What problem does this PR solve?

Issue Number: close #35067

Problem Summary:

What is changed and how it works?

Set paging when building the distsql request, for all executors.
In the past we only do that for IndexLoopUp.

There is still a switch tidb_enable_paging to control the behavior. The default value is still false.
I want coprocessor paging to be the default implementation for all cases, but let's do it step by step.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

mysql> select count(*) from sbtest1;
+----------+
| count(*) |
+----------+
|  7425577 |
+----------+
1 row in set (0.44 sec)

Use this PR, and then set @@tidb_enable_paging=1 to see the difference:

mysql -h 127.0.0.1 -u root -P 4000  -e 'select * from  (select * from sbtest.sbtest1 union all select * from sbtest.sbtest2 union all select * from sbtest.sbtest3 union all select * from sbtest.sbtest4 union all select * from sbtest.sbtest5 union all select * from sbtest.sbtest6 union all select * from sbtest.sbtest7 union all select * from sbtest.sbtest8)' > /dev/null

mysql -h 127.0.0.1 -u root -P 4000  -e 'set @@tidb_enable_paging=1; select * from  (select * from sbtest.sbtest1 union all select * from sbtest.sbtest2 union all select * from sbtest.sbtest3 union all select * from sbtest.sbtest4 union all select * from sbtest.sbtest5 union all select * from sbtest.sbtest6 union all select * from sbtest.sbtest7 union all select * from sbtest.sbtest8)' > /dev/null

Before vs After

It reduce a lot memory footprint ... although we need to handle channel capacity #34849 to completely solve the problem.

• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

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None