Fix metadata deserialization in async mode for PGVector

[shamspias]

Problem

When using asynchronous methods with PGVector (async_mode=True), the metadata field retrieved from the database may be of type Fragment (from asyncpg) or other non-dict types. This causes a ValidationError when the Document class expects metadata to be a dictionary.

Solution

This pull request modifies the _results_to_docs_and_scores method to ensure that metadata is correctly converted into a dictionary before creating Document instances. The method now handles different possible types of metadata and attempts to deserialize it into a dict.

Changes

• Updated _results_to_docs_and_scores method in PGVector class to handle metadata deserialization for different types (e.g., dict, str, Fragment).

Testing

• Tested with async_mode=True and confirmed that the metadata field is correctly deserialized and no longer causes validation errors.
• Ensured that the change does not affect the behavior when async_mode=False.

Related Issues

• Metadata field not properly deserialized when using async_mode=True with PGVector #124

[jaimeescano]

Facing this very same issue. Wondering when this commit could be merged.
Big credits to @shamspias for providing the fix.

Regards

[eyurtsev]

Could you add a relevant unit test(s) for this?

[shamspias]

Hi @eyurtsev,

Thank you for your feedback. I've added unit tests to cover metadata deserialization in asynchronous operations, specifically targeting the _results_to_docs_and_scores method. The new tests ensure that metadata is correctly deserialized and that Document instances receive the proper metadata when using async_mode=True.

Please review the updated tests and let me know if you have any further comments or suggestions.

Best regards,

[shamspias]

@eyurtsev, please let me know if there is anything else I need to do. If not, please merge it.