/*
* txid_snapshot_recv(internal) returns txid_snapshot
*
* binary input function for type txid_snapshot
*
* format: int4 nxip, int8 xmin, int8 xmax, int8 xip
*/
Datum
txid_snapshot_recv(PG_FUNCTION_ARGS)
{
StringInfo buf = (StringInfo) PG_GETARG_POINTER(0);
TxidSnapshot *snap;
txid last = 0;
int nxip;
int i;
txid xmin,
xmax;
/* load and validate nxip */
nxip = pq_getmsgint(buf, 4);
if (nxip < 0 || nxip > TXID_SNAPSHOT_MAX_NXIP)
goto bad_format;
xmin = pq_getmsgint64(buf);
xmax = pq_getmsgint64(buf);
if (xmin == 0 || xmax == 0 || xmin > xmax || xmax > MAX_TXID)
goto bad_format;
snap = palloc(TXID_SNAPSHOT_SIZE(nxip));
snap->xmin = xmin;
snap->xmax = xmax;
for (i = 0; i < nxip; i++)
{
txid cur = pq_getmsgint64(buf);
if (cur < last || cur < xmin || cur >= xmax)
goto bad_format;
/* skip duplicate xips */
if (cur == last)
{
i--;
nxip--;
continue;
}
snap->xip[i] = cur;
last = cur;
}
snap->nxip = nxip;
SET_VARSIZE(snap, TXID_SNAPSHOT_SIZE(nxip));
PG_RETURN_POINTER(snap);
bad_format:
ereport(ERROR,
(errcode(ERRCODE_INVALID_BINARY_REPRESENTATION),
errmsg("invalid external txid_snapshot data")));
PG_RETURN_POINTER(NULL); /* keep compiler quiet */
}
/*
* txid_snapshot_recv(internal) returns txid_snapshot
*
* binary input function for type txid_snapshot
*
* format: int4 nxip, int8 xmin, int8 xmax, int8 xip
*/
Datum
txid_snapshot_recv(PG_FUNCTION_ARGS)
{
StringInfo buf = (StringInfo) PG_GETARG_POINTER(0);
TxidSnapshot *snap;
txid last = 0;
int nxip;
int i;
txid xmin,
xmax;
/* load and validate nxip */
nxip = pq_getmsgint(buf, 4);
if (nxip < 0 || nxip > TXID_SNAPSHOT_MAX_NXIP)
goto bad_format;
xmin = pq_getmsgint64(buf);
xmax = pq_getmsgint64(buf);
if (xmin == 0 || xmax == 0 || xmin > xmax || xmax > MAX_TXID)
goto bad_format;
snap = static_cast<TxidSnapshot *>(palloc(TXID_SNAPSHOT_SIZE(nxip)));
snap->xmin = xmin;
snap->xmax = xmax;
for (i = 0; i < nxip; i++)
{
txid cur = pq_getmsgint64(buf);
if (cur < last || cur < xmin || cur >= xmax)
goto bad_format;
/* skip duplicate xips */
if (cur == last)
{
i--;
nxip--;
continue;
}
snap->xip[i] = cur;
last = cur;
}
snap->nxip = nxip;
SET_VARSIZE(snap, TXID_SNAPSHOT_SIZE(nxip));
PG_RETURN_POINTER(snap);
bad_format:
elog(ERROR, "invalid snapshot data");
return (Datum) NULL;
}
/*
* txid_snapshot_recv(internal) returns txid_snapshot
*
* binary input function for type txid_snapshot
*
* format: int4 nxip, int8 xmin, int8 xmax, int8 xip
*/
Datum
txid_snapshot_recv(PG_FUNCTION_ARGS)
{
StringInfo buf = (StringInfo) PG_GETARG_POINTER(0);
TxidSnapshot *snap;
txid last = 0;
int nxip;
int i;
int avail;
int expect;
txid xmin,
xmax;
/*
* load nxip and check for nonsense.
*
* (nxip > avail) check is against int overflows in 'expect'.
