Hi,
PG9.5 allows us to add an oid system column to foreign tables, using
ALTER FOREIGN TABLE SET WITH OIDS, but currently, that column reads as
zeroes in postgres_fdw. That seems to me like a bug. So, I'd like to
propose to fix that, by retrieving that column from the remote server
when requested. I'm attaching a proposed patch for that.
Best regards,
Etsuro Fujita
*** a/contrib/postgres_fdw/deparse.c
--- b/contrib/postgres_fdw/deparse.c
***************
*** 287,298 **** foreign_expr_walker(Node *node,
/* Var belongs to foreign table */
/*
! * System columns other than ctid should not be sent to
! * the remote, since we don't make any effort to ensure
! * that local and remote values match (tableoid, in
* particular, almost certainly doesn't match).
*/
if (var->varattno < 0 &&
var->varattno != SelfItemPointerAttributeNumber)
return false;
--- 287,299 ----
/* Var belongs to foreign table */
/*
! * System columns other than oid and ctid should not be
! * sent to the remote, since we don't make any effort to
! * ensure that local and remote values match (tableoid, in
* particular, almost certainly doesn't match).
*/
if (var->varattno < 0 &&
+ var->varattno != ObjectIdAttributeNumber &&
var->varattno != SelfItemPointerAttributeNumber)
return false;
***************
*** 911,919 **** deparseTargetList(StringInfo buf,
}
/*
! * Add ctid if needed. We currently don't support retrieving any other
! * system columns.
*/
if (bms_is_member(SelfItemPointerAttributeNumber - FirstLowInvalidHeapAttributeNumber,
attrs_used))
{
--- 912,936 ----
}
/*
! * Add oid and ctid if needed. We currently don't support retrieving any
! * other system columns.
*/
+ if (bms_is_member(ObjectIdAttributeNumber - FirstLowInvalidHeapAttributeNumber,
+ attrs_used))
+ {
+ if (!first)
+ appendStringInfoString(buf, ", ");
+ else if (is_returning)
+ appendStringInfoString(buf, " RETURNING ");
+ first = false;
+
+ if (qualify_col)
+ ADD_REL_QUALIFIER(buf, rtindex);
+ appendStringInfoString(buf, "oid");
+
+ *retrieved_attrs = lappend_int(*retrieved_attrs,
+ ObjectIdAttributeNumber);
+ }
if (bms_is_member(SelfItemPointerAttributeNumber - FirstLowInvalidHeapAttributeNumber,
attrs_used))
{
***************
*** 1467,1474 **** deparseColumnRef(StringInfo buf, int varno, int varattno, PlannerInfo *root,
{
RangeTblEntry *rte;
! /* varattno can be a whole-row reference, ctid or a regular table column */
! if (varattno == SelfItemPointerAttributeNumber)
{
if (qualify_col)
ADD_REL_QUALIFIER(buf, varno);
--- 1484,1500 ----
{
RangeTblEntry *rte;
! /*
! * varattno can be an oid, a ctid, a whole-row reference, or a regular
! * table column
! */
! if (varattno == ObjectIdAttributeNumber)
! {
! if (qualify_col)
! ADD_REL_QUALIFIER(buf, varno);
! appendStringInfoString(buf, "oid");
! }
! else if (varattno == SelfItemPointerAttributeNumber)
{
if (qualify_col)
ADD_REL_QUALIFIER(buf, varno);
*** a/contrib/postgres_fdw/postgres_fdw.c
--- b/contrib/postgres_fdw/postgres_fdw.c
***************
*** 3744,3749 **** make_tuple_from_result_row(PGresult *res,
--- 3744,3750 ----
TupleDesc tupdesc;
Datum *values;
bool *nulls;
+ Oid oid = InvalidOid;
ItemPointer ctid = NULL;
ConversionLocation errpos;
ErrorContextCallback errcallback;
***************
*** 3802,3808 **** make_tuple_from_result_row(PGresult *res,
else
valstr = PQgetvalue(res, row, j);
! /* convert value to internal representation */
errpos.cur_attno = i;
if (i > 0)
{
--- 3803,3813 ----
else
valstr = PQgetvalue(res, row, j);
! /*
! * convert value to internal representation
! *
! * Note: we ignore system columns other than oid and ctid in result
! */
errpos.cur_attno = i;
if (i > 0)
{
***************
*** 3815,3823 **** make_tuple_from_result_row(PGresult *res,
attinmeta->attioparams[i - 1],
attinmeta->atttypmods[i - 1]);
}
else if (i == SelfItemPointerAttributeNumber)
{
! /* ctid --- note we ignore any other system column in result */
if (valstr != NULL)
{
Datum datum;
--- 3820,3839 ----
attinmeta->attioparams[i - 1],
attinmeta->atttypmods[i - 1]);
}
+ else if (i == ObjectIdAttributeNumber)
+ {
+ /* oid */
+ if (valstr != NULL)
+ {
+ Datum datum;
+
+ datum = DirectFunctionCall1(oidin, CStringGetDatum(valstr));
+ oid = DatumGetObjectId(datum);
+ }
+ }
else if (i == SelfItemPointerAttributeNumber)
{
! /* ctid */
if (valstr != NULL)
{
Datum datum;
***************
*** 3849,3854 **** make_tuple_from_result_row(PGresult *res,
--- 3865,3876 ----
tuple = heap_form_tuple(tupdesc, values, nulls);
/*
+ * If we have an OID to return, install it.
+ */
+ if (OidIsValid(oid))
+ HeapTupleSetOid(tuple, oid);
+
+ /*
* If we have a CTID to return, install it in both t_self and t_ctid.
* t_self is the normal place, but if the tuple is converted to a
* composite Datum, t_self will be lost; setting t_ctid allows CTID to be
***************
*** 3881,3886 **** conversion_error_callback(void *arg)
--- 3903,3910 ----
if (errpos->cur_attno > 0 && errpos->cur_attno <= tupdesc->natts)
attname = NameStr(tupdesc->attrs[errpos->cur_attno - 1]->attname);
+ else if (errpos->cur_attno == ObjectIdAttributeNumber)
+ attname = "oid";
else if (errpos->cur_attno == SelfItemPointerAttributeNumber)
attname = "ctid";
--
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