From df4cf7b38e5aa50037681efb588acf39cbd2ac9f Mon Sep 17 00:00:00 2001
From: Tim Vaillancourt <tim@timvaillancourt.com>
Date: Fri, 21 Oct 2022 17:47:39 +0200
Subject: [PATCH 01/19] Add basic test for hooks (#1179)

---
 go/logic/hooks.go      |  11 ++--
 go/logic/hooks_test.go | 113 +++++++++++++++++++++++++++++++++++++++++
 go/logic/migrator.go   |  13 +----
 script/test            |   2 +-
 4 files changed, 120 insertions(+), 19 deletions(-)
 create mode 100644 go/logic/hooks_test.go

diff --git a/go/logic/hooks.go b/go/logic/hooks.go
index 0ff296d..2543f8e 100644
--- a/go/logic/hooks.go
+++ b/go/logic/hooks.go
@@ -7,6 +7,7 @@ package logic
 
 import (
 	"fmt"
+	"io"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -34,18 +35,16 @@ const (
 
 type HooksExecutor struct {
 	migrationContext *base.MigrationContext
+	writer           io.Writer
 }
 
 func NewHooksExecutor(migrationContext *base.MigrationContext) *HooksExecutor {
 	return &HooksExecutor{
 		migrationContext: migrationContext,
+		writer:           os.Stderr,
 	}
 }
 
-func (this *HooksExecutor) initHooks() error {
-	return nil
-}
-
 func (this *HooksExecutor) applyEnvironmentVariables(extraVariables ...string) []string {
 	env := os.Environ()
 	env = append(env, fmt.Sprintf("GH_OST_DATABASE_NAME=%s", this.migrationContext.DatabaseName))
@@ -76,13 +75,13 @@ func (this *HooksExecutor) applyEnvironmentVariables(extraVariables ...string) [
 }
 
 // executeHook executes a command, and sets relevant environment variables
-// combined output & error are printed to gh-ost's standard error.
+// combined output & error are printed to the configured writer.
 func (this *HooksExecutor) executeHook(hook string, extraVariables ...string) error {
 	cmd := exec.Command(hook)
 	cmd.Env = this.applyEnvironmentVariables(extraVariables...)
 
 	combinedOutput, err := cmd.CombinedOutput()
-	fmt.Fprintln(os.Stderr, string(combinedOutput))
+	fmt.Fprintln(this.writer, string(combinedOutput))
 	return log.Errore(err)
 }
 
diff --git a/go/logic/hooks_test.go b/go/logic/hooks_test.go
new file mode 100644
index 0000000..3b28afe
--- /dev/null
+++ b/go/logic/hooks_test.go
@@ -0,0 +1,113 @@
+/*
+   Copyright 2022 GitHub Inc.
+         See https://github.com/github/gh-ost/blob/master/LICENSE
+*/
+
+package logic
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/openark/golib/tests"
+
+	"github.com/github/gh-ost/go/base"
+)
+
+func TestHooksExecutorExecuteHooks(t *testing.T) {
+	migrationContext := base.NewMigrationContext()
+	migrationContext.AlterStatement = "ENGINE=InnoDB"
+	migrationContext.DatabaseName = "test"
+	migrationContext.Hostname = "test.example.com"
+	migrationContext.OriginalTableName = "tablename"
+	migrationContext.RowsDeltaEstimate = 1
+	migrationContext.RowsEstimate = 122
+	migrationContext.TotalRowsCopied = 123456
+	migrationContext.SetETADuration(time.Minute)
+	migrationContext.SetProgressPct(50)
+	hooksExecutor := NewHooksExecutor(migrationContext)
+
+	writeTmpHookFunc := func(testName, hookName, script string) (path string, err error) {
+		if path, err = os.MkdirTemp("", testName); err != nil {
+			return path, err
+		}
+		err = os.WriteFile(filepath.Join(path, hookName), []byte(script), 0777)
+		return path, err
+	}
+
+	t.Run("does-not-exist", func(t *testing.T) {
+		migrationContext.HooksPath = "/does/not/exist"
+		tests.S(t).ExpectNil(hooksExecutor.executeHooks("test-hook"))
+	})
+
+	t.Run("failed", func(t *testing.T) {
+		var err error
+		if migrationContext.HooksPath, err = writeTmpHookFunc(
+			"TestHooksExecutorExecuteHooks-failed",
+			"failed-hook",
+			"#!/bin/sh\nexit 1",
+		); err != nil {
+			panic(err)
+		}
+		defer os.RemoveAll(migrationContext.HooksPath)
+		tests.S(t).ExpectNotNil(hooksExecutor.executeHooks("failed-hook"))
+	})
+
+	t.Run("success", func(t *testing.T) {
+		var err error
+		if migrationContext.HooksPath, err = writeTmpHookFunc(
+			"TestHooksExecutorExecuteHooks-success",
+			"success-hook",
+			"#!/bin/sh\nenv",
+		); err != nil {
+			panic(err)
+		}
+		defer os.RemoveAll(migrationContext.HooksPath)
+
+		var buf bytes.Buffer
+		hooksExecutor.writer = &buf
+		tests.S(t).ExpectNil(hooksExecutor.executeHooks("success-hook", "TEST="+t.Name()))
+
+		scanner := bufio.NewScanner(&buf)
+		for scanner.Scan() {
+			split := strings.SplitN(scanner.Text(), "=", 2)
+			switch split[0] {
+			case "GH_OST_COPIED_ROWS":
+				copiedRows, _ := strconv.ParseInt(split[1], 10, 64)
+				tests.S(t).ExpectEquals(copiedRows, migrationContext.TotalRowsCopied)
+			case "GH_OST_DATABASE_NAME":
+				tests.S(t).ExpectEquals(split[1], migrationContext.DatabaseName)
+			case "GH_OST_DDL":
+				tests.S(t).ExpectEquals(split[1], migrationContext.AlterStatement)
+			case "GH_OST_DRY_RUN":
+				tests.S(t).ExpectEquals(split[1], "false")
+			case "GH_OST_ESTIMATED_ROWS":
+				estimatedRows, _ := strconv.ParseInt(split[1], 10, 64)
+				tests.S(t).ExpectEquals(estimatedRows, int64(123))
+			case "GH_OST_ETA_SECONDS":
+				etaSeconds, _ := strconv.ParseInt(split[1], 10, 64)
+				tests.S(t).ExpectEquals(etaSeconds, int64(60))
+			case "GH_OST_EXECUTING_HOST":
+				tests.S(t).ExpectEquals(split[1], migrationContext.Hostname)
+			case "GH_OST_GHOST_TABLE_NAME":
+				tests.S(t).ExpectEquals(split[1], fmt.Sprintf("_%s_gho", migrationContext.OriginalTableName))
+			case "GH_OST_OLD_TABLE_NAME":
+				tests.S(t).ExpectEquals(split[1], fmt.Sprintf("_%s_del", migrationContext.OriginalTableName))
+			case "GH_OST_PROGRESS":
+				progress, _ := strconv.ParseFloat(split[1], 64)
+				tests.S(t).ExpectEquals(progress, 50.0)
+			case "GH_OST_TABLE_NAME":
+				tests.S(t).ExpectEquals(split[1], migrationContext.OriginalTableName)
+			case "TEST":
+				tests.S(t).ExpectEquals(split[1], t.Name())
+			}
+		}
+	})
+}
diff --git a/go/logic/migrator.go b/go/logic/migrator.go
index 865814d..ccaf160 100644
--- a/go/logic/migrator.go
+++ b/go/logic/migrator.go
@@ -98,6 +98,7 @@ type Migrator struct {
 func NewMigrator(context *base.MigrationContext, appVersion string) *Migrator {
 	migrator := &Migrator{
 		appVersion:                 appVersion,
+		hooksExecutor:              NewHooksExecutor(context),
 		migrationContext:           context,
 		parser:                     sql.NewAlterTableParser(),
 		ghostTableMigrated:         make(chan bool),
@@ -113,15 +114,6 @@ func NewMigrator(context *base.MigrationContext, appVersion string) *Migrator {
 	return migrator
 }
 
