synapse-product/synapse/storage/databases/state/store.py

# Copyright 2014-2016 OpenMarket Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import logging
from typing import (
    TYPE_CHECKING,
    Collection,
    Dict,
    Iterable,
    Optional,
    Sequence,
    Set,
    Tuple,
)

import attr
from sortedcontainers import SortedDict

from twisted.internet import defer

from synapse.api.constants import EventTypes
from synapse.logging.context import make_deferred_yieldable, run_in_background
from synapse.storage._base import SQLBaseStore
from synapse.storage.database import (
    DatabasePool,
    LoggingDatabaseConnection,
    LoggingTransaction,
)
from synapse.storage.databases.state.bg_updates import StateBackgroundUpdateStore
from synapse.storage.state import StateFilter
from synapse.storage.types import Cursor
from synapse.storage.util.sequence import build_sequence_generator
from synapse.types import MutableStateMap, StateKey, StateMap
from synapse.util import unwrapFirstError
from synapse.util.async_helpers import (
    AbstractObservableDeferred,
    ObservableDeferred,
    yieldable_gather_results,
)
from synapse.util.caches.descriptors import cached
from synapse.util.caches.dictionary_cache import DictionaryCache

if TYPE_CHECKING:
    from synapse.server import HomeServer

logger = logging.getLogger(__name__)

MAX_STATE_DELTA_HOPS = 100
MAX_INFLIGHT_REQUESTS_PER_GROUP = 5


@attr.s(slots=True, frozen=True, auto_attribs=True)
class _GetStateGroupDelta:
    """Return type of get_state_group_delta that implements __len__, which lets
    us use the iterable flag when caching
    """

    prev_group: Optional[int]
    delta_ids: Optional[StateMap[str]]

    def __len__(self) -> int:
        return len(self.delta_ids) if self.delta_ids else 0


def state_filter_rough_priority_comparator(
    state_filter: StateFilter,
) -> Tuple[int, int]:
    """
    Returns a comparable value that roughly indicates the relative size of this
    state filter compared to others.
    'Larger' state filters should sort first when using ascending order, so
    this is essentially the opposite of 'size'.
    It should be treated as a rough guide only and should not be interpreted to
    have any particular meaning. The representation may also change

    The current implementation returns a tuple of the form:
        * -1 for include_others, 0 otherwise
        * -(number of entries in state_filter.types)
    """
    return -int(state_filter.include_others), -len(state_filter.types)


class StateGroupDataStore(StateBackgroundUpdateStore, SQLBaseStore):
    """A data store for fetching/storing state groups."""

    def __init__(
        self,
        database: DatabasePool,
        db_conn: LoggingDatabaseConnection,
        hs: "HomeServer",
    ):
        super().__init__(database, db_conn, hs)

        # Originally the state store used a single DictionaryCache to cache the
        # event IDs for the state types in a given state group to avoid hammering
        # on the state_group* tables.
        #
        # The point of using a DictionaryCache is that it can cache a subset
        # of the state events for a given state group (i.e. a subset of the keys for a
        # given dict which is an entry in the cache for a given state group ID).
        #
        # However, this poses problems when performing complicated queries
        # on the store - for instance: "give me all the state for this group, but
        # limit members to this subset of users", as DictionaryCache's API isn't
        # rich enough to say "please cache any of these fields, apart from this subset".
        # This is problematic when lazy loading members, which requires this behaviour,
        # as without it the cache has no choice but to speculatively load all
        # state events for the group, which negates the efficiency being sought.
        #
        # Rather than overcomplicating DictionaryCache's API, we instead split the
        # state_group_cache into two halves - one for tracking non-member events,
        # and the other for tracking member_events.  This means that lazy loading
        # queries can be made in a cache-friendly manner by querying both caches
        # separately and then merging the result.  So for the example above, you
        # would query the members cache for a specific subset of state keys
        # (which DictionaryCache will handle efficiently and fine) and the non-members
        # cache for all state (which DictionaryCache will similarly handle fine)
        # and then just merge the results together.
        #
        # We size the non-members cache to be smaller than the members cache as the
        # vast majority of state in Matrix (today) is member events.

        self._state_group_cache: DictionaryCache[int, StateKey, str] = DictionaryCache(
            "*stateGroupCache*",
            # TODO: this hasn't been tuned yet
            50000,
        )
        self._state_group_members_cache: DictionaryCache[
            int, StateKey, str
        ] = DictionaryCache(
            "*stateGroupMembersCache*",
            500000,
        )

