Re: enable/disable trigger (Re: Fwd: [HACKERS] Open items)

Hi,

BTW, the Postgres convention is to submit patches in context diff format
(diff -c).

Satoshi Nagayasu wrote:
> +    while (HeapTupleIsValid(tuple = systable_getnext(tgscan)))
> +    {
> +        HeapTuple newtup = heap_copytuple(tuple);
> +        Form_pg_trigger pg_trigger = (Form_pg_trigger) GETSTRUCT(newtup);
> +
> +        if ( pg_trigger->tgenabled==true && enable==false )
> +        {
> +            pg_trigger->tgenabled = false;
> +        }
> +        else if ( pg_trigger->tgenabled==false && enable==true )
> +        {
> +            pg_trigger->tgenabled = true;
> +        }
> +
> +        simple_heap_update(tgrel, &newtup->t_self, newtup);

Wouldn't it just be easier to set pg_trigger->tgenabled = enable ?

Also, you should probably skip the simple_heap_update() if the user
tries to disable an already-disabled trigger, to avoid pointless MVCC
bloat (and same for enabling an already-enabled trigger, of course).

> --- pgsql.orig/src/backend/parser/gram.y    2005-06-30 05:34:13.000000000 +0900
> +++ pgsql/src/backend/parser/gram.y    2005-07-01 14:21:25.000000000 +0900
> @@ -348,9 +348,9 @@
>
>      DATABASE DAY_P DEALLOCATE DEC DECIMAL_P DECLARE DEFAULT DEFAULTS
>      DEFERRABLE DEFERRED DEFINER DELETE_P DELIMITER DELIMITERS
> -    DESC DISTINCT DO DOMAIN_P DOUBLE_P DROP
> +    DESC DISABLE DISTINCT DO DOMAIN_P DOUBLE_P DROP
>
> -    EACH ELSE ENCODING ENCRYPTED END_P ESCAPE EXCEPT EXCLUDING
> +    EACH ELSE ENABLE ENCODING ENCRYPTED END_P ESCAPE EXCEPT EXCLUDING
>      EXCLUSIVE EXECUTE EXISTS EXPLAIN EXTERNAL EXTRACT

You also need to add these to unreserved_keywords (see gram.y:7903).

> --- pgsql.orig/src/include/commands/trigger.h    2005-05-30 16:20:58.000000000 +0900
> +++ pgsql/src/include/commands/trigger.h    2005-07-01 15:50:09.000000000 +0900
> @@ -164,6 +164,7 @@
>
>  extern void AfterTriggerSetState(ConstraintsSetStmt *stmt);
>
> +void EnableDisableTrigger(Relation rel, const char *tgname, bool enable);

The Postgres convention is to use the "extern" keyword in declarations
of global functions.

If someone pg_dump's a table with a disabled trigger, should the dump
enable or disable the trigger? I'd be inclined to say pg_dump should
preserve the state of the database it is dumping, and so the trigger
should be disabled. In that case I believe pg_dump needs to be updated.

The patch needs to update the documentation and add regression tests.
psql tab completion might also be worth adding.

-Neil