canal_json don't support nil value for uint64

[maxshuang]

What did you do?

1. Setup kafka inetgration test
2. Create table t1(id int primary key, c1 unsigned int);
3. insert into t1(id) values(1);

What did you expect to see?

kafka sink work normally

What did you see instead?

Error like:
[2022/03/01 18:27:11.489 +08:00] [PANIC] [canal.go:167] [“unsigned value not in type uint64”] [column="{“name”:“mch_id”,“type”:8,“flag”:193,“value”:null}"]

Detail:
trigger senarios:
column define default null at creating + insert without explicit column

tiflow/cdc/entry/mounter.go

Line 526 in 9fdebd6

if !mysql.HasNotNullFlag(col.Flag) {

tiflow/cdc/sink/codec/canal.go

Line 166 in 9fdebd6

switch v := c.Value.(type) {

Versions of the cluster

Upstream TiDB cluster version (execute SELECT tidb_version(); in a MySQL client):

v5.4.0

Upstream TiKV version (execute tikv-server --version):

v5.4.0

TiCDC version (execute cdc version):

v5.4.0

[3AceShowHand]

[column="{“name”:“mch_id”,“type”:8,“flag”:193,“value”:null}"]

Flag = 193 = 128 + 64 + 1 == UnsignedFlag ｜ NullableFlag ｜ BinaryFlag