I understand that due to a lack of nested transaction support, it is not possible to use START TRANSACTION within a PL/PgSQL function. What I, however, do not understand is why I can't use SAVEPOINT either. I'm writing long test functions wherein, at the start of the function, I'd like to define all test data followed by a "SAVEPOINT fresh_test_data;". Will this become possible in the (near) future? I mean, savepoints are of limited use to me if they imply that I can't stick my tests in stored procedures.
On a side note: I've seen a comment on this list that the error message of trying to use a SAVEPOINT in PL/pgSQL isn't too clear (compared with the error message for using SAVEPOINT in an SQL function). I can second this. However, I noticed that the message is much clearer when you EXECUTE the SAVEPOINT command.
On 19 Dec 2006 07:05:10 -0800, "BigSmoke" <bigsm...@gmail.com> wrote:
> I understand that due to a lack of nested transaction support, it is > not possible to use START TRANSACTION within a PL/PgSQL function. What > I, however, do not understand is why I can't use SAVEPOINT either. I'm > writing long test functions wherein, at the start of the function, I'd > like to define all test data followed by a "SAVEPOINT > fresh_test_data;". Will this become possible in the (near) future? I > mean, savepoints are of limited use to me if they imply that I can't > stick my tests in stored procedures.
Use
BEGIN
...
EXCEPTION
...
END;
Blocks instead. The pl/pgsql exception handling is implemented on top of PostgreSQL's SAVEPOINT infrastructure. We are lacking user defined exception support, but you can raise generic errors with RAISE EXCEPTION.
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> On 19 Dec 2006 07:05:10 -0800, "BigSmoke" <bigsm...@gmail.com> wrote:
> > I understand that due to a lack of nested transaction support, it is > > not possible to use START TRANSACTION within a PL/PgSQL function. What > > I, however, do not understand is why I can't use SAVEPOINT either. I'm > > writing long test functions wherein, at the start of the function, I'd > > like to define all test data followed by a "SAVEPOINT > > fresh_test_data;". Will this become possible in the (near) future? I > > mean, savepoints are of limited use to me if they imply that I can't > > stick my tests in stored procedures.Use
> BEGIN
> ...
> EXCEPTION
> ...
> END;
> Blocks instead. The pl/pgsql exception handling is implemented on top > of PostgreSQL's SAVEPOINT infrastructure. We are lacking user defined > exception support, but you can raise generic errors with RAISE EXCEPTION.
I can't solve my problem with a BEGIN EXCEPTION END block because of what I do in these functions. Here's an example function.
CREATE OR REPLACE FUNCTION test_something() RETURNS VOID AS $$ BEGIN -- Define some test data
-- SAVEPOINT fresh_test_data; -- If only I could ...
IF some_test_assertion_fails THEN RAISE EXCEPTION 'Some informative message'; END IF;
-- ROLLBACK TO SAVEPOINT fresh_test_data; END; $$ LANGUAGE plpgsql;
In these functions, I raise an exception whenever a test fails. Now, If I want to create an implicit savepoint using BEGIN/END blocks around individual tests, I don't see how I can still sanely preserve this behavior without the most horrid of hacks. The following code is what I think I would need to do to emulate savepoints without direct access to them. :-( (I hope that I'm missing something.)
CREATE OR REPLACE FUNCTION test_something() RETURNS VOID AS $$ BEGIN -- Define some test data
BEGIN -- This is a useful test ;-) IF TRUE THEN RAISE EXCEPTION 'Aaargh! The test failed!'; END IF;
RAISE EXCEPTION '__dummy_restore_state__';
EXCEPTION WHEN raise_exception THEN IF SQLERRM != '__dummy_restore_state__' THEN RAISE EXCEPTION '%', SQLERRM; END IF; END; END; $$ LANGUAGE plpgsql;
> On Dec 19, 4:16 pm, maili...@oopsware.de (Bernd Helmle) wrote:
> > On 19 Dec 2006 07:05:10 -0800, "BigSmoke" <bigsm...@gmail.com> wrote:
> > > I understand that due to a lack of nested transaction support, it is > > > not possible to use START TRANSACTION within a PL/PgSQL function. What > > > I, however, do not understand is why I can't use SAVEPOINT either. I'm > > > writing long test functions wherein, at the start of the function, I'd > > > like to define all test data followed by a "SAVEPOINT > > > fresh_test_data;". Will this become possible in the (near) future? I > > > mean, savepoints are of limited use to me if they imply that I can't > > > stick my tests in stored procedures.Use
> > BEGIN
> > ...
