534f9a9eb6
* Add resolve-state helper * Tweaks * Refactor forward extremities, again * Tweaks * Minor optimisation * Make path a bit clearer * Only process state/membership if forward extremities have changed * Usage comments in resolve-state
422 lines
15 KiB
Go
422 lines
15 KiB
Go
// Copyright 2017 Vector Creations Ltd
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// Copyright 2018 New Vector Ltd
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// Copyright 2019-2020 The Matrix.org Foundation C.I.C.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package input
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import (
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"context"
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"fmt"
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"github.com/matrix-org/dendrite/internal/sqlutil"
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"github.com/matrix-org/dendrite/roomserver/api"
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"github.com/matrix-org/dendrite/roomserver/state"
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"github.com/matrix-org/dendrite/roomserver/storage/shared"
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"github.com/matrix-org/dendrite/roomserver/types"
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"github.com/matrix-org/gomatrixserverlib"
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"github.com/matrix-org/util"
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)
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// updateLatestEvents updates the list of latest events for this room in the database and writes the
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// event to the output log.
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// The latest events are the events that aren't referenced by another event in the database:
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//
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// Time goes down the page. 1 is the m.room.create event (root).
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//
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// 1 After storing 1 the latest events are {1}
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// | After storing 2 the latest events are {2}
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// 2 After storing 3 the latest events are {3}
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// / \ After storing 4 the latest events are {3,4}
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// 3 4 After storing 5 the latest events are {5,4}
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// | | After storing 6 the latest events are {5,6}
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// 5 6 <--- latest After storing 7 the latest events are {6,7}
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// |
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// 7 <----- latest
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//
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// Can only be called once at a time
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func (r *Inputer) updateLatestEvents(
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ctx context.Context,
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roomInfo *types.RoomInfo,
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stateAtEvent types.StateAtEvent,
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event gomatrixserverlib.Event,
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sendAsServer string,
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transactionID *api.TransactionID,
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rewritesState bool,
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) (err error) {
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updater, err := r.DB.GetLatestEventsForUpdate(ctx, *roomInfo)
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if err != nil {
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return fmt.Errorf("r.DB.GetLatestEventsForUpdate: %w", err)
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}
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succeeded := false
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defer sqlutil.EndTransactionWithCheck(updater, &succeeded, &err)
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u := latestEventsUpdater{
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ctx: ctx,
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api: r,
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updater: updater,
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roomInfo: roomInfo,
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stateAtEvent: stateAtEvent,
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event: event,
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sendAsServer: sendAsServer,
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transactionID: transactionID,
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rewritesState: rewritesState,
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}
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if err = u.doUpdateLatestEvents(); err != nil {
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return fmt.Errorf("u.doUpdateLatestEvents: %w", err)
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}
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succeeded = true
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return
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}
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// latestEventsUpdater tracks the state used to update the latest events in the
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// room. It mostly just ferries state between the various function calls.
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// The state could be passed using function arguments, but it becomes impractical
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// when there are so many variables to pass around.
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type latestEventsUpdater struct {
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ctx context.Context
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api *Inputer
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updater *shared.LatestEventsUpdater
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roomInfo *types.RoomInfo
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stateAtEvent types.StateAtEvent
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event gomatrixserverlib.Event
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transactionID *api.TransactionID
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rewritesState bool
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// Which server to send this event as.
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sendAsServer string
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// The eventID of the event that was processed before this one.
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lastEventIDSent string
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// The latest events in the room after processing this event.
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latest []types.StateAtEventAndReference
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// The state entries removed from and added to the current state of the
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// room as a result of processing this event. They are sorted lists.
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removed []types.StateEntry
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added []types.StateEntry
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// The state entries that are removed and added to recover the state before
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// the event being processed. They are sorted lists.
