COPY a query resultset to external file

[sunng87]

What problem does the new feature solve?

Currently we can only copy entire table to an external file, for some scenarios, we would like to add a where filter, or combine data from multiple tables.

What does the feature do?

Add support for SQL syntax like:

COPY (SELECT * FROM tbl WHERE ...) TO '/xxx/xxx/output.parquet' WITH (FORMAT = 'parquet');

Similar approaches:

COPY TO can also copy the results of a SELECT query.

• https://www.postgresql.org/docs/current/sql-copy.html
• https://ieftimov.com/posts/postgresql-copy/#using-a-select-query

Implementation challenges

No response