Remove dead forceSync parameter of XactLogCommitRecord().

The function has been reading global variable forceSyncCommit, mirroring
the intent of the caller that passed forceSync=forceSyncCommit.  The
other caller, RecordTransactionCommitPrepared(), passed false.  Since
COMMIT PREPARED can't share a transaction with any command, it certainly
doesn't share a transaction with a command that sets forceSyncCommit.

Reviewed by Michael Paquier.

Discussion: https://postgr.es/m/20200617032615.GC2916904@rfd.leadboat.com

src/backend/access/transam/twophase.c

@@ -2217,7 +2217,7 @@ RecordTransactionCommitPrepared(TransactionId xid,
 	recptr = XactLogCommitRecord(committs,
 								 nchildren, children, nrels, rels,
 								 ninvalmsgs, invalmsgs,
-								 initfileinval, false,
+								 initfileinval,
 								 MyXactFlags | XACT_FLAGS_ACQUIREDACCESSEXCLUSIVELOCK,
 								 xid, gid);
 

src/backend/access/transam/xact.c

@@ -1048,7 +1048,9 @@ CommandCounterIncrement(void)
  * ForceSyncCommit
  *
  * Interface routine to allow commands to force a synchronous commit of the
- * current top-level transaction
+ * current top-level transaction.  Currently, two-phase commit does not
+ * persist and restore this variable.  So long as all callers use
+ * PreventInTransactionBlock(), that omission has no consequences.
  */
 void
 ForceSyncCommit(void)
@@ -1315,7 +1317,7 @@ RecordTransactionCommit(void)
 		XactLogCommitRecord(xactStopTimestamp,
 							nchildren, children, nrels, rels,
 							nmsgs, invalMessages,
-							RelcacheInitFileInval, forceSyncCommit,
+							RelcacheInitFileInval,
 							MyXactFlags,
 							InvalidTransactionId, NULL /* plain commit */ );
 
@@ -5468,7 +5470,7 @@ XactLogCommitRecord(TimestampTz commit_time,
 					int nsubxacts, TransactionId *subxacts,
 					int nrels, RelFileNode *rels,
 					int nmsgs, SharedInvalidationMessage *msgs,
-					bool relcacheInval, bool forceSync,
+					bool relcacheInval,
 					int xactflags, TransactionId twophase_xid,
 					const char *twophase_gid)
 {

src/include/access/xact.h

@@ -434,7 +434,7 @@ extern XLogRecPtr XactLogCommitRecord(TimestampTz commit_time,
 									  int nsubxacts, TransactionId *subxacts,
 									  int nrels, RelFileNode *rels,
 									  int nmsgs, SharedInvalidationMessage *msgs,
-									  bool relcacheInval, bool forceSync,
+									  bool relcacheInval,
 									  int xactflags,
 									  TransactionId twophase_xid,
 									  const char *twophase_gid);