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stateBeforeEventRemoves []types.StateEntry
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stateBeforeEventAdds []types.StateEntry
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// The snapshots of current state before and after processing this event
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oldStateNID types.StateSnapshotNID
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newStateNID types.StateSnapshotNID
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}
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func (u *latestEventsUpdater) doUpdateLatestEvents() error {
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u.lastEventIDSent = u.updater.LastEventIDSent()
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u.oldStateNID = u.updater.CurrentStateSnapshotNID()
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// If we are doing a regular event update then we will get the
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// previous latest events to use as a part of the calculation. If
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// we are overwriting the latest events because we have a complete
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// state snapshot from somewhere else, e.g. a federated room join,
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// then start with an empty set - none of the forward extremities
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// that we knew about before matter anymore.
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oldLatest := []types.StateAtEventAndReference{}
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if !u.stateAtEvent.Overwrite {
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oldLatest = u.updater.LatestEvents()
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}
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// If the event has already been written to the output log then we
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// don't need to do anything, as we've handled it already.
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if hasBeenSent, err := u.updater.HasEventBeenSent(u.stateAtEvent.EventNID); err != nil {
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return fmt.Errorf("u.updater.HasEventBeenSent: %w", err)
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} else if hasBeenSent {
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return nil
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}
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// Work out what the latest events are. This will include the new
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// event if it is not already referenced.
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extremitiesChanged, err := u.calculateLatest(
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oldLatest, &u.event,
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types.StateAtEventAndReference{
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EventReference: u.event.EventReference(),
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StateAtEvent: u.stateAtEvent,
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},
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)
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if err != nil {
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return fmt.Errorf("u.calculateLatest: %w", err)
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}
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// Now that we know what the latest events are, it's time to get the
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// latest state.
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var updates []api.OutputEvent
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if extremitiesChanged {
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if err = u.latestState(); err != nil {
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return fmt.Errorf("u.latestState: %w", err)
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}
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// If we need to generate any output events then here's where we do it.
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// TODO: Move this!
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if updates, err = u.api.updateMemberships(u.ctx, u.updater, u.removed, u.added); err != nil {
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return fmt.Errorf("u.api.updateMemberships: %w", err)
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}
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}
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update, err := u.makeOutputNewRoomEvent()
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if err != nil {
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return fmt.Errorf("u.makeOutputNewRoomEvent: %w", err)
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}
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updates = append(updates, *update)
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// Send the event to the output logs.
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// We do this inside the database transaction to ensure that we only mark an event as sent if we sent it.
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// (n.b. this means that it's possible that the same event will be sent twice if the transaction fails but
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// the write to the output log succeeds)
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// TODO: This assumes that writing the event to the output log is synchronous. It should be possible to
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// send the event asynchronously but we would need to ensure that 1) the events are written to the log in
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// the correct order, 2) that pending writes are resent across restarts. In order to avoid writing all the
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// necessary bookkeeping we'll keep the event sending synchronous for now.
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if err = u.api.WriteOutputEvents(u.event.RoomID(), updates); err != nil {
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return fmt.Errorf("u.api.WriteOutputEvents: %w", err)
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}
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if err = u.updater.SetLatestEvents(u.roomInfo.RoomNID, u.latest, u.stateAtEvent.EventNID, u.newStateNID); err != nil {
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return fmt.Errorf("u.updater.SetLatestEvents: %w", err)
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}
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if err = u.updater.MarkEventAsSent(u.stateAtEvent.EventNID); err != nil {
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return fmt.Errorf("u.updater.MarkEventAsSent: %w", err)
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}
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return nil
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}
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func (u *latestEventsUpdater) latestState() error {
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var err error
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roomState := state.NewStateResolution(u.api.DB, *u.roomInfo)
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// Get a list of the current latest events. This may or may not
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// include the new event from the input path, depending on whether
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// it is a forward extremity or not.
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latestStateAtEvents := make([]types.StateAtEvent, len(u.latest))
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for i := range u.latest {
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latestStateAtEvents[i] = u.latest[i].StateAtEvent
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}
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// Takes the NIDs of the latest events and creates a state snapshot
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// of the state after the events. The snapshot state will be resolved
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// using the correct state resolution algorithm for the room.
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u.newStateNID, err = roomState.CalculateAndStoreStateAfterEvents(
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u.ctx, latestStateAtEvents,
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)
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if err != nil {
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return fmt.Errorf("roomState.CalculateAndStoreStateAfterEvents: %w", err)
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}
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// If we are overwriting the state then we should make sure that we
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// don't send anything out over federation again, it will very likely
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// be a repeat.
