[Spanner] CacheSessionPool::clear deletes the entire cache

[taka-oyama]

It shouldn't be doing that.
It should only delete the key(s) that are relevant.

Environment details

Irrelevant.

Steps to reproduce

1. Set unrelated item to the CacheItemPool
2. create new CacheSessionPool using CacheItemPool
3. Call CacheSessionPool::clear()

Code example

$cache = new \Symfony\Component\Cache\Adapter\ArrayAdapter();

// set an unrelated item
$item = $cache->getItem('dummy')->set('hi');
$cache->save($item);

$connection = (new SpannerClient())->connect(
    getenv('SPANNER_INSTANCE'),
    getenv('SPANNER_DATABASE'),
    ['sessionPool' => new CacheSessionPool($cache)],
);

var_dump($cache->hasItem('dummy')); // true

$connection->sessionPool()?->clear();

var_dump($cache->hasItem('dummy')); // false

See the code below.

google-cloud-php/Spanner/src/Session/CacheSessionPool.php

Line 514 in 4b490ad

$this->cacheItemPool->clear();

This should probably be $this->cacheItemPool->deleteItem($item);.