- Patch #225450 by Crell, chx, bjaspan, catch, swentel, recidive et al: next generation database layer for Drupal 7.

4 files changed, 818 insertions, 0 deletions

diff --git a/includes/database/pgsql/database.inc b/includes/database/pgsql/database.inc
new file mode 100644
index 000000000..f6ce65051
--- /dev/null
+++ b/includes/database/pgsql/database.inc
@@ -0,0 +1,130 @@
+<?php
+// $Id$
+
+/**
+ * @file
+ * Database interface code for PostgreSQL database servers.
+ */
+
+/**
+ * @ingroup database
+ * @{
+ */
+
+class DatabaseConnection_pgsql extends DatabaseConnection {
+
+  protected $transactionSupport;
+  //protected $lastInsertInfo = NULL;
+
+  public function __construct(Array $connection_options = array()) {
+
+    $connection_options += array(
+      'transactions' => TRUE,
+    );
+    $this->transactionSupport = $connection_options['transactions'];
+
+    $dsn = 'pgsql:host=' . $connection_options['host'] . ' dbname=' . $connection_options['database'];
+    if (!empty($connection_options['port'])) {
+      $dsn .= ' port=' . $connection_options['port'];
+    }
+
+    parent::__construct($dsn, $connection_options['username'], $connection_options['password'], array(PDO::ATTR_STRINGIFY_FETCHES => TRUE));
+  }
+
+  public function query($query, Array $args = array(), $options = array()) {
+
+    $options += $this->defaultOptions();
+    
+    try {
+      if ($query instanceof DatabaseStatement) {
+        $stmt = $query;
+        $stmt->execute(NULL, $options);
+      }
+      else {
+        $stmt = $this->prepareQuery($query);
+        $stmt->execute($args, $options);
+      }
+      
+      switch ($options['return']) {
+        case Database::RETURN_STATEMENT:
+          return $stmt;
+        case Database::RETURN_AFFECTED:
+          return $stmt->rowCount();
+        case Database::RETURN_INSERT_ID:
+          return $this->lastInsertId($options['sequence_name']);
+        case Database::RETURN_NULL:
+          return;
+        default:
+          throw new PDOException('Invalid return directive: ' . $options['return']);
+      }
+    }
+    catch (PDOException $e) {
+      if (!function_exists('module_implements')) {
+        _db_need_install();
+      }
+      //watchdog('database', var_export($e, TRUE) . $e->getMessage(), NULL, WATCHDOG_ERROR);
+      if ($options['throw_exception']) {
+        if ($query instanceof DatabaseStatement) {
+          $query_string = $stmt->queryString;
+        }
+        else {
+          $query_string = $query;
+        }
+        throw new PDOException($query_string . " - \n" . print_r($args,1) . $e->getMessage());
+      }
+      return NULL;
+    }
+  }
+  
+  public function queryRange($query, Array $args, $from, $count, Array $options) {
+    // Backward compatibility hack, temporary.
+    $query = str_replace(array('%d' , '%f' , '%b' , "'%s'"), '?', $query);
+
+    return $this->query($query . ' LIMIT ' . $count . ' OFFSET ' . $from, $args, $options);
+  }
+
+  public function queryTemporary($query, Array $args, $tablename) {
+    $query = preg_replace('/^SELECT/i', 'CREATE TEMPORARY TABLE ' . $tablename . ' Engine=HEAP SELECT', $this->prefixTables($query));
+
+    return $this->query($query, $args, $options);
+  }
+
+  public function driver() {
+    return 'pgsql';
+  }
+
+  public function databaseType() {
+    return 'pgsql';
+  }
+
+  public function supportsTransactions() {
+    return $this->transactionSupport;
+  }
+
+  public function escapeTable($table) {
+    return preg_replace('/[^A-Za-z0-9_]+/', '', $table);
+  }
+
+  public function mapConditionOperator($operator) {
+    static $specials = array(
+      // In PostgreSQL, 'LIKE' is case-sensitive.  For case-insensitive LIKE
+      // statements, we need to use ILIKE instead.
+      'LIKE' => array('operator' => 'ILIKE'),
+    );
+
+    return isset($specials[$operator]) ? $specials[$operator] : NULL;
+  }
+
+  /**
+   * @todo Remove this as soon as db_rewrite_sql() has been exterminated.