-// initiateHooksExecutor
-func (this *Migrator) initiateHooksExecutor() (err error) {
-	this.hooksExecutor = NewHooksExecutor(this.migrationContext)
-	if err := this.hooksExecutor.initHooks(); err != nil {
-		return err
-	}
-	return nil
-}
-
 // sleepWhileTrue sleeps indefinitely until the given function returns 'false'
 // (or fails with error)
 func (this *Migrator) sleepWhileTrue(operation func() (bool, error)) error {
@@ -342,9 +334,6 @@ func (this *Migrator) Migrate() (err error) {
 
 	go this.listenOnPanicAbort()
 
-	if err := this.initiateHooksExecutor(); err != nil {
-		return err
-	}
 	if err := this.hooksExecutor.onStartup(); err != nil {
 		return err
 	}
diff --git a/script/test b/script/test
index 7e757b5..5c32b37 100755
--- a/script/test
+++ b/script/test
@@ -14,4 +14,4 @@ script/build
 cd .gopath/src/github.com/github/gh-ost
 
 echo "Running unit tests"
-go test ./go/...
+go test -v -covermode=atomic ./go/...

From 9b3fa793ac2500a08dda89a9b8ee4497167bccbf Mon Sep 17 00:00:00 2001
From: Tim Vaillancourt <tim@timvaillancourt.com>
Date: Fri, 21 Oct 2022 18:02:06 +0200
Subject: [PATCH 02/19] Enable more `golangci-lint` linters (#1181)

---
 .golangci.yml         |  6 ++++++
 go/base/context.go    |  4 ++--
 go/logic/applier.go   |  2 +-
 go/logic/inspect.go   |  7 +++----
 go/logic/migrator.go  | 10 ++++------
 go/logic/throttler.go |  2 ++
 go/sql/parser.go      | 10 ++++------
 go/sql/parser_test.go | 14 +++++++-------
 8 files changed, 29 insertions(+), 26 deletions(-)

diff --git a/.golangci.yml b/.golangci.yml
index 4621e5c..e4ee4ab 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -4,14 +4,19 @@ linters:
   disable:
     - errcheck
   enable:
+    - bodyclose
+    - containedctx
     - contextcheck
+    - dogsled
     - durationcheck
     - errname
+    - errorlint
     - execinquery
     - gofmt
     - ifshort
     - misspell
     - nilerr
+    - nilnil
     - noctx
     - nolintlint
     - nosprintfhostport
@@ -19,6 +24,7 @@ linters:
     - rowserrcheck
     - sqlclosecheck
     - unconvert
+    - unparam
     - unused
     - wastedassign
     - whitespace
diff --git a/go/base/context.go b/go/base/context.go
index f3fe712..270b7a0 100644
--- a/go/base/context.go
+++ b/go/base/context.go
@@ -858,7 +858,7 @@ func (this *MigrationContext) ReadConfigFile() error {
 	if cfg.Section("osc").HasKey("chunk_size") {
 		this.config.Osc.Chunk_Size, err = cfg.Section("osc").Key("chunk_size").Int64()
 		if err != nil {
-			return fmt.Errorf("Unable to read osc chunk size: %s", err.Error())
+			return fmt.Errorf("Unable to read osc chunk size: %w", err)
 		}
 	}
 
@@ -873,7 +873,7 @@ func (this *MigrationContext) ReadConfigFile() error {
 	if cfg.Section("osc").HasKey("max_lag_millis") {
 		this.config.Osc.Max_Lag_Millis, err = cfg.Section("osc").Key("max_lag_millis").Int64()
 		if err != nil {
-			return fmt.Errorf("Unable to read max lag millis: %s", err.Error())
+			return fmt.Errorf("Unable to read max lag millis: %w", err)
 		}
 	}
 
diff --git a/go/logic/applier.go b/go/logic/applier.go
index 89e1995..50fd9bd 100644
--- a/go/logic/applier.go
+++ b/go/logic/applier.go
@@ -1134,7 +1134,7 @@ func (this *Applier) ApplyDMLEventQueries(dmlEvents [](*binlog.BinlogDMLEvent))
 				}
 				result, err := tx.Exec(buildResult.query, buildResult.args...)
 				if err != nil {
-					err = fmt.Errorf("%s; query=%s; args=%+v", err.Error(), buildResult.query, buildResult.args)
+					err = fmt.Errorf("%w; query=%s; args=%+v", err, buildResult.query, buildResult.args)
 					return rollback(err)
 				}
 
diff --git a/go/logic/inspect.go b/go/logic/inspect.go
index 4df80fe..3ece8ab 100644
--- a/go/logic/inspect.go
+++ b/go/logic/inspect.go
@@ -8,6 +8,7 @@ package logic
 import (
 	"context"
 	gosql "database/sql"
+	"errors"
 	"fmt"
 	"reflect"
 	"strings"
@@ -554,13 +555,11 @@ func (this *Inspector) CountTableRows(ctx context.Context) error {
 	query := fmt.Sprintf(`select /* gh-ost */ count(*) as count_rows from %s.%s`, sql.EscapeName(this.migrationContext.DatabaseName), sql.EscapeName(this.migrationContext.OriginalTableName))
 	var rowsEstimate int64
 	if err := conn.QueryRowContext(ctx, query).Scan(&rowsEstimate); err != nil {
-		switch err {
-		case context.Canceled, context.DeadlineExceeded:
+		if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
 			this.migrationContext.Log.Infof("exact row count cancelled (%s), likely because I'm about to cut over. I'm going to kill that query.", ctx.Err())
 			return mysql.Kill(this.db, connectionID)
-		default:
-			return err
 		}
+		return err
 	}
 
 	// row count query finished. nil out the cancel func, so the main migration thread
diff --git a/go/logic/migrator.go b/go/logic/migrator.go
index ccaf160..b443d69 100644
--- a/go/logic/migrator.go
+++ b/go/logic/migrator.go
@@ -391,9 +391,9 @@ func (this *Migrator) Migrate() (err error) {
 	if err := this.applier.ReadMigrationRangeValues(); err != nil {
 		return err
 	}
-	if err := this.initiateThrottler(); err != nil {
-		return err
-	}
+
+	this.initiateThrottler()
+
 	if err := this.hooksExecutor.onBeforeRowCopy(); err != nil {
 		return err
 	}
@@ -1096,7 +1096,7 @@ func (this *Migrator) addDMLEventsListener() error {
 }
 
 // initiateThrottler kicks in the throttling collection and the throttling checks.
-func (this *Migrator) initiateThrottler() error {
+func (this *Migrator) initiateThrottler() {
 	this.throttler = NewThrottler(this.migrationContext, this.applier, this.inspector, this.appVersion)
 
 	go this.throttler.initiateThrottlerCollection(this.firstThrottlingCollected)
@@ -1106,8 +1106,6 @@ func (this *Migrator) initiateThrottler() error {
 	<-this.firstThrottlingCollected // other, general metrics
 	this.migrationContext.Log.Infof("First throttle metrics collected")
 	go this.throttler.initiateThrottlerChecks()
-
-	return nil
 }
 
 func (this *Migrator) initiateApplier() error {
diff --git a/go/logic/throttler.go b/go/logic/throttler.go
index 1e7bc97..9c8dcfc 100644
--- a/go/logic/throttler.go
+++ b/go/logic/throttler.go
@@ -308,6 +308,8 @@ func (this *Throttler) collectThrottleHTTPStatus(firstThrottlingCollected chan<-
 		if err != nil {
 			return false, err
 		}
+		defer resp.Body.Close()
+
 		atomic.StoreInt64(&this.migrationContext.ThrottleHTTPStatusCode, int64(resp.StatusCode))
 		return false, nil
 	}
diff --git a/go/sql/parser.go b/go/sql/parser.go
index a72af33..2ddc60f 100644
--- a/go/sql/parser.go
+++ b/go/sql/parser.go
@@ -62,7 +62,7 @@ func NewParserFromAlterStatement(alterStatement string) *AlterTableParser {
 	return parser
 }
 
