How to get the number of deleted rows in PostgreSQL?

Question

I am looking for a way to return the number of rows affected by a DELETE clause in PostgreSQL. The documentation states that;

On successful completion, a DELETE command returns a command tag of the form

DELETE count

The count is the number of rows deleted. If count is 0, no rows matched the condition (this is not considered an error).

If the DELETE command contains a RETURNING clause, the result will be similar to that of a SELECT statement containing the columns and values defined in the RETURNING list, computed over the row(s) deleted by the command.

But I am having trouble finding a good example of it. Can anyone help me with this, how can I find out how many rows were deleted?

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EDIT: I accepted Milen's solution, but I wanted to present an alternative that I have found later. It can be found in here, explained under 38.5.5. Obtaining the Result Status title.

Answer 1

You need the PQcmdTuples function from libpq. Which in PHP for example is wrapped as pg_affected_rows.

Answer 2

You can use RETURNING clause:

DELETE FROM table WHERE condition IS TRUE RETURNING *;

After that you just have to check number of rows returned. You can streamline it with CTE:

WITH deleted AS (DELETE FROM table WHERE condition IS TRUE RETURNING *) SELECT count(*) FROM deleted;

This should return just the number of deleted rows.

Answer 3

This should be simple in Java.

Statement stmt = connection.createStatement();
int rowsAffected = stmt.executeUpdate("delete from your_table");
System.out.println("deleted: " + rowsAffected);

See java.sql.Statement.

Answer 4

GET DIAGNOSTICS is used to display number of modified/deleted records.

Sample code

CREATE OR REPLACE FUNCTION fnName()
  RETURNS void AS
$BODY$
        declare
         count numeric;
       begin
              count := 0;
            LOOP
             -- condition here update or delete;
             GET DIAGNOSTICS count = ROW_COUNT;
             raise notice 'Value: %', count;
             end loop;
        end;
$BODY$a

Answer 5

in Python using psycopg2, the rowcount attribute can be used. Here is an example to find out how many rows were deleted...

cur = connection.cursor()
try:
    cur.execute("DELETE FROM table WHERE col1 = %s", (value,))
    connection.commit()
    count = cur.rowcount
    cur.close()
    print("A total of %s rows were deleted." % count)
except:
    connection.rollback()
    print("An error as occurred, No rows were deleted")