> > EXCEPTION
> > ...
> > END;
> > Blocks instead. The pl/pgsql exception handling is implemented on top > > of PostgreSQL's SAVEPOINT infrastructure. We are lacking user defined > > exception support, but you can raise generic errors with RAISE EXCEPTION.I can't solve my problem with a BEGIN EXCEPTION END block because of > what I do in these functions. Here's an example function.
> CREATE OR REPLACE FUNCTION test_something() RETURNS VOID AS $$ > BEGIN > -- Define some test data
> -- SAVEPOINT fresh_test_data; -- If only I could ...
> IF some_test_assertion_fails THEN > RAISE EXCEPTION 'Some informative message'; > END IF;
> -- ROLLBACK TO SAVEPOINT fresh_test_data; > END; > $$ LANGUAGE plpgsql;
> In these functions, I raise an exception whenever a test fails. Now, If > I want to create an implicit savepoint using BEGIN/END blocks around > individual tests, I don't see how I can still sanely preserve this > behavior without the most horrid of hacks. The following code is what I > think I would need to do to emulate savepoints without direct access to > them. :-( (I hope that I'm missing something.)
> CREATE OR REPLACE FUNCTION test_something() RETURNS VOID AS $$ > BEGIN > -- Define some test data
> BEGIN > -- This is a useful test ;-) > IF TRUE THEN > RAISE EXCEPTION 'Aaargh! The test failed!'; > END IF;
> RAISE EXCEPTION '__dummy_restore_state__';
> EXCEPTION WHEN raise_exception THEN > IF SQLERRM != '__dummy_restore_state__' THEN > RAISE EXCEPTION '%', SQLERRM; > END IF; > END; > END; > $$ LANGUAGE plpgsql;
What would solve my problem is if there was a method to, at the end of a begin/end block, I could rollback the changes made in that block without having to raise an exception. Is it somehow possible to explicitly rollback to one of these savepoints which are created by begin/end blocks?
> On Dec 19, 5:00 pm, "BigSmoke" <bigsm...@gmail.com> wrote:
> > On Dec 19, 4:16 pm, maili...@oopsware.de (Bernd Helmle) wrote:
> > > On 19 Dec 2006 07:05:10 -0800, "BigSmoke" <bigsm...@gmail.com> wrote:
> > > > I understand that due to a lack of nested transaction support, it is > > > > not possible to use START TRANSACTION within a PL/PgSQL function. What > > > > I, however, do not understand is why I can't use SAVEPOINT either. I'm > > > > writing long test functions wherein, at the start of the function, I'd > > > > like to define all test data followed by a "SAVEPOINT > > > > fresh_test_data;". Will this become possible in the (near) future? I > > > > mean, savepoints are of limited use to me if they imply that I can't > > > > stick my tests in stored procedures.Use
> > > BEGIN
> > > ...
> > > EXCEPTION
> > > ...
> > > END;
> > > Blocks instead. The pl/pgsql exception handling is implemented on top > > > of PostgreSQL's SAVEPOINT infrastructure. We are lacking user defined > > > exception support, but you can raise generic errors with RAISE EXCEPTION.I can't solve my problem with a BEGIN EXCEPTION END block because of > > what I do in these functions. Here's an example function.
> > CREATE OR REPLACE FUNCTION test_something() RETURNS VOID AS $$ > > BEGIN > > -- Define some test data
> > -- SAVEPOINT fresh_test_data; -- If only I could ...
