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Remove catalog function currtid()

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currtid() and currtid2() are an undocumented set of functions whose sole
known user is the Postgres ODBC driver, able to retrieve the latest TID
version for a tuple given by the caller of those functions.

As used by Postgres ODBC, currtid() is a shortcut able to retrieve the
last TID loaded into a backend by passing an OID of 0 (magic value)
after a tuple insertion.  This is removed in this commit, as it became
obsolete after the driver began using "RETURNING ctid" with inserts, a
clause supported since Postgres 8.2 (using RETURNING is better for
performance anyway as it reduces the number of round-trips to the
backend).

currtid2() is still used by the driver, so this remains around for now.
Note that this function is kept in its original shape for backward
compatibility reasons.

Per discussion with many people, including Andres Freund, Peter
Eisentraut, Álvaro Herrera, Hiroshi Inoue, Tom Lane and myself.

Bump catalog version.

Discussion: https://postgr.es/m/20200603021448.GB89559@paquier.xyz
This commit is contained in:
Michael Paquier
2020-11-25 12:18:26 +09:00
parent 660b89928d
commit 7b94e99960
7 changed files with 56 additions and 133 deletions
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137
src/backend/utils/adt/tid.c
View File

@ -47,6 +47,8 @@
#define DELIM ','
#define NTIDARGS 2
static ItemPointer currtid_for_view(Relation viewrel, ItemPointer tid);
/* ----------------------------------------------------------------
* tidin
* ----------------------------------------------------------------
@ -275,12 +277,44 @@ hashtidextended(PG_FUNCTION_ARGS)
* Maybe these implementations should be moved to another place
*/
static ItemPointerData Current_last_tid = {{0, 0}, 0};
void
setLastTid(const ItemPointer tid)
/*
* Utility wrapper for current CTID functions.
* Returns the latest version of a tuple pointing at "tid" for
* relation "rel".
*/
static ItemPointer
currtid_internal(Relation rel, ItemPointer tid)
{
Current_last_tid = *tid;
ItemPointer result;
AclResult aclresult;
Snapshot snapshot;
TableScanDesc scan;
result = (ItemPointer) palloc(sizeof(ItemPointerData));
aclresult = pg_class_aclcheck(RelationGetRelid(rel), GetUserId(),
ACL_SELECT);
if (aclresult != ACLCHECK_OK)
aclcheck_error(aclresult, get_relkind_objtype(rel->rd_rel->relkind),
RelationGetRelationName(rel));
if (rel->rd_rel->relkind == RELKIND_VIEW)
return currtid_for_view(rel, tid);
if (!RELKIND_HAS_STORAGE(rel->rd_rel->relkind))
elog(ERROR, "cannot look at latest visible tid for relation \"%s.%s\"",
get_namespace_name(RelationGetNamespace(rel)),
RelationGetRelationName(rel));
ItemPointerCopy(tid, result);
snapshot = RegisterSnapshot(GetLatestSnapshot());
scan = table_beginscan_tid(rel, snapshot);
table_tuple_get_latest_tid(scan, result);
table_endscan(scan);
UnregisterSnapshot(snapshot);
return result;
}
/*
@ -288,7 +322,7 @@ setLastTid(const ItemPointer tid)
* CTID should be defined in the view and it must
* correspond to the CTID of a base relation.
*/
static Datum
static ItemPointer
currtid_for_view(Relation viewrel, ItemPointer tid)
{
TupleDesc att = RelationGetDescr(viewrel);
@ -338,12 +372,12 @@ currtid_for_view(Relation viewrel, ItemPointer tid)
rte = rt_fetch(var->varno, query->rtable);
if (rte)
{
Datum result;
ItemPointer result;
Relation rel;
result = DirectFunctionCall2(currtid_byreloid,
ObjectIdGetDatum(rte->relid),
PointerGetDatum(tid));
table_close(viewrel, AccessShareLock);
rel = table_open(rte->relid, AccessShareLock);
result = currtid_internal(rel, tid);
table_close(rel, AccessShareLock);
return result;
}
}
@ -352,56 +386,14 @@ currtid_for_view(Relation viewrel, ItemPointer tid)
}
}
elog(ERROR, "currtid cannot handle this view");
return (Datum) 0;
}
Datum
currtid_byreloid(PG_FUNCTION_ARGS)
{
Oid reloid = PG_GETARG_OID(0);
ItemPointer tid = PG_GETARG_ITEMPOINTER(1);
ItemPointer result;
Relation rel;
AclResult aclresult;
Snapshot snapshot;
TableScanDesc scan;
result = (ItemPointer) palloc(sizeof(ItemPointerData));
if (!reloid)
{
*result = Current_last_tid;
PG_RETURN_ITEMPOINTER(result);
}
rel = table_open(reloid, AccessShareLock);
aclresult = pg_class_aclcheck(RelationGetRelid(rel), GetUserId(),
ACL_SELECT);
if (aclresult != ACLCHECK_OK)
aclcheck_error(aclresult, get_relkind_objtype(rel->rd_rel->relkind),
RelationGetRelationName(rel));
if (rel->rd_rel->relkind == RELKIND_VIEW)
return currtid_for_view(rel, tid);
if (!RELKIND_HAS_STORAGE(rel->rd_rel->relkind))
elog(ERROR, "cannot look at latest visible tid for relation \"%s.%s\"",
get_namespace_name(RelationGetNamespace(rel)),
RelationGetRelationName(rel));
ItemPointerCopy(tid, result);
snapshot = RegisterSnapshot(GetLatestSnapshot());
scan = table_beginscan_tid(rel, snapshot);
table_tuple_get_latest_tid(scan, result);
table_endscan(scan);
UnregisterSnapshot(snapshot);
table_close(rel, AccessShareLock);
PG_RETURN_ITEMPOINTER(result);
return NULL;
}
/*
* currtid_byrelname
* Get the latest tuple version of the tuple pointing at a CTID, for a
* given relation name.
*/
Datum
currtid_byrelname(PG_FUNCTION_ARGS)
{
@ -410,35 +402,12 @@ currtid_byrelname(PG_FUNCTION_ARGS)
ItemPointer result;
RangeVar *relrv;
Relation rel;
AclResult aclresult;
Snapshot snapshot;
TableScanDesc scan;
relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
rel = table_openrv(relrv, AccessShareLock);
aclresult = pg_class_aclcheck(RelationGetRelid(rel), GetUserId(),
ACL_SELECT);
if (aclresult != ACLCHECK_OK)
aclcheck_error(aclresult, get_relkind_objtype(rel->rd_rel->relkind),
RelationGetRelationName(rel));
if (rel->rd_rel->relkind == RELKIND_VIEW)
return currtid_for_view(rel, tid);
if (!RELKIND_HAS_STORAGE(rel->rd_rel->relkind))
elog(ERROR, "cannot look at latest visible tid for relation \"%s.%s\"",
get_namespace_name(RelationGetNamespace(rel)),
RelationGetRelationName(rel));
result = (ItemPointer) palloc(sizeof(ItemPointerData));
ItemPointerCopy(tid, result);
snapshot = RegisterSnapshot(GetLatestSnapshot());
scan = table_beginscan_tid(rel, snapshot);
table_tuple_get_latest_tid(scan, result);
table_endscan(scan);
UnregisterSnapshot(snapshot);
/* grab the latest tuple version associated to this CTID */
result = currtid_internal(rel, tid);
table_close(rel, AccessShareLock);