+   */
+  public function distinctField($table, $field, $query) {
+    $field_to_select = 'DISTINCT(' . $table . '.' . $field . ')';
+    // (?<!text) is a negative look-behind (no need to rewrite queries that already use DISTINCT).
+    return preg_replace('/(SELECT.*)(?:' . $table . '\.|\s)(?<!DISTINCT\()(?<!DISTINCT\(' . $table . '\.)' . $field . '(.*FROM )/AUsi', '\1 ' . $field_to_select . '\2', $query);
+  }
+}
+
+/**
+ * @} End of "ingroup database".
+ */
diff --git a/includes/database/pgsql/install.inc b/includes/database/pgsql/install.inc
new file mode 100644
index 000000000..921e21402
--- /dev/null
+++ b/includes/database/pgsql/install.inc
@@ -0,0 +1,12 @@
+<?php
+// $Id$
+
+// PostgreSQL specific install functions
+
+class DatabaseInstaller_pgsql extends DatabaseInstaller {
+  protected $pdoDriver = 'pgsql';
+  public function name() {
+    return 'PostgreSQL';
+  }
+}
+
diff --git a/includes/database/pgsql/query.inc b/includes/database/pgsql/query.inc
new file mode 100644
index 000000000..4f3a08da6
--- /dev/null
+++ b/includes/database/pgsql/query.inc
@@ -0,0 +1,167 @@
+<?php
+// $Id$
+
+
+/**
+ * @ingroup database
+ * @{
+ */
+
+class InsertQuery_pgsql extends InsertQuery {
+
+  public function __construct($connection, $table, Array $options = array()) {
+    parent::__construct($connection, $table, $options);
+    $this->queryOptions['return'] = Database::RETURN_NULL;
+  }
+  
+  public function execute() {
+    
+    // Confirm that the user did not try to specify an identical
+    //  field and default field.
+    if (array_intersect($this->insertFields, $this->defaultFields)) {
+      throw new PDOException('You may not specify the same field to have a value and a schema-default value.');
+    }
+
+    $schema = drupal_get_schema($this->table);
+
+    $stmt = $this->connection->prepareQuery((string)$this);
+
+    $max_placeholder = 0;
+    $blobs = array();
+    $blob_cnt = 0;
+    foreach ($this->insertValues as &$insert_values) {
+      foreach ($this->insertFields as $idx => $field) {
+        switch ($schema['fields'][$field]['type']) {
+          case 'blob':
+            $blobs[$blob_cnt] = fopen('php://memory', 'a');
+            fwrite($blobs[$blob_cnt], $insert_values[$idx]);
+            rewind($blobs[$blob_cnt]);
+
+            $stmt->bindParam(':db_insert_placeholder_' . $max_placeholder++, $blobs[$blob_cnt], PDO::PARAM_LOB);
+
+            ++$blob_cnt;
+
+            break;
+          default:
+            $stmt->bindParam(':db_insert_placeholder_'. $max_placeholder++, $insert_values[$idx]);
+            break;
+        }
+      }
+    }
+
+    // PostgreSQL requires the table name to be specified explicitly
+    // when requesting the last insert ID, so we pass that in via
+    // the options array.
+    $options = $this->queryOptions;
+    
+    if ($schema['fields'][$schema['primary key'][0]]['type'] == 'serial') {
+      $options['sequence_name'] = $this->connection->makeSequenceName($this->table, $schema['primary key'][0]);
+      $options['return'] = Database::RETURN_INSERT_ID;
+    }
+    $last_insert_id = $this->connection->query($stmt, array(), $options);
+    
+    // Re-initialize the values array so that we can re-use this query.
+    $this->insertValues = array();
+
+    return $last_insert_id;
+  }
+
+  public function __toString() {
+    
+    // Default fields are always placed first for consistency.
+    $insert_fields = array_merge($this->defaultFields, $this->insertFields);
+
+    $query = "INSERT INTO {" . $this->table . '} (' . implode(', ', $insert_fields) . ') VALUES ';
+
+    $max_placeholder = 0;
+    $values = array();
+      if (count($this->insertValues)) {
+      foreach ($this->insertValues as $insert_values) {
+        $placeholders = array();
+        
+        // Default fields aren't really placeholders, but this is the most convenient
+        // way to handle them.