> > IF some_test_assertion_fails THEN > > RAISE EXCEPTION 'Some informative message'; > > END IF;
> > -- ROLLBACK TO SAVEPOINT fresh_test_data; > > END; > > $$ LANGUAGE plpgsql;
> > In these functions, I raise an exception whenever a test fails. Now, If > > I want to create an implicit savepoint using BEGIN/END blocks around > > individual tests, I don't see how I can still sanely preserve this > > behavior without the most horrid of hacks. The following code is what I > > think I would need to do to emulate savepoints without direct access to > > them. :-( (I hope that I'm missing something.)
> > CREATE OR REPLACE FUNCTION test_something() RETURNS VOID AS $$ > > BEGIN > > -- Define some test data
> > BEGIN > > -- This is a useful test ;-) > > IF TRUE THEN > > RAISE EXCEPTION 'Aaargh! The test failed!'; > > END IF;
> > RAISE EXCEPTION '__dummy_restore_state__';
> > EXCEPTION WHEN raise_exception THEN > > IF SQLERRM != '__dummy_restore_state__' THEN > > RAISE EXCEPTION '%', SQLERRM; > > END IF; > > END; > > END; > > $$ LANGUAGE plpgsql;What would solve my problem is if there was a method to, at the end of > a begin/end block, I could rollback the changes made in that block > without having to raise an exception. Is it somehow possible to > explicitly rollback to one of these savepoints which are created by > begin/end blocks?
I'm sorry for the sloppy English. Of course I meant to say "at the end of a begin/end block, rollback" instead of "at the end of a begin/end block, I could rollback". Hopefully, this didn't add in the confusion.
On 19 Dec 2006 08:37:01 -0800, "BigSmoke" <bigsm...@gmail.com> wrote:
[...]
What would solve my problem is if there was a
> method to, at the end of >> a begin/end block, I could rollback the changes made in that block >> without having to raise an exception. Is it somehow possible to >> explicitly rollback to one of these savepoints which are created by >> begin/end blocks?
> I'm sorry for the sloppy English. Of course I meant to say "at the end > of a begin/end block, rollback" instead of "at the end of a begin/end > block, I could rollback". Hopefully, this didn't add in the confusion.
If you are hoping you could adopt exact Oracle behavior, i have to regret, you have to do as you've already done. There's no such thing like 'explicit transaction control' in plpgsql. Wouldn't it be easier to wrap your tests into self-contained testfunctions like
SAVEPOINT A; SELECT testcase1(); ROLLBACK TO A; SELECT testcase2(); ROLLBACK TO A; ...
and to evaluate return codes into your application? Maybe someone knows better, but that's the only solution that comes to my mind off-hand....
Bernd
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> On 19 Dec 2006 08:37:01 -0800, "BigSmoke" <bigsm...@gmail.com> wrote:
> > What would solve my problem is if there was a > > method to, at the end of a begin/end block, > > rollback the changes made in that block > > without having to raise an exception. Is it somehow possible to > > explicitly rollback to one of these savepoints which are created by > > begin/end blocks?
> If you are hoping you could adopt exact Oracle behavior, i have to regret, > you have to do as you've already done. There's no such thing like 'explicit > transaction control' in plpgsql. Wouldn't it be easier to wrap your tests into > self-contained testfunctions like
> SAVEPOINT A; > SELECT testcase1(); > ROLLBACK TO A; > SELECT testcase2(); > ROLLBACK TO A; > ...
> and to evaluate return codes into your application? Maybe someone knows better, but > that's the only solution that comes to my mind off-hand....
Well, I'm already doing a full rollback after each test function in my application, because I want test functions to be able to run independently of each other. (I have multiple tests/assertions per test function, which I why I wanted to use savepoints in these functions.) But, I guess I _could_ make groups of tests with one test per function where the functions in each group share some test data in the way you describe. However, the sharing of test data would be cumbersome with this method because I'd have to pass a lot of keys (with pointers to the interesting rows in the test sets) to each test function.
I'll probably just stick with using tainted test data between the individual tests in each test function. I guess I can't have everything. ;-)
