AW: Get the name of the target Relation from Query struct? SOLVED!
Hello, > Please don't break threads by changing subject line. > As I suggested in the other mail, please use rt_fetch() or OK and OK. Best regards, Ernst-Georg
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
AW: Get the name of the target Relation from Query struct? SOLVED!
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) The comment "rtable index of target relation for INSERT/UPDATE/DELETE/MERGE; 0 for SELECT" on resultRelation in parsenodes.h, Line 120 is misleading. It is _not_ a direct index into rtable, you have to subtract 1 first! And now it works...checked against 9.6.8 and 10.3. Best regards, Ernst-Georg
AW: Get the name of the target Relation from Query struct?
Unfortunately it still crashes with Signal 11 even with a more strict check:
if(parse->commandType == CMD_INSERT) {
best regards,
Ernst-Georg
AW: Get the name of the target Relation from Query struct?
Hello, the crashing query is INSERT INTO blah.blahfasel (id) VALUES (1). But I'll check specifically for INSERTs now and try again. BTW: What exactly is a UTILITY command? Something like e.g. TRUNCATE or VACUUM? Best regards, Ernst-Georg
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
AW: Get the name of the target Relation from Query struct?
Hello again,
unfortunately this:
>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.
gives me a Signal 11.
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).
But the list_nth() reliably crashes the backend with a Signal 11.
Here is the complete function:
static PlannedStmt *
limit_func(Query *parse, int cursorOptions, ParamListInfo boundParams)
{
PlannedStmt *result;
RangeTblEntry *rte;
char *target_table;
char *target_schema;
/* this way we can daisy chain planner hooks if necessary */
if (prev_planner_hook != NULL)
result = (*prev_planner_hook) (parse, cursorOptions,
boundParams);
else
result = standard_planner(parse, cursorOptions, boundParams);
if(parse->commandType != CMD_SELECT) {
int resultRelation = parse->resultRelation;
rte = (RangeTblEntry *) list_nth(parse->rtable, resultRelation);
//target_table = get_rel_name(rte->relid);
//target_schema = get_namespace_name(get_rel_namespace(rte->relid));
ereport(NOTICE, (errcode(ERRCODE_SUCCESSFUL_COMPLETION), errmsg("%i",
resultRelation)));
}
return result;
}
If I comment out the line:rte = (RangeTblEntry *)
list_nth(parse->rtable, resultRelation);
it works and sends me the resultRelation to a NOTICE in the log output.
What am I doing wrong? It's a 10.3 on Ubuntu 16.04 compiled from sources.
Everything else, e.g. multicorn and other extensions work, so I guess it must
be my code and not a problem of the build system or PostgreSQL itself.
Best regards,
Ernst-Georg
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
AW: Get the name of the target Relation from Query struct?
Thank you David, so I am on the right track. >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? Best regards, Ernst-Georg
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
Get the name of the target Relation from Query struct?
Hello, 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? And if yes, what would rtable give me as list entry? An OID or a Relation or something else? Best regards, Ernst-Georg