        # Current ongoing get_state_for_groups in-flight requests
        # {group ID -> {StateFilter -> ObservableDeferred}}
        self._state_group_inflight_requests: Dict[
            int, SortedDict[StateFilter, AbstractObservableDeferred[StateMap[str]]]
        ] = {}

        def get_max_state_group_txn(txn: Cursor) -> int:
            txn.execute("SELECT COALESCE(max(id), 0) FROM state_groups")
            return txn.fetchone()[0]  # type: ignore

        self._state_group_seq_gen = build_sequence_generator(
            db_conn,
            self.database_engine,
            get_max_state_group_txn,
            "state_group_id_seq",
            table="state_groups",
            id_column="id",
        )

    @cached(max_entries=10000, iterable=True)
    async def get_state_group_delta(self, state_group: int) -> _GetStateGroupDelta:
        """Given a state group try to return a previous group and a delta between
        the old and the new.

        Returns:
            _GetStateGroupDelta containing prev_group and delta_ids, where both may be None.
        """

        def _get_state_group_delta_txn(txn: LoggingTransaction) -> _GetStateGroupDelta:
            prev_group = self.db_pool.simple_select_one_onecol_txn(
                txn,
                table="state_group_edges",
                keyvalues={"state_group": state_group},
                retcol="prev_state_group",
                allow_none=True,
            )

            if not prev_group:
                return _GetStateGroupDelta(None, None)

            delta_ids = self.db_pool.simple_select_list_txn(
                txn,
                table="state_groups_state",
                keyvalues={"state_group": state_group},
                retcols=("type", "state_key", "event_id"),
            )

            return _GetStateGroupDelta(
                prev_group,
                {(row["type"], row["state_key"]): row["event_id"] for row in delta_ids},
            )

        return await self.db_pool.runInteraction(
            "get_state_group_delta", _get_state_group_delta_txn
        )

    async def _get_state_groups_from_groups(
        self, groups: Sequence[int], state_filter: StateFilter
    ) -> Dict[int, StateMap[str]]:
        """Returns the state groups for a given set of groups from the
        database, filtering on types of state events.

        Args:
            groups: list of state group IDs to query
            state_filter: The state filter used to fetch state
                from the database.
        Returns:
            Dict of state group to state map.
        """
        results: Dict[int, StateMap[str]] = {}

        chunks = [groups[i : i + 100] for i in range(0, len(groups), 100)]
        for chunk in chunks:
            res = await self.db_pool.runInteraction(
                "_get_state_groups_from_groups",
                self._get_state_groups_from_groups_txn,
                chunk,
                state_filter,
            )
            results.update(res)

        return results

    def _get_state_for_group_using_cache(
        self,
        cache: DictionaryCache[int, StateKey, str],
        group: int,
        state_filter: StateFilter,
    ) -> Tuple[MutableStateMap[str], bool]:
        """Checks if group is in cache. See `_get_state_for_groups`

        Args:
            cache: the state group cache to use
            group: The state group to lookup
            state_filter: The state filter used to fetch state from the database.

        Returns:
             2-tuple (`state_dict`, `got_all`).
                `got_all` is a bool indicating if we successfully retrieved all
                requests state from the cache, if False we need to query the DB for the
                missing state.
        """
        cache_entry = cache.get(group)
        state_dict_ids = cache_entry.value

        if cache_entry.full or state_filter.is_full():
            # Either we have everything or want everything, either way
            # `is_all` tells us whether we've gotten everything.
            return state_filter.filter_state(state_dict_ids), cache_entry.full

        # tracks whether any of our requested types are missing from the cache
        missing_types = False

        if state_filter.has_wildcards():
            # We don't know if we fetched all the state keys for the types in
            # the filter that are wildcards, so we have to assume that we may
            # have missed some.
            missing_types = True
        else:
            # There aren't any wild cards, so `concrete_types()` returns the
            # complete list of event types we're wanting.
            for key in state_filter.concrete_types():
                if key not in state_dict_ids and key not in cache_entry.known_absent:
                    missing_types = True
                    break

        return state_filter.filter_state(state_dict_ids), not missing_types

    def _get_state_for_group_gather_inflight_requests(
        self, group: int, state_filter_left_over: StateFilter
    ) -> Tuple[Sequence[AbstractObservableDeferred[StateMap[str]]], StateFilter]:
        """
        Attempts to gather in-flight requests and re-use them to retrieve state
        for the given state group, filtered with the given state filter.

