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"""A database consists of multiple databases."""

from tvm_ffi import register_object

from .. import _ffi_api
from .database import Database


@register_object("s_tir.meta_schedule.UnionDatabase")
class UnionDatabase(Database):
    """A database composed of multiple databases, allowing users to guide IR rewriting using
    combined knowledge of those databases. To each query, it returns the best record among all the
    databases given.

    Examples
    --------
    Examples below demonstrate the usecases of and difference between UnionDatabase and
    OrderDatabase.

    Assumption:
    * db1, db2 do not have tuning records for the target workload.
    * Each of db3, db4, db5 has tuning records r3, r4, r5 for target workload respectively.

    .. code-block:: python

        #### Case 1. `UnionDatabase`:
        merged_db = ms.database.UnionDatabase(
            db1, # no record
            db2, # no record
            db3, # has r3
            db4  # has r4
        )
        # returns the better one between r3 and r4
        merged_db.query_tuning_record(..., target_workload)

        ### Case 2. `OrderedUnionDatabase`
        merged_db = ms.database.OrderedUnionDatabase(
            db1, # no record
            db2, # no record
            db3, # has r3
            db4  # has r4
        )
        # returns r3
        merged_db.query_tuning_record(..., target_workload)

        ### Case 3. Mix-use scenario
        merged_db = ms.database.UnionDatabase(
            db1, # no record
            db2, # no record
            db3, # has r3
            ms.database.OrderedUnionDatabase( # returns r4
                db4,  # has r4
                db5,  # has r5
            )
        )
        # returns the better one between r3 and r4
        merged_db.query_tuning_record(..., target_workload)

        ### Case 4. Another mix-use scenario
        merged_db = ms.database.UnionDatabase(
            db1, # no record
            db2, # no record
            db3, # has r3
            ms.database.UnionDatabase( # returns best one between r4 and r5
                db4,  # has r4
                db5,  # has r5
            )
        )
        # returns the best one among r3, r4 and r5
        merged_db.query_tuning_record(..., target_workload)

        ### Case 5. Yet another mix-use scenario
        merged_db = ms.database.OrderedUnionDatabase(
            db1, # no record
            db2, # no record
            ms.database.UnionDatabase( # returns best one between r3 and r4
                db3, # has r3
                db4,  # has r4
            )
            db5,  # has r5
        )
        # returns the better one between r3 and r4
        merged_db.query_tuning_record(..., target_workload)
    """

    def __init__(self, *databases: Database) -> None:
        """Construct a merged database from multiple databases.

        Parameters
        ----------
        *databases : Database
            The list of databases to combine.
        """
        self.__init_handle_by_constructor__(
            _ffi_api.DatabaseUnionDatabase,  # type: ignore # pylint: disable=no-member
            databases,
        )
