```
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.
1. Support where clause in export stmt which only export selected rows.
The syntax is following:
Export table [table name]
where [expr]
To xxx
xxxx
It will filter table rows.
Only rows that meet the where condition can be exported.
2. Support utf8 separator
3. Support export to local
The syntax is following:
Export table [table name]
To (file:///xxx/xx/xx)
If user export rows to local, the broker properties is not requried.
User only need to create a local folder to store data, and fill in the path of the folder starting with file://
Change-Id: Ib7e7ece5accb3e359a67310b0bf006d42cd3f6f5
