lancedb/python/python/lancedb/embeddings/base.py

# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright The LanceDB Authors

from abc import ABC, abstractmethod
import copy
from typing import List, Union

from lancedb.util import add_note
import numpy as np
import pyarrow as pa
from pydantic import BaseModel, Field, PrivateAttr

from .utils import TEXT, retry_with_exponential_backoff


class EmbeddingFunction(BaseModel, ABC):
    """
    An ABC for embedding functions.

    All concrete embedding functions must implement the following methods:
    1. compute_query_embeddings() which takes a query and returns a list of embeddings
    2. compute_source_embeddings() which returns a list of embeddings for
       the source column
    For text data, the two will be the same. For multi-modal data, the source column
    might be images and the vector column might be text.
    3. ndims() which returns the number of dimensions of the vector column
    """

    max_retries: int = (
        7  # Setting 0 disables retires. Maybe this should not be enabled by default,
    )
    _ndims: int = PrivateAttr()
    _original_args: dict = PrivateAttr()

    @classmethod
    def create(cls, **kwargs):
        """
        Create an instance of the embedding function
        """
        resolved_kwargs = cls.__resolveVariables(kwargs)
        instance = cls(**resolved_kwargs)
        instance._original_args = kwargs
        return instance

    @classmethod
    def __resolveVariables(cls, args: dict) -> dict:
        """
        Resolve variables in the args
        """
        from .registry import EmbeddingFunctionRegistry

        new_args = copy.deepcopy(args)

        registry = EmbeddingFunctionRegistry.get_instance()
        sensitive_keys = cls.sensitive_keys()
        for k, v in new_args.items():
            if isinstance(v, str) and not v.startswith("$var:") and k in sensitive_keys:
                exc = ValueError(
                    f"Sensitive key '{k}' cannot be set to a hardcoded value"
                )
                add_note(exc, "Help: Use $var: to set sensitive keys to variables")
                raise exc

            if isinstance(v, str) and v.startswith("$var:"):
                parts = v[5:].split(":", maxsplit=1)
                if len(parts) == 1:
                    try:
                        new_args[k] = registry.get_var(parts[0])
                    except KeyError:
                        exc = ValueError(
                            "Variable '{}' not found in registry".format(parts[0])
                        )
                        add_note(
                            exc,
                            "Help: Variables are reset in new Python sessions. "
                            "Use `registry.set_var` to set variables.",
                        )
                        raise exc
                else:
                    name, default = parts
                    try:
                        new_args[k] = registry.get_var(name)
                    except KeyError:
                        new_args[k] = default
        return new_args

    @staticmethod
    def sensitive_keys() -> List[str]:
        """
        Return a list of keys that are sensitive and should not be allowed
        to be set to hardcoded values in the config. For example, API keys.
        """
        return []

    @abstractmethod
    def compute_query_embeddings(self, *args, **kwargs) -> list[Union[np.array, None]]:
        """
        Compute the embeddings for a given user query

        Returns
        -------
        A list of embeddings for each input. The embedding of each input can be None
        when the embedding is not valid.
        """
        pass

    @abstractmethod
    def compute_source_embeddings(self, *args, **kwargs) -> list[Union[np.array, None]]:
        """Compute the embeddings for the source column in the database

        Returns
        -------
        A list of embeddings for each input. The embedding of each input can be None
        when the embedding is not valid.
        """
        pass

    def compute_query_embeddings_with_retry(
        self, *args, **kwargs
    ) -> list[Union[np.array, None]]:
        """Compute the embeddings for a given user query with retries

        Returns
        -------
        A list of embeddings for each input. The embedding of each input can be None
        when the embedding is not valid.
        """
        return retry_with_exponential_backoff(
            self.compute_query_embeddings, max_retries=self.max_retries
        )(
            *args,
            **kwargs,
        )

    def compute_source_embeddings_with_retry(
        self, *args, **kwargs
    ) -> list[Union[np.array, None]]:
        """Compute the embeddings for the source column in the database with retries.

        Returns
        -------
        A list of embeddings for each input. The embedding of each input can be None
        when the embedding is not valid.
        """
        return retry_with_exponential_backoff(
            self.compute_source_embeddings, max_retries=self.max_retries
        )(*args, **kwargs)

    def sanitize_input(self, texts: TEXT) -> Union[List[str], np.ndarray]:
        """
        Sanitize the input to the embedding function.
        """
        if isinstance(texts, str):
            texts = [texts]
        elif isinstance(texts, pa.Array):
            texts = texts.to_pylist()
        elif isinstance(texts, pa.ChunkedArray):
            texts = texts.combine_chunks().to_pylist()
        return texts

    def safe_model_dump(self):
        if not hasattr(self, "_original_args"):
            raise ValueError(
                "EmbeddingFunction was not created with EmbeddingFunction.create()"
            )
        return self._original_args

    @abstractmethod
    def ndims(self) -> int:
        """
        Return the dimensions of the vector column
        """
        pass

    def SourceField(self, **kwargs):
        """
        Creates a pydantic Field that can automatically annotate
        the source column for this embedding function
        """
        return Field(json_schema_extra={"source_column_for": self}, **kwargs)

    def VectorField(self, **kwargs):
        """
        Creates a pydantic Field that can automatically annotate
        the target vector column for this embedding function
        """
        return Field(json_schema_extra={"vector_column_for": self}, **kwargs)

    def __eq__(self, __value: object) -> bool:
        if not hasattr(__value, "__dict__"):
            return False
        return vars(self) == vars(__value)

    def __hash__(self) -> int:
        return hash(frozenset(vars(self).items()))


class EmbeddingFunctionConfig(BaseModel):
    """
    This model encapsulates the configuration for a embedding function
    in a lancedb table. It holds the embedding function, the source column,
    and the vector column
    """

    vector_column: str
    source_column: str
    function: EmbeddingFunction


class TextEmbeddingFunction(EmbeddingFunction):
    """
    A callable ABC for embedding functions that take text as input
    """

    def compute_query_embeddings(
        self, query: str, *args, **kwargs
    ) -> list[Union[np.array, None]]:
        return self.compute_source_embeddings(query, *args, **kwargs)

    def compute_source_embeddings(
        self, texts: TEXT, *args, **kwargs
    ) -> list[Union[np.array, None]]:
        texts = self.sanitize_input(texts)
        return self.generate_embeddings(texts)

    @abstractmethod
    def generate_embeddings(
        self, texts: Union[List[str], np.ndarray], *args, **kwargs
    ) -> list[Union[np.array, None]]:
        """Generate the embeddings for the given texts"""
        pass