PostgreSQL Exception Handling
I am new to PostgreSQL. Could anybody please correct this query.
BEGIN TRANSACTION;
BEGIN;
CREATE TABLE "Logs"."Events"
(
EventId BIGSERIAL NOT NULL PRIMARY KEY,
PrimaryKeyId bigint NOT NULL,
EventDateTime date NOT NULL DEFAULT(now()),
Action varchar(12) NOT NULL,
UserId integer NOT NULL REFERENCES "Office"."Users"(UserId),
PrincipalUserId varchar(50) NOT NULL DEFAULT(user)
);
CREATE TABLE "Logs"."EventDetails"
(
EventDetailId BIGSERIAL NOT NULL PRIMARY KEY,
EventId bigint NOT NULL REFERENCES "Logs"."Events"(EventId),
Resource varchar(64) NOT NULL,
OldVal varchar(4000) NOT NULL,
NewVal varchar(4000) NOT NULL
);
COMMIT TRANSACTION;
RAISE NOTICE 'Task completed sucessfully.'
EXCEPTION;
ROLLBACK TRANSACTION;
RAISE ERROR @ErrorMessage, @LineNumber, @ErrorState --how to catch errors and display them????
END;
Questions:
- How to print a message like 'PRINT' in T-SQL?
- How to raise errors with exception information?
Solution 1:
To catch the error message and its code:
do $$
begin
create table yyy(a int);
create table yyy(a int); -- this will cause an error
exception when others then
raise notice 'The transaction is in an uncommittable state. '
'Transaction was rolled back';
raise notice '% %', SQLERRM, SQLSTATE;
end; $$
language 'plpgsql';
Haven't found the line number yet
UPDATE April, 16, 2019
As suggested by Diego Scaravaggi, for Postgres 9.2 and up, use GET STACKED DIAGNOSTICS:
do language plpgsql $$
declare
v_state TEXT;
v_msg TEXT;
v_detail TEXT;
v_hint TEXT;
v_context TEXT;
begin
create table yyy(a int);
create table yyy(a int); -- this will cause an error
exception when others then
get stacked diagnostics
v_state = returned_sqlstate,
v_msg = message_text,
v_detail = pg_exception_detail,
v_hint = pg_exception_hint,
v_context = pg_exception_context;
raise notice E'Got exception:
state : %
message: %
detail : %
hint : %
context: %', v_state, v_msg, v_detail, v_hint, v_context;
raise notice E'Got exception:
SQLSTATE: %
SQLERRM: %', SQLSTATE, SQLERRM;
raise notice '%', message_text; -- invalid. message_text is contextual to GET STACKED DIAGNOSTICS only
end; $$;
Result:
NOTICE: Got exception:
state : 42P07
message: relation "yyy" already exists
detail :
hint :
context: SQL statement "create table yyy(a int)"
PL/pgSQL function inline_code_block line 11 at SQL statement
NOTICE: Got exception:
SQLSTATE: 42P07
SQLERRM: relation "yyy" already exists
ERROR: column "message_text" does not exist
LINE 1: SELECT message_text
^
QUERY: SELECT message_text
CONTEXT: PL/pgSQL function inline_code_block line 33 at RAISE
SQL state: 42703
Aside from GET STACKED DIAGNOSTICS
is SQL standard-compliant, its diagnostics variables (e.g., message_text
) are contextual to GSD only. So if you have a field named message_text
in your table, there's no chance that GSD can interfere with your field's value.
Still no line number though.
Solution 2:
Use the DO statement, a new option in version 9.0:
DO LANGUAGE plpgsql
$$
BEGIN
CREATE TABLE "Logs"."Events"
(
EventId BIGSERIAL NOT NULL PRIMARY KEY,
PrimaryKeyId bigint NOT NULL,
EventDateTime date NOT NULL DEFAULT(now()),
Action varchar(12) NOT NULL,
UserId integer NOT NULL REFERENCES "Office"."Users"(UserId),
PrincipalUserId varchar(50) NOT NULL DEFAULT(user)
);
CREATE TABLE "Logs"."EventDetails"
(
EventDetailId BIGSERIAL NOT NULL PRIMARY KEY,
EventId bigint NOT NULL REFERENCES "Logs"."Events"(EventId),
Resource varchar(64) NOT NULL,
OldVal varchar(4000) NOT NULL,
NewVal varchar(4000) NOT NULL
);
RAISE NOTICE 'Task completed sucessfully.';
END;
$$;