FEATURE (backups): Add zstd 5 compression level for PostgreSQL >= 16

Author: RostislavDugin

backend/internal/features/backups/backups/usecases/postgresql/create_backup_uc.go

@@ -60,8 +60,7 @@ func (uc *CreatePostgresqlBackupUsecase) Execute(
 	}
 
 	args := []string{
-		"-Fc",     // custom format with built-in compression
-		"-Z", "6", // balanced compression level (0-9, 6 is balanced)
+		"-Fc",           // custom format with built-in compression
 		"--no-password", // Use environment variable for password, prevent prompts
 		"-h", pg.Host,
 		"-p", strconv.Itoa(pg.Port),
@@ -70,6 +69,16 @@ func (uc *CreatePostgresqlBackupUsecase) Execute(
 		"--verbose", // Add verbose output to help with debugging
 	}
 
+	// Use zstd compression level 5 for PostgreSQL 15+ (better compression and speed)
+	// Fall back to gzip compression level 5 for older versions
+	if pg.Version == tools.PostgresqlVersion13 || pg.Version == tools.PostgresqlVersion14 || pg.Version == tools.PostgresqlVersion15 {
+		args = append(args, "-Z", "5")
+		uc.logger.Info("Using gzip compression level 5 (zstd not available)", "version", pg.Version)
+	} else {
+		args = append(args, "--compress=zstd:5")
+		uc.logger.Info("Using zstd compression level 5", "version", pg.Version)
+	}
+
 	return uc.streamToStorage(
 		backupID,
 		backupConfig,