C++ LWLockRelease函数代码示例

/*
 * Find a page in a shared buffer, reading it in if necessary.
 * The page number must correspond to an already-initialized page.
 *
 * If write_ok is true then it is OK to return a page that is in
 * WRITE_IN_PROGRESS state; it is the caller's responsibility to be sure
 * that modification of the page is safe.  If write_ok is false then we
 * will not return the page until it is not undergoing active I/O.
 *
 * The passed-in xid is used only for error reporting, and may be
 * InvalidTransactionId if no specific xid is associated with the action.
 *
 * Return value is the shared-buffer slot number now holding the page.
 * The buffer's LRU access info is updated.
 *
 * Control lock must be held at entry, and will be held at exit.
 */
int
SimpleLruReadPage(SlruCtl ctl, int pageno, bool write_ok,
				  TransactionId xid)
{
	SlruShared	shared = ctl->shared;

	/* Outer loop handles restart if we must wait for someone else's I/O */
	for (;;)
	{
		int			slotno;
		bool		ok;

		/* See if page already is in memory; if not, pick victim slot */
		slotno = SlruSelectLRUPage(ctl, pageno);

		/* Did we find the page in memory? */
		if (shared->page_number[slotno] == pageno &&
			shared->page_status[slotno] != SLRU_PAGE_EMPTY)
		{
			/*
			 * If page is still being read in, we must wait for I/O.  Likewise
			 * if the page is being written and the caller said that's not OK.
			 */
			if (shared->page_status[slotno] == SLRU_PAGE_READ_IN_PROGRESS ||
				(shared->page_status[slotno] == SLRU_PAGE_WRITE_IN_PROGRESS &&
				 !write_ok))
			{
				SimpleLruWaitIO(ctl, slotno);
				/* Now we must recheck state from the top */
				continue;
			}
			/* Otherwise, it's ready to use */
			SlruRecentlyUsed(shared, slotno);
			return slotno;
		}

		/* We found no match; assert we selected a freeable slot */
		Assert(shared->page_status[slotno] == SLRU_PAGE_EMPTY ||
			   (shared->page_status[slotno] == SLRU_PAGE_VALID &&
				!shared->page_dirty[slotno]));

		/* Mark the slot read-busy */
		shared->page_number[slotno] = pageno;
		shared->page_status[slotno] = SLRU_PAGE_READ_IN_PROGRESS;
		shared->page_dirty[slotno] = false;

		/* Acquire per-buffer lock (cannot deadlock, see notes at top) */
		LWLockAcquire(shared->buffer_locks[slotno], LW_EXCLUSIVE);

		/* Release control lock while doing I/O */
		LWLockRelease(shared->ControlLock);

		/* Do the read */
		ok = SlruPhysicalReadPage(ctl, pageno, slotno);

		/* Set the LSNs for this newly read-in page to zero */
		SimpleLruZeroLSNs(ctl, slotno);

		/* Re-acquire control lock and update page state */
		LWLockAcquire(shared->ControlLock, LW_EXCLUSIVE);

		Assert(shared->page_number[slotno] == pageno &&
			   shared->page_status[slotno] == SLRU_PAGE_READ_IN_PROGRESS &&
			   !shared->page_dirty[slotno]);

		shared->page_status[slotno] = ok ? SLRU_PAGE_VALID : SLRU_PAGE_EMPTY;

		LWLockRelease(shared->buffer_locks[slotno]);

		/* Now it's okay to ereport if we failed */
		if (!ok)
			SlruReportIOError(ctl, pageno, xid);

		SlruRecentlyUsed(shared, slotno);
		return slotno;
	}
}

/*
 * SIInsertDataEntries
 *		Add new invalidation message(s) to the buffer.
 */
void
SIInsertDataEntries(const SharedInvalidationMessage *data, int n)
{
	SISeg	   *segP = shmInvalBuffer;

	/*
	 * N can be arbitrarily large.	We divide the work into groups of no more
	 * than WRITE_QUANTUM messages, to be sure that we don't hold the lock for
	 * an unreasonably long time.  (This is not so much because we care about
	 * letting in other writers, as that some just-caught-up backend might be
	 * trying to do SICleanupQueue to pass on its signal, and we don't want it
	 * to have to wait a long time.)  Also, we need to consider calling
	 * SICleanupQueue every so often.
	 */
	while (n > 0)
	{
		int			nthistime = Min(n, WRITE_QUANTUM);
		int			numMsgs;
		int			max;

		n -= nthistime;

