Send all account data on complete sync by default

Squashed commit of the following:

commit 0ec8de57261d573a5f88577aa9d7a1174d3999b9
Author: Neil Alexander <neilalexander@users.noreply.github.com>
Date:   Tue Apr 26 16:56:30 2022 +0100

    Select filter onto provided target filter

commit da40b6fffbf5737864b223f49900048f557941f9
Author: Neil Alexander <neilalexander@users.noreply.github.com>
Date:   Tue Apr 26 16:48:00 2022 +0100

    Specify other field too

commit ffc0b0801f63bb4d3061b6813e3ce5f3b4c8fbcb
Author: Neil Alexander <neilalexander@users.noreply.github.com>
Date:   Tue Apr 26 16:45:44 2022 +0100

    Send as much account data as possible during complete sync

7 files changed, 30 insertions, 26 deletions

diff --git a/syncapi/routing/filter.go b/syncapi/routing/filter.go
index baa4d841..1a10bd64 100644
--- a/syncapi/routing/filter.go
+++ b/syncapi/routing/filter.go
@@ -44,8 +44,8 @@ func GetFilter(
 		return jsonerror.InternalServerError()
 	}
 
-	filter, err := syncDB.GetFilter(req.Context(), localpart, filterID)
-	if err != nil {
+	filter := gomatrixserverlib.DefaultFilter()
+	if err := syncDB.GetFilter(req.Context(), &filter, localpart, filterID); err != nil {
 		//TODO better error handling. This error message is *probably* right,
 		// but if there are obscure db errors, this will also be returned,
 		// even though it is not correct.
diff --git a/syncapi/storage/interface.go b/syncapi/storage/interface.go
index 13065fa6..43aaa358 100644
--- a/syncapi/storage/interface.go
+++ b/syncapi/storage/interface.go
@@ -125,10 +125,10 @@ type Database interface {
 	// CleanSendToDeviceUpdates removes all send-to-device messages BEFORE the specified
 	// from position, preventing the send-to-device table from growing indefinitely.
 	CleanSendToDeviceUpdates(ctx context.Context, userID, deviceID string, before types.StreamPosition) (err error)
-	// GetFilter looks up the filter associated with a given local user and filter ID.
-	// Returns a filter structure. Otherwise returns an error if no such filter exists
+	// GetFilter looks up the filter associated with a given local user and filter ID
+	// and populates the target filter. Otherwise returns an error if no such filter exists
 	// or if there was an error talking to the database.
-	GetFilter(ctx context.Context, localpart string, filterID string) (*gomatrixserverlib.Filter, error)
+	GetFilter(ctx context.Context, target *gomatrixserverlib.Filter, localpart string, filterID string) error
 	// PutFilter puts the passed filter into the database.
 	// Returns the filterID as a string. Otherwise returns an error if something
 	// goes wrong.
diff --git a/syncapi/storage/postgres/filter_table.go b/syncapi/storage/postgres/filter_table.go
index dfd3d696..c82ef092 100644
--- a/syncapi/storage/postgres/filter_table.go
+++ b/syncapi/storage/postgres/filter_table.go
@@ -73,21 +73,20 @@ func NewPostgresFilterTable(db *sql.DB) (tables.Filter, error) {
 }
 
 func (s *filterStatements) SelectFilter(
-	ctx context.Context, localpart string, filterID string,
-) (*gomatrixserverlib.Filter, error) {
+	ctx context.Context, target *gomatrixserverlib.Filter, localpart string, filterID string,
+) error {
 	// Retrieve filter from database (stored as canonical JSON)
 	var filterData []byte
 	err := s.selectFilterStmt.QueryRowContext(ctx, localpart, filterID).Scan(&filterData)
 	if err != nil {
-		return nil, err
+		return err
 	}
 
 	// Unmarshal JSON into Filter struct
-	filter := gomatrixserverlib.DefaultFilter()
-	if err = json.Unmarshal(filterData, &filter); err != nil {
-		return nil, err
+	if err = json.Unmarshal(filterData, &target); err != nil {
+		return err
 	}
-	return &filter, nil
+	return nil
 }
 
 func (s *filterStatements) InsertFilter(
diff --git a/syncapi/storage/shared/syncserver.go b/syncapi/storage/shared/syncserver.go
index 69bceb62..25aca50a 100644
--- a/syncapi/storage/shared/syncserver.go
+++ b/syncapi/storage/shared/syncserver.go
@@ -513,9 +513,9 @@ func (d *Database) StreamToTopologicalPosition(
 }
 