*/
nxip = pq_getmsgint(buf, 4);
avail = buf->len - buf->cursor;
expect = 8 + 8 + nxip * 8;
if (nxip < 0 || nxip > avail || expect > avail)
goto bad_format;
xmin = pq_getmsgint64(buf);
xmax = pq_getmsgint64(buf);
if (xmin == 0 || xmax == 0 || xmin > xmax || xmax > MAX_TXID)
goto bad_format;
snap = palloc(TXID_SNAPSHOT_SIZE(nxip));
snap->xmin = xmin;
snap->xmax = xmax;
snap->nxip = nxip;
SET_VARSIZE(snap, TXID_SNAPSHOT_SIZE(nxip));
for (i = 0; i < nxip; i++)
{
txid cur = pq_getmsgint64(buf);
if (cur <= last || cur < xmin || cur >= xmax)
goto bad_format;
snap->xip[i] = cur;
last = cur;
}
PG_RETURN_POINTER(snap);
bad_format:
elog(ERROR, "invalid snapshot data");
return (Datum) NULL;
}
/*
* txid_current_snapshot() returns txid_snapshot
*
* Return current snapshot in TXID format
*
* Note that only top-transaction XIDs are included in the snapshot.
*/
Datum
txid_current_snapshot(PG_FUNCTION_ARGS)
{
TxidSnapshot *snap;
uint32 nxip,
i,
size;
TxidEpoch state;
Snapshot cur;
cur = GetActiveSnapshot();
if (cur == NULL)
elog(ERROR, "no active snapshot set");
load_xid_epoch(&state);
/* allocate */
nxip = cur->xcnt;
size = TXID_SNAPSHOT_SIZE(nxip);
snap = palloc(size);
SET_VARSIZE(snap, size);
/* fill */
snap->xmin = convert_xid(cur->xmin, &state);
snap->xmax = convert_xid(cur->xmax, &state);
snap->nxip = nxip;
for (i = 0; i < nxip; i++)
snap->xip[i] = convert_xid(cur->xip[i], &state);
/* we want them guaranteed to be in ascending order */
sort_snapshot(snap);
PG_RETURN_POINTER(snap);
}
/*
* txid_current_snapshot() returns txid_snapshot
*
* Return current snapshot in TXID format
*
* Note that only top-transaction XIDs are included in the snapshot.
*/
Datum
txid_current_snapshot(PG_FUNCTION_ARGS)
{
TxidSnapshot *snap;
uint32 nxip,
i;
TxidEpoch state;
Snapshot cur;
cur = GetActiveSnapshot();
if (cur == NULL)
elog(ERROR, "no active snapshot set");
load_xid_epoch(&state);
/*
* Compile-time limits on the procarray (MAX_BACKENDS processes plus
* MAX_BACKENDS prepared transactions) guarantee nxip won't be too large.
*/
StaticAssertStmt(MAX_BACKENDS * 2 <= TXID_SNAPSHOT_MAX_NXIP,
"possible overflow in txid_current_snapshot()");
/* allocate */
nxip = cur->xcnt;
snap = palloc(TXID_SNAPSHOT_SIZE(nxip));
/* fill */
snap->xmin = convert_xid(cur->xmin, &state);
snap->xmax = convert_xid(cur->xmax, &state);
snap->nxip = nxip;
for (i = 0; i < nxip; i++)
snap->xip[i] = convert_xid(cur->xip[i], &state);
/*
* We want them guaranteed to be in ascending order. This also removes
* any duplicate xids. Normally, an XID can only be assigned to one
* backend, but when preparing a transaction for two-phase commit, there
* is a transient state when both the original backend and the dummy
* PGPROC entry reserved for the prepared transaction hold the same XID.
*/
sort_snapshot(snap);
/* set size after sorting, because it may have removed duplicate xips */
SET_VARSIZE(snap, TXID_SNAPSHOT_SIZE(snap->nxip));
PG_RETURN_POINTER(snap);
}
static StringInfo
buf_init(txid xmin, txid xmax)
{
TxidSnapshot snap;
StringInfo buf;
snap.xmin = xmin;
snap.xmax = xmax;
snap.nxip = 0;
buf = makeStringInfo();
appendBinaryStringInfo(buf, (char *) &snap, TXID_SNAPSHOT_SIZE(0));
return buf;
}