		LWLockAcquire(SInvalWriteLock, LW_EXCLUSIVE);

		/*
		 * If the buffer is full, we *must* acquire some space.  Clean the
		 * queue and reset anyone who is preventing space from being freed.
		 * Otherwise, clean the queue only when it's exceeded the next
		 * fullness threshold.	We have to loop and recheck the buffer state
		 * after any call of SICleanupQueue.
		 */
		for (;;)
		{
			numMsgs = segP->maxMsgNum - segP->minMsgNum;
			if (numMsgs + nthistime > MAXNUMMESSAGES ||
				numMsgs >= segP->nextThreshold)
				SICleanupQueue(true, nthistime);
			else
				break;
		}

		/*
		 * Insert new message(s) into proper slot of circular buffer
		 */
		max = segP->maxMsgNum;
		while (nthistime-- > 0)
		{
			segP->buffer[max % MAXNUMMESSAGES] = *data++;
			max++;
		}

		/* Update current value of maxMsgNum using spinlock */
		{
			/* use volatile pointer to prevent code rearrangement */
			volatile SISeg *vsegP = segP;

			SpinLockAcquire(&vsegP->msgnumLock);
			vsegP->maxMsgNum = max;
			SpinLockRelease(&vsegP->msgnumLock);
		}

		LWLockRelease(SInvalWriteLock);
	}
}

//.........这里部分代码省略.........
	/* Lock out all writers and readers */
	if (!callerHasWriteLock)
		LWLockAcquire(SInvalWriteLock, LW_EXCLUSIVE);
	LWLockAcquire(SInvalReadLock, LW_EXCLUSIVE);

	/*
	 * Recompute minMsgNum = minimum of all backends' nextMsgNum, identify the
	 * furthest-back backend that needs signaling (if any), and reset any
	 * backends that are too far back.	Note that because we ignore sendOnly
	 * backends here it is possible for them to keep sending messages without
	 * a problem even when they are the only active backend.
	 */
	min = segP->maxMsgNum;
	minsig = min - SIG_THRESHOLD;
	lowbound = min - MAXNUMMESSAGES + minFree;

	for (i = 0; i < segP->lastBackend; i++)
	{
		ProcState  *stateP = &segP->procState[i];
		int			n = stateP->nextMsgNum;

		/* Ignore if inactive or already in reset state */
		if (stateP->procPid == 0 || stateP->resetState || stateP->sendOnly)
			continue;

		/*
		 * If we must free some space and this backend is preventing it, force
		 * him into reset state and then ignore until he catches up.
		 */
		if (n < lowbound)
		{
			stateP->resetState = true;
			/* no point in signaling him ... */
			continue;
		}

		/* Track the global minimum nextMsgNum */
		if (n < min)
			min = n;

		/* Also see who's furthest back of the unsignaled backends */
		if (n < minsig && !stateP->signaled)
		{
			minsig = n;
			needSig = stateP;
		}
	}
	segP->minMsgNum = min;

	/*
	 * When minMsgNum gets really large, decrement all message counters so as
	 * to forestall overflow of the counters.  This happens seldom enough that
	 * folding it into the previous loop would be a loser.
	 */
	if (min >= MSGNUMWRAPAROUND)
	{
		segP->minMsgNum -= MSGNUMWRAPAROUND;
		segP->maxMsgNum -= MSGNUMWRAPAROUND;
		for (i = 0; i < segP->lastBackend; i++)
		{
			/* we don't bother skipping inactive entries here */
			segP->procState[i].nextMsgNum -= MSGNUMWRAPAROUND;
		}
	}

	/*
	 * Determine how many messages are still in the queue, and set the
	 * threshold at which we should repeat SICleanupQueue().
	 */
	numMsgs = segP->maxMsgNum - segP->minMsgNum;
	if (numMsgs < CLEANUP_MIN)
		segP->nextThreshold = CLEANUP_MIN;
	else
		segP->nextThreshold = (numMsgs / CLEANUP_QUANTUM + 1) * CLEANUP_QUANTUM;

