
    }
    // Transaction commits here where $transaction looses scope.
  }
}

/**
 * Generic class for a series of conditions in a query.
 */
class DatabaseCondition implements QueryConditionInterface, Countable {

  /**
   * Array of conditions.
   *
   * @var array
   */
  protected $conditions = array();

  /**
   * Array of arguments.
   *
   * @var array
   */
  protected $arguments = array();

  /**
   * Whether the conditions have been changed.
   *
   * TRUE if the condition has been changed since the last compile.
   * FALSE if the condition has been compiled and not changed.
   *
   * @var bool
   */
  protected $changed = TRUE;

  /**
   * Constructs a DataBaseCondition object.
   *
   * @param string $conjunction
   *   The operator to use to combine conditions: 'AND' or 'OR'.
   */
  public function __construct($conjunction) {
    $this->conditions['#conjunction'] = $conjunction;
  }

  /**
   * Implements Countable::count().
   *
   * Returns the size of this conditional. The size of the conditional is the
   * size of its conditional array minus one, because one element is the the
   * conjunction.
   */
  public function count() {
    return count($this->conditions) - 1;
  }

  /**
   * Implements QueryConditionInterface::condition().
   */
  public function condition($field, $value = NULL, $operator = NULL) {
    if (!isset($operator)) {
      if (is_array($value)) {
        $operator = 'IN';
      }
      elseif (!isset($value)) {
        $operator = 'IS NULL';
      }
      else {
        $operator = '=';
      }
    }
    $this->conditions[] = array(
      'field' => $field,
      'value' => $value,
      'operator' => $operator,
    );

    $this->changed = TRUE;

    return $this;
  }

  /**
   * Implements QueryConditionInterface::where().
   */
  public function where($snippet, $args = array()) {
    $this->conditions[] = array(
      'field' => $snippet,
      'value' => $args,
      'operator' => NULL,
    );
    $this->changed = TRUE;

    return $this;
  }

  /**
   * Implements QueryConditionInterface::isNull().
   */
  public function isNull($field) {
    return $this->condition($field);
  }

  /**
   * Implements QueryConditionInterface::isNotNull().
   */
  public function isNotNull($field) {
    return $this->condition($field, NULL, 'IS NOT NULL');
  }

  /**
   * Implements QueryConditionInterface::exists().
   */
  public function exists(SelectQueryInterface $select) {
    return $this->condition('', $select, 'EXISTS');
  }
  
  /**
   * Implements QueryConditionInterface::notExists().
   */
  public function notExists(SelectQueryInterface $select) {
    return $this->condition('', $select, 'NOT EXISTS');
  }
  
  /**
   * Implements QueryConditionInterface::conditions().
   */
  public function &conditions() {
    return $this->conditions;
  }

  /**
   * Implements QueryConditionInterface::arguments().
   */
  public function arguments() {
    // If the caller forgot to call compile() first, refuse to run.
    if ($this->changed) {
      return NULL;
    }
    return $this->arguments;
  }

  /**
   * Implements QueryConditionInterface::compile().
   */
  public function compile(DatabaseConnection $connection, QueryPlaceholderInterface $queryPlaceholder = NULL) {
    if ($this->changed) {
      $condition_fragments = array();
      $arguments = array();

      $conditions = $this->conditions;
      $conjunction = $conditions['#conjunction'];
      unset($conditions['#conjunction']);
      foreach ($conditions as $condition) {
        if (empty($condition['operator'])) {
          // This condition is a literal string, so let it through as is.
          $condition_fragments[] = ' (' . $condition['field'] . ') ';
          $arguments += $condition['value'];
        }
        else {
          // It's a structured condition, so parse it out accordingly.
          // Note that $condition['field'] will only be an object for a dependent
          // DatabaseCondition object, not for a dependent subquery.
          if ($condition['field'] instanceof QueryConditionInterface) {
            // Compile the sub-condition recursively and add it to the list.
            $condition['field']->compile($connection, $queryPlaceholder);
            $condition_fragments[] = '(' . (string) $condition['field'] . ')';
            $arguments += $condition['field']->arguments();
          }
          else {
            // For simplicity, we treat all operators as the same data structure.
            // In the typical degenerate case, this won't get changed.
            $operator_defaults = array(
              'prefix' => '',
              'postfix' => '',
              'delimiter' => '',
              'operator' => $condition['operator'],
              'use_value' => TRUE,
            );
            $operator = $connection->mapConditionOperator($condition['operator']);
            if (!isset($operator)) {
              $operator = $this->mapConditionOperator($condition['operator']);
            }
            $operator += $operator_defaults;

