fix(db): remove temp_store = MEMORY pragmas (#10343)

This reduces database migration memory usage in my test scenario from
3.8 GB to 440 MB. In principle I don't think we're causing many temp
tables to be generated anyway in normal usage, but if we do and someone
can benchmark a performance difference, we can add a tunable. I ran the
database benchmark before and after and didn't see a difference above
the noise level.

Signed-off-by: Jakob Borg <jakob@kastelo.net>

cmd/syncthing/perfstats_unix.go

@@ -16,6 +16,7 @@ import (
 	"syscall"
 	"time"
 
+	"github.com/syncthing/syncthing/lib/build"
 	"github.com/syncthing/syncthing/lib/locations"
 	"github.com/syncthing/syncthing/lib/protocol"
 	"golang.org/x/exp/constraints"
@@ -48,11 +49,16 @@ func savePerfStats(file string) {
 		in, out := protocol.TotalInOut()
 		timeDiff := t.Sub(prevTime)
 
+		rss := curRus.Maxrss
+		if build.IsDarwin {
+			rss /= 1024
+		}
+
 		fmt.Fprintf(fd, "%.03f\t%f\t%d\t%d\t%.0f\t%.0f\t%d\n",
 			t.Sub(t0).Seconds(),
 			rate(cpusec(&prevRus), cpusec(&curRus), timeDiff, 1),
 			(curMem.Sys-curMem.HeapReleased)/1024,
-			curRus.Maxrss/1024,
+			rss,
 			rate(prevIn, in, timeDiff, 1e3),
 			rate(prevOut, out, timeDiff, 1e3),
 			dirsize(locations.Get(locations.Database))/1024,

internal/db/sqlite/db_open.go

@@ -52,8 +52,6 @@ func Open(path string, opts ...Option) (*DB, error) {
 		"journal_mode = WAL",
 		"optimize = 0x10002",
 		"auto_vacuum = INCREMENTAL",
-		"default_temp_store = MEMORY",
-		"temp_store = MEMORY",
 	}
 	schemas := []string{
 		"sql/schema/common/*",
@@ -99,8 +97,6 @@ func Open(path string, opts ...Option) (*DB, error) {
 func OpenForMigration(path string) (*DB, error) {
 	pragmas := []string{
 		"journal_mode = OFF",
-		"default_temp_store = MEMORY",
-		"temp_store = MEMORY",
 		"foreign_keys = 0",
 		"synchronous = 0",
 		"locking_mode = EXCLUSIVE",

internal/db/sqlite/folderdb_open.go

@@ -25,8 +25,6 @@ func openFolderDB(folder, path string, deleteRetention time.Duration) (*folderDB
 		"journal_mode = WAL",
 		"optimize = 0x10002",
 		"auto_vacuum = INCREMENTAL",
-		"default_temp_store = MEMORY",
-		"temp_store = MEMORY",
 	}
 	schemas := []string{
 		"sql/schema/common/*",
@@ -64,8 +62,6 @@ func openFolderDB(folder, path string, deleteRetention time.Duration) (*folderDB
 func openFolderDBForMigration(folder, path string, deleteRetention time.Duration) (*folderDB, error) {
 	pragmas := []string{
 		"journal_mode = OFF",
-		"default_temp_store = MEMORY",
-		"temp_store = MEMORY",
 		"foreign_keys = 0",
 		"synchronous = 0",
 		"locking_mode = EXCLUSIVE",