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<?php
// $Id: database.inc,v 1.39.2.1 2005/04/08 14:24:10 dries Exp $
/**
* @file
* Wrapper for database interface code.
*/
/**
* @defgroup database Database abstraction layer
* @{
* Allow the use of different database servers using the same code base.
*
* Drupal provides a slim database abstraction layer to provide developers with
* the ability to support multiple database servers easily. The intent of this
* layer is to preserve the syntax and power of SQL as much as possible, while
* letting Drupal control the pieces of queries that need to be written
* differently for different servers and provide basic security checks.
*
* Most Drupal database queries are performed by a call to db_query() or
* db_query_range(). Module authors should also consider using pager_query() for
* queries that return results that need to be presented on multiple pages, and
* tablesort_sql() for generating appropriate queries for sortable tables.
*
* For example, one might wish to return a list of the most recent 10 nodes
* authored by a given user. Instead of directly issuing the SQL query
* @code
* SELECT n.title, n.body, n.created FROM node n WHERE n.uid = $uid LIMIT 0, 10;
* @endcode
* one would instead call the Drupal functions:
* @code
* $result = db_query_range('SELECT n.title, n.body, n.created
* FROM {node} n WHERE n.uid = %d', $uid, 0, 10);
* while ($node = db_fetch_object($result)) {
* // Perform operations on $node->body, etc. here.
* }
* @endcode
* Curly braces are used around "node" to provide table prefixing via
* db_prefix_tables(). The explicit use of a user ID is pulled out into an
* argument passed to db_query() so that SQL injection attacks from user input
* can be caught and nullified. The LIMIT syntax varies between database servers,
* so that is abstracted into db_query_range() arguments. Finally, note the
* common pattern of iterating over the result set using db_fetch_object().
*/
/**
* Append a database prefix to all tables in a query.
*
* Queries sent to Drupal should wrap all table names in curly brackets. This
* function searches for this syntax and adds Drupal's table prefix to all
* tables, allowing Drupal to coexist with other systems in the same database if
* necessary.
*
* @param $sql
* A string containing a partial or entire SQL query.
* @return
* The properly-prefixed string.
*/
function db_prefix_tables($sql) {
global $db_prefix;
if (is_array($db_prefix)) {
if (array_key_exists('default', $db_prefix)) {
$tmp = $db_prefix;
unset($tmp['default']);
foreach ($tmp as $key => $val) {
$sql = strtr($sql, array('{'. $key. '}' => $val. $key));
}
return strtr($sql, array('{' => $db_prefix['default'], '}' => ''));
}
else {
foreach ($db_prefix as $key => $val) {
$sql = strtr($sql, array('{'. $key. '}' => $val. $key));
}
return strtr($sql, array('{' => '', '}' => ''));
}
}
else {
return strtr($sql, array('{' => $db_prefix, '}' => ''));
}
}
/**
* Activate a database for future queries.
*
* If it is necessary to use external databases in a project, this function can
* be used to change where database queries are sent. If the database has not
* yet been used, it is initialized using the URL specified for that name in
* Drupal's configuration file. If this name is not defined, a duplicate of the
* default connection is made instead.
*
* Be sure to change the connection back to the default when done with custom
* code.
*
* @param $name
* The name assigned to the newly active database connection. If omitted, the
* default connection will be made active.
*/
function db_set_active($name = 'default') {
global $db_url, $db_type, $active_db;
static $db_conns;
if (!isset($db_conns[$name])) {
// Initiate a new connection, using the named DB URL specified.
if (is_array($db_url)) {
$connect_url = array_key_exists($name, $db_url) ? $db_url[$name] : $db_url['default'];
}
else {
$connect_url = $db_url;
}
$db_type = substr($connect_url, 0, strpos($connect_url, '://'));
$handler = "includes/database.$db_type.inc";
if (is_file($handler)) {
include_once($handler);
}
else {
die('Unsupported database type');
}
$db_conns[$name] = db_connect($connect_url);
}
// Set the active connection.
$active_db = $db_conns[$name];
}
/**
* Runs a basic query in the active database.
*
* User-supplied arguments to the query should be passed in as separate parameters
* so that they can be properly escaped to avoid SQL injection attacks.
*
* @param $query
* A string containing an SQL query.
* @param ...
* A variable number of arguments which are substituted into the query using
* printf() syntax. Instead of a variable number of query arguments, you may
* also pass a single array containing the query arguments.