+        $placeholders = array_pad($placeholders, count($this->defaultFields), 'default');
+        
+        $new_placeholder = $max_placeholder + count($insert_values);
+        for ($i = $max_placeholder; $i < $new_placeholder; ++$i) {
+          $placeholders[] = ':db_insert_placeholder_' . $i;
+        }
+        $max_placeholder = $new_placeholder;
+        $values[] = '(' . implode(', ', $placeholders) . ')';
+      }
+    }
+    else {
+      // If there are no values, then this is a default-only query.  We still need to handle that.
+      $placeholders = array_fill(0, count($this->defaultFields), 'default');
+      $values[] = '(' . implode(', ', $placeholders) .')';
+    }
+
+    $query .= implode(', ', $values);
+
+    return $query;
+  }
+}
+
+class UpdateQuery_pgsql extends UpdateQuery { 
+  public function execute() {
+    $max_placeholder = 0;
+    $blobs = array();
+    $blob_count = 0;
+    
+    $schema = drupal_get_schema($this->table);
+    
+    // Because we filter $fields the same way here and in __toString(), the
+    // placeholders will all match up properly.
+    $stmt = $this->connection->prepareQuery((string)$this);
+    
+    // Expressions take priority over literal fields, so we process those first
+    // and remove any literal fields that conflict.
+    $fields = $this->fields;
+    $expression_fields = array();
+    foreach ($this->expressionFields as $field => $data) {
+      if (!empty($data['arguments'])) {
+        foreach ($data['arguments'] as $placeholder => $argument) {
+          // We assume that an expression will never happen on a BLOB field,
+          // which is a fairly safe assumption to make since in most cases
+          // it would be an invalid query anyway.
+          $stmt->bindParam($placeholder, $argument);
+        }
+      }
+      unset($fields[$field]);
+    }
+    
+    foreach ($fields as $field => &$value) {
+      $placeholder = ':db_update_placeholder_' . ($max_placeholder++);
+
+      switch ($schema['fields'][$field]['type']) {
+        case 'blob':
+          $blobs[$blob_count] = fopen('php://memory', 'a');
+          fwrite($blobs[$blob_count], $value);
+          rewind($blobs[$blob_count]);
+          $stmt->bindParam($placeholder, $blobs[$blob_count], PDO::PARAM_LOB);
+          ++$blob_count;
+          break;
+        default:
+          $stmt->bindParam($placeholder, $value);
+          break;
+      }
+    }
+
+    if (count($this->condition)) {
+      $this->condition->compile($this->connection);
+
+      $arguments = $this->condition->arguments();
+      foreach ($arguments as $placeholder => &$value) {
+        $stmt->bindParam($placeholder, $value);
+      }
+    }
+
+    $options = $this->queryOptions;
+    $options['already_prepared'] = TRUE;
+    $this->connection->query($stmt, $options);
+    
+    //$stmt->execute(NULL, $this->queryOptions);
+    return $stmt->rowCount();
+  }
+}
diff --git a/includes/database/pgsql/schema.inc b/includes/database/pgsql/schema.inc
new file mode 100644
index 000000000..fa817c4d1
--- /dev/null
+++ b/includes/database/pgsql/schema.inc
@@ -0,0 +1,509 @@
+<?php
+// $Id$
+
+/**
+ * @file
+ * Database schema code for PostgreSQL database servers.
+ */
+
+/**
+ * @ingroup schemaapi
+ * @{
+ */
+
+class DatabaseSchema_pgsql extends DatabaseSchema {
+
+  public function tableExists($table) {
+    return (bool) db_result(db_query("SELECT COUNT(*) FROM pg_class WHERE relname = '{" . db_escape_table($table) . "}'"));
+  }
+  
+  public function columnExists($table, $column) {
+    return (bool) db_result(db_query("SELECT COUNT(pg_attribute.attname) FROM pg_class, pg_attribute WHERE pg_attribute.attrelid = pg_class.oid AND pg_class.relname = '{" . db_escape_table($table) . "}' AND attname = '" . db_escape_table($column) . "'"));
+  }
+
+  /**
+   * Generate SQL to create a new table from a Drupal schema definition.
