Обсуждение: BUG #15645: \COPY command not printing output in batch mode

The following bug has been logged on the website:

Bug reference:      15645
Logged by:          placebo
Email address:      sandeshyapuram@gmail.com
PostgreSQL version: 11.2
Operating system:   Linux/Mac
Description:

I am trying to truncate a table and copy data into the same table using
\copy. In this process, I need to print number of rows deleted and copied.

I am using this command:
echo -e "begin; delete from test; \\\copy test from test.csv CSV HEADER;
end;" | psql -hlocalhost -dpostgres -Upostgres

Expected output:
---------------------
BEGIN
DELETE 4
COPY 2
COMMIT
---------------------

Actual output:
---------------------
BEGIN
DELETE 4
COMMIT
---------------------

As you can see, the output clearly is missing the copy count.

Interestingly, this works if I try the following command:
echo -e "begin;\ndelete from test;\n\\\copy test from test.csv CSV
HEADER;\nend;" | psql -hlocalhost -dpostgres -Upostgres

Why do I need to add a new line character when I am already using the
separator?

    PG Bug reporting form wrote:

> I am trying to truncate a table and copy data into the same table using
> \copy. In this process, I need to print number of rows deleted and copied.
>
> I am using this command:
> echo -e "begin; delete from test; \\\copy test from test.csv CSV HEADER;
> end;" | psql -hlocalhost -dpostgres -Upostgres

As answered at [1] where it was asked as a question,
it's not a bug, but the effect of \copy processing the whole line,
as documented:

  "Unlike most other meta-commands, the entire remainder of the line
   is always taken to be the arguments of \copy"

plus the fact that from the COPY + END commands executed in the
same compound statement, only the last result is handled/displayed
by psql, which is also known and documented.

Suggested workarounds:
1. use psql -1 instead of adding your own BEGIN/END commands.
2. use the heredoc syntax for multi-line SQL scripts embedded into
shell commands.

[1] https://dba.stackexchange.com/questions/230230/

Best regards,
--
Daniel Vérité
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Twitter: @DanielVerite