ddl, util: Handle default values for generating column expressions when adding an index

[zimulala]

What problem does this PR solve?

Fix #9311
Before this PR:

tidb> create table t(id int primary key);
Query OK, 0 rows affected (0.01 sec)
tidb> insert into t values(1);
Query OK, 1 row affected (0.00 sec)
tidb> ALTER TABLE t ADD COLUMN d date DEFAULT '9999-12-31';
Query OK, 0 rows affected (0.02 sec)
tidb> ALTER TABLE t ADD COLUMN d1 date as (DATE_SUB(d, INTERVAL 31 DAY));
Query OK, 0 rows affected (0.02 sec)
tidb> ALTER TABLE t ADD INDEX idx_d(d1);
ERROR 1105 (HY000): cannot decode index value, because [types:1292]invalid time format: '{0 0 0 0 0 0 0}'
tidb> ALTER TABLE t ADD COLUMN id1 int as (id+1);
Query OK, 0 rows affected (0.02 sec)
tidb> ALTER TABLE t ADD INDEX idx1(id1); // The idx1's value is 0 in store. 
Query OK, 0 rows affected (0.02 sec)
tidb> select id1 from t use index(idx1); // The idx'1 value is 0, but we will do `cast(plus(test.t.id, 1))`.
+------+
| id1  |
+------+
|    2 |
+------+
1 row in set (0.00 sec)

Now:

tidb> create table t(id int primary key);
Query OK, 0 rows affected (0.01 sec)
tidb> insert into t values(1);
Query OK, 1 row affected (0.00 sec)
tidb> ALTER TABLE t ADD COLUMN d date DEFAULT '9999-12-31';
Query OK, 0 rows affected (0.02 sec)
tidb> ALTER TABLE t ADD COLUMN d1 date as (DATE_SUB(d, INTERVAL 31 DAY));
Query OK, 0 rows affected (0.02 sec)
tidb> ALTER TABLE t ADD INDEX idx_d(d1);
Query OK, 0 rows affected (0.07 sec)
tidb> ALTER TABLE t ADD COLUMN id1 int as (id+1);
Query OK, 0 rows affected (0.02 sec)
tidb> ALTER TABLE t ADD INDEX idx1(id1);
Query OK, 0 rows affected (0.02 sec)
tidb> select id1 from t use index(idx1);
+------+
| id1  |
+------+
|    2 |
+------+
1 row in set (0.00 sec)

What is changed and how it works?

Add default value and handle value to the row before evaluating the generated expression.

Check List

Tests

• Unit test

Code changes

• Has exported function/method change

Related changes

• Need to cherry-pick to the release branch

[zimulala]

/run-all-tests

[codecov-io]

Codecov Report

Merging #9371 into master will increase coverage by <.01%.
The diff coverage is 88.88%.

@@            Coverage Diff             @@
##           master    #9371      +/-   ##
==========================================
+ Coverage   67.41%   67.42%   +<.01%     
==========================================
  Files         373      373              
  Lines       78557    78557              
==========================================
+ Hits        52962    52966       +4     
+ Misses      20840    20837       -3     
+ Partials     4755     4754       -1

Impacted Files	Coverage Δ
ddl/index.go	80.45% <100%> (ø)	⬆️
util/admin/admin.go	65.85% <80%> (ø)	⬆️
expression/schema.go	93.75% <0%> (-0.79%)	⬇️
executor/distsql.go	71.78% <0%> (-0.46%)	⬇️
executor/executor.go	68.16% <0%> (+0.13%)	⬆️
executor/join.go	79.58% <0%> (+0.51%)	⬆️
store/tikv/scan.go	77.31% <0%> (+3.36%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 45f9d6a...0192452. Read the comment docs.

[zimulala]

PTAL @winkyao @crazycs520

[zimulala]

PTAL @winkyao @crazycs520

[crazycs520]

LGTM

[crazycs520]

/run-all-tests

[winkyao]

LGTM

[tiancaiamao]

LGTM