Online DDL: migration with same context and SQL now considered duplicate and silently marked as complete

go/test/endtoend/cluster/vtctlclient_process.go

@@ -38,8 +38,9 @@ type VtctlClientProcess struct {
 
 // VtctlClientParams encapsulated params to provide if non-default
 type VtctlClientParams struct {
-	DDLStrategy   string
-	SkipPreflight bool
+	DDLStrategy    string
+	RequestContext string
+	SkipPreflight  bool
 }
 
 // InitShardPrimary executes vtctlclient command to make specified tablet the primary for the shard.
@@ -61,6 +62,9 @@ func (vtctlclient *VtctlClientProcess) ApplySchemaWithOutput(Keyspace string, SQ
 		"ApplySchema",
 		"-sql", SQL,
 	}
+	if params.RequestContext != "" {
+		args = append(args, "-request_context", params.RequestContext)
+	}
 	if params.DDLStrategy != "" {
 		args = append(args, "-ddl_strategy", params.DDLStrategy)
 	}

go/test/endtoend/onlineddl/declarative/onlineddl_declarative_test.go

@@ -90,6 +90,7 @@ var (
 	cell                  = "zone1"
 	schemaChangeDirectory = ""
 	tableName             = `stress_test`
+	requestContext        = "1111-2222-3333"
 	createStatement1      = `
 		CREATE TABLE stress_test (
 			id bigint(20) not null,
@@ -147,6 +148,9 @@ var (
 	alterStatement = `
 		ALTER TABLE stress_test modify hint_col varchar(64) not null default 'this-should-fail'
 	`
+	trivialAlterStatement = `
+		ALTER TABLE stress_test ENGINE=InnoDB
+	`
 	insertRowStatement = `
 		INSERT IGNORE INTO stress_test (id, rand_val) VALUES (%d, left(md5(rand()), 8))
 	`
@@ -450,6 +454,39 @@ func TestSchemaChange(t *testing.T) {
 		checkTable(t, tableName, true)
 		testSelectTableMetrics(t)
 	})
+
+	// ### The following tests are not strictly 'declarative' but are best served under this endtoend test
+
+	// Test duplicate context/SQL
+	t.Run("Trivial statement with request context is successful", func(t *testing.T) {
+		uuid := testOnlineDDLStatement(t, trivialAlterStatement, "online", "vtctl", "", "")
+		uuids = append(uuids, uuid)
+		onlineddl.CheckMigrationStatus(t, &vtParams, shards, uuid, schema.OnlineDDLStatusComplete)
+		// the table existed, so we expect no changes in this non-declarative DDL
+		checkTable(t, tableName, true)
+
+		rs := onlineddl.ReadMigrations(t, &vtParams, uuid)
+		require.NotNil(t, rs)
+		for _, row := range rs.Named().Rows {
+			message := row["message"].ToString()
+			require.NotContains(t, message, "duplicate DDL")
+		}
+	})
+	t.Run("Duplicate trivial statement with request context is successful", func(t *testing.T) {
+		uuid := testOnlineDDLStatement(t, trivialAlterStatement, "online", "vtctl", "", "")
+		uuids = append(uuids, uuid)
+		onlineddl.CheckMigrationStatus(t, &vtParams, shards, uuid, schema.OnlineDDLStatusComplete)
+		// the table existed, so we expect no changes in this non-declarative DDL
+		checkTable(t, tableName, true)
+
+		rs := onlineddl.ReadMigrations(t, &vtParams, uuid)
+		require.NotNil(t, rs)
+		for _, row := range rs.Named().Rows {
+			message := row["message"].ToString()
+			// Message suggests that the migration was identified as duplicate
+			require.Contains(t, message, "duplicate DDL")
+		}
+	})
 	// Piggyride this test suite, let's also test --allow-zero-in-date for 'direct' strategy
 	t.Run("drop non_online", func(t *testing.T) {
 		_ = testOnlineDDLStatement(t, dropZeroDateStatement, "direct", "vtctl", "", "")
@@ -474,7 +511,7 @@ func testOnlineDDLStatement(t *testing.T, alterStatement string, ddlStrategy str
 			uuid = row.AsString("uuid", "")
 		}
 	} else {
-		output, err := clusterInstance.VtctlclientProcess.ApplySchemaWithOutput(keyspaceName, alterStatement, cluster.VtctlClientParams{DDLStrategy: ddlStrategy, SkipPreflight: true})
+		output, err := clusterInstance.VtctlclientProcess.ApplySchemaWithOutput(keyspaceName, alterStatement, cluster.VtctlClientParams{DDLStrategy: ddlStrategy, RequestContext: requestContext, SkipPreflight: true})
 		if expectError == "" {
 			assert.NoError(t, err)
 			uuid = output

go/vt/vttablet/onlineddl/executor.go

@@ -1946,6 +1946,27 @@ func (e *Executor) evaluateDeclarativeDiff(ctx context.Context, onlineDDL *schem
 	return alterClause, nil
 }
 