 func (d *Database) GetFilter(
-	ctx context.Context, localpart string, filterID string,
-) (*gomatrixserverlib.Filter, error) {
-	return d.Filter.SelectFilter(ctx, localpart, filterID)
+	ctx context.Context, target *gomatrixserverlib.Filter, localpart string, filterID string,
+) error {
+	return d.Filter.SelectFilter(ctx, target, localpart, filterID)
 }
 
 func (d *Database) PutFilter(
diff --git a/syncapi/storage/sqlite3/filter_table.go b/syncapi/storage/sqlite3/filter_table.go
index 0cfebef2..6081a48b 100644
--- a/syncapi/storage/sqlite3/filter_table.go
+++ b/syncapi/storage/sqlite3/filter_table.go
@@ -77,21 +77,20 @@ func NewSqliteFilterTable(db *sql.DB) (tables.Filter, error) {
 }
 
 func (s *filterStatements) SelectFilter(
-	ctx context.Context, localpart string, filterID string,
-) (*gomatrixserverlib.Filter, error) {
+	ctx context.Context, target *gomatrixserverlib.Filter, localpart string, filterID string,
+) error {
 	// Retrieve filter from database (stored as canonical JSON)
 	var filterData []byte
 	err := s.selectFilterStmt.QueryRowContext(ctx, localpart, filterID).Scan(&filterData)
 	if err != nil {
-		return nil, err
+		return err
 	}
 
 	// Unmarshal JSON into Filter struct
-	filter := gomatrixserverlib.DefaultFilter()
-	if err = json.Unmarshal(filterData, &filter); err != nil {
-		return nil, err
+	if err = json.Unmarshal(filterData, &target); err != nil {
+		return err
 	}
-	return &filter, nil
+	return nil
 }
 
 func (s *filterStatements) InsertFilter(
diff --git a/syncapi/storage/tables/interface.go b/syncapi/storage/tables/interface.go
index 32b1c34e..4ff4689e 100644
--- a/syncapi/storage/tables/interface.go
+++ b/syncapi/storage/tables/interface.go
@@ -157,7 +157,7 @@ type SendToDevice interface {
 }
 
 type Filter interface {
-	SelectFilter(ctx context.Context, localpart string, filterID string) (*gomatrixserverlib.Filter, error)
+	SelectFilter(ctx context.Context, target *gomatrixserverlib.Filter, localpart string, filterID string) error
 	InsertFilter(ctx context.Context, filter *gomatrixserverlib.Filter, localpart string) (filterID string, err error)
 }
 
diff --git a/syncapi/sync/request.go b/syncapi/sync/request.go
index f04f172d..c9ee8e4a 100644
--- a/syncapi/sync/request.go
+++ b/syncapi/sync/request.go
@@ -18,6 +18,7 @@ import (
 	"database/sql"
 	"encoding/json"
 	"fmt"
+	"math"
 	"net/http"
 	"strconv"
 	"time"
@@ -47,6 +48,13 @@ func newSyncRequest(req *http.Request, device userapi.Device, syncDB storage.Dat
 	}
 	// TODO: read from stored filters too
 	filter := gomatrixserverlib.DefaultFilter()
+	if since.IsEmpty() {
+		// Send as much account data down for complete syncs as possible
+		// by default, otherwise clients do weird things while waiting
+		// for the rest of the data to trickle down.
+		filter.AccountData.Limit = math.MaxInt
+		filter.Room.AccountData.Limit = math.MaxInt
+	}
 	filterQuery := req.URL.Query().Get("filter")
 	if filterQuery != "" {
 		if filterQuery[0] == '{' {
@@ -61,11 +69,9 @@ func newSyncRequest(req *http.Request, device userapi.Device, syncDB storage.Dat
 				util.GetLogger(req.Context()).WithError(err).Error("gomatrixserverlib.SplitID failed")
 				return nil, fmt.Errorf("gomatrixserverlib.SplitID: %w", err)
 			}
-			if f, err := syncDB.GetFilter(req.Context(), localpart, filterQuery); err != nil && err != sql.ErrNoRows {
+			if err := syncDB.GetFilter(req.Context(), &filter, localpart, filterQuery); err != nil && err != sql.ErrNoRows {
 				util.GetLogger(req.Context()).WithError(err).Error("syncDB.GetFilter failed")
 				return nil, fmt.Errorf("syncDB.GetFilter: %w", err)
-			} else if f != nil {
-				filter = *f
 			}
 		}
 	}