pgvector vectorstore produces double-quoting for filters, breaking them

[dredozubov]

Describe the bug
pgvector VectorStore implementation incorrectly filters the result, resulting in no matches. Current implementation double-quotes json string values instead of single-quoting them.

To Reproduce
Steps to reproduce the behavior:

1. Enable query logging in postgres:

ALTER SYSTEM SET log_statement = 'all';
ALTER SYSTEM SET log_duration = on;
ALTER SYSTEM SET log_min_duration_statement = 0;

# Reload configuration
SELECT pg_reload_conf();

2. Run similarity search via pgvector vectorstore
3. See that queries are rendered this way: WHERE (data.cmetadata ->> 'doc_type') = '"earnings_transcript"' instead of WHERE (data.cmetadata ->> 'doc_type') = "earnings_transcript"
4. Filtering won't return any result:

db=# WITH filtered_embedding_dims AS MATERIALIZED (
    SELECT
        *
    FROM
        vs_embeddings
    WHERE
        vector_dims(embedding) = '1536'
)
SELECT COUNT(*)
FROM
    filtered_embedding_dims
    JOIN vs_collections ON filtered_embedding_dims.collection_id = vs_collections.uuid
WHERE
    vs_collections.name = 'langchain'
    AND (filtered_embedding_dims.cmetadata ->> 'doc_type') = '"earnings_transcript"' ;
 count
-------
     0
(1 row)

Expected behavior

db=# WITH filtered_embedding_dims AS MATERIALIZED (
    SELECT
        *
    FROM
        vs_embeddings
    WHERE
        vector_dims(embedding) = '1536'
)
SELECT COUNT(*)
FROM
    filtered_embedding_dims
    JOIN vs_collections ON filtered_embedding_dims.collection_id = vs_collections.uuid
WHERE
    vs_collections.name = 'langchain'
    AND (filtered_embedding_dims.cmetadata ->> 'doc_type') = 'earnings_transcript' ;
 count
-------
    26
(1 row)

Desktop (please complete the following information):

• OS: OS X Ventura 13.6.9
• Version: langchain-rust = { version = "4.6.0", features = ["postgres"] }

[dredozubov]

Made a quick fix there: #269

[dredozubov]

@Abraxas-365 Hi! Is this repo still maintained?

[Abraxas-365]

@dredozubov yes sorry I was on vacations, I'm running the checks

[dredozubov]

@Abraxas-365 Sure thing, I didn't mean to pressure you. Just genuinely interested in the state of the repo.