        If there are more than MAX_INFLIGHT_REQUESTS_PER_GROUP in-flight requests,
        and there *still* isn't enough information to complete the request by solely
        reusing others, a full state filter will be requested to ensure that subsequent
        requests can reuse this request.

        Used as part of _get_state_for_group_using_inflight_cache.

        Returns:
            Tuple of two values:
                A sequence of ObservableDeferreds to observe
                A StateFilter representing what else needs to be requested to fulfill the request
        """

        inflight_requests = self._state_group_inflight_requests.get(group)
        if inflight_requests is None:
            # no requests for this group, need to retrieve it all ourselves
            return (), state_filter_left_over

        # The list of ongoing requests which will help narrow the current request.
        reusable_requests = []

        # Iterate over existing requests in roughly biggest-first order.
        for request_state_filter in inflight_requests:
            request_deferred = inflight_requests[request_state_filter]
            new_state_filter_left_over = state_filter_left_over.approx_difference(
                request_state_filter
            )
            if new_state_filter_left_over == state_filter_left_over:
                # Reusing this request would not gain us anything, so don't bother.
                continue

            reusable_requests.append(request_deferred)
            state_filter_left_over = new_state_filter_left_over
            if state_filter_left_over == StateFilter.none():
                # we have managed to collect enough of the in-flight requests
                # to cover our StateFilter and give us the state we need.
                break

        if (
            state_filter_left_over != StateFilter.none()
            and len(inflight_requests) >= MAX_INFLIGHT_REQUESTS_PER_GROUP
        ):
            # There are too many requests for this group.
            # To prevent even more from building up, we request the whole
            # state filter to guarantee that we can be reused by any subsequent
            # requests for this state group.
            return (), StateFilter.all()

        return reusable_requests, state_filter_left_over

    async def _get_state_for_group_fire_request(
        self, group: int, state_filter: StateFilter
    ) -> StateMap[str]:
        """
        Fires off a request to get the state at a state group,
        potentially filtering by type and/or state key.

        This request will be tracked in the in-flight request cache and automatically
        removed when it is finished.

        Used as part of _get_state_for_group_using_inflight_cache.

        Args:
            group: ID of the state group for which we want to get state
            state_filter: the state filter used to fetch state from the database
        """
        cache_sequence_nm = self._state_group_cache.sequence
        cache_sequence_m = self._state_group_members_cache.sequence

        # Help the cache hit ratio by expanding the filter a bit
        db_state_filter = state_filter.return_expanded()

        async def _the_request() -> StateMap[str]:
            group_to_state_dict = await self._get_state_groups_from_groups(
                (group,), state_filter=db_state_filter
            )

            # Now let's update the caches
            self._insert_into_cache(
                group_to_state_dict,
                db_state_filter,
                cache_seq_num_members=cache_sequence_m,
                cache_seq_num_non_members=cache_sequence_nm,
            )

            # Remove ourselves from the in-flight cache
            group_request_dict = self._state_group_inflight_requests[group]
            del group_request_dict[db_state_filter]
            if not group_request_dict:
                # If there are no more requests in-flight for this group,
                # clean up the cache by removing the empty dictionary
                del self._state_group_inflight_requests[group]

            return group_to_state_dict[group]

        # We don't immediately await the result, so must use run_in_background
        # But we DO await the result before the current log context (request)
        # finishes, so don't need to run it as a background process.
        request_deferred = run_in_background(_the_request)
        observable_deferred = ObservableDeferred(request_deferred, consumeErrors=True)

        # Insert the ObservableDeferred into the cache
        group_request_dict = self._state_group_inflight_requests.setdefault(
            group, SortedDict(state_filter_rough_priority_comparator)
        )
        group_request_dict[db_state_filter] = observable_deferred

        return await make_deferred_yieldable(observable_deferred.observe())

    async def _get_state_for_group_using_inflight_cache(
        self, group: int, state_filter: StateFilter
    ) -> MutableStateMap[str]:
        """
        Gets the state at a state group, potentially filtering by type and/or
        state key.

        1. Calls _get_state_for_group_gather_inflight_requests to gather any
           ongoing requests which might overlap with the current request.
        2. Fires a new request, using _get_state_for_group_fire_request,
           for any state which cannot be gathered from ongoing requests.

