Remove long-unused TransactionIdIsActive()

TransactionIdIsActive() has not been used since bb38fb0, in 2014. There
are no known uses in extensions either and it's hard to see valid uses for
it. Therefore remove TransactionIdIsActive().

Discussion: https://postgr.es/m/odgftbtwp5oq7cxjgf4kjkmyq7ypoftmqy7eqa7w3awnouzot6@hrwnl5tdqrgu

Author: anarazel

src/backend/storage/ipc/procarray.c

@@ -1622,58 +1622,6 @@ TransactionIdIsInProgress(TransactionId xid)
 	return false;
 }
 
-/*
- * TransactionIdIsActive -- is xid the top-level XID of an active backend?
- *
- * This differs from TransactionIdIsInProgress in that it ignores prepared
- * transactions, as well as transactions running on the primary if we're in
- * hot standby.  Also, we ignore subtransactions since that's not needed
- * for current uses.
- */
-bool
-TransactionIdIsActive(TransactionId xid)
-{
-	bool		result = false;
-	ProcArrayStruct *arrayP = procArray;
-	TransactionId *other_xids = ProcGlobal->xids;
-	int			i;
-
-	/*
-	 * Don't bother checking a transaction older than RecentXmin; it could not
-	 * possibly still be running.
-	 */
-	if (TransactionIdPrecedes(xid, RecentXmin))
-		return false;
-
-	LWLockAcquire(ProcArrayLock, LW_SHARED);
-
-	for (i = 0; i < arrayP->numProcs; i++)
-	{
-		int			pgprocno = arrayP->pgprocnos[i];
-		PGPROC	   *proc = &allProcs[pgprocno];
-		TransactionId pxid;
-
-		/* Fetch xid just once - see GetNewTransactionId */
-		pxid = UINT32_ACCESS_ONCE(other_xids[i]);
-
-		if (!TransactionIdIsValid(pxid))
-			continue;
-
-		if (proc->pid == 0)
-			continue;			/* ignore prepared transactions */
-
-		if (TransactionIdEquals(pxid, xid))
-		{
-			result = true;
-			break;
-		}
-	}
-
-	LWLockRelease(ProcArrayLock);
-
-	return result;
-}
-
 
 /*
  * Determine XID horizons.

src/include/storage/procarray.h

@@ -53,7 +53,6 @@ extern bool ProcArrayInstallRestoredXmin(TransactionId xmin, PGPROC *proc);
 extern RunningTransactions GetRunningTransactionData(void);
 
 extern bool TransactionIdIsInProgress(TransactionId xid);
-extern bool TransactionIdIsActive(TransactionId xid);
 extern TransactionId GetOldestNonRemovableTransactionId(Relation rel);
 extern TransactionId GetOldestTransactionIdConsideredRunning(void);
 extern TransactionId GetOldestActiveTransactionId(void);