commit 1b95b791a97a04321b101e70969dbce08dd5f80d
Author: DamZ <damz@mb21.local>
Date:   Thu Jan 22 18:11:23 2009 +0100

    #74308: preliminary MS SQL support.

diff --git includes/database/mssql/database.inc includes/database/mssql/database.inc
new file mode 100755
index 0000000..bd40aeb
--- /dev/null
+++ includes/database/mssql/database.inc
@@ -0,0 +1,176 @@
+<?php
+// $Id $
+
+/**
+ * @file
+ * Database interface code for Microsoft SQL Server.
+ */
+
+/**
+ * @ingroup database
+ * @{
+ */
+
+include_once DRUPAL_ROOT . '/includes/database/prefetch.inc';
+ 
+class DatabaseConnection_mssql extends DatabaseConnection {
+
+  public $connection = NULL;
+  
+  public function __construct(array $connection_options = array()) {
+    $this->connection = sqlsrv_connect($connection_options['host'], array(
+      'Database' => $connection_options['database'],
+      'UID' => $connection_options['username'],
+      'PWD' => $connection_options['password'],
+    ));
+    if (!$this->connection) {
+      throw new PDOException("Unable to connect.");
+    }
+  }
+
+  public function prepare($query, array $options = array()) {
+    return new DatabaseStatement_mssql($this, $query, $options);
+  }
+
+  public function prepareQuery($query) {
+    return $this->prepare($query);
+  }
+
+  public function queryRange($query, array $args, $from, $count, array $options = array()) {
+    // Backward compatibility hack, temporary.
+    $query = str_replace(array('%d' , '%f' , '%b' , "'%s'"), '?', $query);
+    $query = preg_replace("/\s*(SELECT|UPDATE|INSERT)/", "$1 TOP(" . $count . ")", $query);
+    return $this->query($query, $args, $options);
+  }
+
+  public function queryTemporary($query, array $args, $tablename, array $options = array()) {
+    $query = preg_replace('/^SELECT/i', 'CREATE TEMPORARY TABLE ' . $tablename . ' SELECT', $this->prefixTables($query));
+
+    return $this->query($query, $args, $options);
+  }
+
+  public function driver() {
+    return 'mssql';
+  }
+
+  public function databaseType() {
+    return 'mssql';
+  }
+
+  public function mapConditionOperator($operator) {
+    return 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', $query);
+  }
+
+  public function errorInfo() {
+    return array(
+      '00000',
+      'No specific error message',
+      'No details supplied',
+    );
+  }
+
+  public function beginTransaction() {
+    sqlsrv_begin_transaction($this->connection);
+  }
+
+  public function commit() {
+    sqlsrv_commit($this->connection);
+  }
+
+  public function rollBack() {
+    sqlsrv_roll_back($this->connection);
+  }
+
+  function lastInsertId($sequence = NULL) {
+    $result = sqlsrv_query($this->connection, "SELECT @@IDENTITY");
+    if (sqlsrv_fetch($result)) {
+      return sqlsrv_get_field($result, 0);
+    }
+  }
+}
+
+class DatabaseStatementBase_mssql {
+  protected $statement = NULL;
+
+  public function __construct(DatabaseConnection_mssql $dbh, $query, $args) {
+
+    // Emulate named placeholders in sqlsrv.
+    if (count($args)) {
+      // This is using named placeholders.
+      if (range(0, count($args) - 1) !== array_keys($args)) {
+        foreach ($args as $placeholder => $value) {
+          // When replacing the placeholders, make sure we search for the
+          // exact placeholder. For example, if searching for
+          // ':db_placeholder_1', do not replace ':db_placeholder_11'.
+          $query = preg_replace('/' . preg_quote($placeholder) . '\b/', '?', $query);
+        }
+      }
+    }
+
+    // Force quotes around some SQL Server reserved keywords.
