Here is an example using postgres_fdw.
[Terminal 1]
postgres=# create table t (a int, b int);
CREATE TABLE
postgres=# insert into t values (1, 1);
INSERT 0 1
postgres=# begin;
BEGIN
postgres=# update t set b = b * 2;
UPDATE 1
[Terminal 2]
postgres=# create foreign table ft (a int) server loopback options
(table_name 'lbt');
CREATE FOREIGN TABLE
postgres=# insert into ft values (1);
INSERT 0 1
postgres=# select tableoid, ctid, * from ft;
tableoid | ctid | a
----------+-------+---
25092 | (0,1) | 1
(1 row)
postgres=# select ft.tableoid, ft.ctid, ft.* from t, ft where t.a = ft.a
for update;
[Terminal 1]
postgres=# commit;
COMMIT
[Terminal 2]
postgres=# select ft.tableoid, ft.ctid, ft.* from t, ft where t.a = ft.a
for update;
tableoid | ctid | a
----------+----------------+---
0 | (4294967295,0) | 1
(1 row)
Note that tableoid and ctid have been changed!
I think the reason for that is because EvalPlanQualFetchRowMarks doesn't
properly set tableoid and ctid for foreign tables, IIUC. I think this
should be fixed. Please find attached a patch. The patch slightly
relates to [1], so if it is reasonable, I'll update [1] on top of this.
[1] https://commitfest.postgresql.org/action/patch_view?id=1386
Best regards,
Etsuro Fujita
*** a/contrib/postgres_fdw/postgres_fdw.c
--- b/contrib/postgres_fdw/postgres_fdw.c
***************
*** 2947,2953 **** make_tuple_from_result_row(PGresult *res,
tuple = heap_form_tuple(tupdesc, values, nulls);
if (ctid)
! tuple->t_self = *ctid;
/* Clean up */
MemoryContextReset(temp_context);
--- 2947,2953 ----
tuple = heap_form_tuple(tupdesc, values, nulls);
if (ctid)
! tuple->t_self = tuple->t_data->t_ctid = *ctid;
/* Clean up */
MemoryContextReset(temp_context);
*** a/src/backend/executor/execMain.c
--- b/src/backend/executor/execMain.c
***************
*** 795,800 **** InitPlan(QueryDesc *queryDesc, int eflags)
--- 795,801 ----
{
PlanRowMark *rc = (PlanRowMark *) lfirst(l);
Oid relid;
+ char relkind;
Relation relation;
ExecRowMark *erm;
***************
*** 817,826 **** InitPlan(QueryDesc *queryDesc, int eflags)
--- 818,833 ----
break;
case ROW_MARK_COPY:
/* there's no real table here ... */
+ relkind = rt_fetch(rc->rti, rangeTable)->relkind;
+ if (relkind == RELKIND_FOREIGN_TABLE)
+ relid = getrelid(rc->rti, rangeTable);
+ else
+ relid = InvalidOid;
relation = NULL;
break;
default:
elog(ERROR, "unrecognized markType: %d", rc->markType);
+ relid = InvalidOid;
relation = NULL; /* keep compiler quiet */
break;
}
***************
*** 831,836 **** InitPlan(QueryDesc *queryDesc, int eflags)
--- 838,844 ----
erm = (ExecRowMark *) palloc(sizeof(ExecRowMark));
erm->relation = relation;
+ erm->relid = relid;
erm->rti = rc->rti;
erm->prti = rc->prti;
erm->rowmarkId = rc->rowmarkId;
***************
*** 2318,2325 **** EvalPlanQualFetchRowMarks(EPQState *epqstate)
/* build a temporary HeapTuple control structure */
tuple.t_len = HeapTupleHeaderGetDatumLength(td);
! ItemPointerSetInvalid(&(tuple.t_self));
! tuple.t_tableOid = InvalidOid;
tuple.t_data = td;
/* copy and store tuple */
--- 2326,2342 ----
/* build a temporary HeapTuple control structure */
tuple.t_len = HeapTupleHeaderGetDatumLength(td);
! /* if relid is valid, rel is a foreign table; set system columns */
! if (OidIsValid(erm->relid))
! {
! tuple.t_self = td->t_ctid;
! tuple.t_tableOid = erm->relid;
! }
! else
! {
! ItemPointerSetInvalid(&(tuple.t_self));
! tuple.t_tableOid = InvalidOid;
! }
tuple.t_data = td;
/* copy and store tuple */
*** a/src/backend/executor/nodeForeignscan.c
--- b/src/backend/executor/nodeForeignscan.c
***************
*** 22,27 ****
--- 22,28 ----
*/
#include "postgres.h"
+ #include "access/htup_details.h"
#include "executor/executor.h"
#include "executor/nodeForeignscan.h"
#include "foreign/fdwapi.h"
***************
*** 53,65 **** ForeignNext(ForeignScanState *node)
/*
* If any system columns are requested, we have to force the tuple into
* physical-tuple form to avoid "cannot extract system attribute from
! * virtual tuple" errors later. We also insert a valid value for
! * tableoid, which is the only actually-useful system column.
*/
if (plan->fsSystemCol && !TupIsNull(slot))
{
HeapTuple tup = ExecMaterializeSlot(slot);
tup->t_tableOid = RelationGetRelid(node->ss.ss_currentRelation);
}
--- 54,69 ----
/*
* If any system columns are requested, we have to force the tuple into
* physical-tuple form to avoid "cannot extract system attribute from
! * virtual tuple" errors later. We also insert a valid value for TID
! * and tableoid, which are the only actually-useful system columns.
*/
if (plan->fsSystemCol && !TupIsNull(slot))
{
HeapTuple tup = ExecMaterializeSlot(slot);
+ /* We assume that t_ctid is initialized with its own TID */
+ tup->t_self = tup->t_data->t_ctid;
+
tup->t_tableOid = RelationGetRelid(node->ss.ss_currentRelation);
}
*** a/src/include/nodes/execnodes.h
--- b/src/include/nodes/execnodes.h
***************
*** 425,430 **** typedef struct EState
--- 425,431 ----
typedef struct ExecRowMark
{
Relation relation; /* opened and suitably locked relation */
+ Oid relid; /* its relation Oid */
Index rti; /* its range table index */
Index prti; /* parent range table index, if child */
Index rowmarkId; /* unique identifier for resjunk columns */
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