-func (this *AlterTableParser) tokenizeAlterStatement(alterStatement string) (tokens []string, err error) {
+func (this *AlterTableParser) tokenizeAlterStatement(alterStatement string) (tokens []string) {
 	terminatingQuote := rune(0)
 	f := func(c rune) bool {
 		switch {
@@ -86,7 +86,7 @@ func (this *AlterTableParser) tokenizeAlterStatement(alterStatement string) (tok
 	for i := range tokens {
 		tokens[i] = strings.TrimSpace(tokens[i])
 	}
-	return tokens, nil
+	return tokens
 }
 
 func (this *AlterTableParser) sanitizeQuotesFromAlterStatement(alterStatement string) (strippedStatement string) {
@@ -95,7 +95,7 @@ func (this *AlterTableParser) sanitizeQuotesFromAlterStatement(alterStatement st
 	return strippedStatement
 }
 
-func (this *AlterTableParser) parseAlterToken(alterToken string) (err error) {
+func (this *AlterTableParser) parseAlterToken(alterToken string) {
 	{
 		// rename
 		allStringSubmatch := renameColumnRegexp.FindAllStringSubmatch(alterToken, -1)
@@ -131,7 +131,6 @@ func (this *AlterTableParser) parseAlterToken(alterToken string) (err error) {
 			this.isAutoIncrementDefined = true
 		}
 	}
-	return nil
 }
 
 func (this *AlterTableParser) ParseAlterStatement(alterStatement string) (err error) {
@@ -151,8 +150,7 @@ func (this *AlterTableParser) ParseAlterStatement(alterStatement string) (err er
 			break
 		}
 	}
-	alterTokens, _ := this.tokenizeAlterStatement(this.alterStatementOptions)
-	for _, alterToken := range alterTokens {
+	for _, alterToken := range this.tokenizeAlterStatement(this.alterStatementOptions) {
 		alterToken = this.sanitizeQuotesFromAlterStatement(alterToken)
 		this.parseAlterToken(alterToken)
 		this.alterTokens = append(this.alterTokens, alterToken)
diff --git a/go/sql/parser_test.go b/go/sql/parser_test.go
index 79a9b7b..df92842 100644
--- a/go/sql/parser_test.go
+++ b/go/sql/parser_test.go
@@ -99,37 +99,37 @@ func TestTokenizeAlterStatement(t *testing.T) {
 	parser := NewAlterTableParser()
 	{
 		alterStatement := "add column t int"
-		tokens, _ := parser.tokenizeAlterStatement(alterStatement)
+		tokens := parser.tokenizeAlterStatement(alterStatement)
 		test.S(t).ExpectTrue(reflect.DeepEqual(tokens, []string{"add column t int"}))
 	}
 	{
 		alterStatement := "add column t int, change column i int"
-		tokens, _ := parser.tokenizeAlterStatement(alterStatement)
+		tokens := parser.tokenizeAlterStatement(alterStatement)
 		test.S(t).ExpectTrue(reflect.DeepEqual(tokens, []string{"add column t int", "change column i int"}))
 	}
 	{
 		alterStatement := "add column t int, change column i int 'some comment'"
-		tokens, _ := parser.tokenizeAlterStatement(alterStatement)
+		tokens := parser.tokenizeAlterStatement(alterStatement)
 		test.S(t).ExpectTrue(reflect.DeepEqual(tokens, []string{"add column t int", "change column i int 'some comment'"}))
 	}
 	{
 		alterStatement := "add column t int, change column i int 'some comment, with comma'"
-		tokens, _ := parser.tokenizeAlterStatement(alterStatement)
+		tokens := parser.tokenizeAlterStatement(alterStatement)
 		test.S(t).ExpectTrue(reflect.DeepEqual(tokens, []string{"add column t int", "change column i int 'some comment, with comma'"}))
 	}
 	{
 		alterStatement := "add column t int, add column d decimal(10,2)"
-		tokens, _ := parser.tokenizeAlterStatement(alterStatement)
+		tokens := parser.tokenizeAlterStatement(alterStatement)
 		test.S(t).ExpectTrue(reflect.DeepEqual(tokens, []string{"add column t int", "add column d decimal(10,2)"}))
 	}
 	{
 		alterStatement := "add column t int, add column e enum('a','b','c')"
-		tokens, _ := parser.tokenizeAlterStatement(alterStatement)
+		tokens := parser.tokenizeAlterStatement(alterStatement)
 		test.S(t).ExpectTrue(reflect.DeepEqual(tokens, []string{"add column t int", "add column e enum('a','b','c')"}))
 	}
 	{
 		alterStatement := "add column t int(11), add column e enum('a','b','c')"
-		tokens, _ := parser.tokenizeAlterStatement(alterStatement)
+		tokens := parser.tokenizeAlterStatement(alterStatement)
 		test.S(t).ExpectTrue(reflect.DeepEqual(tokens, []string{"add column t int(11)", "add column e enum('a','b','c')"}))
 	}
 }

From 2793e2b6b317465e06a9e9a99f4af52ebd64a304 Mon Sep 17 00:00:00 2001
From: Hasan Mshawrab <63023909+hasanMshawrab@users.noreply.github.com>
Date: Wed, 26 Oct 2022 10:28:27 +0300
Subject: [PATCH 03/19] Fix: Change table name

table name is 'tbl' not 'tble'
---
 doc/shared-key.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/shared-key.md b/doc/shared-key.md
index c7f24cc..3dfa39b 100644
--- a/doc/shared-key.md
+++ b/doc/shared-key.md
@@ -29,7 +29,7 @@ CREATE TABLE tbl (
 
 (This is also the definition of the _ghost_ table, except that that table would be called `_tbl_gho`). 
 
-In this migration, the _before_ and _after_ versions contain the same unique not-null key (the PRIMARY KEY). To run this migration, `gh-ost` would iterate through the `tbl` table using the primary key, copy rows from `tbl` to the _ghost_ table `_tbl_gho` in primary key order, while also applying the binlog event writes from `tble` onto `_tbl_gho`.
+In this migration, the _before_ and _after_ versions contain the same unique not-null key (the PRIMARY KEY). To run this migration, `gh-ost` would iterate through the `tbl` table using the primary key, copy rows from `tbl` to the _ghost_ table `_tbl_gho` in primary key order, while also applying the binlog event writes from `tbl` onto `_tbl_gho`.
 
 The applying of the binlog events is what requires the shared unique key. For example, an `UPDATE` statement to `tbl` translates to a `REPLACE` statement which `gh-ost` applies to `_tbl_gho`. A `REPLACE` statement expects to insert or replace an existing row based on its row's values and the table's unique key constraints. In particular, if inserting that row would result in a unique key violation (e.g., a row with that primary key already exists), it would _replace_ that existing row with the new values.
 