+    $quote = array('external');
+    foreach ($quote as $field) {
+      $query = preg_replace('/\[' . preg_quote($field) . '\]/', $field, $query);
+      $query = preg_replace('/(' . preg_quote($field) . ')\b/', '[' . $field . ']', $query);
+    }
+
+    $this->statement = sqlsrv_query($dbh->connection, $query, (array) $args);
+    if ($this->statement === FALSE) {
+      if ($errors = sqlsrv_errors()) {
+         foreach($errors as $error) {
+           throw new PDOException("SQLSTATE[" . $error['SQLSTATE'] . "]: Error " . $error['code'] . ": " . $error['message']);
+         }
+      }
+    }
+  }
+
+  public function execute($args) {
+    // Do nothing.
+    return $this;
+  }
+  
+  function fetchAll() {
+    $metadata = sqlsrv_field_metadata($this->statement);
+    $result_set = array();
+    while (sqlsrv_fetch($this->statement)) {
+      $row = array();
+      foreach ($metadata as $idx => $field) {
+        if ($field['Type'] == -9 || ($field['Type'] >= SQLSRV_SQLTYPE_NVARCHAR(1) && $field['Type'] <= SQLSRV_SQLTYPE_NVARCHAR(8000))
+          || ($field['Type'] >= SQLSRV_SQLTYPE_NCHAR(1) && $field['Type'] <= SQLSRV_SQLTYPE_NCHAR(8000))
+          || $field['Type'] == SQLSRV_SQLTYPE_NVARCHAR('max') || $field['Type'] == SQLSRV_SQLTYPE_NCHAR('max')) {
+          $data = sqlsrv_get_field($this->statement, $idx, SQLSRV_PHPTYPE_STRING(SQLSRV_ENC_BINARY));
+          $row[$field['Name']] = iconv('utf-16le', 'utf-8', $data);
+        }
+        else {
+          $row[$field['Name']] = sqlsrv_get_field($this->statement, $idx);
+        }
+      }
+      $result_set[] = $row;
+    }
+    return $result_set;
+  }
+
+  function rowCount() {
+    return sqlsrv_rows_affected($this->statement);
+  }
+}
+
+class DatabaseStatement_mssql extends DatabaseStatementPrefetch implements Iterator, DatabaseStatementInterface {
+  protected function getStatement($query, &$args = array()) {
+    $query = $this->dbh->prefixTables($query);
+    return new DatabaseStatementBase_mssql($this->dbh, $query, $args);
+  }
+}
+
+/**
+ * @} End of "ingroup database".
+ */
diff --git includes/database/mssql/install.inc includes/database/mssql/install.inc
new file mode 100755
index 0000000..1d9df2c
--- /dev/null
+++ includes/database/mssql/install.inc
@@ -0,0 +1,12 @@
+<?php
+// $Id $
+
+// Microsoft SQL Server specific install functions
+
+class DatabaseInstaller_mssql extends DatabaseInstaller {
+  protected $pdoDriver = 'mssql';
+  public function name() {
+    return 'Microsoft SQL Server';
+  }
+}
+
diff --git includes/database/mssql/query.inc includes/database/mssql/query.inc
new file mode 100755
index 0000000..77dc2ad
--- /dev/null
+++ includes/database/mssql/query.inc
@@ -0,0 +1,89 @@
+<?php
+// $Id $
+
+/**
+ * @ingroup database
+ * @{
+ */
+
+class InsertQuery_mssql extends InsertQuery {
+
+  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);
+
+    $max_placeholder = 0;
+    foreach ($this->insertValues as &$insert_values) {
+      foreach ($this->insertFields as $idx => $field) {
+        if ($schema['fields'][$field]['type'] == 'blob') {
+          $blob = fopen('data://image/png,' . $insert_values[$idx], 'r');
+
+          $insert_values[$idx] = array($insert_values[$idx], NULL, SQLSRV_PHPTYPE_STRING(SQLSRV_ENC_BINARY), SQLSRV_SQLTYPE_VARBINARY('max'));
+        }
+      }
+    }
+
+    return parent::execute();
+  }
+}
+
+class UpdateQuery_mssql extends UpdateQuery {
+  public function execute() {
+    $max_placeholder = 0;
+    $blobs = array();
+    $blob_count = 0;
+
+    $schema = drupal_get_schema($this->table);
+
+    // Expressions take priority over literal fields, so we process those first
+    // and remove any literal fields that conflict.
+    $args = array();
+    $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.