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if u.stateAtEvent.Overwrite {
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u.sendAsServer = ""
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}
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// Now that we have a new state snapshot based on the latest events,
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// we can compare that new snapshot to the previous one and see what
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// has changed. This gives us one list of removed state events and
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// another list of added ones. Replacing a value for a state-key tuple
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// will result one removed (the old event) and one added (the new event).
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u.removed, u.added, err = roomState.DifferenceBetweeenStateSnapshots(
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u.ctx, u.oldStateNID, u.newStateNID,
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)
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if err != nil {
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return fmt.Errorf("roomState.DifferenceBetweenStateSnapshots: %w", err)
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}
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// Also work out the state before the event removes and the event
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// adds.
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u.stateBeforeEventRemoves, u.stateBeforeEventAdds, err = roomState.DifferenceBetweeenStateSnapshots(
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u.ctx, u.newStateNID, u.stateAtEvent.BeforeStateSnapshotNID,
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)
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if err != nil {
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return fmt.Errorf("roomState.DifferenceBetweeenStateSnapshots: %w", err)
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}
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return nil
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}
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// calculateLatest works out the new set of forward extremities. Returns
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// true if the new event is included in those extremites, false otherwise.
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func (u *latestEventsUpdater) calculateLatest(
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oldLatest []types.StateAtEventAndReference,
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newEvent *gomatrixserverlib.Event,
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newStateAndRef types.StateAtEventAndReference,
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) (bool, error) {
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// First of all, get a list of all of the events in our current
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// set of forward extremities.
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existingRefs := make(map[string]*types.StateAtEventAndReference)
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existingNIDs := make([]types.EventNID, len(oldLatest))
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for i, old := range oldLatest {
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existingRefs[old.EventID] = &oldLatest[i]
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existingNIDs[i] = old.EventNID
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}
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// Look up the old extremity events. This allows us to find their
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// prev events.
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events, err := u.api.DB.Events(u.ctx, existingNIDs)
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if err != nil {
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return false, fmt.Errorf("u.api.DB.Events: %w", err)
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}
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// Make a list of all of the prev events as referenced by all of
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// the current forward extremities.
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existingPrevs := make(map[string]struct{})
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for _, old := range events {
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for _, prevEventID := range old.PrevEventIDs() {
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existingPrevs[prevEventID] = struct{}{}
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}
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}
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// If the "new" event is already referenced by a forward extremity
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// then do nothing - it's not a candidate to be a new extremity if
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// it has been referenced.
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if _, ok := existingPrevs[newEvent.EventID()]; ok {
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return false, nil
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}
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// If the "new" event is already a forward extremity then stop, as
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// nothing changes.
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for _, event := range events {
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if event.EventID() == newEvent.EventID() {
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return false, nil
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}
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}
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// Include our new event in the extremities.
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newLatest := []types.StateAtEventAndReference{newStateAndRef}
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// Then run through and see if the other extremities are still valid.
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// If our new event references them then they are no longer good
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// candidates.
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for _, prevEventID := range newEvent.PrevEventIDs() {
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delete(existingRefs, prevEventID)
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}
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// Ensure that we don't add any candidate forward extremities from
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// the old set that are, themselves, referenced by the old set of
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// forward extremities. This shouldn't happen but guards against
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// the possibility anyway.
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for prevEventID := range existingPrevs {
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delete(existingRefs, prevEventID)
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}
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// Then re-add any old extremities that are still valid after all.