From 515aa72d3d9b756e454b0168b4e57bc599b45e36 Mon Sep 17 00:00:00 2001
From: Nicholas Calugar <nicholas.calugar@gusto.com>
Date: Thu, 27 Oct 2022 11:42:12 -0700
Subject: [PATCH 04/19] Print status to migration context logger

---
 go/logic/migrator.go | 1 +
 1 file changed, 1 insertion(+)

diff --git a/go/logic/migrator.go b/go/logic/migrator.go
index b443d69..22b7c9f 100644
--- a/go/logic/migrator.go
+++ b/go/logic/migrator.go
@@ -1036,6 +1036,7 @@ func (this *Migrator) printStatus(rule PrintStatusRule, writers ...io.Writer) {
 	)
 	w := io.MultiWriter(writers...)
 	fmt.Fprintln(w, status)
+	this.migrationContext.Log.Infof(status)
 
 	hooksStatusIntervalSec := this.migrationContext.HooksStatusIntervalSec
 	if hooksStatusIntervalSec > 0 && elapsedSeconds%hooksStatusIntervalSec == 0 {

From 1be6a4c0823d3ed22f58ff1ff77bc34eff7797a0 Mon Sep 17 00:00:00 2001
From: Morgan Tocker <mtocker@squareup.com>
Date: Wed, 9 Nov 2022 20:11:49 -0700
Subject: [PATCH 05/19] Attempt instant DDL if supported

---
 go/base/context.go    |  1 +
 go/cmd/gh-ost/main.go |  2 ++
 go/logic/applier.go   | 48 +++++++++++++++++++++++++++++++++++++++++++
 go/logic/migrator.go  | 25 ++++++++++++++++++++++
 4 files changed, 76 insertions(+)

diff --git a/go/base/context.go b/go/base/context.go
index 270b7a0..6032a93 100644
--- a/go/base/context.go
+++ b/go/base/context.go
@@ -101,6 +101,7 @@ type MigrationContext struct {
 	AliyunRDS                bool
 	GoogleCloudPlatform      bool
 	AzureMySQL               bool
+	AttemptInstantDDL        bool
 
 	config            ContextConfig
 	configMutex       *sync.Mutex
diff --git a/go/cmd/gh-ost/main.go b/go/cmd/gh-ost/main.go
index b99e70b..660c492 100644
--- a/go/cmd/gh-ost/main.go
+++ b/go/cmd/gh-ost/main.go
@@ -67,6 +67,8 @@ func main() {
 	flag.StringVar(&migrationContext.DatabaseName, "database", "", "database name (mandatory)")
 	flag.StringVar(&migrationContext.OriginalTableName, "table", "", "table name (mandatory)")
 	flag.StringVar(&migrationContext.AlterStatement, "alter", "", "alter statement (mandatory)")
+	flag.BoolVar(&migrationContext.AttemptInstantDDL, "attempt-instant-ddl", true, "Attempt to use instant DDL for this migration first.")
+
 	flag.BoolVar(&migrationContext.CountTableRows, "exact-rowcount", false, "actually count table rows as opposed to estimate them (results in more accurate progress estimation)")
 	flag.BoolVar(&migrationContext.ConcurrentCountTableRows, "concurrent-rowcount", true, "(with --exact-rowcount), when true (default): count rows after row-copy begins, concurrently, and adjust row estimate later on; when false: first count rows, then start row copy")
 	flag.BoolVar(&migrationContext.AllowedRunningOnMaster, "allow-on-master", false, "allow this migration to run directly on master. Preferably it would run on a replica")
diff --git a/go/logic/applier.go b/go/logic/applier.go
index 50fd9bd..b9313a3 100644
--- a/go/logic/applier.go
+++ b/go/logic/applier.go
@@ -188,6 +188,54 @@ func (this *Applier) ValidateOrDropExistingTables() error {
 	return nil
 }
 
+// AttemptInstantDDL attempts to use instant DDL (from MySQL 8.0, and earlier in Aurora and some others.)
+// to apply the ALTER statement immediately. If it errors, the original
+// gh-ost algorithm can be used. However, if it's successful -- a lot
+// of time can potentially be saved. Instant operations include:
+// - Adding a column
+// - Dropping a column
+// - Dropping an index
+// - Extending a varchar column
+// It is safer to attempt the change than try and parse the DDL, since
+// there might be specifics about the table which make it not possible to apply instantly.
+func (this *Applier) AttemptInstantDDL() error {
+
+	query := fmt.Sprintf(`ALTER /* gh-ost */ TABLE %s.%s %s, ALGORITHM=INSTANT`,
+		sql.EscapeName(this.migrationContext.DatabaseName),
+		sql.EscapeName(this.migrationContext.OriginalTableName),
+		this.migrationContext.AlterStatementOptions,
+	)
+	this.migrationContext.Log.Infof("INSTANT DDL Query is: %s", query)
+
+	err := func() error {
+		tx, err := this.db.Begin()
+		if err != nil {
+			return err
+		}
+		defer tx.Rollback()
+
+		sessionQuery := fmt.Sprintf(`SET SESSION time_zone = '%s'`, this.migrationContext.ApplierTimeZone)
+		sessionQuery = fmt.Sprintf("%s, %s", sessionQuery, this.generateSqlModeQuery())
+
+		if _, err := tx.Exec(sessionQuery); err != nil {
+			return err
+		}
+		if _, err := tx.Exec(query); err != nil {
+			this.migrationContext.Log.Infof("INSTANT DDL failed: %s", err)
+			return err
+		}
+		if err := tx.Commit(); err != nil {
+			// Neither SET SESSION nor ALTER are really transactional, so strictly speaking
+			// there's no need to commit; but let's do this the legit way anyway.
+			return err
+		}
+		return nil
+	}()
+
+	return err
+
+}
+
 // CreateGhostTable creates the ghost table on the applier host
 func (this *Applier) CreateGhostTable() error {
 	query := fmt.Sprintf(`create /* gh-ost */ table %s.%s like %s.%s`,
diff --git a/go/logic/migrator.go b/go/logic/migrator.go
index b443d69..40415d0 100644
--- a/go/logic/migrator.go
+++ b/go/logic/migrator.go
@@ -351,12 +351,26 @@ func (this *Migrator) Migrate() (err error) {
 	if err := this.initiateInspector(); err != nil {
 		return err
 	}
+	// In MySQL 8.0 (and possibly earlier) some DDL statements can be applied instantly.
+	// As just a metadata change. We can't detect this unless we attempt the statement
+	// (i.e. there is no explain for DDL).
+	if this.migrationContext.AttemptInstantDDL {
+		this.migrationContext.Log.Infof("Attempting to execute ALTER TABLE as INSTANT DDL")
+		if err := this.attemptInstantDDL(); err == nil {
+			this.migrationContext.Log.Infof("Success! Table %s.%s migrated instantly", sql.EscapeName(this.migrationContext.DatabaseName), sql.EscapeName(this.migrationContext.OriginalTableName))
+			return nil
+		} else {
+			this.migrationContext.Log.Infof("INSTANT DDL failed, will proceed with original algorithm: %s", err)
+		}
+	}
+
 	if err := this.initiateStreaming(); err != nil {
 		return err
 	}
 	if err := this.initiateApplier(); err != nil {
 		return err
 	}
+
 	if err := this.createFlagFiles(); err != nil {
 		return err
 	}
@@ -734,6 +748,17 @@ func (this *Migrator) initiateServer() (err error) {
 	return nil
 }
 
+// attemptInstantDDL tries to apply the DDL statement directly to the table
+// using a ALGORITHM=INSTANT assertion. If this fails, it will return an error,
+// in which case the original algorithm should be used.
+func (this *Migrator) attemptInstantDDL() (err error) {
+	this.applier = NewApplier(this.migrationContext)
+	if err := this.applier.InitDBConnections(); err != nil {
+		return err
+	}
+	return this.applier.AttemptInstantDDL()
+}
+
 // initiateInspector connects, validates and inspects the "inspector" server.
 // The "inspector" server is typically a replica; it is where we issue some
 // queries such as:

From 05f32ebf297456ee759ced15aaa124acb6e7d207 Mon Sep 17 00:00:00 2001
From: Morgan Tocker <mtocker@squareup.com>
Date: Thu, 10 Nov 2022 09:30:13 -0700
Subject: [PATCH 06/19] minor cleanup

