String length exceeds DDL length: Truncate string length to Redshift max

Since Redshift only support 65535 characters if the col as more, then trucate it to Redshift max.

```
colname         | summary
type            | varchar
col_length      | 65535
err_code        | 1204
err_reason      | String length exceeds DDL length
```

At present this does not happens, and breaks table load. Also fixes the source should be the permanent fix.