Support flexible data exporting demand in copy to

[MichaelScofield]

What problem does the new feature solve?

copy to can only export data within a time range, which is not sufficient for various data exporting demand sometimes.

What does the feature do?

To meet the various data exporting demand, I think it's best for user to write queries in the copy to statement. Like this:

COPY tbl TO '/xxx/xxx/output.parquet' WITH (FORMAT = 'parquet', Q = 'select a, b from tbl where c = 1');

Only the data populated by the "Q" is exported. In this way, user could express his data exporting demand in the query, which is very flexible.

Implementation challenges

No response