From 1ed1b0d156b4af2832db2b086c864ef0b83754e6 Mon Sep 17 00:00:00 2001
From: Shlomi Noach <shlomi-noach@github.com>
Date: Fri, 22 Apr 2016 13:41:20 -0700
Subject: [PATCH] - `quick-and-bumpy-swap-tables` uses quicker swap tables, at
 the expense of a period where the table does not exist (non atomic renames) -
 refactored lock-and-swap code, in preparation for atomic swap

---
 go/base/context.go   |  6 ++++++
 go/logic/applier.go  | 24 ++++++++++++++++++++++--
 go/logic/migrator.go |  4 ++--
 3 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/go/base/context.go b/go/base/context.go
index 3a060fa..33e52f2 100644
--- a/go/base/context.go
+++ b/go/base/context.go
@@ -123,6 +123,12 @@ func (this *MigrationContext) GetChangelogTableName() string {
 	return fmt.Sprintf("_%s_OSC", this.OriginalTableName)
 }
 
+// GetVoluntaryLockName returns a name of a voluntary lock to be used throughout
+// the swap-tables process.
+func (this *MigrationContext) GetVoluntaryLockName() string {
+	return fmt.Sprintf("%s.%s.lock", this.DatabaseName, this.OriginalTableName)
+}
+
 // RequiresBinlogFormatChange is `true` when the original binlog format isn't `ROW`
 func (this *MigrationContext) RequiresBinlogFormatChange() bool {
 	return this.OriginalBinlogFormat != "ROW"
diff --git a/go/logic/applier.go b/go/logic/applier.go
index c7ff916..314d683 100644
--- a/go/logic/applier.go
+++ b/go/logic/applier.go
@@ -427,8 +427,8 @@ func (this *Applier) UnlockTables() error {
 	return nil
 }
 
-// LockTables
-func (this *Applier) SwapTables() error {
+// SwapTablesQuickAndBumpy
+func (this *Applier) SwapTablesQuickAndBumpy() error {
 	// query := fmt.Sprintf(`rename /* gh-osc */ table %s.%s to %s.%s, %s.%s to %s.%s`,
 	// 	sql.EscapeName(this.migrationContext.DatabaseName),
 	// 	sql.EscapeName(this.migrationContext.OriginalTableName),
@@ -468,6 +468,26 @@ func (this *Applier) SwapTables() error {
 	return nil
 }
 
+// SwapTablesQuickAndBumpy
+func (this *Applier) SwapTablesAtomic() error {
+	query := fmt.Sprintf(`rename /* gh-osc */ table %s.%s to %s.%s, %s.%s to %s.%s`,
+		sql.EscapeName(this.migrationContext.DatabaseName),
+		sql.EscapeName(this.migrationContext.OriginalTableName),
+		sql.EscapeName(this.migrationContext.DatabaseName),
+		sql.EscapeName(this.migrationContext.GetOldTableName()),
+		sql.EscapeName(this.migrationContext.DatabaseName),
+		sql.EscapeName(this.migrationContext.GetGhostTableName()),
+		sql.EscapeName(this.migrationContext.DatabaseName),
+		sql.EscapeName(this.migrationContext.OriginalTableName),
+	)
+	log.Infof("Renaming tables")
+	if _, err := sqlutils.ExecNoPrepare(this.singletonDB, query); err != nil {
+		return err
+	}
+	log.Infof("Tables renamed")
+	return nil
+}
+
 // StopSlaveIOThread is applicable with --test-on-replica; it stops the IO thread
 func (this *Applier) StopSlaveIOThread() error {
 	query := `stop /* gh-osc */ slave io_thread`
diff --git a/go/logic/migrator.go b/go/logic/migrator.go
index 2d328cb..df6eaba 100644
--- a/go/logic/migrator.go
+++ b/go/logic/migrator.go
@@ -322,7 +322,7 @@ func (this *Migrator) stopWritesAndCompleteMigrationOnMasterQuickAndBumpy() (err
 	<-this.allEventsUpToLockProcessed
 	log.Debugf("Done waiting for events up to lock")
 
-	if err := this.retryOperation(this.applier.SwapTables); err != nil {
+	if err := this.retryOperation(this.applier.SwapTablesQuickAndBumpy); err != nil {
 		return err
 	}
 	if err := this.retryOperation(this.applier.UnlockTables); err != nil {
@@ -353,7 +353,7 @@ func (this *Migrator) stopWritesAndCompleteMigrationOnMasterViaLock() (err error
 	<-this.allEventsUpToLockProcessed
 	log.Debugf("Done waiting for events up to lock")
 
-	if err := this.retryOperation(this.applier.SwapTables); err != nil {
+	if err := this.retryOperation(this.applier.SwapTablesAtomic); err != nil {
 		return err
 	}
 	if err := this.retryOperation(this.applier.UnlockTables); err != nil {