`AttributeError: 'CrateTypeCompiler' object has no attribute 'visit_JSONPATH'`

[amotl]

Problem

When deriving a CrateDB adapter for LangChain from langchain-postgres, we are observing this error when invoking a test case.

pytest -vvv -k "test_cratedb_with_metadata_filters_2 and filter10"

self = JSONPATH(), visitor = <sqlalchemy_cratedb.compiler.CrateTypeCompiler object at 0x10e44c290>
kw = {'ambiguous_table_name_map': {}, 'from_linter': None, 'identifier_preparer': <sqlalchemy_cratedb.compiler.CrateIdentifierPreparer object at 0x10e44c350>, 'type_expression': <sqlalchemy.sql.elements.TypeClause object at 0x10d0f6240>, ...}

    def _compiler_dispatch(
        self: Visitable, visitor: Any, **kw: Any
    ) -> str:
        """Look for an attribute named "visit_<visit_name>" on the
        visitor, and call it with the same kw params.

        """
        try:
>           meth = getter(visitor)
E           AttributeError: 'CrateTypeCompiler' object has no attribute 'visit_JSONPATH'

.venv/lib/python3.12/site-packages/sqlalchemy/sql/visitors.py:137: AttributeError

[amotl]

JSONPath in PostgreSQL is out of reach of CrateDB.

Converting a search constraint into an SQLAlchemy filter expression is located at PGVector._handle_field_filter, and looks like this:

elif operator == "$between":
    # Use AND with two comparisons
    low, high = filter_value

    lower_bound = func.jsonb_path_match(
        self.EmbeddingStore.cmetadata,
        cast(f"$.{field} >= $value", JSONPATH),
        cast({"value": low}, JSONB),
    )
    upper_bound = func.jsonb_path_match(
        self.EmbeddingStore.cmetadata,
        cast(f"$.{field} <= $value", JSONPATH),
        cast({"value": high}, JSONB),
    )
    return sqlalchemy.and_(lower_bound, upper_bound)

It would be sweet to provide an alternative handler, to convert that into SQL instead, how the previous one might have been working.