Mysql8 rename table

go/logic/applier.go

@@ -542,6 +542,29 @@ func (this *Applier) UnlockTables() error {
 	return nil
 }
 
+func (this *Applier) RenameTablesMySQL8() error {
+	query := fmt.Sprintf(`set session lock_wait_timeout:=%d`, this.migrationContext.CutOverLockTimeoutSeconds)
+	if _, err := sqlutils.ExecNoPrepare(this.singletonDB, query); err != nil {
+		return err
+	}
+
+	query = fmt.Sprintf(`rename /* gh-ost */ 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("Issuing and expecting this to succeed: %s", query)
+	if _, err := sqlutils.ExecNoPrepare(this.singletonDB, query); err != nil {
+		return err
+	}
+	return nil
+}
+
 // SwapTablesQuickAndBumpy issues a two-step swap table operation:
 // - rename original table to _old
 // - rename ghost table to original
@@ -977,62 +1000,6 @@ func (this *Applier) buildDMLEventQuery(dmlEvent *binlog.BinlogDMLEvent) (result
 	return append(results, newDmlBuildResultError(fmt.Errorf("Unknown dml event type: %+v", dmlEvent.DML)))
 }
 
-// ApplyDMLEventQuery writes an entry to the ghost table, in response to an intercepted
-// original-table binlog event
-func (this *Applier) ApplyDMLEventQuery(dmlEvent *binlog.BinlogDMLEvent) error {
-	for _, buildResult := range this.buildDMLEventQuery(dmlEvent) {
-		if buildResult.err != nil {
-			return buildResult.err
-		}
-		// TODO The below is in preparation for transactional writes on the ghost tables.
-		// Such writes would be, for example:
-		// - prepended with sql_mode setup
-		// - prepended with time zone setup
-		// - prepended with SET SQL_LOG_BIN=0
-		// - prepended with SET FK_CHECKS=0
-		// etc.
-		//
-		// a known problem: https://github.com/golang/go/issues/9373 -- bitint unsigned values, not supported in database/sql
-		// is solved by silently converting unsigned bigints to string values.
-		//
-
-		err := func() error {
-			tx, err := this.db.Begin()
-			if err != nil {
-				return err
-			}
-			rollback := func(err error) error {
-				tx.Rollback()
-				return err
-			}
-			sessionQuery := fmt.Sprintf("SET SESSION time_zone = '+00:00'")
-			if !this.migrationContext.SkipStrictMode {
-				sessionQuery += ", sql_mode = CONCAT(@@session.sql_mode, ',STRICT_ALL_TABLES')"
-			}
-			if _, err := tx.Exec(sessionQuery); err != nil {
-				return rollback(err)
-			}
-			if _, err := tx.Exec(buildResult.query, buildResult.args...); err != nil {
-				return rollback(err)
-			}
-			if err := tx.Commit(); err != nil {
-				return err
-			}
-			return nil
-		}()
-
-		if err != nil {
-			err = fmt.Errorf("%s; query=%s; args=%+v", err.Error(), buildResult.query, buildResult.args)
-			return log.Errore(err)
-		}
-		// no error
-		atomic.AddInt64(&this.migrationContext.TotalDMLEventsApplied, 1)
-		if this.migrationContext.CountTableRows {
-			atomic.AddInt64(&this.migrationContext.RowsDeltaEstimate, buildResult.rowsDelta)
-		}
-	}
-	return nil
-}
 
 // ApplyDMLEventQueries applies multiple DML queries onto the _ghost_ table
 func (this *Applier) ApplyDMLEventQueries(dmlEvents [](*binlog.BinlogDMLEvent)) error {

