executor: fix scatter region timeout issues and "show processlist" display issues

[zimulala]

What problem does this PR solve?

• Fix a single scatter region timeout does not exit

• When processing "split table/index", the result of executing "show processlist" is as follows:

+------+------+-----------+------+---------+------+-------+------------------+
| Id   | User | Host      | db   | Command | Time | State | Info             |
+------+------+-----------+------+---------+------+-------+------------------+
|    1 | root | 127.0.0.1 | test | Query   |    0 | 2     | show processlist |
|    2 | root | 127.0.0.1 | test | Sleep   |  552 | 2     | NULL             |
+------+------+-----------+------+---------+------+-------+------------------+

What is changed and how it works?

• Add a check when encounter timeout error. And update logs.

• Put the operations of splitting and scattering region into Next. After the PR:

tidb> show processlist;
+------+------+-----------+------+---------+------+-------+------------------------------------------------------+
| Id   | User | Host      | db   | Command | Time | State | Info                                                 |
+------+------+-----------+------+---------+------+-------+------------------------------------------------------+
|    2 | root | 127.0.0.1 | test | Query   |    2 | 2     | split table x between (0) and (1000000) regions 1000 |
|    1 | root | 127.0.0.1 | test | Query   |    0 | 2     | show processlist                                     |
+------+------+-----------+------+---------+------+-------+------------------------------------------------------+
2 rows in set (0.00 sec)

Check List

Tests

• Unit test

[codecov]

Codecov Report

Merging #12057 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master    #12057   +/-   ##
=========================================
  Coverage   81.492%   81.492%           
=========================================
  Files          457       457           
  Lines       101448    101448           
=========================================
  Hits         82672     82672           
  Misses       12971     12971           
  Partials      5805      5805

[zimulala]

PTAL @crazycs520 @bb7133 @winkyao

[bb7133]

Why moving getSplitIdxKeys() to Open?

[zimulala]

Because we do some checks in getSplitIdxKeys, if put it to Next some test cases will be failed and I think best to put it before Next.

[crazycs520]

LGTM

[bb7133]

LGTM

[sre-bot]

/run-all-tests

[zimulala]

Related PR #6861