            $placeholders = array();
            if ($condition['value'] instanceof SelectQueryInterface) {
              $condition['value']->compile($connection, $queryPlaceholder);
              $placeholders[] = (string) $condition['value'];
              $arguments += $condition['value']->arguments();
              // Subqueries are the actual value of the operator, we don't
              // need to add another below.
              $operator['use_value'] = FALSE;
            }
            // We assume that if there is a delimiter, then the value is an
            // array. If not, it is a scalar. For simplicity, we first convert
            // up to an array so that we can build the placeholders in the same way.
            elseif (!$operator['delimiter']) {
              $condition['value'] = array($condition['value']);
            }
            if ($operator['use_value']) {
              foreach ($condition['value'] as $value) {
                $placeholder = ':db_condition_placeholder_' . $queryPlaceholder->nextPlaceholder();
                $arguments[$placeholder] = $value;
                $placeholders[] = $placeholder;
              }
            }
            $condition_fragments[] = ' (' . $connection->escapeField($condition['field']) . ' ' . $operator['operator'] . ' ' . $operator['prefix'] . implode($operator['delimiter'], $placeholders) . $operator['postfix'] . ') ';
          }
        }
      }

      $this->changed = FALSE;
      $this->stringVersion = implode($conjunction, $condition_fragments);
      $this->arguments = $arguments;
    }
  }

  /**
   * Implements PHP magic __toString method to convert the conditions to string.
   *
   * @return string
   *   A string version of the conditions.
   */
  public function __toString() {
    // If the caller forgot to call compile() first, refuse to run.
    if ($this->changed) {
      return NULL;
    }
    return $this->stringVersion;
  }

  /**
   * PHP magic __clone() method.
   *
   * Only copies fields that implement QueryConditionInterface. Also sets
   * $this->changed to TRUE.
   */
  function __clone() {
    $this->changed = TRUE;
    foreach ($this->conditions as $key => $condition) {
      if ($condition['field'] instanceOf QueryConditionInterface) {
        $this->conditions[$key]['field'] = clone($condition['field']);
      }
    }
  }

  /**
   * Gets any special processing requirements for the condition operator.
   *
   * Some condition types require special processing, such as IN, because
   * the value data they pass in is not a simple value. This is a simple
   * overridable lookup function.
   *
   * @param $operator
   *   The condition operator, such as "IN", "BETWEEN", etc. Case-sensitive.
   *
   * @return
   *   The extra handling directives for the specified operator, or NULL.
   */
  protected function mapConditionOperator($operator) {
    // $specials does not use drupal_static as its value never changes.
    static $specials = array(
      'BETWEEN' => array('delimiter' => ' AND '),
      'IN' => array('delimiter' => ', ', 'prefix' => ' (', 'postfix' => ')'),
      'NOT IN' => array('delimiter' => ', ', 'prefix' => ' (', 'postfix' => ')'),
      'EXISTS' => array('prefix' => ' (', 'postfix' => ')'),
      'NOT EXISTS' => array('prefix' => ' (', 'postfix' => ')'),
      'IS NULL' => array('use_value' => FALSE),
      'IS NOT NULL' => array('use_value' => FALSE),
      // Use backslash for escaping wildcard characters.
      'LIKE' => array('postfix' => " ESCAPE '\\\\'"),
      'NOT LIKE' => array('postfix' => " ESCAPE '\\\\'"),
      // These ones are here for performance reasons.
      '=' => array(),
      '<' => array(),
      '>' => array(),
      '>=' => array(),
      '<=' => array(),
    );
    if (isset($specials[$operator])) {
      $return = $specials[$operator];
    }
    else {
      // We need to upper case because PHP index matches are case sensitive but
      // do not need the more expensive drupal_strtoupper because SQL statements are ASCII.
      $operator = strtoupper($operator);
      $return = isset($specials[$operator]) ? $specials[$operator] : array();
    }

    $return += array('operator' => $operator);

    return $return;
  }

}

/**
 * @} End of "ingroup database".
 */

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