make default value OS dependent

docs/content/doc/advanced/config-cheat-sheet.en-us.md

@@ -382,7 +382,7 @@ The following configuration set `Content-Type: application/vnd.android.package-a
     - `verify-ca`: Enable TLS with verification of the database server certificate against its root certificate.
     - `verify-full`: Enable TLS and verify the database server name matches the given certificate in either the `Common Name` or `Subject Alternative Name` fields.
 - `SQLITE_TIMEOUT`: **500**: Query timeout for SQLite3 only.
-- `SQLITE_JOURNAL_MODE`: **DELETE**: Change journal mode for SQlite3. Can be used to enable [WAL mode](https://www.sqlite.org/wal.html) when high load causes write congestion. See [SQlite3 docs](https://www.sqlite.org/pragma.html#pragma_journal_mode) for possible values.
+- `SQLITE_JOURNAL_MODE`: on windows & linux: **WAL**, otherwise **DELETE**: Change journal mode for SQlite3. See [SQlite3 docs](https://www.sqlite.org/pragma.html#pragma_journal_mode) for possible values.
 - `ITERATE_BUFFER_SIZE`: **50**: Internal buffer size for iterating.
 - `CHARSET`: **utf8mb4**: For MySQL only, either "utf8" or "utf8mb4". NOTICE: for "utf8mb4" you must use MySQL InnoDB > 5.6. Gitea is unable to check this.
 - `PATH`: **data/gitea.db**: For SQLite3 only, the database file path.

modules/setting/database.go

@@ -11,6 +11,7 @@ import (
 	"os"
 	"path"
 	"path/filepath"
+	"runtime"
 	"strings"
 	"time"
 
@@ -90,9 +91,22 @@ func InitDBConfig() {
 		log.Error("Deprecated database mysql charset utf8 support, please use utf8mb4 or convert utf8 to utf8mb4.")
 	}
 
-	Database.Path = sec.Key("PATH").MustString(filepath.Join(AppDataPath, "gitea.db"))
-	Database.Timeout = sec.Key("SQLITE_TIMEOUT").MustInt(500)
-	Database.SQliteJournalMode = sec.Key("SQLITE_JOURNAL_MODE").MustString("DELETE")
+	if Database.UseSQLite3 {
+		Database.Path = sec.Key("PATH").MustString(filepath.Join(AppDataPath, "gitea.db"))
+		Database.Timeout = sec.Key("SQLITE_TIMEOUT").MustInt(500)
+
+		// WAL mode is preferred for better concurent write performance, but needs special VFS driver features,
+		// which are guaranteed to be available for unix & windows OSes
+		var defaultJournalMode string
+		switch runtime.GOOS {
+		// probably the BSDs are supported too, but i found no information on this - better safe than sorry.
+		case "windows", "linux": // "darwin", "freebsd", "openbsd", "netbsd":
+			defaultJournalMode = "WAL"
+		default:
+			defaultJournalMode = "DELETE"
+		}
+		Database.SQliteJournalMode = sec.Key("SQLITE_JOURNAL_MODE").MustString(defaultJournalMode)
+	}
 
 	Database.MaxIdleConns = sec.Key("MAX_IDLE_CONNS").MustInt(2)
 	if Database.UseMySQL {