Re: pg_restore with --disable-triggers discards ENABLE ALWAYS

Hi Laurenz,

On 12/09/2024 22:02, Laurenz Albe wrote:
> On Thu, 2024-09-12 at 10:27 +0200, Duncan Sands wrote:
>> CREATE TABLE test_table(x int);
>> CREATE FUNCTION test_function() RETURNS trigger AS $$ BEGIN RETURN NULL; END; $$
>> LANGUAGE plpgsql;
>> CREATE TRIGGER test_trigger AFTER UPDATE ON test_table FOR EACH ROW EXECUTE
>> FUNCTION test_function();
>> ALTER TABLE test_table ENABLE ALWAYS TRIGGER test_trigger;
>>
>> Checking the table:
>>
>> duncan=> \d test_table
>>               Table "public.test_table"
>>   Column |  Type   | Collation | Nullable | Default
>> --------+---------+-----------+----------+---------
>>   x      | integer |           |          |
>> Triggers firing always:
>>      test_trigger AFTER UPDATE ON test_table FOR EACH ROW EXECUTE FUNCTION
>> test_function()
>>
>> ^ Observe "Triggers firing always".
>>
>>
>> Now for the dump + restore:
>>
>> pg_dump -f dump.custom -Fc --table test_table
>> pg_restore --data-only --disable-triggers --dbname duncan dump.custom
>>
>> Checking the table:
>>
>> duncan=> \d test_table
>>               Table "public.test_table"
>>   Column |  Type   | Collation | Nullable | Default
>> --------+---------+-----------+----------+---------
>>   x      | integer |           |          |
>> Triggers:
>>      test_trigger AFTER UPDATE ON test_table FOR EACH ROW EXECUTE FUNCTION
>> test_function()
>>
>> ^ Observe that "Triggers firing always" has disappeared.
>
> This looks like a user error to me.
> If you restore with --data-only, the table and constraint definitions
> are not restored at all. So the table "test_table" in database "duncan"
> must already have existed before the restore, and the trigger was already
> defined like that.

No, the trigger was ENABLE ALWAYS when dumped, and restoring zapped that. To
confirm that it was ENABLE ALWAYS when dumped:

$ pg_restore -f - dump.custom | grep 'ENABLE ALWAYS'
ALTER TABLE public.test_table ENABLE ALWAYS TRIGGER test_trigger;

To summarize: the table existed before the restore, and the trigger was ENABLE
ALWAYS at the moment it was dumped as shown in the steps to reproduce above: I
create the table, make an ENABLE ALWAYS trigger, then dump the table, then
restore the dump with --data-only and --disable-triggers. At which point (in
spite of --data-only) the table has been modified: the trigger is no longer an
ENABLE ALWAYS trigger.

Best wishes, Duncan.