On 09/18/2018 03:36 PM, Andrew Dunstan wrote:
>
>
> Tomas Vondra has pointed out to me that there's an issue with triggers
> not getting expanded tuples for columns with fast defaults. Here is an
> example that shows the issue:
>
>
> andrew=# create table blurfl (id int);
> CREATE TABLE
> andrew=# insert into blurfl select x from generate_series(1,5) x;
> INSERT 0 5
> andrew=# alter table blurfl add column x int default 100;
> ALTER TABLE
> andrew=# create or replace function showmej() returns trigger
> language plpgsql as $$ declare j json; begin j := to_json(old);
> raise notice 'old x: %', j->>'x'; return new; end; $$;
> CREATE FUNCTION
> andrew=# create trigger show_x before update on blurfl for each row
> execute procedure showmej();
> CREATE TRIGGER
> andrew=# update blurfl set id = id where id = 1;
> NOTICE: old x: <NULL>
> UPDATE 1
> andrew=# update blurfl set id = id where id = 1;
> NOTICE: old x: 100
> UPDATE 1
> andrew=#
>
>
> The error is fixed with this patch:
>
>
> diff --git a/src/backend/commands/trigger.c
> b/src/backend/commands/trigger.c
> index 2436692..f34a72a 100644
> --- a/src/backend/commands/trigger.c
> +++ b/src/backend/commands/trigger.c
> @@ -3396,7 +3396,11 @@ ltrmark:;
> LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
> }
> - result = heap_copytuple(&tuple);
> + if (HeapTupleHeaderGetNatts(tuple.t_data) <
> relation->rd_att->natts)
> + result = heap_expand_tuple(&tuple, relation->rd_att);
> + else
> + result = heap_copytuple(&tuple);
> +
> ReleaseBuffer(buffer);
> return result;
>
> I'm going to re-check the various places that this might have been
> missed. I guess it belongs on the open items list.
>
>
>
I haven't found anything further that is misbehaving. I paid particular
attention to indexes and index-only scans.
I propose to commit this along with an appropriate regression test.
cheers
andrew
--
Andrew Dunstan https://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services