translator.py

from typing import Dict, Tuple, Union

from langchain_core.structured_query import (
    Comparator,
    Comparison,
    Operation,
    Operator,
    StructuredQuery,
    Visitor,
)


class PGVectorTranslator(Visitor):
    """Translate `PGVector` internal query language elements to valid filters."""

    allowed_operators = [Operator.AND, Operator.OR]
    """Subset of allowed logical operators."""
    allowed_comparators = [
        Comparator.EQ,
        Comparator.NE,
        Comparator.GT,
        Comparator.LT,
        Comparator.IN,
        Comparator.NIN,
        Comparator.CONTAIN,
        Comparator.LIKE,
    ]
    """Subset of allowed logical comparators."""

    def _format_func(self, func: Union[Operator, Comparator]) -> str:
        self._validate_func(func)
        return f"${func.value}"

    def visit_operation(self, operation: Operation) -> Dict:
        args = [arg.accept(self) for arg in operation.arguments]
        return {self._format_func(operation.operator): args}

    def visit_comparison(self, comparison: Comparison) -> Dict:
        return {
            comparison.attribute: {
                self._format_func(comparison.comparator): comparison.value
            }
        }

    def visit_structured_query(
        self, structured_query: StructuredQuery
    ) -> Tuple[str, dict]:
        if structured_query.filter is None:
            kwargs = {}
        else:
            kwargs = {"filter": structured_query.filter.accept(self)}
        return structured_query.query, kwargs