Postgres Copy from Variable with CSV data

问题:

I know you can run a copy command like this from a file:

"COPY zip_codes FROM '/path/to/csv/ZIP_CODES.txt' DELIMITER ',' CSV;"

I'd like to copy csv data from a ruby variable so I can do like so

"COPY zip_codes FROM '#{csv_data}' DELIMITER ',' CSV;"

回答1:

That's not possible with the SQL COPY command. COPY only copies from a file or STDIN.

You can either write the content of the variable to a file or pipe it via STDIN. Only makes sense for more than a couple of rows.

---

I think I misunderstood your question before the update, you probably don't need this:

The file path can not be exchanged like other data items, and you can't use a prepared statement for that. Build the whole statement before executing or resort to dynamic SQL with a server-side function like:

CREATE OR REPLACE FUNCTION f_cp(_file text)
  RETURNS void AS
$BODY$
BEGIN
EXECUTE format($$COPY zip_codes FROM %L DELIMITER ',' CSV$$, $1);
END
$BODY$
  LANGUAGE plpgsql;

Call:

SELECT f_cp('/var/lib/postgres/sync/myfile.csv')

format() requires Postgres 9.1 or later.