	/*
	 * Lastly, signal anyone who needs a catchup interrupt.  Since
	 * SendProcSignal() might not be fast, we don't want to hold locks while
	 * executing it.
	 */
	if (needSig)
	{
		pid_t		his_pid = needSig->procPid;
		BackendId	his_backendId = (needSig - &segP->procState[0]) + 1;

		needSig->signaled = true;
		LWLockRelease(SInvalReadLock);
		LWLockRelease(SInvalWriteLock);
		elog(DEBUG4, "sending sinval catchup signal to PID %d", (int) his_pid);
		SendProcSignal(his_pid, PROCSIG_CATCHUP_INTERRUPT, his_backendId);
		if (callerHasWriteLock)
			LWLockAcquire(SInvalWriteLock, LW_EXCLUSIVE);
	}
	else
	{
		LWLockRelease(SInvalReadLock);
		if (!callerHasWriteLock)
			LWLockRelease(SInvalWriteLock);
	}
}

/*
 * CommitTS resource manager's routines
 */
void
commit_ts_redo(XLogReaderState *record)
{
	uint8		info = XLogRecGetInfo(record) & ~XLR_INFO_MASK;

	/* Backup blocks are not used in commit_ts records */
	Assert(!XLogRecHasAnyBlockRefs(record));

	if (info == COMMIT_TS_ZEROPAGE)
	{
		int			pageno;
		int			slotno;

		memcpy(&pageno, XLogRecGetData(record), sizeof(int));

		LWLockAcquire(CommitTsControlLock, LW_EXCLUSIVE);

		slotno = ZeroCommitTsPage(pageno, false);
		SimpleLruWritePage(CommitTsCtl, slotno);
		Assert(!CommitTsCtl->shared->page_dirty[slotno]);

		LWLockRelease(CommitTsControlLock);
	}
	else if (info == COMMIT_TS_TRUNCATE)
	{
		int			pageno;

		memcpy(&pageno, XLogRecGetData(record), sizeof(int));

		/*
		 * During XLOG replay, latest_page_number isn't set up yet; insert a
		 * suitable value to bypass the sanity test in SimpleLruTruncate.
		 */
		CommitTsCtl->shared->latest_page_number = pageno;

		SimpleLruTruncate(CommitTsCtl, pageno);
	}
	else if (info == COMMIT_TS_SETTS)
	{
		xl_commit_ts_set *setts = (xl_commit_ts_set *) XLogRecGetData(record);
		int			nsubxids;
		TransactionId *subxids;

		nsubxids = ((XLogRecGetDataLen(record) - SizeOfCommitTsSet) /
					sizeof(TransactionId));
		if (nsubxids > 0)
		{
			subxids = palloc(sizeof(TransactionId) * nsubxids);
			memcpy(subxids,
				   XLogRecGetData(record) + SizeOfCommitTsSet,
				   sizeof(TransactionId) * nsubxids);
		}
		else
			subxids = NULL;

		TransactionTreeSetCommitTsData(setts->mainxid, nsubxids, subxids,
									   setts->timestamp, setts->nodeid, true);
		if (subxids)
			pfree(subxids);
	}
	else
		elog(PANIC, "commit_ts_redo: unknown op code %u", info);
}

/*
 * task_tracker_assign_task creates a new task in the shared hash or updates an
 * already existing task. The function also creates a schema for the job if it
 * doesn't already exist.
 */
Datum
task_tracker_assign_task(PG_FUNCTION_ARGS)
{
	uint64 jobId = PG_GETARG_INT64(0);
	uint32 taskId = PG_GETARG_UINT32(1);
	text *taskCallStringText = PG_GETARG_TEXT_P(2);

	StringInfo jobSchemaName = JobSchemaName(jobId);
	bool schemaExists = false;

	WorkerTask *workerTask = NULL;
	char *taskCallString = text_to_cstring(taskCallStringText);
	uint32 taskCallStringLength = strlen(taskCallString);

	/* check that we have a running task tracker on this host */
	bool taskTrackerRunning = TaskTrackerRunning();
	if (!taskTrackerRunning)
	{
		ereport(ERROR, (errcode(ERRCODE_CANNOT_CONNECT_NOW),
						errmsg("the task tracker has been disabled or shut down")));
	}