+   *
+   * @param $name
+   *   The name of the table to create.
+   * @param $table
+   *   A Schema API table definition array.
+   * @return
+   *   An array of SQL statements to create the table.
+   */
+  protected function createTableSql($name, $table) {
+    $sql_fields = array();
+    foreach ($table['fields'] as $field_name => $field) {
+      $sql_fields[] = $this->createFieldSql($field_name, $this->processField($field));
+    }
+
+    $sql_keys = array();
+    if (isset($table['primary key']) && is_array($table['primary key'])) {
+      $sql_keys[] = 'PRIMARY KEY (' . implode(', ', $table['primary key']) . ')';
+    }
+    if (isset($table['unique keys']) && is_array($table['unique keys'])) {
+      foreach ($table['unique keys'] as $key_name => $key) {
+        $sql_keys[] = 'CONSTRAINT {' . $name . '}_' . $key_name . '_key UNIQUE (' . implode(', ', $key) . ')';
+      }
+    }
+
+    $sql = "CREATE TABLE {" . $name . "} (\n\t";
+    $sql .= implode(",\n\t", $sql_fields);
+    if (count($sql_keys) > 0) {
+      $sql .= ",\n\t";
+    }
+    $sql .= implode(",\n\t", $sql_keys);
+    $sql .= "\n)";
+    $statements[] = $sql;
+
+    if (isset($table['indexes']) && is_array($table['indexes'])) {
+      foreach ($table['indexes'] as $key_name => $key) {
+        $statements[] = $this->_createIndexSql($name, $key_name, $key);
+      }
+    }
+
+    return $statements;
+  }
+
+  /**
+   * Create an SQL string for a field to be used in table creation or
+   * alteration.
+   *
+   * Before passing a field out of a schema definition into this
+   * function it has to be processed by _db_process_field().
+   *
+   * @param $name
+   *    Name of the field.
+   * @param $spec
+   *    The field specification, as per the schema data structure format.
+   */
+  protected function createFieldSql($name, $spec) {
+    $sql = $name . ' ' . $spec['pgsql_type'];
+
+    if ($spec['type'] == 'serial') {
+      unset($spec['not null']);
+    }
+    if (!empty($spec['unsigned'])) {
+      if ($spec['type'] == 'serial') {
+        $sql .= " CHECK ($name >= 0)";
+      }
+      else {
+        $sql .= '_unsigned';
+      }
+    }
+
+    if (!empty($spec['length'])) {
+      $sql .= '(' . $spec['length'] . ')';
+    }
+    elseif (isset($spec['precision']) && isset($spec['scale'])) {
+      $sql .= '(' . $spec['precision'] . ', ' . $spec['scale'] . ')';
+    }
+
+    if (isset($spec['not null']) && $spec['not null']) {
+      $sql .= ' NOT NULL';
+    }
+    if (isset($spec['default'])) {
+      $default = is_string($spec['default']) ? "'" . $spec['default'] . "'" : $spec['default'];
+      $sql .= " default $default";
+    }
+
+    return $sql;
+  }
+
+  /**
+   * Set database-engine specific properties for a field.
+   *
+   * @param $field
+   *   A field description array, as specified in the schema documentation.
+   */
+  protected function processField($field) {
+    if (!isset($field['size'])) {
+      $field['size'] = 'normal';
+    }
+    // Set the correct database-engine specific datatype.
+    if (!isset($field['pgsql_type'])) {
+      $map = $this->getFieldTypeMap();
+      $field['pgsql_type'] = $map[$field['type'] . ':' . $field['size']];
+    }
+    if ($field['type'] == 'serial') {
+      unset($field['not null']);
+    }
+    return $field;
+  }
+
+
+  /**
+   * This maps a generic data type in combination with its data size
+   * to the engine-specific data type.
+   */
+  function getFieldTypeMap() {
+    // Put :normal last so it gets preserved by array_flip.  This makes
+    // it much easier for modules (such as schema.module) to map
+    // database types back into schema types.