go/logic/migrator.go

@@ -518,19 +518,23 @@ func (this *Migrator) cutOver() (err error) {
 			}
 		}
 	}
-	if this.migrationContext.CutOverType == base.CutOverAtomic {
+	var cutOverFunc func() error
+	if !mysql.IsSmallerMinorVersion(this.migrationContext.ApplierMySQLVersion, "8.0.13") {
+		// This is MySQL 8.0 or above. We can utilize a new ALTER TABLE featiure that supports
+		// RENAME while the table is locked.
+		cutOverFunc = this.cutOverMySQL8013
+	} else if this.migrationContext.CutOverType == base.CutOverAtomic {
 		// Atomic solution: we use low timeout and multiple attempts. But for
 		// each failed attempt, we throttle until replication lag is back to normal
-		err := this.atomicCutOver()
-		this.handleCutOverResult(err)
-		return err
-	}
-	if this.migrationContext.CutOverType == base.CutOverTwoStep {
-		err := this.cutOverTwoStep()
-		this.handleCutOverResult(err)
-		return err
+		cutOverFunc = this.atomicCutOver
+	} else if this.migrationContext.CutOverType == base.CutOverTwoStep {
+		cutOverFunc = this.cutOverTwoStep
+	} else {
+		return log.Fatalf("Unknown cut-over type: %d; should never get here!", this.migrationContext.CutOverType)
 	}
-	return log.Fatalf("Unknown cut-over type: %d; should never get here!", this.migrationContext.CutOverType)
+	err = cutOverFunc()
+	this.handleCutOverResult(err)
+	return err
 }
 
 // Inject the "AllEventsUpToLockProcessed" state hint, wait for it to appear in the binary logs,
@@ -573,6 +577,34 @@ func (this *Migrator) waitForEventsUpToLock() (err error) {
 	return nil
 }
 
+// cutOverMySQL8013 utilizes a new deveopment starting MySQL 8.0.13 where RENAME TABLE is
+// possible where a table is LOCKED under WRITE LOCK.
+// This feature was developed specifically at the request of the `gh-ost` maintainers.
+func (this *Migrator) cutOverMySQL8013() (err error) {
+	atomic.StoreInt64(&this.migrationContext.InCutOverCriticalSectionFlag, 1)
+	defer atomic.StoreInt64(&this.migrationContext.InCutOverCriticalSectionFlag, 0)
+	atomic.StoreInt64(&this.migrationContext.AllEventsUpToLockProcessedInjectedFlag, 0)
+
+	if err := this.retryOperation(this.applier.LockOriginalTable); err != nil {
+		return err
+	}
+
+	if err := this.retryOperation(this.waitForEventsUpToLock); err != nil {
+		return err
+	}
+	if err := this.retryOperation(this.applier.RenameTablesMySQL8); err != nil {
+		return err
+	}
+	if err := this.retryOperation(this.applier.UnlockTables); err != nil {
+		return err
+	}
+
+	lockAndRenameDuration := this.migrationContext.RenameTablesEndTime.Sub(this.migrationContext.LockTablesStartTime)
+	renameDuration := this.migrationContext.RenameTablesEndTime.Sub(this.migrationContext.RenameTablesStartTime)
+	log.Debugf("Lock & rename duration: %s (rename only: %s). During this time, queries on %s were locked or failing", lockAndRenameDuration, renameDuration, sql.EscapeName(this.migrationContext.OriginalTableName))
+	return nil
+}
+
 // cutOverTwoStep will lock down the original table, execute
 // what's left of last DML entries, and **non-atomically** swap original->old, then new->original.
 // There is a point in time where the "original" table does not exist and queries are non-blocked

go/logic/server.go

@@ -144,7 +144,7 @@ func (this *Server) applyServerCommand(command string, writer *bufio.Writer) (pr
 	switch command {
 	case "help":
 		{
-			fmt.Fprintln(writer, `available commands:
+			fmt.Fprint(writer, `available commands:
 status                               # Print a detailed status message
 sup                                  # Print a short status message
 coordinates													 # Print the currently inspected coordinates