	/* check that we have enough space in our shared hash for this string */
	if (taskCallStringLength >= TASK_CALL_STRING_SIZE)
	{
		ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
						errmsg("task call string exceeds maximum assignable length")));
	}

	/*
	 * If the schema does not exist, we create it. However, the schema does not
	 * become visible to other processes until the transaction commits, and we
	 * therefore do not release the resource lock in this case. Otherwise, the
	 * schema is already visible, and we immediately release the resource lock.
	 */
	LockJobResource(jobId, AccessExclusiveLock);
	schemaExists = JobSchemaExists(jobSchemaName);
	if (!schemaExists)
	{
		/* lock gets automatically released upon return from this function */
		CreateJobSchema(jobSchemaName);
	}
	else
	{
		UnlockJobResource(jobId, AccessExclusiveLock);
	}

	LWLockAcquire(&WorkerTasksSharedState->taskHashLock, LW_EXCLUSIVE);

	/* check if we already have the task in our shared hash */
	workerTask = WorkerTasksHashFind(jobId, taskId);
	if (workerTask == NULL)
	{
		CreateTask(jobId, taskId, taskCallString);
	}
	else
	{
		UpdateTask(workerTask, taskCallString);
	}

	LWLockRelease(&WorkerTasksSharedState->taskHashLock);

	PG_RETURN_VOID();
}

/*
 * shmem_startup hook: allocate or attach to shared memory,
 * then load any pre-existing statistics from file.
 */
static void
pgss_shmem_startup(void)
{
	bool		found;
	HASHCTL		info;
	FILE	   *file;
	uint32		header;
	int32		num;
	int32		i;
	int			query_size;
	int			buffer_size;
	char	   *buffer = NULL;

	if (prev_shmem_startup_hook)
		prev_shmem_startup_hook();

	/* reset in case this is a restart within the postmaster */
	pgss = NULL;
	pgss_hash = NULL;

	/*
	 * Create or attach to the shared memory state, including hash table
	 */
	LWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE);

	pgss = ShmemInitStruct("pg_stat_statements",
						   sizeof(pgssSharedState),
						   &found);

	if (!found)
	{
		/* First time through ... */
		pgss->lock = LWLockAssign();
		pgss->query_size = pgstat_track_activity_query_size;
	}

	/* Be sure everyone agrees on the hash table entry size */
	query_size = pgss->query_size;

	memset(&info, 0, sizeof(info));
	info.keysize = sizeof(pgssHashKey);
	info.entrysize = offsetof(pgssEntry, query) +query_size;
	info.hash = pgss_hash_fn;
	info.match = pgss_match_fn;
	pgss_hash = ShmemInitHash("pg_stat_statements hash",
							  pgss_max, pgss_max,
							  &info,
							  HASH_ELEM | HASH_FUNCTION | HASH_COMPARE);

	LWLockRelease(AddinShmemInitLock);

	/*
	 * If we're in the postmaster (or a standalone backend...), set up a shmem
	 * exit hook to dump the statistics to disk.
	 */
	if (!IsUnderPostmaster)
		on_shmem_exit(pgss_shmem_shutdown, (Datum) 0);

	/*
	 * Attempt to load old statistics from the dump file, if this is the first
	 * time through and we weren't told not to.
	 */
	if (found || !pgss_save)
		return;

	/*
	 * Note: we don't bother with locks here, because there should be no other
	 * processes running when this code is reached.
	 */
	file = AllocateFile(PGSS_DUMP_FILE, PG_BINARY_R);
	if (file == NULL)
	{
		if (errno == ENOENT)
			return;				/* ignore not-found error */
		goto error;
	}

	buffer_size = query_size;
	buffer = (char *) palloc(buffer_size);

	if (fread(&header, sizeof(uint32), 1, file) != 1 ||
		header != PGSS_FILE_HEADER ||
		fread(&num, sizeof(int32), 1, file) != 1)
		goto error;

	for (i = 0; i < num; i++)
	{
		pgssEntry	temp;
		pgssEntry  *entry;

		if (fread(&temp, offsetof(pgssEntry, mutex), 1, file) != 1)
			goto error;

		/* Encoding is the only field we can easily sanity-check */
		if (!PG_VALID_BE_ENCODING(temp.key.encoding))
			goto error;
//.........这里部分代码省略.........