        Args:
            group: ID of the state group for which we want to get state
            state_filter: the state filter used to fetch state from the database
        Returns:
            state map
        """

        # first, figure out whether we can re-use any in-flight requests
        # (and if so, what would be left over)
        (
            reusable_requests,
            state_filter_left_over,
        ) = self._get_state_for_group_gather_inflight_requests(group, state_filter)

        if state_filter_left_over != StateFilter.none():
            # Fetch remaining state
            remaining = await self._get_state_for_group_fire_request(
                group, state_filter_left_over
            )
            assembled_state: MutableStateMap[str] = dict(remaining)
        else:
            assembled_state = {}

        gathered = await make_deferred_yieldable(
            defer.gatherResults(
                (r.observe() for r in reusable_requests), consumeErrors=True
            )
        ).addErrback(unwrapFirstError)

        # assemble our result.
        for result_piece in gathered:
            assembled_state.update(result_piece)

        # Filter out any state that may be more than what we asked for.
        return state_filter.filter_state(assembled_state)

    async def _get_state_for_groups(
        self, groups: Iterable[int], state_filter: Optional[StateFilter] = None
    ) -> Dict[int, MutableStateMap[str]]:
        """Gets the state at each of a list of state groups, optionally
        filtering by type/state_key

        Args:
            groups: list of state groups for which we want
                to get the state.
            state_filter: The state filter used to fetch state
                from the database.
        Returns:
            Dict of state group to state map.
        """
        state_filter = state_filter or StateFilter.all()

        member_filter, non_member_filter = state_filter.get_member_split()

        # Now we look them up in the member and non-member caches
        (
            non_member_state,
            incomplete_groups_nm,
        ) = self._get_state_for_groups_using_cache(
            groups, self._state_group_cache, state_filter=non_member_filter
        )

        (member_state, incomplete_groups_m,) = self._get_state_for_groups_using_cache(
            groups, self._state_group_members_cache, state_filter=member_filter
        )

        state = dict(non_member_state)
        for group in groups:
            state[group].update(member_state[group])

        # Now fetch any missing groups from the database

        incomplete_groups = incomplete_groups_m | incomplete_groups_nm

        if not incomplete_groups:
            return state

        async def get_from_cache(group: int, state_filter: StateFilter) -> None:
            state[group] = await self._get_state_for_group_using_inflight_cache(
                group, state_filter
            )

        await yieldable_gather_results(
            get_from_cache,
            incomplete_groups,
            state_filter,
        )

        return state

    def _get_state_for_groups_using_cache(
        self,
        groups: Iterable[int],
        cache: DictionaryCache[int, StateKey, str],
        state_filter: StateFilter,
    ) -> Tuple[Dict[int, MutableStateMap[str]], Set[int]]:
        """Gets the state at each of a list of state groups, optionally
        filtering by type/state_key, querying from a specific cache.

        Args:
            groups: list of state groups for which we want to get the state.
            cache: the cache of group ids to state dicts which
                we will pass through - either the normal state cache or the
                specific members state cache.
            state_filter: The state filter used to fetch state from the
                database.

        Returns:
            Tuple of dict of state_group_id to state map of entries in the
            cache, and the state group ids either missing from the cache or
            incomplete.
        """
        results = {}
        incomplete_groups = set()
        for group in set(groups):
            state_dict_ids, got_all = self._get_state_for_group_using_cache(
                cache, group, state_filter
            )
            results[group] = state_dict_ids

            if not got_all:
                incomplete_groups.add(group)

        return results, incomplete_groups

    def _insert_into_cache(
        self,
        group_to_state_dict: Dict[int, StateMap[str]],
        state_filter: StateFilter,
        cache_seq_num_members: int,
        cache_seq_num_non_members: int,
    ) -> None:
        """Inserts results from querying the database into the relevant cache.

