[Store] Add PSR-6 support for vector store

[Guikingone]

Q	A
Bug fix?	no
New feature?	yes
Docs?	yes
Issues	None
License	MIT

Hi 👋🏻

This PR aims to introduce a CacheStore based on PSR-6, it's heavily inspired by the CacheStore from MessageStore layer, this store introduce a refactoring of the InMemoryStore to use common logic for both stores (as we can't rely on the CacheItemPool implementation).

Thanks for the feedback.

[chr-hertel]

That is really an interesting idea, since the PSR 6 cache has quite some implementations. I wonder tho if we would still recommend to use that only in testing or development. I would assume that it doesn't scale well with a lot of documents since the search needs to happen in PHP runtime with all documents loaded, right?

[Guikingone]

Not sure about the performances side, IMO, that's not a big problem (we already use the Cache layer from Sf for heavy operations, that's not a big deal), If you fear that it can impact applications, we can recommend to use it only in dev/test envs, it's just a documentation concern 🤔

[chr-hertel]

Thanks @Guikingone - especially for going the extra mile of refactoring/extracting the calculation - def worth it tho 👍

[Guikingone]

The configuration in the bundle package has been added (better to do it now than in another PR 😄 )

[Copilot]

Pull Request Overview

This PR introduces PSR-6 cache support for vector stores by adding a new CacheStore implementation and refactoring the existing InMemoryStore to use shared distance calculation logic.

Key changes:

• Refactored distance calculation logic into a separate DistanceCalculator class with a DistanceStrategy enum
• Added new CacheStore implementation that uses PSR-6 cache interfaces for persistent vector storage
• Updated documentation and configuration to include the new cache store option

Reviewed Changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/store/src/CacheStore.php	New PSR-6 cache-based vector store implementation
src/store/src/DistanceCalculator.php	Extracted distance calculation logic from InMemoryStore
src/store/src/DistanceStrategy.php	Enum defining available distance calculation strategies
src/store/src/InMemoryStore.php	Refactored to use shared DistanceCalculator
src/store/tests/CacheStoreTest.php	Comprehensive test coverage for CacheStore
src/store/tests/InMemoryStoreTest.php	Updated tests to use new DistanceCalculator API
src/ai-bundle/src/AiBundle.php	Bundle configuration for cache store integration
src/ai-bundle/config/options.php	Configuration schema for cache store
examples/rag/cache.php	Example demonstrating cache store usage
src/store/doc/index.rst	Documentation updates for cache store

[OskarStark]

Suggested change

	PS: Both `InMemory` and `PSR-6 cache` vector stores will load all the data into the memory of the PHP process.
	They can be used only the amount of data fits in the PHP memory limit, typically for testing.
	.. note::
	Both `InMemory` and `PSR-6 cache` vector stores will load all the data into the
	memory of the PHP process. They can be used only the amount of data fits in the
	PHP memory limit, typically for testing.

[OskarStark]

Can w use something like:

// The callable will only be executed on a cache miss.
$value = $pool->get('my_cache_key', function (ItemInterface $item): string {
    $item->expiresAfter(3600);

    // ... do some HTTP request or heavy computations
    $computedValue = 'foobar';

    return $computedValue;
});