diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml
index cba6661..24c57fb 100644
--- a/doc/src/sgml/protocol.sgml
+++ b/doc/src/sgml/protocol.sgml
@@ -2192,7 +2192,7 @@ psql "dbname=postgres replication=database" -c "IDENTIFY_SYSTEM;"
- The following option is supported:
+ The following options are supported:
diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index f710030..b426f0b 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -2689,7 +2689,7 @@ LookupGXact(const char *gid, XLogRecPtr prepare_end_lsn,
* Return the GID in the supplied buffer.
*/
void
-TwoPhaseTransactionGid(Oid subid, TransactionId xid, char *gid, int szgid)
+TwoPhaseTransactionGid(Oid subid, TransactionId xid, char *gid_res, int szgid)
{
Assert(subid != InvalidRepOriginId);
@@ -2698,7 +2698,7 @@ TwoPhaseTransactionGid(Oid subid, TransactionId xid, char *gid, int szgid)
(errcode(ERRCODE_PROTOCOL_VIOLATION),
errmsg_internal("invalid two-phase transaction ID")));
- snprintf(gid, szgid, "pg_gid_%u_%u", subid, xid);
+ snprintf(gid_res, szgid, "pg_gid_%u_%u", subid, xid);
}
/*
@@ -2710,20 +2710,26 @@ static bool
IsTwoPhaseTransactionGidForSubid(Oid subid, char *gid)
{
int ret;
- Oid subid_written;
- TransactionId xid;
+ Oid subid_from_gid;
+ TransactionId xid_from_gid;
char gid_generated[GIDSIZE];
- ret = sscanf(gid, "pg_gid_%u_%u", &subid_written, &xid);
+ /* Extract the subid and xid from the given GID. */
+ ret = sscanf(gid, "pg_gid_%u_%u", &subid_from_gid, &xid_from_gid);
- /* Return false if the given GID has different format */
- if (ret != 2 || subid != subid_written)
+ /*
+ * Check that the given GID has expected format, and at least the subid
+ * matches.
+ */
+ if (ret != 2 || subid != subid_from_gid)
return false;
- /* Construct the format GID based on the got xid */
- TwoPhaseTransactionGid(subid, xid, gid_generated, sizeof(gid));
-
- /* ...And check whether the given GID is exact same as the format GID */
+ /*
+ * Reconstruct a tmp GID based on the subid and xid extracted from
+ * the given GID. Check that the tmp GID and the given GID match.
+ */
+ TwoPhaseTransactionGid(subid_from_gid, xid_from_gid,
+ gid_generated, sizeof(gid_generated));
return strcmp(gid, gid_generated) == 0;
}