+    $map = array(
+      'varchar:normal' => 'varchar',
+      'char:normal' => 'character',
+
+      'text:tiny' => 'text',
+      'text:small' => 'text',
+      'text:medium' => 'text',
+      'text:big' => 'text',
+      'text:normal' => 'text',
+
+      'int:tiny' => 'smallint',
+      'int:small' => 'smallint',
+      'int:medium' => 'int',
+      'int:big' => 'bigint',
+      'int:normal' => 'int',
+
+      'float:tiny' => 'real',
+      'float:small' => 'real',
+      'float:medium' => 'real',
+      'float:big' => 'double precision',
+      'float:normal' => 'real',
+
+      'numeric:normal' => 'numeric',
+
+      'blob:big' => 'bytea',
+      'blob:normal' => 'bytea',
+
+      'datetime:normal' => 'timestamp',
+
+      'serial:tiny' => 'serial',
+      'serial:small' => 'serial',
+      'serial:medium' => 'serial',
+      'serial:big' => 'bigserial',
+      'serial:normal' => 'serial',
+      );
+    return $map;
+  }
+
+  protected function _createKeySql($fields) {
+    $ret = array();
+    foreach ($fields as $field) {
+      if (is_array($field)) {
+        $ret[] = 'substr(' . $field[0] . ', 1, ' . $field[1] . ')';
+      }
+      else {
+        $ret[] = $field;
+      }
+    }
+    return implode(', ', $ret);
+  }
+
+  /**
+   * Rename a table.
+   *
+   * @param $ret
+   *   Array to which query results will be added.
+   * @param $table
+   *   The table to be renamed.
+   * @param $new_name
+   *   The new name for the table.
+   */
+  function renameTable(&$ret, $table, $new_name) {
+    $ret[] = update_sql('ALTER TABLE {' . $table . '} RENAME TO {' . $new_name . '}');
+  }
+
+  /**
+   * Drop a table.
+   *
+   * @param $ret
+   *   Array to which query results will be added.
+   * @param $table
+   *   The table to be dropped.
+   */
+  public function dropTable(&$ret, $table) {
+    $ret[] = update_sql('DROP TABLE {' . $table . '}');
+  }
+
+  /**
+   * Add a new field to a table.
+   *
+   * @param $ret
+   *   Array to which query results will be added.
+   * @param $table
+   *   Name of the table to be altered.
+   * @param $field
+   *   Name of the field to be added.
+   * @param $spec
+   *   The field specification array, as taken from a schema definition.
+   *   The specification may also contain the key 'initial', the newly
+   *   created field will be set to the value of the key in all rows.
+   *   This is most useful for creating NOT NULL columns with no default
+   *   value in existing tables.
+   * @param $keys_new
+   *   Optional keys and indexes specification to be created on the
+   *   table along with adding the field. The format is the same as a
+   *   table specification but without the 'fields' element.  If you are
+   *   adding a type 'serial' field, you MUST specify at least one key
+   *   or index including it in this array. @see db_change_field for more
+   *   explanation why.
+   */
+  public function addField(&$ret, $table, $field, $spec, $new_keys = array()) {
+    $fixnull = FALSE;
+    if (!empty($spec['not null']) && !isset($spec['default'])) {
+      $fixnull = TRUE;
+      $spec['not null'] = FALSE;
+    }
+    $query = 'ALTER TABLE {' . $table . '} ADD COLUMN ';
+    $query .= $this->_createFieldSql($field, $this->_processField($spec));
+    $ret[] = update_sql($query);
+    if (isset($spec['initial'])) {
+      // All this because update_sql does not support %-placeholders.
+      $sql = 'UPDATE {' . $table . '} SET ' . $field . ' = ' . db_type_placeholder($spec['type']);
+      $result = db_query($sql, $spec['initial']);
+      $ret[] = array('success' => $result !== FALSE, 'query' => check_plain($sql . ' (' . $spec['initial'] . ')'));
+    }
+    if ($fixnull) {
+      $ret[] = update_sql("ALTER TABLE {" . $table . "} ALTER $field SET NOT NULL");
+    }
+    if (isset($new_keys)) {
+      $this->_createKeys($ret, $table, $new_keys);
+    }
+  }
+
+  /**
+   * Drop a field.
+   *
+   * @param $ret
+   *   Array to which query results will be added.
+   * @param $table
+   *   The table to be altered.
