Re: Retrieving multiple error messages via libpq

I am working on a client that interfaces to the database via libpq, but cannot see how to get all error messages in some cases.

For testing purposes, I created the following table:

CREATE TABLE IdOnly
(
id INTEGER PRIMARY KEY
);

When I submit the following SQL statement for execution via the psql client:

'BEGIN TRANSACTION; INSERT INTO IdOnly (id) VALUES (40); INSERT INTO IdOnly (id) VALUES (21); INSERT INTO IdOnly (id) VALUES (42); COMMIT TRANSACTION;'

I get the following error messages (this failure is expected):

ERROR: duplicate key violates unique constraint "idonly_pkey"
ERROR: current transaction is aborted, commands ignored until end of transaction block

However, when retreiving the error message via PQresultErrorMessage(), I get:
ERROR: duplicate key violates unique constraint "idonly_pkey"

and through PQresultErrorField(, PGresult*, PG_DIAG_MESSAGE_PRIMARY ), I get only:
duplicate key violates unique constraint "idonly_pkey"

Calling PQresultErrorField( PGresult*, PG_DIAG_MESSAGE_DETAIL )" returns no additional information.

How is the additional error message retrieved?

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Jeffrey Brendecke <yakhki(at)yahoo(dot)de> writes:
> When I submit the following SQL statement for execution via the psql client:

> 'BEGIN TRANSACTION; INSERT INTO IdOnly (id) VALUES (40); INSERT INTO IdOnly (id) VALUES (21); INSERT INTO IdOnly (id) VALUES (42); COMMIT TRANSACTION;'

> I get the following error messages (this failure is expected):

> ERROR: duplicate key violates unique constraint "idonly_pkey"
> ERROR: current transaction is aborted, commands ignored until end of transaction block

> However, when retreiving the error message via PQresultErrorMessage(), I get:
> ERROR: duplicate key violates unique constraint "idonly_pkey"

> How is the additional error message retrieved?

It isn't, because there isn't any additional message. When you submit
multiple commands in a single PQexec string (as I suspect you did),
the backend abandons processing the string as soon as there's one error.
psql, however, chops up its input at semicolons and submits each command
as a separate PQexec.

regards, tom lane