hotfix: set sortByPK to false and add backoff retry time.

[3pointer]

What problem does this PR solve?

What is changed and how it works?

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Possible performance regression
• Increased code complexity
• Breaking backward compatibility

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation

Release note

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[lichunzhu]

SortByPK won't sort the data in memory. Here is the plan:

mysql> explain select a from t1 order by a;
+--------------------+------------+------+----------------------------------------------+
| id                 | count      | task | operator info                                |
+--------------------+------------+------+----------------------------------------------+
| TableReader_11     | 8480000.00 | root | data:TableScan_10                            |
| └─TableScan_10     | 8480000.00 | cop  | table:t1, range:[-inf,+inf], keep order:true |
+--------------------+------------+------+----------------------------------------------+
2 rows in set (0.01 sec)

mysql> explain select b from t1 order by b;
+---------------------+------------+------+-----------------------------------------------+
| id                  | count      | task | operator info                                 |
+---------------------+------------+------+-----------------------------------------------+
| Sort_4              | 8480000.00 | root | test.t1.b:asc                                 |
| └─TableReader_8     | 8480000.00 | root | data:TableScan_7                              |
|   └─TableScan_7     | 8480000.00 | cop  | table:t1, range:[-inf,+inf], keep order:false |
+---------------------+------------+------+-----------------------------------------------+
3 rows in set (0.00 sec)

mysql> explain select * from t3 order by _tidb_rowid;
+----------------------+------------+------+----------------------------------------------+
| id                   | count      | task | operator info                                |
+----------------------+------------+------+----------------------------------------------+
| Projection_5         | 8000000.00 | root | test.t3.a, test.t3.b, test.t3.c, test.t3.d   |
| └─TableReader_11     | 8000000.00 | root | data:TableScan_10                            |
|   └─TableScan_10     | 8000000.00 | cop  | table:t3, range:[-inf,+inf], keep order:true |
+----------------------+------------+------+----------------------------------------------+
3 rows in set (0.01 sec)

mysql> explain select * from t3;
+-------------------+------------+------+-----------------------------------------------+
| id                | count      | task | operator info                                 |
+-------------------+------------+------+-----------------------------------------------+
| TableReader_5     | 8000000.00 | root | data:TableScan_4                              |
| └─TableScan_4     | 8000000.00 | cop  | table:t3, range:[-inf,+inf], keep order:false |
+-------------------+------------+------+-----------------------------------------------+
2 rows in set (0.00 sec)