Re: returning the number of rows output by a copy command from a function

On 01/16/2013 08:30 AM, James Sharrett wrote:
> I have a function that generates a table of records and then a SQL
> statement that does a COPY into a text file. I want to return the
> number of records output into the text file from my function. The
> number of rows in the table is not necessarily the number of rows in the
> file due to summarization of data in the table on the way out. Here is
> a very shortened version of what I'm doing:
>
>
> CREATE OR REPLACE FUNCTION export_data(list of parameters)
> RETURNS integer AS
> $BODY$
>
> declare
> My variables
>
> Begin
>
> { A lot of SQL to build and populate the table of records to export}
>
>
> strSQL := 'copy (select MyColumns from MyExportTable) to MyFile.csv with
> CSV HEADER;';
> Execute strSQL;
>
> Return 0;
>
> end
> $BODY$
> LANGUAGE plpgsql VOLATILE
>
> strSQL gets dynamically generated so it's not a static statement.
>
> This all works exactly as I want. But when I try to get the row count
> back out I cannot get it. I've tried the following:
>
> 1.
> strSQL := 'copy (select MyColumns from MyExportTable) to MyFile.csv with
> CSV HEADER;';
> Execute strSQL into export_count;
>
> Return export_count;
>
> This give me an error saying that I've tried to use the INTO statement
> with a command that doesn't return data.
>
>
> 2.
> strSQL := 'copy (select MyColumns from MyExportTable) to MyFile.csv with
> CSV HEADER;';
> Execute strSQL;
>
> Get diagnostics export_count = row_count;
>
> This always returns zero.
>
> 3.
> strSQL := 'copy (select MyColumns from MyExportTable) to MyFile.csv with
> CSV HEADER;';
> Execute strSQL;
>
> Return row_count;
>
> This returns a null.
>
> Any way to do this?

If it helps:
http://www.postgresql.org/docs/9.2/interactive/sql-copy.html
"
On successful completion, a COPY command returns a command tag of the form

COPY count
The count is the number of rows copied.
"

So it looks like you will need to parse the string for the count.

>
>
> Thanks in advance,
> James
>

--
Adrian Klaver
adrian(dot)klaver(at)gmail(dot)com