fd9c925a7b
This drop a lot of non-core features code and delegate their maintainance to third parties. Also it open the door to any missing implementation out of the box, such as Redis for the moment. Finally this consistently enforce a constraint where there can be one and only one active cell at any point in time in code. This used to be true for non-default implementation of cache, but it was not true for default implementation where all cells were kept in-memory and thus were never detached from their worksheet and thus were all kept functionnal at any point in time. This inconsistency of behavior between in-memory and off-memory could lead to bugs when changing cache system if the end-user code was badly written. Now end-user will never be able to write buggy code in the first place, avoiding future headache when introducing caching. Closes #3
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Memory saving
PhpSpreadsheet uses an average of about 1k per cell in your worksheets, so large workbooks can quickly use up available memory. Cell caching provides a mechanism that allows PhpSpreadsheet to maintain the cell objects in a smaller size of memory, or off-memory (eg: on disk, in APCu, memcache or redis). This allows you to reduce the memory usage for large workbooks, although at a cost of speed to access cell data.
By default, PhpSpreadsheet holds all cell objects in memory, but you can specify alternatives by providing your own PSR-16 implementation. PhpSpreadsheet keys are automatically namespaced, and cleaned up after use, so a single cache instance may be shared across several usage of PhpSpreadsheet or even with other cache usages.
To enable cell caching, you must provide your own implementation of cache like so:
$cache = new MyCustomPsr16Implementation();
\PhpOffice\PhpSpreadsheet\Settings::setCache($cache);
A separate cache is maintained for each individual worksheet, and is automatically created when the worksheet is instantiated based on the settings that you have configured. You cannot change the configuration settings once you have started to read a workbook, or have created your first worksheet.
Beware of TTL
As opposed to common cache concept, PhpSpreadsheet data cannot be re-generated from scratch. If some data is stored and later is not retrievable, PhpSpreadsheet will throw an exception.
That means that the data stored in cache must not be deleted by a third-party or via TTL mechanism.
So be sure that TTL is either de-activated or long enough to cover the entire usage of PhpSpreadsheet.
Common use cases
PhpSpreadsheet does not ship with alternative cache implementation. It is up to you to select the most appropriate implementation for your environnement. You can either implement PSR-16 from scratch, or use pre-existing libraries.
One such library is PHP Cache which provides a wide range of alternatives. Refers to their documentation for details, but here are a few suggestions that should get you started.
APCu
Require the packages into your project:
composer require cache/simple-cache-bridge cache/apcu-adapter
Configure PhpSpreadsheet with something like:
$pool = new \Cache\Adapter\Apcu\ApcuCachePool();
$simpleCache = new \Cache\Bridge\SimpleCache\SimpleCacheBridge($pool);
\PhpOffice\PhpSpreadsheet\Settings::setCache($simpleCache);
Redis
Require the packages into your project:
composer require cache/simple-cache-bridge cache/redis-adapter
Configure PhpSpreadsheet with something like:
$client = new \Redis();
$client->connect('127.0.0.1', 6379);
$pool = new \Cache\Adapter\Redis\RedisCachePool($client);
$simpleCache = new \Cache\Bridge\SimpleCache\SimpleCacheBridge($pool);
\PhpOffice\PhpSpreadsheet\Settings::setCache($simpleCache);
Memcache
Require the packages into your project:
composer require cache/simple-cache-bridge cache/memcache-adapter
Configure PhpSpreadsheet with something like:
$client = new \Memcache();
$client->connect('localhost', 11211);
$pool = new \Cache\Adapter\Memcache\MemcacheCachePool($client);
$simpleCache = new \Cache\Bridge\SimpleCache\SimpleCacheBridge($pool);
\PhpOffice\PhpSpreadsheet\Settings::setCache($simpleCache);