//.........这里部分代码省略.........
	Oid			userid = GetUserId();
	bool		is_superuser = superuser();
	HASH_SEQ_STATUS hash_seq;
	pgssEntry  *entry;

	if (!pgss || !pgss_hash)
		ereport(ERROR,
				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				 errmsg("pg_stat_statements must be loaded via shared_preload_libraries")));

	/* check to see if caller supports us returning a tuplestore */
	if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("set-valued function called in context that cannot accept a set")));
	if (!(rsinfo->allowedModes & SFRM_Materialize))
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("materialize mode required, but it is not " \
						"allowed in this context")));

	/* Build a tuple descriptor for our result type */
	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
		elog(ERROR, "return type must be a row type");

	per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
	oldcontext = MemoryContextSwitchTo(per_query_ctx);

	tupstore = tuplestore_begin_heap(true, false, work_mem);
	rsinfo->returnMode = SFRM_Materialize;
	rsinfo->setResult = tupstore;
	rsinfo->setDesc = tupdesc;

	MemoryContextSwitchTo(oldcontext);

	LWLockAcquire(pgss->lock, LW_SHARED);

	hash_seq_init(&hash_seq, pgss_hash);
	while ((entry = hash_seq_search(&hash_seq)) != NULL)
	{
		Datum		values[PG_STAT_STATEMENTS_COLS];
		bool		nulls[PG_STAT_STATEMENTS_COLS];
		int			i = 0;
		Counters	tmp;

		memset(values, 0, sizeof(values));
		memset(nulls, 0, sizeof(nulls));

		values[i++] = ObjectIdGetDatum(entry->key.userid);
		values[i++] = ObjectIdGetDatum(entry->key.dbid);

		if (is_superuser || entry->key.userid == userid)
		{
			char	   *qstr;

			qstr = (char *)
				pg_do_encoding_conversion((unsigned char *) entry->query,
										  entry->key.query_len,
										  entry->key.encoding,
										  GetDatabaseEncoding());
			values[i++] = CStringGetTextDatum(qstr);
			if (qstr != entry->query)
				pfree(qstr);
		}
		else
			values[i++] = CStringGetTextDatum("<insufficient privilege>");

		/* copy counters to a local variable to keep locking time short */
		{
			volatile pgssEntry *e = (volatile pgssEntry *) entry;

			SpinLockAcquire(&e->mutex);
			tmp = e->counters;
			SpinLockRelease(&e->mutex);
		}

		values[i++] = Int64GetDatumFast(tmp.calls);
		values[i++] = Float8GetDatumFast(tmp.total_time);
		values[i++] = Int64GetDatumFast(tmp.rows);
		values[i++] = Int64GetDatumFast(tmp.shared_blks_hit);
		values[i++] = Int64GetDatumFast(tmp.shared_blks_read);
		values[i++] = Int64GetDatumFast(tmp.shared_blks_written);
		values[i++] = Int64GetDatumFast(tmp.local_blks_hit);
		values[i++] = Int64GetDatumFast(tmp.local_blks_read);
		values[i++] = Int64GetDatumFast(tmp.local_blks_written);
		values[i++] = Int64GetDatumFast(tmp.temp_blks_read);
		values[i++] = Int64GetDatumFast(tmp.temp_blks_written);

		Assert(i == PG_STAT_STATEMENTS_COLS);

		tuplestore_putvalues(tupstore, tupdesc, values, nulls);
	}

	LWLockRelease(pgss->lock);

	/* clean up and return the tuplestore */
	tuplestore_donestoring(tupstore);

	return (Datum) 0;
}

//.........这里部分代码省略.........
	if (spcNode == GLOBALTABLESPACE_OID)
		return;

	Assert(OidIsValid(spcNode));
	Assert(OidIsValid(dbNode));

	dir = GetDatabasePath(dbNode, spcNode);

	if (stat(dir, &st) < 0)
	{
		/* Directory does not exist? */
		if (errno == ENOENT)
		{
			/*
			 * Acquire TablespaceCreateLock to ensure that no DROP TABLESPACE
			 * or TablespaceCreateDbspace is running concurrently.
			 */
			LWLockAcquire(TablespaceCreateLock, LW_EXCLUSIVE);

