Commit d577495f authored by Dries's avatar Dries

- Patch #402896 by berdir, catch, andypost, dmitrig01, chx, pounard, sun,...

- Patch #402896 by berdir, catch, andypost, dmitrig01, chx, pounard, sun, sdboyer: introduce DrupalCacheArray and use it for drupal_get_schema().
parent be357fab
......@@ -225,6 +225,195 @@
*/
define('DRUPAL_PHP_FUNCTION_PATTERN', '[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*');
/**
* Provides a caching wrapper to be used in place of large array structures.
*
* This class should be extended by systems that need to cache large amounts
* of data and have it represented as an array to calling functions. These
* arrays can become very large, so ArrayAccess is used to allow different
* strategies to be used for caching internally (lazy loading, building caches
* over time etc.). This can dramatically reduce the amount of data that needs
* to be loaded from cache backends on each request, and memory usage from
* static caches of that same data.
*
* Note that array_* functions do not work with ArrayAccess. Systems using
* DrupalCacheArray should use this only internally. If providing API functions
* that return the full array, this can be cached separately or returned
* directly. However since DrupalCacheArray holds partial content by design, it
* should be a normal PHP array or otherwise contain the full structure.
*
* Note also that due to limitations in PHP prior to 5.3.4, it is impossible to
* write directly to the contents of nested arrays contained in this object.
* Only writes to the top-level array elements are possible. So if you
* previously had set $object['foo'] = array(1, 2, 'bar' => 'baz'), but later
* want to change the value of 'bar' from 'baz' to 'foobar', you cannot do so
* a targeted write like $object['foo']['bar'] = 'foobar'. Instead, you must
* overwrite the entire top-level 'foo' array with the entire set of new
* values: $object['foo'] = array(1, 2, 'bar' => 'foobar'). Due to this same
* limitation, attempts to create references to any contained data, nested or
* otherwise, will fail silently. So $var = &$object['foo'] will not throw an
* error, and $var will be populated with the contents of $object['foo'], but
* that data will be passed by value, not reference. For more information on
* the PHP limitation, see the note in the official PHP documentation at·
* http://php.net/manual/en/arrayaccess.offsetget.php on
* ArrayAccess::offsetGet().
*
* By default, the class accounts for caches where calling functions might
* request keys in the array that won't exist even after a cache rebuild. This
* prevents situations where a cache rebuild would be triggered over and over
* due to a 'missing' item. These cases are stored internally as a value of
* NULL. This means that the offsetGet() and offsetExists() methods
* must be overridden if caching an array where the top level values can
* legitimately be NULL, and where $object->offsetExists() needs to correctly
* return (equivalent to array_key_exists() vs. isset()). This should not
* be necessary in the majority of cases.
*
* Classes extending this class must override at least the
* resolveCacheMiss() method to have a working implementation.
*
* offsetSet() is not overridden by this class by default. In practice this
* means that assigning an offset via arrayAccess will only apply while the
* object is in scope and will not be written back to the persistent cache.
* This follows a similar pattern to static vs. persistent caching in
* procedural code. Extending classes may wish to alter this behaviour, for
* example by overriding offsetSet() and adding an automatic call to persist().
*
* @see SchemaCache
*/
abstract class DrupalCacheArray implements ArrayAccess {
/**
* A cid to pass to cache_set() and cache_get().
*/
private $cid;
/**
* A bin to pass to cache_set() and cache_get().
*/
private $bin;
/**
* An array of keys to add to the cache at the end of the request.
*/
protected $keysToPersist = array();
/**
* Storage for the data itself.
*/
protected $storage = array();
/**
* Constructor.
*
* @param $cid
* The cid for the array being cached.
* @param $bin
* The bin to cache the array.
*/
public function __construct($cid, $bin) {
$this->cid = $cid;
$this->bin = $bin;
if ($cached = cache_get($this->cid, $this->bin)) {
$this->storage = $cached->data;
}
}
public function offsetExists($offset) {
return $this->offsetGet($offset) !== NULL;
}
public function offsetGet($offset) {
if (isset($this->storage[$offset]) || array_key_exists($offset, $this->storage)) {
return $this->storage[$offset];
}
else {
return $this->resolveCacheMiss($offset);
}
}
public function offsetSet($offset, $value) {
$this->storage[$offset] = $value;
}
public function offsetUnset($offset) {
unset($this->storage[$offset]);
}
/**
* Flags an offset value to be written to the persistent cache.
