supporting --timestamp-old-table

Author: Shlomi Noach

go/base/context.go

@@ -121,6 +121,7 @@ type MigrationContext struct {
 	OkToDropTable                bool
 	InitiallyDropOldTable        bool
 	InitiallyDropGhostTable      bool
+	TimestampOldTable            bool // Should old table name include a timestamp
 	CutOverType                  CutOver
 	ReplicaServerId              uint
 
@@ -234,11 +235,12 @@ func (this *MigrationContext) GetGhostTableName() string {
 
 // GetOldTableName generates the name of the "old" table, into which the original table is renamed.
 func (this *MigrationContext) GetOldTableName() string {
-	if this.TestOnReplica {
-		return fmt.Sprintf("_%s_ght", this.OriginalTableName)
-	}
-	if this.MigrateOnReplica {
-		return fmt.Sprintf("_%s_ghr", this.OriginalTableName)
+	if this.TimestampOldTable {
+		t := this.StartTime
+		timestamp := fmt.Sprintf("%d%02d%02d%02d%02d%02d",
+			t.Year(), t.Month(), t.Day(),
+			t.Hour(), t.Minute(), t.Second())
+		return fmt.Sprintf("_%s_%s_del", this.OriginalTableName, timestamp)
 	}
 	return fmt.Sprintf("_%s_del", this.OriginalTableName)
 }

go/cmd/gh-ost/main.go

@@ -77,6 +77,7 @@ func main() {
 	flag.BoolVar(&migrationContext.OkToDropTable, "ok-to-drop-table", false, "Shall the tool drop the old table at end of operation. DROPping tables can be a long locking operation, which is why I'm not doing it by default. I'm an online tool, yes?")
 	flag.BoolVar(&migrationContext.InitiallyDropOldTable, "initially-drop-old-table", false, "Drop a possibly existing OLD table (remains from a previous run?) before beginning operation. Default is to panic and abort if such table exists")
 	flag.BoolVar(&migrationContext.InitiallyDropGhostTable, "initially-drop-ghost-table", false, "Drop a possibly existing Ghost table (remains from a previous run?) before beginning operation. Default is to panic and abort if such table exists")
+	flag.BoolVar(&migrationContext.TimestampOldTable, "timestamp-old-table", false, "Use a timestamp in old table name. This makes old table names unique and non conflicting cross migrations")
 	cutOver := flag.String("cut-over", "atomic", "choose cut-over type (default|atomic, two-step)")
 	flag.BoolVar(&migrationContext.ForceNamedCutOverCommand, "force-named-cut-over", false, "When true, the 'unpostpone|cut-over' interactive command must name the migrated table")
 

localtests/test.sh

@@ -85,6 +85,7 @@ test_single() {
     --switch-to-rbr \
     --initially-drop-old-table \
     --initially-drop-ghost-table \
+    --timestamp-old-table \
     --throttle-query='select timestampdiff(second, min(last_update), now()) < 5 from _gh_ost_test_ghc' \
     --serve-socket-file=/tmp/gh-ost.test.sock \
     --initially-drop-socket-file \