* @return
* A database query result resource, or FALSE if the query was not executed
* correctly.
*/
function db_query($query) {
$args = func_get_args();
$query = db_prefix_tables($query);
if (count($args) > 1) {
if (is_array($args[1])) {
$args = array_merge(array($query), $args[1]);
}
$args = array_map('db_escape_string', $args);
$args[0] = $query;
$query = call_user_func_array('sprintf', $args);
}
return _db_query($query);
}
/**
* Debugging version of db_query().
*
* Echoes the query to the browser.
*/
function db_queryd($query) {
$args = func_get_args();
$query = db_prefix_tables($query);
if (count($args) > 1) {
if (is_array($args[1])) {
$args = array_merge(array($query), $args[1]);
}
$args = array_map('db_escape_string', $args);
$args[0] = $query;
$query = call_user_func_array('sprintf', $args);
}
return _db_query($query, 1);
}
/**
* Helper function for db_rewrite_sql.
*
* Collects JOIN and WHERE statements via hook_sql.
* Decides whether to select primary_key or DISTINCT(primary_key)
*
* @param $query
* Query to be rewritten.
* @param $primary_table
* Name or alias of the table which has the primary key field for this query. Possible values are: comments, forum, node, term_data, vocabulary.
* @param $primary_field
* Name of the primary field.
* @param $args
* Array of additional arguments.
* @return
* An array: join statements, where statements, field or DISTINCT(field).
*/
function _db_rewrite_sql($query = '', $primary_table = 'n', $primary_field = 'nid', $args = array()) {
$where = array();
$join = array();
$distinct = FALSE;
foreach (module_implements('db_rewrite_sql') as $module) {
$result = module_invoke($module, 'db_rewrite_sql', $query, $primary_table, $primary_field, $args);
if (is_array($result)) {
if (isset($result['where'])) {
$where[] .= $result['where'];
}
if (isset($result['join'])) {
$join[] .= $result['join'];
}
if (isset($result['distinct']) && $result['distinct']) {
$distinct = TRUE;
}
}
elseif (isset($result)) {
$where[] .= $result;
}
}
$where = empty($where) ? '' : '('. implode(') AND (', $where) .')';
$join = empty($join) ? '' : implode(' ', $join);
return array($join, $where, $distinct);
}
/**
* Rewrites node queries.
*
* @param $query
* Query to be rewritten.
* @param $primary_table
* Name or alias of the table which has the primary key field for this query. Possible values are: comments, forum, node, term_data, vocabulary.
* @param $primary_field
* Name of the primary field.
* @param $args
* An array of arguments, passed to the implementations of hook_db_rewrite_sql.
* @return
* The original query with JOIN and WHERE statements inserted from hook_db_rewrite_sql implementations. nid is rewritten if needed.
*/
function db_rewrite_sql($query, $primary_table = 'n', $primary_field = 'nid', $args = array()) {
list($join, $where, $distinct) = _db_rewrite_sql($query, $primary_table, $primary_field, $args);
if ($distinct) {
$field_to_select = 'DISTINCT('. $primary_table .'.'. $primary_field .')';
// (?<!text) is a negative look-behind (no need to rewrite queries that already use DISTINCT).
$query = preg_replace('/(SELECT.*)('. $primary_table .'\.)?(?<!DISTINCT\()(?<!DISTINCT\('. $primary_table .'\.)'. $primary_field .'(.*FROM)/AUsi', '\1'. $field_to_select .'\3', $query);
}
if (!empty($join)) {
$query = preg_replace('|FROM[^[:upper:]/,]+|','\0 '. $join .' ', $query);
}
if (!empty($where)) {
if (strpos($query, 'WHERE')) {
$replace = 'WHERE';
$add = 'AND';
}
elseif (strpos($query, 'GROUP')) {
$replace = 'GROUP';
$add = 'GROUP';
}
elseif (strpos($query, 'ORDER')) {
$replace = 'ORDER';
$add = 'ORDER';
}
elseif (strpos($query, 'LIMIT')) {
$replace = 'LIMIT';
$add = 'LIMIT';
}
else {
$query .= ' WHERE '. $where;
}
if (isset($replace)) {
$query = str_replace($replace, 'WHERE '. $where .' '. $add .' ', $query);
}
}
return $query;
}
/**
* @} End of "defgroup database".
*/
// Initialize the default database.
db_set_active();
?>
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