+   * @param $field
+   *   The field to be dropped.
+   */
+  public function dropField(&$ret, $table, $field) {
+    $ret[] = update_sql('ALTER TABLE {' . $table . '} DROP COLUMN ' . $field);
+  }
+
+  /**
+   * Set the default value for a field.
+   *
+   * @param $ret
+   *   Array to which query results will be added.
+   * @param $table
+   *   The table to be altered.
+   * @param $field
+   *   The field to be altered.
+   * @param $default
+   *   Default value to be set. NULL for 'default NULL'.
+   */
+  public function fieldSetDefault(&$ret, $table, $field, $default) {
+    if ($default == NULL) {
+      $default = 'NULL';
+    }
+    else {
+      $default = is_string($default) ? "'$default'" : $default;
+    }
+
+    $ret[] = update_sql('ALTER TABLE {' . $table . '} ALTER COLUMN ' . $field . ' SET DEFAULT ' . $default);
+  }
+
+  /**
+   * Set a field to have no default value.
+   *
+   * @param $ret
+   *   Array to which query results will be added.
+   * @param $table
+   *   The table to be altered.
+   * @param $field
+   *   The field to be altered.
+   */
+  public function fieldSetNoDefault(&$ret, $table, $field) {
+    $ret[] = update_sql('ALTER TABLE {' . $table . '} ALTER COLUMN ' . $field . ' DROP DEFAULT');
+  }
+
+  /**
+   * Add a primary key.
+   *
+   * @param $ret
+   *   Array to which query results will be added.
+   * @param $table
+   *   The table to be altered.
+   * @param $fields
+   *   Fields for the primary key.
+   */
+  public function addPrimaryKey(&$ret, $table, $fields) {
+    $ret[] = update_sql('ALTER TABLE {' . $table . '} ADD PRIMARY KEY (' . implode(',', $fields) . ')');
+  }
+
+  /**
+   * Drop the primary key.
+   *
+   * @param $ret
+   *   Array to which query results will be added.
+   * @param $table
+   *   The table to be altered.
+   */
+  public function dropPrimaryKey(&$ret, $table) {
+    $ret[] = update_sql('ALTER TABLE {' . $table . '} DROP CONSTRAINT {' . $table . '}_pkey');
+  }
+
+  /**
+   * Add a unique key.
+   *
+   * @param $ret
+   *   Array to which query results will be added.
+   * @param $table
+   *   The table to be altered.
+   * @param $name
+   *   The name of the key.
+   * @param $fields
+   *   An array of field names.
+   */
+  function addUniqueKey(&$ret, $table, $name, $fields) {
+    $name = '{' . $table . '}_' . $name . '_key';
+    $ret[] = update_sql('ALTER TABLE {' . $table . '} ADD CONSTRAINT ' . $name . ' UNIQUE (' . implode(',', $fields) . ')');
+  }
+
+  /**
+   * Drop a unique key.
+   *
+   * @param $ret
+   *   Array to which query results will be added.
+   * @param $table
+   *   The table to be altered.
+   * @param $name
+   *   The name of the key.
+   */
+  public function dropUniqueKey(&$ret, $table, $name) {
+    $name = '{' . $table . '}_' . $name . '_key';
+    $ret[] = update_sql('ALTER TABLE {' . $table . '} DROP CONSTRAINT ' . $name);
+  }
+
+  /**
+   * Add an index.
+   *
+   * @param $ret
+   *   Array to which query results will be added.
+   * @param $table
+   *   The table to be altered.
+   * @param $name
+   *   The name of the index.
+   * @param $fields
+   *   An array of field names.
+   */
+  public function addIndex(&$ret, $table, $name, $fields) {
+    $ret[] = update_sql($this->_createIndexSql($table, $name, $fields));
+  }
+
+  /**
+   * Drop an index.
+   *
+   * @param $ret
+   *   Array to which query results will be added.
+   * @param $table
+   *   The table to be altered.
+   * @param $name
+   *   The name of the index.
+   */
+  public function dropIndex(&$ret, $table, $name) {
+    $name = '{' . $table . '}_' . $name . '_idx';
+    $ret[] = update_sql('DROP INDEX ' . $name);
+  }
+
+  /**
+   * Change a field definition.