+          $args[$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]);
+          $args[$placeholder] = $blobs[$blob_count];
+          ++$blob_count;
+          break;
+        default:
+          $args[$placeholder] = $value;
+          break;
+      }
+    }
+
+    if (count($this->condition)) {
+      $this->condition->compile($this->connection);
+
+      $arguments = $this->condition->arguments();
+      foreach ($arguments as $placeholder => &$value) {
+        $args[$placeholder] = $value;
+      }
+    }
+
+    $options = $this->queryOptions;
+    return $this->connection->query((string) $this, $args, $options);
+  }
+}
diff --git includes/database/mssql/schema.inc includes/database/mssql/schema.inc
new file mode 100755
index 0000000..1be9b2f
--- /dev/null
+++ includes/database/mssql/schema.inc
@@ -0,0 +1,524 @@
+<?php
+// $Id: schema.inc,v 1.2 2008/09/15 20:48:07 webchick Exp $
+
+/**
+ * @file
+ * Database schema code for PostgreSQL database servers.
+ */
+
+/**
+ * @ingroup schemaapi
+ * @{
+ */
+
+class DatabaseSchema_mssql extends DatabaseSchema {
+
+  public function tableExists($table) {
+    return (bool) db_result(db_query_range("SELECT TABLE_NAME FROM INFORMATION_SCHEMA WHERE TABLE_NAME = '{" . db_escape_table($table) . "}'"));
+  }
+
+  public function columnExists($table, $column) {
+    return (bool) db_result(db_query("SELECT column_name FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = '{" . db_escape_table($table) . "}' AND COLUMN_NAME = '" . db_escape_table($column) . "'"));
+  }
+
+  public function quoteIdentifier($identifier) {
+    return '[' . $identifier .']';
+  }
+
+  public function quoteIdentifiers($identifiers) {
+    return array_map(array($this, 'quoteIdentifier'), $identifiers);;
+  }
+
+  /**
+   * 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(', ', $this->quoteIdentifiers($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 = $this->quoteIdentifier($name) . ' ' . $spec['mssql_type'];
+
+    if (!empty($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']) ? "N'" . $spec['default'] . "'" : $spec['default'];
+      $sql .= " DEFAULT $default";
+    }
+    if (!empty($spec['identity'])) {
+      $sql .= " IDENTITY";
+    }
+    if (!empty($spec['unsigned'])) {
+      $sql .= " CHECK ($name >= 0)";
+    }
+    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['mssql_type'])) {
+      $map = $this->getFieldTypeMap();
+      $field['mssql_type'] = $map[$field['type'] . ':' . $field['size']];
+    }
+    if ($field['type'] == 'serial') {
+      $field['identity'] = TRUE;
+    }
+    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' => 'nvarchar(max)',
+      'text:small' => 'nvarchar(max)',
+      'text:medium' => 'nvarchar(max)',
+      'text:big' => 'nvarchar(max)',
+      'text:normal' => 'nvarchar(max)',
+
+      'serial:tiny'     => 'smallint',
+      'serial:small'    => 'smallint',
+      'serial:medium'   => 'int',
+      'serial:big'      => 'bigint',
+      'serial:normal'   => 'int',
+
+      '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' => 'float(53)',
+      'float:normal' => 'real',
+
+      'numeric:normal' => 'numeric',
+
+      'blob:big' => 'varbinary(max)',
+      'blob:normal' => 'varbinary(max)',
+
+      'datetime:normal' => 'timestamp',
+      );
+    return $map;
+  }
+
+  protected function _createKeySql($fields) {
+    /*
+     Here we need to create a computed PERSISTENT column, and index that, when
+     the type is not allowed in an index.
+     */
+    $ret = array();
+    foreach ($fields as $field) {
+      if (is_array($field)) {
+        $ret[] = $field[0];
+      }
+      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) ? "N'$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) {
+    // We need to unbind the default
+    /*
+    IF EXISTS (SELECT name FROM sys.objects
+         WHERE name = 'phonedflt' 
+            AND type = 'D')
+   BEGIN 
+      EXEC sp_unbindefault 'Person.Contact.Phone'
+      DROP DEFAULT phonedflt
+   END
+   */
+    $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);
+      }
+    }
+  }
+}