types: fix string to integer cast

[amyangfei]

What problem does this PR solve?

part of #11223 fix issue #11179

What is changed and how it works?

add a ConvertStrToIntStrict to control the way we convert string to int.

• if ConvertStrToIntStrict is false, the cast way is getValidFloatPrefix, then floatStrToIntStr
• otherwise, we cast string to integer prefix in a strict way, only extract 0-9, (+ or - in first bit).

only set ConvertStrToIntStrict to true in select/explain context, which is compatible with MySQL

following is the cast behavior in insert of MySQL 5.7

mysql> select version();
+------------+
| version()  |
+------------+
| 5.7.24-log |
+------------+
1 row in set (0.01 sec)

mysql> use test;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> drop table if exists t;                                                                                                                                                    Query OK, 0 rows affected (0.04 sec)

mysql> create table t (id int);
Query OK, 0 rows affected (0.06 sec)

mysql> insert into t values ('1e2'), ('10e-1'), ('0.123e3');
Query OK, 3 rows affected (0.03 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> select * from t;
+------+
| id   |
+------+
|  100 |
|    1 |
|  123 |
+------+
3 rows in set (0.00 sec)

Check List

Tests

• Unit test
• Integration test

Related changes

• Need to cherry-pick to the release branch

[codecov]

Codecov Report

Merging #11295 into master will decrease coverage by 0.47%.
The diff coverage is 93.1%.

@@            Coverage Diff             @@
##           master   #11295      +/-   ##
==========================================
- Coverage   81.84%   81.36%   -0.48%     
==========================================
  Files         424      424              
  Lines       93108    90833    -2275     
==========================================
- Hits        76202    73906    -2296     
- Misses      11602    11612      +10     
- Partials     5304     5315      +11

Impacted Files	Coverage Δ
sessionctx/stmtctx/stmtctx.go	99.19% <ø> (-0.27%)	⬇️
planner/core/point_get_plan.go	85.24% <0%> (-7.64%)	⬇️
executor/executor.go	78.75% <100%> (-0.27%)	⬇️
types/convert.go	93.03% <100%> (-1.52%)	⬇️
types/datum.go	83.87% <100%> (ø)	⬆️
store/tikv/gcworker/gc_worker.go	61.33% <0%> (-6.66%)	⬇️
store/tikv/snapshot.go	76.66% <0%> (-5.65%)	⬇️
store/tikv/lock_resolver.go	43.75% <0%> (-5.15%)	⬇️
store/tikv/rawkv.go	66.83% <0%> (-4.19%)	⬇️
... and 34 more

---

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[amyangfei]

/run-all-tests tidb-test=pr/863

[qw4990]

LGTM

[amyangfei]

PTAL @zz-jason

[zz-jason]

should we return a warning?

[amyangfei]

warning has been added in truncated error handler

[zz-jason]

if len(str) == 0, validLen can still be zero, but it's not truncated?

[amyangfei]

I checked some behavior in MySQL, and get the following result

mysql> show create table t;                                                                                                                                                                                                                   +-------+--------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                             |
+-------+--------------------------------------------------------------------------------------------------------------------------+
| t     | CREATE TABLE `t` (
  `id` int(11) DEFAULT NULL,
  `val` varchar(255) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
+-------+--------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql> insert into t values ('', 'a');
ERROR 1366 (HY000): Incorrect integer value: '' for column 'id' at row 1
mysql> insert into t values ('0', 'a'), ('1', 'a');
Query OK, 2 rows affected (0.01 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> select * from t where id = '';
+------+------+
| id   | val  |
+------+------+
|    0 | a    |
+------+------+
1 row in set (0.00 sec)

mysql> update t set val = 'b' where id = '';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from t;
+------+------+
| id   | val  |
+------+------+
|    0 | b    |
|    1 | a    |
+------+------+
2 rows in set (0.00 sec)

mysql> select * from t where id = '1.0';
+------+------+
| id   | val  |
+------+------+
|    1 | a    |
+------+------+
1 row in set (0.00 sec)

mysql> update t set val = 'c' where id = '1.0';
Query OK, 1 row affected (0.01 sec)
Rows matched: 1  Changed: 1  Warnings: 0

[amyangfei]

so in select and update context, '' will be cast to 0 without no warnings. Added these two conditions in the first logic of getValidFloatPrefix

[amyangfei]

/run-all-tests

[amyangfei]

/run-all-tests tidb-test=pr/863

[amyangfei]

/run-all-tests tidb-test=pr/863

[amyangfei]

/run-unit-tests

[zz-jason]

LGTM

[sre-bot]

cherry pick to release-2.1 failed

[sre-bot]

cherry pick to release-3.0 failed

[XuHuaiyu]

@amyangfei Please cherry-pick this to release-2.1