About a test sql statement

To complete a recent query from the database results in a lot of features

Start direct all select out

Dahon select this operation is to say no too long

Then check the batch inserted into the batch program

It comes to how to write a statement

Because the frame with the gorm carrying the id of a primary key

So the natural step is to use the id and to select the corresponding results

But explain the execution of the statement found great rows

And behind the limit should be the same figures under ideal conditions

Because of limited time only step is indeed the case

Then I began to suspect that the execution speed of this statement

After a while the investigation

I decided to compare two different statements

One is to use offset restrictions

SELECT * FROM `task_file_result`  WHERE (step = 5) LIMIT 100 OFFSET 100000;

One is used where restrictions

SELECT * FROM `task_file_result`  WHERE (id > 100000 and step = 5) LIMIT 100;

Types of statements can achieve the same effect

I first built a table of 1000w

RDS.CreateTable(TaskFileResult{})
insertList := make([]interface{}, 0)
for i := 1; i <= 1000000; i++ {
  res := ""
  for j := 1; j <= 10; j++ {
	res += "x"
	insertList = append(insertList, TaskFileResult{
	  TaskID:     1,
	  TaskFileID: uint(i),
	  Step:       uint(j),
	})
  }
}

if err = run.Insert(RDS, insertList, 5000); err != nil {
  println(err)
}

Then supplement statement

  offset := 100000
  limit := 100
  chooseStep := 5
  RDS.Table("task_file_result").Where("step = ?", chooseStep).Limit(limit).Offset(offset).Find(&resultList)
  RDS.Table("task_file_result").Where("id > ? and step = ?", offset, chooseStep).Limit(limit).Find(&resultList)

  offset = 500000
  RDS.Table("task_file_result").Where("step = ?", chooseStep).Limit(limit).Offset(offset).Find(&resultList)
  RDS.Table("task_file_result").Where("id > ? and step = ?", offset, chooseStep).Limit(limit).Find(&resultList)

  offset = 1000000
  RDS.Table("task_file_result").Where("step = ?", chooseStep).Limit(limit).Offset(offset).Find(&resultList)
  RDS.Table("task_file_result").Where("id > ? and step = ?", offset, chooseStep).Limit(limit).Find(&resultList)

Finally, where the results expressed better

It seems a lot of row sweep speed may soon be possible because this row with the two fields was increasing

About a test sql statement

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