---
 go/logic/applier.go  | 32 +++-----------------------------
 go/logic/migrator.go |  1 -
 2 files changed, 3 insertions(+), 30 deletions(-)

diff --git a/go/logic/applier.go b/go/logic/applier.go
index b9313a3..abda2b0 100644
--- a/go/logic/applier.go
+++ b/go/logic/applier.go
@@ -199,41 +199,15 @@ func (this *Applier) ValidateOrDropExistingTables() error {
 // It is safer to attempt the change than try and parse the DDL, since
 // there might be specifics about the table which make it not possible to apply instantly.
 func (this *Applier) AttemptInstantDDL() error {
-
 	query := fmt.Sprintf(`ALTER /* gh-ost */ TABLE %s.%s %s, ALGORITHM=INSTANT`,
 		sql.EscapeName(this.migrationContext.DatabaseName),
 		sql.EscapeName(this.migrationContext.OriginalTableName),
 		this.migrationContext.AlterStatementOptions,
 	)
-	this.migrationContext.Log.Infof("INSTANT DDL Query is: %s", query)
-
-	err := func() error {
-		tx, err := this.db.Begin()
-		if err != nil {
-			return err
-		}
-		defer tx.Rollback()
-
-		sessionQuery := fmt.Sprintf(`SET SESSION time_zone = '%s'`, this.migrationContext.ApplierTimeZone)
-		sessionQuery = fmt.Sprintf("%s, %s", sessionQuery, this.generateSqlModeQuery())
-
-		if _, err := tx.Exec(sessionQuery); err != nil {
-			return err
-		}
-		if _, err := tx.Exec(query); err != nil {
-			this.migrationContext.Log.Infof("INSTANT DDL failed: %s", err)
-			return err
-		}
-		if err := tx.Commit(); err != nil {
-			// Neither SET SESSION nor ALTER are really transactional, so strictly speaking
-			// there's no need to commit; but let's do this the legit way anyway.
-			return err
-		}
-		return nil
-	}()
-
+	this.migrationContext.Log.Infof("INSTANT DDL query is: %s", query)
+	// We don't need a trx, because for instant DDL the SQL mode doesn't matter.
+	_, err := this.db.Exec(query)
 	return err
-
 }
 
 // CreateGhostTable creates the ghost table on the applier host
diff --git a/go/logic/migrator.go b/go/logic/migrator.go
index 40415d0..25989f8 100644
--- a/go/logic/migrator.go
+++ b/go/logic/migrator.go
@@ -370,7 +370,6 @@ func (this *Migrator) Migrate() (err error) {
 	if err := this.initiateApplier(); err != nil {
 		return err
 	}
-
 	if err := this.createFlagFiles(); err != nil {
 		return err
 	}

From 9cbb42b92492757639c704e5c601ec5cac602909 Mon Sep 17 00:00:00 2001
From: dm-2 <45519614+dm-2@users.noreply.github.com>
Date: Mon, 14 Nov 2022 15:00:50 +0000
Subject: [PATCH 07/19] fix CI tests to ubuntu-20.04 because ubuntu-22.04
 (current -latest) doesn't support MySQL 5.7

---
 .github/workflows/ci.yml            | 2 +-
 .github/workflows/replica-tests.yml | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8d5a07b..0b83bd7 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -5,7 +5,7 @@ on: [pull_request]
 jobs:
   build:
 
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
 
     steps:
     - uses: actions/checkout@v2
diff --git a/.github/workflows/replica-tests.yml b/.github/workflows/replica-tests.yml
index e28c2bc..0a82f00 100644
--- a/.github/workflows/replica-tests.yml
+++ b/.github/workflows/replica-tests.yml
@@ -5,7 +5,7 @@ on: [pull_request]
 jobs:
   build:
 
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     strategy:
       matrix:
         version: [mysql-5.7.25,mysql-8.0.16]

From 75a346be93a7ab3b9097fe05ef2451adeadccbdd Mon Sep 17 00:00:00 2001
From: Morgan Tocker <mtocker@squareup.com>
Date: Mon, 14 Nov 2022 11:29:26 -0700
Subject: [PATCH 08/19] Add tests, incorporate feedback

---
 doc/command-line-flags.md                 | 16 +++++++++++
 go/cmd/gh-ost/main.go                     |  2 +-
 go/logic/applier.go                       | 33 ++++++++++++++---------
 go/logic/applier_test.go                  | 14 ++++++++++
 go/logic/migrator.go                      |  9 +++----
 localtests/attempt-instant-ddl/create.sql | 13 +++++++++
 localtests/attempt-instant-ddl/extra_args |  1 +
 7 files changed, 70 insertions(+), 18 deletions(-)
 create mode 100644 localtests/attempt-instant-ddl/create.sql
 create mode 100644 localtests/attempt-instant-ddl/extra_args

diff --git a/doc/command-line-flags.md b/doc/command-line-flags.md
index dc481d0..b496b04 100644
--- a/doc/command-line-flags.md
+++ b/doc/command-line-flags.md
@@ -45,6 +45,22 @@ If you happen to _know_ your servers use RBR (Row Based Replication, i.e. `binlo
 Skipping this step means `gh-ost` would not need the `SUPER` privilege in order to operate.
 You may want to use this on Amazon RDS.
 
+### attempt-instant-ddl
+
+MySQL 8.0 support "instant DDL" for some operations. If an alter statement can be completed with instant DDL, only a metadata change is required internally, so MySQL will return _instantly_ (only requiring a metadata lock to complete). Instant operations include:
+
+- Adding a column
+- Dropping a column
+- Dropping an index
+- Extending a varchar column
+- Adding a virtual generated column
+
+It is not reliable to parse the `ALTER` statement to determine if it is instant or not. This is because the table might be in an older row format, or have some other incompatibility that is difficult to identify.
+
+The risks of attempting to instant DDL are relatively minor: Gh-ost may need to acquire a metadata lock at the start of the operation. This is not a problem for most scenarios, but it could be a problem for users that start the DDL during a period with long running transactions.
+
+gh-ost will automatically fallback to the normal DDL process if the attempt to use instant DDL is unsuccessful.
+
 ### conf
 
 `--conf=/path/to/my.cnf`: file where credentials are specified. Should be in (or contain) the following format:
diff --git a/go/cmd/gh-ost/main.go b/go/cmd/gh-ost/main.go
index 660c492..c00b206 100644
--- a/go/cmd/gh-ost/main.go
+++ b/go/cmd/gh-ost/main.go
@@ -67,7 +67,7 @@ func main() {
 	flag.StringVar(&migrationContext.DatabaseName, "database", "", "database name (mandatory)")
 	flag.StringVar(&migrationContext.OriginalTableName, "table", "", "table name (mandatory)")
 	flag.StringVar(&migrationContext.AlterStatement, "alter", "", "alter statement (mandatory)")
-	flag.BoolVar(&migrationContext.AttemptInstantDDL, "attempt-instant-ddl", true, "Attempt to use instant DDL for this migration first.")
+	flag.BoolVar(&migrationContext.AttemptInstantDDL, "attempt-instant-ddl", false, "Attempt to use instant DDL for this migration first")
 
 	flag.BoolVar(&migrationContext.CountTableRows, "exact-rowcount", false, "actually count table rows as opposed to estimate them (results in more accurate progress estimation)")
 	flag.BoolVar(&migrationContext.ConcurrentCountTableRows, "concurrent-rowcount", true, "(with --exact-rowcount), when true (default): count rows after row-copy begins, concurrently, and adjust row estimate later on; when false: first count rows, then start row copy")
diff --git a/go/logic/applier.go b/go/logic/applier.go
index abda2b0..ad6368e 100644
--- a/go/logic/applier.go
+++ b/go/logic/applier.go
@@ -135,6 +135,16 @@ func (this *Applier) generateSqlModeQuery() string {
 	return fmt.Sprintf("sql_mode = %s", sqlModeQuery)
 }
 