+   *
+   * IMPORTANT NOTE: To maintain database portability, you have to explicitly
+   * recreate all indices and primary keys that are using the changed field.
+   *
+   * That means that you have to drop all affected keys and indexes with
+   * db_drop_{primary_key,unique_key,index}() before calling db_change_field().
+   * To recreate the keys and indices, pass the key definitions as the
+   * optional $new_keys argument directly to db_change_field().
+   *
+   * For example, suppose you have:
+   * @code
+   * $schema['foo'] = array(
+   *   'fields' => array(
+   *     'bar' => array('type' => 'int', 'not null' => TRUE)
+   *   ),
+   *   'primary key' => array('bar')
+   * );
+   * @endcode
+   * and you want to change foo.bar to be type serial, leaving it as the
+   * primary key.  The correct sequence is:
+   * @code
+   * db_drop_primary_key($ret, 'foo');
+   * db_change_field($ret, 'foo', 'bar', 'bar',
+   *   array('type' => 'serial', 'not null' => TRUE),
+   *   array('primary key' => array('bar')));
+   * @endcode
+   *
+   * The reasons for this are due to the different database engines:
+   *
+   * On PostgreSQL, changing a field definition involves adding a new field
+   * and dropping an old one which* causes any indices, primary keys and
+   * sequences (from serial-type fields) that use the changed field to be dropped.
+   *
+   * On MySQL, all type 'serial' fields must be part of at least one key
+   * or index as soon as they are created.  You cannot use
+   * db_add_{primary_key,unique_key,index}() for this purpose because
+   * the ALTER TABLE command will fail to add the column without a key
+   * or index specification.  The solution is to use the optional
+   * $new_keys argument to create the key or index at the same time as
+   * field.
+   *
+   * You could use db_add_{primary_key,unique_key,index}() in all cases
+   * unless you are converting a field to be type serial. You can use
+   * the $new_keys argument in all cases.
+   *
+   * @param $ret
+   *   Array to which query results will be added.
+   * @param $table
+   *   Name of the table.
+   * @param $field
+   *   Name of the field to change.
+   * @param $field_new
+   *   New name for the field (set to the same as $field if you don't want to change the name).
+   * @param $spec
+   *   The field specification for the new field.
+   * @param $new_keys
+   *   Optional keys and indexes specification to be created on the
+   *   table along with changing the field. The format is the same as a
+   *   table specification but without the 'fields' element.
+   */
+  public function changeField(&$ret, $table, $field, $field_new, $spec, $new_keys = array()) {
+    $ret[] = update_sql("ALTER TABLE {" . $table . "} RENAME $field TO " . $field . "_old");
+    $not_null = isset($spec['not null']) ? $spec['not null'] : FALSE;
+    unset($spec['not null']);
+
+    $this->addField($ret, $table, "$field_new", $spec);
+
+    $ret[] = update_sql("UPDATE {" . $table . "} SET $field_new = " . $field . "_old");
+
+    if ($not_null) {
+      $ret[] = update_sql("ALTER TABLE {" . $table . "} ALTER $field_new SET NOT NULL");
+    }
+
+    $this->dropField($ret, $table, $field . '_old');
+
+    if (isset($new_keys)) {
+      $this->_createKeys($ret, $table, $new_keys);
+    }
+  }
+
+  protected function _createIndexSql($table, $name, $fields) {
+    $query = 'CREATE INDEX {' . $table . '}_' . $name . '_idx ON {' . $table . '} (';
+    $query .= $this->_createKeySql($fields) . ')';
+    return $query;
+  }
+
+  protected function _createKeys(&$ret, $table, $new_keys) {
+    if (isset($new_keys['primary key'])) {
+      $this->addPrimaryKey($ret, $table, $new_keys['primary key']);
+    }
+    if (isset($new_keys['unique keys'])) {
+      foreach ($new_keys['unique keys'] as $name => $fields) {
+        $this->addUniqueKey($ret, $table, $name, $fields);
+      }
+    }
+    if (isset($new_keys['indexes'])) {
+      foreach ($new_keys['indexes'] as $name => $fields) {
+        $this->addIndex($ret, $table, $name, $fields);
+      }
+    }
+  }
+}