Fix fragility of selectEventsWithEventIDsSQL queries (#2757)

This fixes a temporary workaround with the `selectEventsWithEventIDsSQL`
queries where fields need to be artificially added to the queries so the
row results match the format of the `syncapi_output_room_events` table.
I made similar functions that accept row results from the
`syncapi_current_room_state` table and convert them into StreamEvents
without the fields that are specific to output room events.

There is also a unit test in the first commit to ensure the resulting
behavior doesn't change from the modified queries and functions.

Fixes #601.

### Pull Request Checklist

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* [x] I have added tests for PR _or_ I have justified why this PR
doesn't need tests.
* [x] Pull request includes a [sign
off](https://github.com/matrix-org/dendrite/blob/main/docs/CONTRIBUTING.md#sign-off)

Signed-off-by: `Ashley Nelson <fant@shley.email>`

Co-authored-by: Neil Alexander <neilalexander@users.noreply.github.com>

3 files changed, 150 insertions, 14 deletions

diff --git a/syncapi/storage/postgres/current_room_state_table.go b/syncapi/storage/postgres/current_room_state_table.go
index 4ffd2961..2ccf0be1 100644
--- a/syncapi/storage/postgres/current_room_state_table.go
+++ b/syncapi/storage/postgres/current_room_state_table.go
@@ -104,12 +104,7 @@ const selectStateEventSQL = "" +
 	"SELECT headered_event_json FROM syncapi_current_room_state WHERE room_id = $1 AND type = $2 AND state_key = $3"
 
 const selectEventsWithEventIDsSQL = "" +
-	// TODO: The session_id and transaction_id blanks are here because
-	// the rowsToStreamEvents expects there to be exactly seven columns. We need to
-	// figure out if these really need to be in the DB, and if so, we need a
-	// better permanent fix for this. - neilalexander, 2 Jan 2020
-	"SELECT event_id, added_at, headered_event_json, 0 AS session_id, false AS exclude_from_sync, '' AS transaction_id, history_visibility" +
-	" FROM syncapi_current_room_state WHERE event_id = ANY($1)"
+	"SELECT event_id, added_at, headered_event_json, history_visibility FROM syncapi_current_room_state WHERE event_id = ANY($1)"
 
 const selectSharedUsersSQL = "" +
 	"SELECT state_key FROM syncapi_current_room_state WHERE room_id = ANY(" +
@@ -365,7 +360,36 @@ func (s *currentRoomStateStatements) SelectEventsWithEventIDs(
 		return nil, err
 	}
 	defer internal.CloseAndLogIfError(ctx, rows, "selectEventsWithEventIDs: rows.close() failed")
-	return rowsToStreamEvents(rows)
+	return currentRoomStateRowsToStreamEvents(rows)
+}
+
+func currentRoomStateRowsToStreamEvents(rows *sql.Rows) ([]types.StreamEvent, error) {
+	var events []types.StreamEvent
+	for rows.Next() {
+		var (
+			eventID           string
+			streamPos         types.StreamPosition
+			eventBytes        []byte
+			historyVisibility gomatrixserverlib.HistoryVisibility
+		)
+		if err := rows.Scan(&eventID, &streamPos, &eventBytes, &historyVisibility); err != nil {
+			return nil, err
+		}
+		// TODO: Handle redacted events
+		var ev gomatrixserverlib.HeaderedEvent
+		if err := ev.UnmarshalJSONWithEventID(eventBytes, eventID); err != nil {
+			return nil, err
+		}
+
+		ev.Visibility = historyVisibility
+
+		events = append(events, types.StreamEvent{
+			HeaderedEvent:  &ev,
+			StreamPosition: streamPos,
+		})
+	}
+
+	return events, nil
 }
 
 func rowsToEvents(rows *sql.Rows) ([]*gomatrixserverlib.HeaderedEvent, error) {
diff --git a/syncapi/storage/sqlite3/current_room_state_table.go b/syncapi/storage/sqlite3/current_room_state_table.go
index c4019fed..ff45e786 100644
--- a/syncapi/storage/sqlite3/current_room_state_table.go
+++ b/syncapi/storage/sqlite3/current_room_state_table.go
@@ -88,12 +88,7 @@ const selectStateEventSQL = "" +
 	"SELECT headered_event_json FROM syncapi_current_room_state WHERE room_id = $1 AND type = $2 AND state_key = $3"
 
 const selectEventsWithEventIDsSQL = "" +
-	// TODO: The session_id and transaction_id blanks are here because
-	// the rowsToStreamEvents expects there to be exactly seven columns. We need to
-	// figure out if these really need to be in the DB, and if so, we need a
-	// better permanent fix for this. - neilalexander, 2 Jan 2020
-	"SELECT event_id, added_at, headered_event_json, 0 AS session_id, false AS exclude_from_sync, '' AS transaction_id, history_visibility" +
-	" FROM syncapi_current_room_state WHERE event_id IN ($1)"
+	"SELECT event_id, added_at, headered_event_json, history_visibility FROM syncapi_current_room_state WHERE event_id IN ($1)"
 
 const selectSharedUsersSQL = "" +
 	"SELECT state_key FROM syncapi_current_room_state WHERE room_id IN(" +
@@ -378,7 +373,7 @@ func (s *currentRoomStateStatements) SelectEventsWithEventIDs(
 			return nil, err
 		}
 		start = start + n
-		events, err := rowsToStreamEvents(rows)
+		events, err := currentRoomStateRowsToStreamEvents(rows)
 		internal.CloseAndLogIfError(ctx, rows, "selectEventsWithEventIDs: rows.close() failed")
 		if err != nil {
 			return nil, err
@@ -388,6 +383,35 @@ func (s *currentRoomStateStatements) SelectEventsWithEventIDs(
 	return res, nil
 }
 