+// generateInstantDDLQuery returns the SQL for this ALTER operation
+// with an INSTANT assertion (requires MySQL 8.0+)
+func (this *Applier) generateInstantDDLQuery() string {
+	return fmt.Sprintf(`ALTER /* gh-ost */ TABLE %s.%s %s, ALGORITHM=INSTANT`,
+		sql.EscapeName(this.migrationContext.DatabaseName),
+		sql.EscapeName(this.migrationContext.OriginalTableName),
+		this.migrationContext.AlterStatementOptions,
+	)
+}
+
 // readTableColumns reads table columns on applier
 func (this *Applier) readTableColumns() (err error) {
 	this.migrationContext.Log.Infof("Examining table structure on applier")
@@ -188,22 +198,21 @@ func (this *Applier) ValidateOrDropExistingTables() error {
 	return nil
 }
 
-// AttemptInstantDDL attempts to use instant DDL (from MySQL 8.0, and earlier in Aurora and some others.)
-// to apply the ALTER statement immediately. If it errors, the original
-// gh-ost algorithm can be used. However, if it's successful -- a lot
-// of time can potentially be saved. Instant operations include:
+// AttemptInstantDDL attempts to use instant DDL (from MySQL 8.0, and earlier in Aurora and some others).
+// If successful, the operation is only a meta-data change so a lot of time is saved!
+// The risk of attempting to instant DDL when not supported is that a metadata lock may be acquired.
+// This is minor, since gh-ost will eventually require a metadata lock anyway, but at the cut-over stage.
+// Instant operations include:
 // - Adding a column
 // - Dropping a column
 // - Dropping an index
-// - Extending a varchar column
-// It is safer to attempt the change than try and parse the DDL, since
-// there might be specifics about the table which make it not possible to apply instantly.
+// - Extending a VARCHAR column
+// - Adding a virtual generated column
+// It is not reliable to parse the `alter` statement to determine if it is instant or not.
+// This is because the table might be in an older row format, or have some other incompatibility
+// that is difficult to identify.
 func (this *Applier) AttemptInstantDDL() error {
-	query := fmt.Sprintf(`ALTER /* gh-ost */ TABLE %s.%s %s, ALGORITHM=INSTANT`,
-		sql.EscapeName(this.migrationContext.DatabaseName),
-		sql.EscapeName(this.migrationContext.OriginalTableName),
-		this.migrationContext.AlterStatementOptions,
-	)
+	query := this.generateInstantDDLQuery()
 	this.migrationContext.Log.Infof("INSTANT DDL query is: %s", query)
 	// We don't need a trx, because for instant DDL the SQL mode doesn't matter.
 	_, err := this.db.Exec(query)
diff --git a/go/logic/applier_test.go b/go/logic/applier_test.go
index a2c1414..44d1fc7 100644
--- a/go/logic/applier_test.go
+++ b/go/logic/applier_test.go
@@ -170,3 +170,17 @@ func TestApplierBuildDMLEventQuery(t *testing.T) {
 		test.S(t).ExpectEquals(res[0].args[3], 42)
 	})
 }
+
+func TestApplierInstantDDL(t *testing.T) {
+	migrationContext := base.NewMigrationContext()
+	migrationContext.DatabaseName = "test"
+	migrationContext.OriginalTableName = "mytable"
+	migrationContext.AlterStatementOptions = "ADD INDEX (foo)"
+	applier := NewApplier(migrationContext)
+
+	t.Run("instantDDLstmt", func(t *testing.T) {
+		stmt := applier.generateInstantDDLQuery()
+		test.S(t).ExpectEquals(stmt, "ALTER /* gh-ost */ TABLE `test`.`mytable` ADD INDEX (foo), ALGORITHM=INSTANT")
+	})
+
+}
diff --git a/go/logic/migrator.go b/go/logic/migrator.go
index 25989f8..13cbdee 100644
--- a/go/logic/migrator.go
+++ b/go/logic/migrator.go
@@ -352,15 +352,14 @@ func (this *Migrator) Migrate() (err error) {
 		return err
 	}
 	// In MySQL 8.0 (and possibly earlier) some DDL statements can be applied instantly.
-	// As just a metadata change. We can't detect this unless we attempt the statement
-	// (i.e. there is no explain for DDL).
+	// Attempt to do this if AttemptInstantDDL is set.
 	if this.migrationContext.AttemptInstantDDL {
-		this.migrationContext.Log.Infof("Attempting to execute ALTER TABLE as INSTANT DDL")
+		this.migrationContext.Log.Infof("Attempting to execute alter with ALGORITHM=INSTANT")
 		if err := this.attemptInstantDDL(); err == nil {
-			this.migrationContext.Log.Infof("Success! Table %s.%s migrated instantly", sql.EscapeName(this.migrationContext.DatabaseName), sql.EscapeName(this.migrationContext.OriginalTableName))
+			this.migrationContext.Log.Infof("Success! table %s.%s migrated instantly", sql.EscapeName(this.migrationContext.DatabaseName), sql.EscapeName(this.migrationContext.OriginalTableName))
 			return nil
 		} else {
-			this.migrationContext.Log.Infof("INSTANT DDL failed, will proceed with original algorithm: %s", err)
+			this.migrationContext.Log.Infof("ALGORITHM=INSTANT failed, proceeding with original algorithm: %s", err)
 		}
 	}
 
diff --git a/localtests/attempt-instant-ddl/create.sql b/localtests/attempt-instant-ddl/create.sql
new file mode 100644
index 0000000..9371238
--- /dev/null
+++ b/localtests/attempt-instant-ddl/create.sql
@@ -0,0 +1,13 @@
+drop table if exists gh_ost_test;
+create table gh_ost_test (
+  id int auto_increment,
+  i int not null,
+  color varchar(32),
+  primary key(id)
+) auto_increment=1;
+
+drop event if exists gh_ost_test;
+
+insert into gh_ost_test values (null, 11, 'red');
+insert into gh_ost_test values (null, 13, 'green');
+insert into gh_ost_test values (null, 17, 'blue');
diff --git a/localtests/attempt-instant-ddl/extra_args b/localtests/attempt-instant-ddl/extra_args
new file mode 100644
index 0000000..70c8a52
--- /dev/null
+++ b/localtests/attempt-instant-ddl/extra_args
@@ -0,0 +1 @@
+--attempt-instant-ddl

From b06c1cd498b31f601abe857b0b3bd5a4737aa586 Mon Sep 17 00:00:00 2001
From: Morgan Tocker <mtocker@squareup.com>
Date: Mon, 14 Nov 2022 12:30:38 -0700
Subject: [PATCH 09/19] Improve docs

---
 doc/command-line-flags.md | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/doc/command-line-flags.md b/doc/command-line-flags.md
index b496b04..509fa67 100644
--- a/doc/command-line-flags.md
+++ b/doc/command-line-flags.md
@@ -47,7 +47,7 @@ You may want to use this on Amazon RDS.
 
 ### attempt-instant-ddl
 
-MySQL 8.0 support "instant DDL" for some operations. If an alter statement can be completed with instant DDL, only a metadata change is required internally, so MySQL will return _instantly_ (only requiring a metadata lock to complete). Instant operations include:
+MySQL 8.0 supports "instant DDL" for some operations. If an alter statement can be completed with instant DDL, only a metadata change is required internally. Instant operations include:
 
 - Adding a column
 - Dropping a column
@@ -57,9 +57,9 @@ MySQL 8.0 support "instant DDL" for some operations. If an alter statement can b
 
 It is not reliable to parse the `ALTER` statement to determine if it is instant or not. This is because the table might be in an older row format, or have some other incompatibility that is difficult to identify.
 
-The risks of attempting to instant DDL are relatively minor: Gh-ost may need to acquire a metadata lock at the start of the operation. This is not a problem for most scenarios, but it could be a problem for users that start the DDL during a period with long running transactions.
+The risks of attempting instant DDL are relatively minor: `gh-ost` may need to acquire a metadata lock at the start of the operation. This is not a problem for most scenarios, but it could be a problem for users that start the DDL during a period with long running transactions.
 
