cherry-pick #19392 to release-4.0

Signed-off-by: crazycs520 crazycs520@gmail.com

What problem does this PR solve?

Close #18566 (comment)

When tidb log enables desensitization (set @@global.tidb_log_desensitization = 1;), the slow-log and log may still out put the previous statement that doesn't desensitization:

before

...
# Prev_stmt: insert into t values (1,1),(2,2),(3,3),(4,4),(5,5)
commit;

this PR

...
# Prev_stmt: insert into t values ( ... ) , ( ... ) , ( ... ) , ( ... ) , ( ... )
commit;

Related changes

• Need to cherry-pick to the release branch

Check List

Tests

• Unit test
• Manual test

set @@tidb_slow_log_threshold=0;
begin;insert into t values (1,1),(2,2),(3,3),(4,4),(5,5); 
commit;
set @@tidb_slow_log_threshold=100;
-- Then check the tidb-slow-log file.

Side effects

• Performance regression
  • Consumes more CPU

Release note

• Fix log desensitization bug in prestmt