go/mysql/utils.go

@@ -8,6 +8,7 @@ package mysql
 import (
 	gosql "database/sql"
 	"fmt"
+	"strconv"
 	"strings"
 	"sync"
 	"time"
@@ -203,3 +204,47 @@ func GetTableColumns(db *gosql.DB, databaseName, tableName string) (*sql.ColumnL
 	}
 	return sql.NewColumnList(columnNames), sql.NewColumnList(virtualColumnNames), nil
 }
+
+func versionTokens(version string, digits int) []int {
+	v := strings.Split(version, "-")[0]
+	tokens := strings.Split(v, ".")
+	intTokens := make([]int, digits)
+	for i := range tokens {
+		if i >= digits {
+			break
+		}
+		intTokens[i], _ = strconv.Atoi(tokens[i])
+	}
+	return intTokens
+}
+
+func isSmallerVersion(version string, otherVersion string, digits int) bool {
+	v := versionTokens(version, digits)
+	o := versionTokens(otherVersion, digits)
+	for i := 0; i < len(v); i++ {
+		if v[i] < o[i] {
+			return true
+		}
+		if v[i] > o[i] {
+			return false
+		}
+		if i == digits {
+			break
+		}
+	}
+	return false
+}
+
+// IsSmallerMajorVersion tests two versions against another and returns true if
+// the former is a smaller "major" varsion than the latter.
+// e.g. 5.5.36 is NOT a smaller major version as comapred to 5.5.40, but IS as compared to 5.6.9
+func IsSmallerMajorVersion(version string, otherVersion string) bool {
+	return isSmallerVersion(version, otherVersion, 2)
+}
+
+// IsSmallerMinorVersion tests two versions against another and returns true if
+// the former is a smaller "minor" varsion than the latter.
+// e.g. 5.5.36 is a smaller major version as comapred to 5.5.40, as well as compared to 5.6.7
+func IsSmallerMinorVersion(version string, otherVersion string) bool {
+	return isSmallerVersion(version, otherVersion, 3)
+}

go/mysql/utils_test.go

@@ -0,0 +1,56 @@
+/*
+   Copyright 2016 GitHub Inc.
+	 See https://github.com/github/gh-ost/blob/master/LICENSE
+*/
+
+package mysql
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/outbrain/golib/log"
+	test "github.com/outbrain/golib/tests"
+)
+
+func init() {
+	log.SetLevel(log.ERROR)
+}
+
+func TestVersionTokens(t *testing.T) {
+	test.S(t).ExpectTrue(reflect.DeepEqual(versionTokens("5.7.24-log", 3), []int{5, 7, 24}))
+	test.S(t).ExpectTrue(reflect.DeepEqual(versionTokens("8.0.13", 3), []int{8, 0, 13}))
+	test.S(t).ExpectTrue(reflect.DeepEqual(versionTokens("5.5", 2), []int{5, 5}))
+	test.S(t).ExpectTrue(reflect.DeepEqual(versionTokens("5.5", 3), []int{5, 5, 0}))
+	test.S(t).ExpectTrue(reflect.DeepEqual(versionTokens("5.5-log", 3), []int{5, 5, 0}))
+}
+
+func TestIsSmallerMajorVersion(t *testing.T) {
+	i55 := "5.5"
+	i5516 := "5.5.16"
+	i5517 := "5.5.17"
+	i56 := "5.6"
+	i8013 := "8.0.13"
+
+	test.S(t).ExpectFalse(IsSmallerMajorVersion(i55, i5517))
+	test.S(t).ExpectFalse(IsSmallerMajorVersion(i5516, i5517))
+	test.S(t).ExpectFalse(IsSmallerMajorVersion(i56, i5517))
+	test.S(t).ExpectTrue(IsSmallerMajorVersion(i55, i56))
+	test.S(t).ExpectTrue(IsSmallerMajorVersion(i56, i8013))
+	test.S(t).ExpectFalse(IsSmallerMajorVersion(i8013, i56))
+}
+
+func TestIsSmallerMinorVersion(t *testing.T) {
+	i55 := "5.5"
+	i5516 := "5.5.16"
+	i5517 := "5.5.17"
+	i56 := "5.6"
+	i8013 := "8.0.13"
+
+	test.S(t).ExpectTrue(IsSmallerMinorVersion(i55, i5517))
+	test.S(t).ExpectTrue(IsSmallerMinorVersion(i5516, i5517))
+	test.S(t).ExpectFalse(IsSmallerMinorVersion(i56, i5517))
+	test.S(t).ExpectTrue(IsSmallerMinorVersion(i55, i56))
+	test.S(t).ExpectTrue(IsSmallerMinorVersion(i56, i8013))
+	test.S(t).ExpectFalse(IsSmallerMinorVersion(i8013, i56))
+}