        Args:
            group_to_state_dict: The new entries pulled from database.
                Map from state group to state dict
            state_filter: The state filter used to fetch state
                from the database.
            cache_seq_num_members: Sequence number of member cache since
                last lookup in cache
            cache_seq_num_non_members: Sequence number of member cache since
                last lookup in cache
        """

        # We need to work out which types we've fetched from the DB for the
        # member vs non-member caches. This should be as accurate as possible,
        # but can be an underestimate (e.g. when we have wild cards)

        member_filter, non_member_filter = state_filter.get_member_split()
        if member_filter.is_full():
            # We fetched all member events
            member_types = None
        else:
            # `concrete_types()` will only return a subset when there are wild
            # cards in the filter, but that's fine.
            member_types = member_filter.concrete_types()

        if non_member_filter.is_full():
            # We fetched all non member events
            non_member_types = None
        else:
            non_member_types = non_member_filter.concrete_types()

        for group, group_state_dict in group_to_state_dict.items():
            state_dict_members = {}
            state_dict_non_members = {}

            for k, v in group_state_dict.items():
                if k[0] == EventTypes.Member:
                    state_dict_members[k] = v
                else:
                    state_dict_non_members[k] = v

            self._state_group_members_cache.update(
                cache_seq_num_members,
                key=group,
                value=state_dict_members,
                fetched_keys=member_types,
            )

            self._state_group_cache.update(
                cache_seq_num_non_members,
                key=group,
                value=state_dict_non_members,
                fetched_keys=non_member_types,
            )

    async def store_state_group(
        self,
        event_id: str,
        room_id: str,
        prev_group: Optional[int],
        delta_ids: Optional[StateMap[str]],
        current_state_ids: StateMap[str],
    ) -> int:
        """Store a new set of state, returning a newly assigned state group.

        Args:
            event_id: The event ID for which the state was calculated
            room_id
            prev_group: A previous state group for the room, optional.
            delta_ids: The delta between state at `prev_group` and
                `current_state_ids`, if `prev_group` was given. Same format as
                `current_state_ids`.
            current_state_ids: The state to store. Map of (type, state_key)
                to event_id.

        Returns:
            The state group ID
        """

        def _store_state_group_txn(txn: LoggingTransaction) -> int:
            if current_state_ids is None:
                # AFAIK, this can never happen
                raise Exception("current_state_ids cannot be None")

            state_group = self._state_group_seq_gen.get_next_id_txn(txn)

            self.db_pool.simple_insert_txn(
                txn,
                table="state_groups",
                values={"id": state_group, "room_id": room_id, "event_id": event_id},
            )

            # We persist as a delta if we can, while also ensuring the chain
            # of deltas isn't tooo long, as otherwise read performance degrades.
            if prev_group:
                is_in_db = self.db_pool.simple_select_one_onecol_txn(
                    txn,
                    table="state_groups",
                    keyvalues={"id": prev_group},
                    retcol="id",
                    allow_none=True,
                )
                if not is_in_db:
                    raise Exception(
                        "Trying to persist state with unpersisted prev_group: %r"
                        % (prev_group,)
                    )

                potential_hops = self._count_state_group_hops_txn(txn, prev_group)
            if prev_group and potential_hops < MAX_STATE_DELTA_HOPS:
                assert delta_ids is not None

                self.db_pool.simple_insert_txn(
                    txn,
                    table="state_group_edges",
                    values={"state_group": state_group, "prev_state_group": prev_group},
                )

                self.db_pool.simple_insert_many_txn(
                    txn,
                    table="state_groups_state",
                    keys=("state_group", "room_id", "type", "state_key", "event_id"),
                    values=[
                        (state_group, room_id, key[0], key[1], state_id)
                        for key, state_id in delta_ids.items()
                    ],
                )
            else:
                self.db_pool.simple_insert_many_txn(
                    txn,
                    table="state_groups_state",
                    keys=("state_group", "room_id", "type", "state_key", "event_id"),
                    values=[
                        (state_group, room_id, key[0], key[1], state_id)
                        for key, state_id in current_state_ids.items()
                    ],
                )

            # Prefill the state group caches with this group.
            # It's fine to use the sequence like this as the state group map
            # is immutable. (If the map wasn't immutable then this prefill could
            # race with another update)

            current_member_state_ids = {
                s: ev
                for (s, ev) in current_state_ids.items()
                if s[0] == EventTypes.Member
            }
            txn.call_after(
                self._state_group_members_cache.update,
                self._state_group_members_cache.sequence,
                key=state_group,
                value=dict(current_member_state_ids),
            )

            current_non_member_state_ids = {
                s: ev
                for (s, ev) in current_state_ids.items()
                if s[0] != EventTypes.Member
            }
            txn.call_after(
                self._state_group_cache.update,
                self._state_group_cache.sequence,
                key=state_group,
                value=dict(current_non_member_state_ids),
            )

            return state_group

        return await self.db_pool.runInteraction(
            "store_state_group", _store_state_group_txn
        )

    async def purge_unreferenced_state_groups(
        self, room_id: str, state_groups_to_delete: Collection[int]
    ) -> None:
        """Deletes no longer referenced state groups and de-deltas any state
        groups that reference them.