*
* If a value is assigned to a cache object with offsetSet(), by default it
* will not be written to the persistent cache unless it is flagged with this
* method. This allows items to be cached for the duration of a request,
* without necessarily writing back to the persistent cache at the end.
*
* @param $offset
* The array offset that was request.
* @param $persist
* Optional boolean to specify whether the offset should be persisted or
* not, defaults to TRUE. When called with $persist = FALSE the offset will
* be unflagged so that it will not written at the end of the request.
*/
protected function persist($offset, $persist = TRUE) {
$this->keysToPersist[$offset] = $persist;
}
/**
* Resolves a cache miss.
*
* When an offset is not found in the object, this is treated as a cache
* miss. This method allows classes implementing the interface to look up
* the actual value and allow it to be cached.
*
* @param $offset
* The offset that was requested.
*
* @return
* The value of the offset, or NULL if no value was found.
*/
abstract protected function resolveCacheMiss($offset);
/**
* Immediately write a value to the persistent cache.
*
* @param $cid
* The cache ID.
* @param $bin
* The cache bin.
* @param $data
* The data to write to the persistent cache.
* @param $lock
* Whether to acquire a lock before writing to cache.
*/
protected function set($cid, $data, $bin, $lock = TRUE) {
// Lock cache writes to help avoid stampedes.
// To implement locking for cache misses, override __construct().
$lock_name = $cid . ':' . $bin;
if (!$lock || lock_acquire($lock_name)) {
if ($cached = cache_get($cid, $bin)) {
$data = $cached->data + $data;
}
cache_set($cid, $data, $bin);
if ($lock) {
lock_release($lock_name);
}
}
}
public function __destruct() {
$data = array();
foreach ($this->keysToPersist as $offset => $persist) {
if ($persist) {
$data[$offset] = $this->storage[$offset];
}
}
if (!empty($data)) {
$this->set($this->cid, $data, $this->bin);
}
}
}
/**
* Start the timer with the specified name. If you start and stop the same
* timer multiple times, the measured intervals will be accumulated.
......@@ -2548,6 +2737,55 @@ function ip_address() {
* If true, the schema will be rebuilt instead of retrieved from the cache.
*/
function drupal_get_schema($table = NULL, $rebuild = FALSE) {
static $schema;
if ($rebuild || !isset($table)) {
$schema = drupal_get_complete_schema($rebuild);
}
elseif (!isset($schema)) {
$schema = new SchemaCache();
}
if (!isset($table)) {
return $schema;
}
if (isset($schema[$table])) {
return $schema[$table];
}
else {
return FALSE;
}
}
/**
* Extends DrupalCacheArray to allow for dynamic building of the schema cache.
*/
class SchemaCache extends DrupalCacheArray {
public function __construct() {
// Cache by request method.
parent::__construct('schema:runtime:' . $_SERVER['REQUEST_METHOD'] == 'GET', 'cache');
}
protected function resolveCacheMiss($offset) {
$complete_schema = drupal_get_complete_schema();
$value = isset($complete_schema[$offset]) ? $complete_schema[$offset] : NULL;
$this->storage[$offset] = $value;
$this->persist($offset);
return $value;
}
}
/**
* Get the whole database schema.
*
* The returned schema will include any modifications made by any
* module that implements hook_schema_alter().
*
* @param $rebuild
* If true, the schema will be rebuilt instead of retrieved from the cache.
*/
function drupal_get_complete_schema($rebuild = FALSE) {
static $schema = array();
if (empty($schema) || $rebuild) {
......@@ -2589,18 +2827,13 @@ function drupal_get_schema($table = NULL, $rebuild = FALSE) {
if (!empty($schema) && (drupal_get_bootstrap_phase() == DRUPAL_BOOTSTRAP_FULL)) {
cache_set('schema', $schema);
}
if ($rebuild) {
cache_clear_all('schema:', 'cache', TRUE);
}
}
}
if (!isset($table)) {
return $schema;
}
elseif (isset($schema[$table])) {
return $schema[$table];
}
else {
return FALSE;
}
}
/**
......
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