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for _, old := range existingRefs {
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newLatest = append(newLatest, *old)
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}
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u.latest = newLatest
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return true, nil
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}
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func (u *latestEventsUpdater) makeOutputNewRoomEvent() (*api.OutputEvent, error) {
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latestEventIDs := make([]string, len(u.latest))
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for i := range u.latest {
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latestEventIDs[i] = u.latest[i].EventID
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}
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ore := api.OutputNewRoomEvent{
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Event: u.event.Headered(u.roomInfo.RoomVersion),
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RewritesState: u.rewritesState,
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LastSentEventID: u.lastEventIDSent,
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LatestEventIDs: latestEventIDs,
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TransactionID: u.transactionID,
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}
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eventIDMap, err := u.stateEventMap()
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if err != nil {
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return nil, err
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}
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for _, entry := range u.added {
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ore.AddsStateEventIDs = append(ore.AddsStateEventIDs, eventIDMap[entry.EventNID])
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}
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for _, entry := range u.removed {
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ore.RemovesStateEventIDs = append(ore.RemovesStateEventIDs, eventIDMap[entry.EventNID])
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}
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for _, entry := range u.stateBeforeEventRemoves {
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ore.StateBeforeRemovesEventIDs = append(ore.StateBeforeRemovesEventIDs, eventIDMap[entry.EventNID])
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}
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for _, entry := range u.stateBeforeEventAdds {
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ore.StateBeforeAddsEventIDs = append(ore.StateBeforeAddsEventIDs, eventIDMap[entry.EventNID])
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}
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ore.SendAsServer = u.sendAsServer
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// include extra state events if they were added as nearly every downstream component will care about it
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// and we'd rather not have them all hit QueryEventsByID at the same time!
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if len(ore.AddsStateEventIDs) > 0 {
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var err error
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if ore.AddStateEvents, err = u.extraEventsForIDs(u.roomInfo.RoomVersion, ore.AddsStateEventIDs); err != nil {
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return nil, fmt.Errorf("failed to load add_state_events from db: %w", err)
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}
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}
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// State is rewritten if the input room event HasState and we actually produced a delta on state events.
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// Without this check, /get_missing_events which produce events with associated (but not complete) state
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// will incorrectly purge the room and set it to no state. TODO: This is likely flakey, as if /gme produced
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// a state conflict res which just so happens to include 2+ events we might purge the room state downstream.
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ore.RewritesState = len(ore.AddsStateEventIDs) > 1
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return &api.OutputEvent{
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Type: api.OutputTypeNewRoomEvent,
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NewRoomEvent: &ore,
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}, nil
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}
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// extraEventsForIDs returns the full events for the event IDs given, but does not include the current event being
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// updated.
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func (u *latestEventsUpdater) extraEventsForIDs(roomVersion gomatrixserverlib.RoomVersion, eventIDs []string) ([]gomatrixserverlib.HeaderedEvent, error) {
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var extraEventIDs []string
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for _, e := range eventIDs {
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if e == u.event.EventID() {
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continue
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}
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extraEventIDs = append(extraEventIDs, e)
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}
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if len(extraEventIDs) == 0 {
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return nil, nil
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}
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extraEvents, err := u.api.DB.EventsFromIDs(u.ctx, extraEventIDs)
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if err != nil {
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return nil, err
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}
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var h []gomatrixserverlib.HeaderedEvent
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for _, e := range extraEvents {
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h = append(h, e.Headered(roomVersion))
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}
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return h, nil
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}
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// retrieve an event nid -> event ID map for all events that need updating
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func (u *latestEventsUpdater) stateEventMap() (map[types.EventNID]string, error) {
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var stateEventNIDs []types.EventNID
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var allStateEntries []types.StateEntry
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allStateEntries = append(allStateEntries, u.added...)
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allStateEntries = append(allStateEntries, u.removed...)
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allStateEntries = append(allStateEntries, u.stateBeforeEventRemoves...)
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allStateEntries = append(allStateEntries, u.stateBeforeEventAdds...)
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for _, entry := range allStateEntries {
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stateEventNIDs = append(stateEventNIDs, entry.EventNID)
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}
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stateEventNIDs = stateEventNIDs[:util.SortAndUnique(eventNIDSorter(stateEventNIDs))]
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return u.api.DB.EventIDs(u.ctx, stateEventNIDs)
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}
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type eventNIDSorter []types.EventNID
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func (s eventNIDSorter) Len() int { return len(s) }
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func (s eventNIDSorter) Less(i, j int) bool { return s[i] < s[j] }
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func (s eventNIDSorter) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
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