plan: rewrite exact like expression to equal condition

[hhu-cc]

What problem does this PR solve?

Fix #8962

What is changed and how it works?

rewrite such kind of like function to equal function.

Check List

Tests

• Unit test

Related changes

• Need to cherry-pick to the release branch

[codecov-io]

Codecov Report

Merging #9071 into master will increase coverage by 0.01%.
The diff coverage is 90%.

@@            Coverage Diff             @@
##           master    #9071      +/-   ##
==========================================
+ Coverage   67.19%   67.21%   +0.01%     
==========================================
  Files         371      371              
  Lines       76958    76982      +24     
==========================================
+ Hits        51711    51742      +31     
+ Misses      20624    20618       -6     
+ Partials     4623     4622       -1

Impacted Files	Coverage Δ
util/stringutil/string_util.go	98.51% <100%> (+0.05%)	⬆️
planner/core/expression_rewriter.go	73.78% <88%> (+0.2%)	⬆️
util/ranger/points.go	77.35% <0%> (-1.48%)	⬇️
util/ranger/checker.go	63.15% <0%> (-1.32%)	⬇️
executor/executor.go	67.03% <0%> (+0.13%)	⬆️
executor/index_lookup_join.go	77.91% <0%> (+0.63%)	⬆️
expression/schema.go	94.95% <0%> (+0.84%)	⬆️
ddl/delete_range.go	77.77% <0%> (+2.64%)	⬆️
store/tikv/scan.go	77.31% <0%> (+3.36%)	⬆️
util/systimemon/systime_mon.go	100% <0%> (+20%)	⬆️

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[winoros]

Thanks for your contribution!

[winoros]

Actually, you just need to check whether er.ctxStack[l-1] is a string without regex pattern.

[hhu-cc]

@winoros when pattern string contains escape character , we should use the compiled result of the pattern string in the equal condition, eg: a LIKE 'ab\_c' should rewrite to a = 'ab_c' .
So, we can not just check whether er.ctxStack[l-1] is a string without regex pattern.

[winoros]

We need to add ast.Like to expression.UnCacheableFunctions?

[eurekaka]

LGTM

[eurekaka]

We need to add ast.Like to expression.UnCacheableFunctions?

Any specific reason?

[winoros]

@hhxcc @eurekaka
This rewriting changes the expression structure. So when prepare cache enabled, it will produce wrong result.

create table t(a varchar(10));
insert into t values('bbb');
prepare stmt from 'select * from t where concat(a, "b") like ?';
set @a='bbb';
execute stmt using @a;
set @a='b%';
execute stmt using @a;

The second time it use the physical plan cached by the first time then return wrong result.

[winoros]

lgtm
Thanks for your contribution!

[winoros]

/run-all-tests