        Args:
            room_id: The room the state groups belong to (must all be in the
                same room).
            state_groups_to_delete: Set of all state groups to delete.
        """

        await self.db_pool.runInteraction(
            "purge_unreferenced_state_groups",
            self._purge_unreferenced_state_groups,
            room_id,
            state_groups_to_delete,
        )

    def _purge_unreferenced_state_groups(
        self,
        txn: LoggingTransaction,
        room_id: str,
        state_groups_to_delete: Collection[int],
    ) -> None:
        logger.info(
            "[purge] found %i state groups to delete", len(state_groups_to_delete)
        )

        rows = self.db_pool.simple_select_many_txn(
            txn,
            table="state_group_edges",
            column="prev_state_group",
            iterable=state_groups_to_delete,
            keyvalues={},
            retcols=("state_group",),
        )

        remaining_state_groups = {
            row["state_group"]
            for row in rows
            if row["state_group"] not in state_groups_to_delete
        }

        logger.info(
            "[purge] de-delta-ing %i remaining state groups",
            len(remaining_state_groups),
        )

        # Now we turn the state groups that reference to-be-deleted state
        # groups to non delta versions.
        for sg in remaining_state_groups:
            logger.info("[purge] de-delta-ing remaining state group %s", sg)
            curr_state_by_group = self._get_state_groups_from_groups_txn(txn, [sg])
            curr_state = curr_state_by_group[sg]

            self.db_pool.simple_delete_txn(
                txn, table="state_groups_state", keyvalues={"state_group": sg}
            )

            self.db_pool.simple_delete_txn(
                txn, table="state_group_edges", keyvalues={"state_group": sg}
            )

            self.db_pool.simple_insert_many_txn(
                txn,
                table="state_groups_state",
                keys=("state_group", "room_id", "type", "state_key", "event_id"),
                values=[
                    (sg, room_id, key[0], key[1], state_id)
                    for key, state_id in curr_state.items()
                ],
            )

        logger.info("[purge] removing redundant state groups")
        txn.execute_batch(
            "DELETE FROM state_groups_state WHERE state_group = ?",
            ((sg,) for sg in state_groups_to_delete),
        )
        txn.execute_batch(
            "DELETE FROM state_groups WHERE id = ?",
            ((sg,) for sg in state_groups_to_delete),
        )

    async def get_previous_state_groups(
        self, state_groups: Iterable[int]
    ) -> Dict[int, int]:
        """Fetch the previous groups of the given state groups.

        Args:
            state_groups

        Returns:
            A mapping from state group to previous state group.
        """

        rows = await self.db_pool.simple_select_many_batch(
            table="state_group_edges",
            column="prev_state_group",
            iterable=state_groups,
            keyvalues={},
            retcols=("prev_state_group", "state_group"),
            desc="get_previous_state_groups",
        )

        return {row["state_group"]: row["prev_state_group"] for row in rows}

    async def purge_room_state(
        self, room_id: str, state_groups_to_delete: Collection[int]
    ) -> None:
        """Deletes all record of a room from state tables

        Args:
            room_id:
            state_groups_to_delete: State groups to delete
        """

        await self.db_pool.runInteraction(
            "purge_room_state",
            self._purge_room_state_txn,
            room_id,
            state_groups_to_delete,
        )

    def _purge_room_state_txn(
        self,
        txn: LoggingTransaction,
        room_id: str,
        state_groups_to_delete: Collection[int],
    ) -> None:
        # first we have to delete the state groups states
        logger.info("[purge] removing %s from state_groups_state", room_id)

        self.db_pool.simple_delete_many_txn(
            txn,
            table="state_groups_state",
            column="state_group",
            values=state_groups_to_delete,
            keyvalues={},
        )

        # ... and the state group edges
        logger.info("[purge] removing %s from state_group_edges", room_id)

        self.db_pool.simple_delete_many_txn(
            txn,
            table="state_group_edges",
            column="state_group",
            values=state_groups_to_delete,
            keyvalues={},
        )

        # ... and the state groups
        logger.info("[purge] removing %s from state_groups", room_id)

        self.db_pool.simple_delete_many_txn(
            txn,
            table="state_groups",
            column="id",
            values=state_groups_to_delete,
            keyvalues={},
        )