Re: Get the name of the target Relation from Query struct? SOLVED!
Please don't break threads by changing subject line. On Fri, Apr 6, 2018 at 3:42 PM, Ernst-Georg Schmid wrote: > Hello David, > > actually Query->resultRelation is one based and Query->rtable is zero based. > > So the correct call to list_nth is: list_nth(Query->rtable, > Query->resultRelation - 1) As I suggested in the other mail, please use rt_fetch() or planner_rt_fetch() that's future-proof in case we change relids to be something-other-than-one based (an unlikely event, but who knows). -- Best Wishes, Ashutosh Bapat EnterpriseDB Corporation The Postgres Database Company
Re: Get the name of the target Relation from Query struct?
On Fri, Apr 6, 2018 at 2:08 PM, Ernst-Georg Schmid
wrote:
>
> if(parse->commandType != CMD_SELECT) {
> int resultRelation = parse->resultRelation;
>
> rte = (RangeTblEntry *) list_nth(parse->rtable, resultRelation);
>
list_nth() assumes that the lists are 0 based. But relations indexes
are 1 based. Please use rt_fetch() or planner_rt_fetch() as suitable.
--
Best Wishes,
Ashutosh Bapat
EnterpriseDB Corporation
The Postgres Database Company
Re: Get the name of the target Relation from Query struct?
On 6 April 2018 at 20:38, Ernst-Georg Schmid
wrote:
> I can get the resultRelation and it is 1 (which matches the Documentation
> that says that it would be 0 for a SELECT but I exclude SELECTs as you
> suggested).
I didn't quite say exclude SELECT :)
I wrote:
> You'll probably also want to check the query->commandType to ensure
> the command is one that will actually have a valid resultRelation.
> if(parse->commandType != CMD_SELECT) {
Does it perhaps crash on a utility command?
Have a look at parsenodes.h and find the comments for resultRelation,
then find the commandType field and look for the definition of
CmdType. You'll see you need to think a bit harder about which
commandTypes you allow.
--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
Re: Get the name of the target Relation from Query struct?
On 6 April 2018 at 01:20, Ernst-Georg Schmid wrote: >>If you want the relation name from the OID then you'll need something >>like get_rel_name(). > > Hm, lsyscache.c says for get_rel_name(): > > * NOTE: since relation name is not unique, be wary of code that uses this > * for anything except preparing error messages. > > How do I get the schema name too, then? > > Call get_rel_namespace() and then get_rel_name() again with the Oid that was > returned? No, get_rel_name returns the relname from pg_class. What you need is in pg_namespace: namespace from relid: get_namespace_name(get_rel_namespace(relid)) relname from relid: get_rel_name(relid; If you're going to relation_open the rel, then you might want to use: get_namespace_name(RelationGetNamespace(rel)) and RelationGetRelationName(rel; -- David Rowley http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services
Re: Get the name of the target Relation from Query struct?
On 5 April 2018 at 22:34, Ernst-Georg Schmid wrote: > I want to get the target Relation name for a UPDATE / INSERT / DELETE in a > planner_hook. Do I understand struct Query correctly that: > > Query->resultRelation will be the index into Query->rtable to give me the > target Relation? Yes > And if yes, what would rtable give me as list entry? An OID or a Relation or > something else? The list_nth(query->rtable, query->resultRelation) will give you a RangeTblEntry which has a property called relid, which is the Relation's OID as per pg_class.oid. If you want the relation name from the OID then you'll need something like get_rel_name(). You'll probably also want to check the query->commandType to ensure the command is one that will actually have a valid resultRelation. -- David Rowley http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services