-gh-ost will automatically fallback to the normal DDL process if the attempt to use instant DDL is unsuccessful.
+`gh-ost` will automatically fallback to the normal DDL process if the attempt to use instant DDL is unsuccessful.
 
 ### conf
 

From 3f3a10a2133ae7318536f260bcdbd42ad700e2b0 Mon Sep 17 00:00:00 2001
From: Morgan Tocker <mtocker@squareup.com>
Date: Mon, 14 Nov 2022 14:47:00 -0700
Subject: [PATCH 10/19] Address PR feedback

---
 go/logic/applier_test.go |  1 -
 go/logic/migrator.go     | 23 +++++++++--------------
 2 files changed, 9 insertions(+), 15 deletions(-)

diff --git a/go/logic/applier_test.go b/go/logic/applier_test.go
index 44d1fc7..a356351 100644
--- a/go/logic/applier_test.go
+++ b/go/logic/applier_test.go
@@ -182,5 +182,4 @@ func TestApplierInstantDDL(t *testing.T) {
 		stmt := applier.generateInstantDDLQuery()
 		test.S(t).ExpectEquals(stmt, "ALTER /* gh-ost */ TABLE `test`.`mytable` ADD INDEX (foo), ALGORITHM=INSTANT")
 	})
-
 }
diff --git a/go/logic/migrator.go b/go/logic/migrator.go
index 0dcf53f..31e21cc 100644
--- a/go/logic/migrator.go
+++ b/go/logic/migrator.go
@@ -351,6 +351,15 @@ func (this *Migrator) Migrate() (err error) {
 	if err := this.initiateInspector(); err != nil {
 		return err
 	}
+	if err := this.initiateStreaming(); err != nil {
+		return err
+	}
+	if err := this.initiateApplier(); err != nil {
+		return err
+	}
+	if err := this.createFlagFiles(); err != nil {
+		return err
+	}
 	// In MySQL 8.0 (and possibly earlier) some DDL statements can be applied instantly.
 	// Attempt to do this if AttemptInstantDDL is set.
 	if this.migrationContext.AttemptInstantDDL {
@@ -363,16 +372,6 @@ func (this *Migrator) Migrate() (err error) {
 		}
 	}
 
-	if err := this.initiateStreaming(); err != nil {
-		return err
-	}
-	if err := this.initiateApplier(); err != nil {
-		return err
-	}
-	if err := this.createFlagFiles(); err != nil {
-		return err
-	}
-
 	initialLag, _ := this.inspector.getReplicationLag()
 	this.migrationContext.Log.Infof("Waiting for ghost table to be migrated. Current lag is %+v", initialLag)
 	<-this.ghostTableMigrated
@@ -750,10 +749,6 @@ func (this *Migrator) initiateServer() (err error) {
 // using a ALGORITHM=INSTANT assertion. If this fails, it will return an error,
 // in which case the original algorithm should be used.
 func (this *Migrator) attemptInstantDDL() (err error) {
-	this.applier = NewApplier(this.migrationContext)
-	if err := this.applier.InitDBConnections(); err != nil {
-		return err
-	}
 	return this.applier.AttemptInstantDDL()
 }
 

From 1b22f784e3858b21767c78c6f74547db23e90266 Mon Sep 17 00:00:00 2001
From: dm-2 <45519614+dm-2@users.noreply.github.com>
Date: Tue, 15 Nov 2022 15:06:19 +0000
Subject: [PATCH 11/19] temp commit to investigate datetime-with-zero test
 failure

---
 script/cibuild-gh-ost-replica-tests | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/script/cibuild-gh-ost-replica-tests b/script/cibuild-gh-ost-replica-tests
index c4dbfd2..bc8b788 100755
--- a/script/cibuild-gh-ost-replica-tests
+++ b/script/cibuild-gh-ost-replica-tests
@@ -61,7 +61,7 @@ test_mysql_version() {
   gh-ost-test-mysql-master -uroot -e "grant all on *.* to 'gh-ost'@'%'"
 
   echo "### Running gh-ost tests for $mysql_version"
-  ./localtests/test.sh -b bin/gh-ost
+  bash ./localtests/test.sh -b bin/gh-ost datetime-with-zero
 
   find sandboxes -name "stop_all" | bash
 }

From 512751968feb38cea5995c908540d9fe5f583766 Mon Sep 17 00:00:00 2001
From: dm-2 <45519614+dm-2@users.noreply.github.com>
Date: Tue, 15 Nov 2022 16:01:54 +0000
Subject: [PATCH 12/19] more testing

---
 script/cibuild-gh-ost-replica-tests | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/script/cibuild-gh-ost-replica-tests b/script/cibuild-gh-ost-replica-tests
index bc8b788..0c37b27 100755
--- a/script/cibuild-gh-ost-replica-tests
+++ b/script/cibuild-gh-ost-replica-tests
@@ -61,7 +61,7 @@ test_mysql_version() {
   gh-ost-test-mysql-master -uroot -e "grant all on *.* to 'gh-ost'@'%'"
 
   echo "### Running gh-ost tests for $mysql_version"
-  bash ./localtests/test.sh -b bin/gh-ost datetime-with-zero
+  bash -x ./localtests/test.sh -b bin/gh-ost
 
   find sandboxes -name "stop_all" | bash
 }

From 74fb8e80b2a0f848a265b34f04ca8dbfb265743f Mon Sep 17 00:00:00 2001
From: Morgan Tocker <tocker@gmail.com>
Date: Tue, 15 Nov 2022 12:05:27 -0700
Subject: [PATCH 13/19] Update go/logic/migrator.go

Co-authored-by: dm-2 <45519614+dm-2@users.noreply.github.com>
---
 go/logic/migrator.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/go/logic/migrator.go b/go/logic/migrator.go
index 31e21cc..0f4ebba 100644
--- a/go/logic/migrator.go
+++ b/go/logic/migrator.go
@@ -368,7 +368,7 @@ func (this *Migrator) Migrate() (err error) {
 			this.migrationContext.Log.Infof("Success! table %s.%s migrated instantly", sql.EscapeName(this.migrationContext.DatabaseName), sql.EscapeName(this.migrationContext.OriginalTableName))
 			return nil
 		} else {
-			this.migrationContext.Log.Infof("ALGORITHM=INSTANT failed, proceeding with original algorithm: %s", err)
+			this.migrationContext.Log.Infof("ALGORITHM=INSTANT not supported for this operation, proceeding with original algorithm: %s", err)
 		}
 	}
 

From 5283b46ec23c494b4b4256b2e5a43d0b9e4f8974 Mon Sep 17 00:00:00 2001
From: Morgan Tocker <mtocker@squareup.com>
Date: Tue, 15 Nov 2022 12:06:11 -0700
Subject: [PATCH 14/19] Make it clear in docs it is disabled by default but
 safe.

---
 doc/command-line-flags.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/command-line-flags.md b/doc/command-line-flags.md
index 509fa67..56bc642 100644
--- a/doc/command-line-flags.md
+++ b/doc/command-line-flags.md
@@ -57,7 +57,7 @@ MySQL 8.0 supports "instant DDL" for some operations. If an alter statement can
 
 It is not reliable to parse the `ALTER` statement to determine if it is instant or not. This is because the table might be in an older row format, or have some other incompatibility that is difficult to identify.
 
-The risks of attempting instant DDL are relatively minor: `gh-ost` may need to acquire a metadata lock at the start of the operation. This is not a problem for most scenarios, but it could be a problem for users that start the DDL during a period with long running transactions.
+`--attempt-instant-ddl` is disabled by default, but the risks of enabling it are relatively minor: `gh-ost` may need to acquire a metadata lock at the start of the operation. This is not a problem for most scenarios, but it could be a problem for users that start the DDL during a period with long running transactions.
 
