chore: fix first review

Author: cyrinux

doc/command-line-flags.md

@@ -286,6 +286,11 @@ Defaults to 1000 (1 second). Configures the HTTP throttler check timeout in mill
 
 Makes the _old_ table include a timestamp value. The _old_ table is what the original table is renamed to at the end of a successful migration. For example, if the table is `gh_ost_test`, then the _old_ table would normally be `_gh_ost_test_del`. With `--timestamp-old-table` it would be, for example, `_gh_ost_test_20170221103147_del`.
 
+### optimizer-switch
+
+Default is "", this allow to override a `SET GLOBAL optimizer_switch=key=value` by one set on the session with `SET SESSION optimizer_switch=key=value`.
+You can find values on https://dev.mysql.com/doc/refman/8.0/en/switchable-optimizations.html for example.
+
 ### tungsten
 
 See [`tungsten`](cheatsheet.md#tungsten) on the cheatsheet.

go/logic/applier.go

@@ -49,7 +49,7 @@ func newDmlBuildResultError(err error) *dmlBuildResult {
 	}
 }
 
-func (this *Applier) setOptimizer(tx *gosql.Tx) error {
+func (this *Applier) setOptimizerSwitch(tx *gosql.Tx) error {
 	if this.migrationContext.OptimizerSwitch == "" {
 		return nil
 	}
@@ -486,11 +486,6 @@ func (this *Applier) readMigrationMinValues(tx *gosql.Tx, uniqueKey *sql.UniqueK
 		return err
 	}
 
-	err = this.setOptimizer(tx)
-	if err != nil {
-		return err
-	}
-
 	rows, err := tx.Query(query)
 	if err != nil {
 		return err
@@ -516,11 +511,6 @@ func (this *Applier) readMigrationMaxValues(tx *gosql.Tx, uniqueKey *sql.UniqueK
 		return err
 	}
 
-	err = this.setOptimizer(tx)
-	if err != nil {
-		return err
-	}
-
 	rows, err := tx.Query(query)
 	if err != nil {
 		return err
@@ -566,6 +556,11 @@ func (this *Applier) ReadMigrationRangeValues() error {
 	}
 	defer tx.Rollback()
 
+	err = this.setOptimizerSwitch(tx)
+	if err != nil {
+		return err
+	}
+
 	if err := this.readMigrationMinValues(tx, this.migrationContext.UniqueKey); err != nil {
 		return err
 	}