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Re: Command Triggers

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Dimitri Fontaine <dimitri(at)2ndquadrant(dot)fr>
Cc: Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andres Freund <andres(at)anarazel(dot)de>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>, Greg Smith <greg(at)2ndquadrant(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>
Subject: Re: Command Triggers
Date: 2012-01-20 18:14:20
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
On Fri, Jan 20, 2012 at 12:14 PM, Dimitri Fontaine
<dimitri(at)2ndquadrant(dot)fr> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> I think the OID is better than the name, but if it's easy to pass the
>> name and schema, then I'm fine with it.  But I do think this is one of
> It's quite easy to get name and schema from the command yes, here's an
> example of how I'm doing it for some commands:
>                case T_CreateStmt:
>                {
>                        CreateStmt *node = (CreateStmt *)parsetree;
>                        cmd->schemaname = RangeVarGetNamespace(node->relation);
>                        cmd->objectname = node->relation->relname;
>                        break;
>                }
>                case T_AlterTableStmt:
>                {
>                        AlterTableStmt *node = (AlterTableStmt *)parsetree;
>                        cmd->schemaname = RangeVarGetNamespace(node->relation);
>                        cmd->objectname = node->relation->relname;
>                        break;
>                }
>                case T_CreateExtensionStmt:
>                {
>                        cmd->schemaname = NULL;
>                        cmd->objectname = ((CreateExtensionStmt *)parsetree)->extname;
>                        break;
>                }
> Getting the OID on the other hand is much harder, because each command
> implements that part as it wants to, and DefineWhatever() functions are
> returning void. We could maybe have them return the main Oid of the
> object created, or we could have the CommandContext structure I'm using
> be a backend global variable that any command would stuff.
> In any case, adding support for the OID only works for after trigger
> when talking about CREATE commands and for before trigger if talking
> about DROP commands, assuming that the trigger procedure is run after
> we've been locating said Oid.
> It seems to me to be a couple orders of magnitude more work to get the
> Oid here compared to just get the schemaname and objectname. And getting
> those works in all cases as we take them from the command itself (we
> fill in the schema with the first search_path entry when it's not given
> explicitly in the command)
>  CREATE TABLE foo();
>  NOTICE:  enforce_local_style{}: foo

Hmm, OK.  But what happens if the user doesn't specify a schema name explicitly?

Robert Haas
The Enterprise PostgreSQL Company

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