 `gh-ost` will automatically fallback to the normal DDL process if the attempt to use instant DDL is unsuccessful.
 

From 59c1a24774482723f100f1213bb16b16497b40f6 Mon Sep 17 00:00:00 2001
From: Morgan Tocker <mtocker@squareup.com>
Date: Tue, 15 Nov 2022 15:40:21 -0700
Subject: [PATCH 15/19] remove useless func per review

---
 go/logic/migrator.go | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/go/logic/migrator.go b/go/logic/migrator.go
index 0f4ebba..a102188 100644
--- a/go/logic/migrator.go
+++ b/go/logic/migrator.go
@@ -364,7 +364,7 @@ func (this *Migrator) Migrate() (err error) {
 	// Attempt to do this if AttemptInstantDDL is set.
 	if this.migrationContext.AttemptInstantDDL {
 		this.migrationContext.Log.Infof("Attempting to execute alter with ALGORITHM=INSTANT")
-		if err := this.attemptInstantDDL(); err == nil {
+		if err := this.applier.AttemptInstantDDL(); err == nil {
 			this.migrationContext.Log.Infof("Success! table %s.%s migrated instantly", sql.EscapeName(this.migrationContext.DatabaseName), sql.EscapeName(this.migrationContext.OriginalTableName))
 			return nil
 		} else {
@@ -745,13 +745,6 @@ func (this *Migrator) initiateServer() (err error) {
 	return nil
 }
 
-// attemptInstantDDL tries to apply the DDL statement directly to the table
-// using a ALGORITHM=INSTANT assertion. If this fails, it will return an error,
-// in which case the original algorithm should be used.
-func (this *Migrator) attemptInstantDDL() (err error) {
-	return this.applier.AttemptInstantDDL()
-}
-
 // initiateInspector connects, validates and inspects the "inspector" server.
 // The "inspector" server is typically a replica; it is where we issue some
 // queries such as:

From cd65c7e9ada627e0fec413ff1ac6a8e7822ac88c Mon Sep 17 00:00:00 2001
From: dm-2 <45519614+dm-2@users.noreply.github.com>
Date: Fri, 18 Nov 2022 15:11:44 +0000
Subject: [PATCH 16/19] add extra debugging output

---
 localtests/test.sh | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/localtests/test.sh b/localtests/test.sh
index f66c813..a3c8fa4 100755
--- a/localtests/test.sh
+++ b/localtests/test.sh
@@ -116,7 +116,8 @@ test_single() {
     gh-ost-test-mysql-replica --default-character-set=utf8mb4 test -e "set @@global.sql_mode='$(cat $tests_path/$test_name/sql_mode)'"
   fi
 
-  gh-ost-test-mysql-master --default-character-set=utf8mb4 test < $tests_path/$test_name/create.sql
+  cat $tests_path/$test_name/create.sql
+  bash -x gh-ost-test-mysql-master --default-character-set=utf8mb4 test < $tests_path/$test_name/create.sql
 
   extra_args=""
   if [ -f $tests_path/$test_name/extra_args ] ; then

From 7cebc16c6fc56e168f9732a152afa54f9d71a6ae Mon Sep 17 00:00:00 2001
From: dm-2 <45519614+dm-2@users.noreply.github.com>
Date: Fri, 18 Nov 2022 15:32:34 +0000
Subject: [PATCH 17/19] debugging

---
 localtests/test.sh | 1 +
 1 file changed, 1 insertion(+)

diff --git a/localtests/test.sh b/localtests/test.sh
index a3c8fa4..b953861 100755
--- a/localtests/test.sh
+++ b/localtests/test.sh
@@ -118,6 +118,7 @@ test_single() {
 
   cat $tests_path/$test_name/create.sql
   bash -x gh-ost-test-mysql-master --default-character-set=utf8mb4 test < $tests_path/$test_name/create.sql
+  echo $?
 
   extra_args=""
   if [ -f $tests_path/$test_name/extra_args ] ; then

From 756f3d30e8d4252f30f5e7a8721a158e789355d6 Mon Sep 17 00:00:00 2001
From: dm-2 <45519614+dm-2@users.noreply.github.com>
Date: Fri, 18 Nov 2022 15:44:14 +0000
Subject: [PATCH 18/19] add error detection for test setup, sort tests to make
 it easier to track progress

---
 localtests/test.sh                  | 14 ++++++++++----
 script/cibuild-gh-ost-replica-tests |  2 +-
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/localtests/test.sh b/localtests/test.sh
index b953861..5ca06ad 100755
--- a/localtests/test.sh
+++ b/localtests/test.sh
@@ -116,9 +116,15 @@ test_single() {
     gh-ost-test-mysql-replica --default-character-set=utf8mb4 test -e "set @@global.sql_mode='$(cat $tests_path/$test_name/sql_mode)'"
   fi
 
-  cat $tests_path/$test_name/create.sql
-  bash -x gh-ost-test-mysql-master --default-character-set=utf8mb4 test < $tests_path/$test_name/create.sql
-  echo $?
+  gh-ost-test-mysql-master --default-character-set=utf8mb4 test < $tests_path/$test_name/create.sql
+  test_create_result=$?
+
+  if [ $test_create_result -ne 0 ] ; then
+    echo
+    echo "ERROR $test_name create failure. cat $tests_path/$test_name/create.sql:"
+    cat $tests_path/$test_name/create.sql
+    return 1
+  fi
 
   extra_args=""
   if [ -f $tests_path/$test_name/extra_args ] ; then
@@ -257,7 +263,7 @@ build_binary() {
 
 test_all() {
   build_binary
-  find $tests_path ! -path . -type d -mindepth 1 -maxdepth 1 | cut -d "/" -f 3 | egrep "$test_pattern" | while read test_name ; do
+  find $tests_path ! -path . -type d -mindepth 1 -maxdepth 1 | cut -d "/" -f 3 | egrep "$test_pattern" | sort | while read test_name ; do
     test_single "$test_name"
     if [ $? -ne 0 ] ; then
       create_statement=$(gh-ost-test-mysql-replica test -t -e "show create table _gh_ost_test_gho \G")
diff --git a/script/cibuild-gh-ost-replica-tests b/script/cibuild-gh-ost-replica-tests
index 0c37b27..c4dbfd2 100755
--- a/script/cibuild-gh-ost-replica-tests
+++ b/script/cibuild-gh-ost-replica-tests
@@ -61,7 +61,7 @@ test_mysql_version() {
   gh-ost-test-mysql-master -uroot -e "grant all on *.* to 'gh-ost'@'%'"
 
   echo "### Running gh-ost tests for $mysql_version"
-  bash -x ./localtests/test.sh -b bin/gh-ost
+  ./localtests/test.sh -b bin/gh-ost
 
   find sandboxes -name "stop_all" | bash
 }

From 8abd58482651750fc68f9541b76b07b6a16ae50d Mon Sep 17 00:00:00 2001
From: dm-2 <45519614+dm-2@users.noreply.github.com>
Date: Fri, 18 Nov 2022 15:49:04 +0000
Subject: [PATCH 19/19] fix broken test by removing invalid insert statement

---
 localtests/convert-utf8mb4/create.sql | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/localtests/convert-utf8mb4/create.sql b/localtests/convert-utf8mb4/create.sql
index 05f1a13..e35e688 100644
--- a/localtests/convert-utf8mb4/create.sql
+++ b/localtests/convert-utf8mb4/create.sql
@@ -7,9 +7,6 @@ create table gh_ost_test (
   primary key(id)
 ) auto_increment=1;
 
-insert into gh_ost_test values (null, 'átesting');
-
-
 insert into gh_ost_test values (null, 'Hello world, Καλημέρα κόσμε, コンニチハ', 'átesting0', 'initial');
 
 drop event if exists gh_ost_test;