Re: BUG #15977: Inconsistent behavior in chained transactions

Hello,

> COMMIT AND CHAIN in implicit block leaves blockState as TBLOCK_STARTED, 
> which doesn't trigger the chaining. but ROLLBACK AND CHAIN sets the 
> blockState into TBLOCK_ABORT_PENDING, so the chaining is triggered.
>
> I think disabling s->chain beforehand should do the desired behavior.

Patch applies with "patch", although "git apply" complained because of 
CRLF line terminations forced by the octet-stream mime type.

Patch compiles cleanly. Make check ok.

Patch works for me, and solution seems appropriate. It should be committed 
for pg 12.0.

There could be a test added in "regress/sql/transactions.sql", I'd suggest 
something like:

-- implicit transaction and not chained.
COMMIT AND CHAIN;
COMMIT;
ROLLBACK AND CHAIN;
ROLLBACK;

which should show the appropriate "no transaction in progress" warnings.

Doc could be made a little clearer about what to expect when there is no 
explicit transaction in progress.

-- 
Fabien.