+// getCompletedMigrationByContextAndSQL chceks if there exists a completed migration with exact same
+// context and SQL as given migration. If so, it returns its UUID.
+func (e *Executor) getCompletedMigrationByContextAndSQL(ctx context.Context, onlineDDL *schema.OnlineDDL) (completedUUID string, err error) {
+	query, err := sqlparser.ParseAndBind(sqlSelectCompleteMigrationsByContextAndSQL,
+		sqltypes.StringBindVariable(e.keyspace),
+		sqltypes.StringBindVariable(onlineDDL.RequestContext),
+		sqltypes.StringBindVariable(onlineDDL.SQL),
+	)
+	if err != nil {
+		return "", err
+	}
+	r, err := e.execQuery(ctx, query)
+	if err != nil {
+		return "", err
+	}
+	for _, row := range r.Named().Rows {
+		completedUUID = row["migration_uuid"].ToString()
+	}
+	return completedUUID, nil
+}
+
 // failMigration marks a migration as failed
 func (e *Executor) failMigration(ctx context.Context, onlineDDL *schema.OnlineDDL, err error) error {
 	_ = e.updateMigrationStatus(ctx, onlineDDL.UUID, schema.OnlineDDLStatusFailed)
@@ -1972,6 +1993,23 @@ func (e *Executor) executeMigration(ctx context.Context, onlineDDL *schema.Onlin
 		return failMigration(err)
 	}
 
+	// See if this is a duplicate submission. A submission is considered duplicate if it has the exact same
+	// migration context and DDL as a previous one. We are only interested in our scenario in a duplicate
+	// whose predecessor is "complete". If this is the case, then we can mark our own migration as
+	// implicitly "complete", too.
+	if onlineDDL.RequestContext != "" {
+		completedUUID, err := e.getCompletedMigrationByContextAndSQL(ctx, onlineDDL)
+		if err != nil {
+			return err
+		}
+		if completedUUID != "" {
+			// Yep. We mark this migration as implicitly complete, and we're done with it!
+			_ = e.onSchemaMigrationStatus(ctx, onlineDDL.UUID, schema.OnlineDDLStatusComplete, false, progressPctFull, etaSecondsNow, rowsCopiedUnknown)
+			_ = e.updateMigrationMessage(ctx, onlineDDL.UUID, fmt.Sprintf("duplicate DDL as %s for migration context %s", completedUUID, onlineDDL.RequestContext))
+			return nil
+		}
+	}
+
 	if onlineDDL.StrategySetting().IsDeclarative() {
 		switch ddlAction {
 		case sqlparser.RevertDDLAction:
@@ -2194,14 +2232,17 @@ func (e *Executor) runNextMigration(ctx context.Context) error {
 	named := r.Named()
 	for i, row := range named.Rows {
 		onlineDDL := &schema.OnlineDDL{
-			Keyspace: row["keyspace"].ToString(),
-			Table:    row["mysql_table"].ToString(),
-			Schema:   row["mysql_schema"].ToString(),
-			SQL:      row["migration_statement"].ToString(),
-			UUID:     row["migration_uuid"].ToString(),
-			Strategy: schema.DDLStrategy(row["strategy"].ToString()),
-			Options:  row["options"].ToString(),
-			Status:   schema.OnlineDDLStatus(row["migration_status"].ToString()),
+			Keyspace:       row["keyspace"].ToString(),
+			Table:          row["mysql_table"].ToString(),
+			Schema:         row["mysql_schema"].ToString(),
+			SQL:            row["migration_statement"].ToString(),
+			UUID:           row["migration_uuid"].ToString(),
+			Strategy:       schema.DDLStrategy(row["strategy"].ToString()),
+			Options:        row["options"].ToString(),
+			Status:         schema.OnlineDDLStatus(row["migration_status"].ToString()),
+			Retries:        row.AsInt64("retries", 0),
+			TabletAlias:    row["tablet"].ToString(),
+			RequestContext: row["migration_context"].ToString(),
 		}
 		{
 			// We strip out any VT query comments because our simplified parser doesn't work well with comments

go/vt/vttablet/onlineddl/schema.go

@@ -63,6 +63,7 @@ const (
 	alterSchemaMigrationsTableLogFile            = "ALTER TABLE _vt.schema_migrations add column log_file varchar(1024) NOT NULL DEFAULT ''"
 	alterSchemaMigrationsTableRetainArtifacts    = "ALTER TABLE _vt.schema_migrations add column retain_artifacts_seconds bigint NOT NULL DEFAULT 0"
 	alterSchemaMigrationsTablePostponeCompletion = "ALTER TABLE _vt.schema_migrations add column postpone_completion tinyint unsigned NOT NULL DEFAULT 0"
+	alterSchemaMigrationsTableContextIndex       = "ALTER TABLE _vt.schema_migrations add KEY migration_context_idx (migration_context(64))"
 
 	sqlInsertMigration = `INSERT IGNORE INTO _vt.schema_migrations (
 		migration_uuid,
@@ -268,6 +269,17 @@ const (
 			completed_timestamp DESC
 		LIMIT 1
 	`
+	sqlSelectCompleteMigrationsByContextAndSQL = `SELECT
+			migration_uuid,
+			strategy
+		FROM _vt.schema_migrations
+		WHERE
+			migration_status='complete'
+			AND keyspace=%a
+			AND migration_context=%a
+			AND migration_statement=%a
+		LIMIT 1
+	`
 	sqlSelectCountReadyMigrations = `SELECT
 			count(*) as count_ready
 		FROM _vt.schema_migrations
@@ -558,4 +570,5 @@ var ApplyDDL = []string{
 	alterSchemaMigrationsTableLogFile,
 	alterSchemaMigrationsTableRetainArtifacts,
 	alterSchemaMigrationsTablePostponeCompletion,
+	alterSchemaMigrationsTableContextIndex,
 }