```
EXPORT TABLE xxx
...
PROPERTIES
(
"label" = "mylabel",
...
);
```
And than user can use label to get the info by SHOW EXPORT stmt:
```
show export from db where label="mylabel";
```
For compatibility, if not specified, a random label will be used. And for history jobs, the label will be "export_job_id";
Not like LOAD stmt, here we specify label in `properties` because this will not cause grammatical conflicts,
and there is no need to modify the meta version of the metadata.
fcd15edbf9