feat: dryrun migration should only print not-select sqls

[shushenghong]

some driver migration may run select querys to compare schemal change, like postgresql. we should only print not-select sqls when dry run migration

[a631807682]

The select statement is executed by queryTx and will not be printed. The logs you see are all printed by Trace. https://github.com/go-gorm/gorm/blob/master/migrator/migrator.go#L122
In fact, I don't agree with using fmt.Println here. It is equivalent to searching for the record I need in a lot of logs, and it may be inconsistent with the output of the original log settings, and level control cannot be used.
I think we can provide log implementation for migration through documentation, such as writing the change log to a file through the log.

[shushenghong]

postgresql dry run mode still need to run many select method and will printout by this method

[jinzhu]

gorm/migrator/migrator.go

Lines 112 to 114 in 3e2c4fc

	if m.DB.DryRun {
	queryTx.DryRun = false
	execTx = m.DB.Session(&gorm.Session{Logger: &printSQLLogger{Interface: m.DB.Logger}})

It is expected to work in dry run mode.