+func currentRoomStateRowsToStreamEvents(rows *sql.Rows) ([]types.StreamEvent, error) {
+	var events []types.StreamEvent
+	for rows.Next() {
+		var (
+			eventID           string
+			streamPos         types.StreamPosition
+			eventBytes        []byte
+			historyVisibility gomatrixserverlib.HistoryVisibility
+		)
+		if err := rows.Scan(&eventID, &streamPos, &eventBytes, &historyVisibility); err != nil {
+			return nil, err
+		}
+		// TODO: Handle redacted events
+		var ev gomatrixserverlib.HeaderedEvent
+		if err := ev.UnmarshalJSONWithEventID(eventBytes, eventID); err != nil {
+			return nil, err
+		}
+
+		ev.Visibility = historyVisibility
+
+		events = append(events, types.StreamEvent{
+			HeaderedEvent:  &ev,
+			StreamPosition: streamPos,
+		})
+	}
+
+	return events, nil
+}
+
 func rowsToEvents(rows *sql.Rows) ([]*gomatrixserverlib.HeaderedEvent, error) {
 	result := []*gomatrixserverlib.HeaderedEvent{}
 	for rows.Next() {
diff --git a/syncapi/storage/tables/current_room_state_test.go b/syncapi/storage/tables/current_room_state_test.go
new file mode 100644
index 00000000..23287c50
--- /dev/null
+++ b/syncapi/storage/tables/current_room_state_test.go
@@ -0,0 +1,88 @@
+package tables_test
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	"testing"
+
+	"github.com/matrix-org/dendrite/internal/sqlutil"
+	"github.com/matrix-org/dendrite/setup/config"
+	"github.com/matrix-org/dendrite/syncapi/storage/postgres"
+	"github.com/matrix-org/dendrite/syncapi/storage/sqlite3"
+	"github.com/matrix-org/dendrite/syncapi/storage/tables"
+	"github.com/matrix-org/dendrite/syncapi/types"
+	"github.com/matrix-org/dendrite/test"
+)
+
+func newCurrentRoomStateTable(t *testing.T, dbType test.DBType) (tables.CurrentRoomState, *sql.DB, func()) {
+	t.Helper()
+	connStr, close := test.PrepareDBConnectionString(t, dbType)
+	db, err := sqlutil.Open(&config.DatabaseOptions{
+		ConnectionString: config.DataSource(connStr),
+	}, sqlutil.NewExclusiveWriter())
+	if err != nil {
+		t.Fatalf("failed to open db: %s", err)
+	}
+
+	var tab tables.CurrentRoomState
+	switch dbType {
+	case test.DBTypePostgres:
+		tab, err = postgres.NewPostgresCurrentRoomStateTable(db)
+	case test.DBTypeSQLite:
+		var stream sqlite3.StreamIDStatements
+		if err = stream.Prepare(db); err != nil {
+			t.Fatalf("failed to prepare stream stmts: %s", err)
+		}
+		tab, err = sqlite3.NewSqliteCurrentRoomStateTable(db, &stream)
+	}
+	if err != nil {
+		t.Fatalf("failed to make new table: %s", err)
+	}
+	return tab, db, close
+}
+
+func TestCurrentRoomStateTable(t *testing.T) {
+	ctx := context.Background()
+	alice := test.NewUser(t)
+	room := test.NewRoom(t, alice)
+	test.WithAllDatabases(t, func(t *testing.T, dbType test.DBType) {
+		tab, db, close := newCurrentRoomStateTable(t, dbType)
+		defer close()
+		events := room.CurrentState()
+		err := sqlutil.WithTransaction(db, func(txn *sql.Tx) error {
+			for i, ev := range events {
+				err := tab.UpsertRoomState(ctx, txn, ev, nil, types.StreamPosition(i))
+				if err != nil {
+					return fmt.Errorf("failed to UpsertRoomState: %w", err)
+				}
+			}
+			wantEventIDs := []string{
+				events[0].EventID(), events[1].EventID(), events[2].EventID(), events[3].EventID(),
+			}
+			gotEvents, err := tab.SelectEventsWithEventIDs(ctx, txn, wantEventIDs)
+			if err != nil {
+				return fmt.Errorf("failed to SelectEventsWithEventIDs: %w", err)
+			}
+			if len(gotEvents) != len(wantEventIDs) {
+				return fmt.Errorf("SelectEventsWithEventIDs\ngot %d, want %d results", len(gotEvents), len(wantEventIDs))
+			}
+			gotEventIDs := make(map[string]struct{}, len(gotEvents))
+			for _, event := range gotEvents {
+				if event.ExcludeFromSync {
+					return fmt.Errorf("SelectEventsWithEventIDs ExcludeFromSync should be false for current room state event %+v", event)
+				}
+				gotEventIDs[event.EventID()] = struct{}{}
+			}
+			for _, id := range wantEventIDs {
+				if _, ok := gotEventIDs[id]; !ok {
+					return fmt.Errorf("SelectEventsWithEventIDs\nexpected id %q not returned", id)
+				}
+			}
+			return nil
+		})
+		if err != nil {
+			t.Fatalf("err: %v", err)
+		}
+	})
+}