			/*
			 * Recheck to see if someone created the directory while we were
			 * waiting for lock.
			 */
			if (stat(dir, &st) == 0 && S_ISDIR(st.st_mode))
			{
				/* Directory was created */
			}
			else
			{
				/* Directory creation failed? */
				if (mkdir(dir, S_IRWXU) < 0)
				{
					char	   *parentdir;

					/* Failure other than not exists or not in WAL replay? */
					if (errno != ENOENT || !isRedo)
						ereport(ERROR,
								(errcode_for_file_access(),
							  errmsg("could not create directory \"%s\": %m",
									 dir)));

					/*
					 * Parent directories are missing during WAL replay, so
					 * continue by creating simple parent directories rather
					 * than a symlink.
					 */

					/* create two parents up if not exist */
					parentdir = pstrdup(dir);
					get_parent_directory(parentdir);
					get_parent_directory(parentdir);
					/* Can't create parent and it doesn't already exist? */
					if (mkdir(parentdir, S_IRWXU) < 0 && errno != EEXIST)
						ereport(ERROR,
								(errcode_for_file_access(),
							  errmsg("could not create directory \"%s\": %m",
									 parentdir)));
					pfree(parentdir);

					/* create one parent up if not exist */
					parentdir = pstrdup(dir);
					get_parent_directory(parentdir);
					/* Can't create parent and it doesn't already exist? */
					if (mkdir(parentdir, S_IRWXU) < 0 && errno != EEXIST)
						ereport(ERROR,
								(errcode_for_file_access(),
							  errmsg("could not create directory \"%s\": %m",
									 parentdir)));
					pfree(parentdir);

					/* Create database directory */
					if (mkdir(dir, S_IRWXU) < 0)
						ereport(ERROR,
								(errcode_for_file_access(),
							  errmsg("could not create directory \"%s\": %m",
									 dir)));
				}
			}

			LWLockRelease(TablespaceCreateLock);
		}
		else
		{
			ereport(ERROR,
					(errcode_for_file_access(),
					 errmsg("could not stat directory \"%s\": %m", dir)));
		}
	}
	else
	{
		/* Is it not a directory? */
		if (!S_ISDIR(st.st_mode))
			ereport(ERROR,
					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
					 errmsg("\"%s\" exists but is not a directory",
							dir)));
	}

	pfree(dir);
}

void
smgrDoAppendOnlyResyncEofs(bool forCommit)
{
	HASH_SEQ_STATUS iterateStatus;
	AppendOnlyMirrorResyncEofs *entry;

	AppendOnlyMirrorResyncEofs *entryExample = NULL;

	int			appendOnlyMirrorResyncEofsCount;

	if (AppendOnlyMirrorResyncEofsTable == NULL)
		return;

	if (Debug_persistent_print ||
		Debug_persistent_appendonly_commit_count_print)
		elog(Persistent_DebugPrintLevel(),
			 "Storage Manager: Enter Append-Only mirror resync eofs list entries (Append-Only commit work count %d)",
			 FileRepPrimary_GetAppendOnlyCommitWorkCount());

	hash_seq_init(
				  &iterateStatus,
				  AppendOnlyMirrorResyncEofsTable);

	appendOnlyMirrorResyncEofsCount = 0;
	while ((entry = hash_seq_search(&iterateStatus)) != NULL)
	{
		if (entryExample == NULL)
		{
			entryExample = entry;
		}

		if (forCommit)
		{
			PersistentFileSysObj_UpdateAppendOnlyMirrorResyncEofs(&entry->key.relFileNode,
																  entry->key.segmentFileNum,
																  &entry->persistentTid,
																  entry->persistentSerialNum,
																  entry->mirrorCatchupRequired,
																  entry->mirrorNewEof,
																   /* recovery */ false,
																   /* flushToXLog */ false);
		}
		else
		{
			/*
			 * Abort case.
			 */
			if (entry->didIncrementCommitCount)
			{
				int			systemAppendOnlyCommitWorkCount;

				LWLockAcquire(FileRepAppendOnlyCommitCountLock, LW_EXCLUSIVE);

				systemAppendOnlyCommitWorkCount =
					FileRepPrimary_FinishedAppendOnlyCommitWork(1);

				if (entry->isDistributedTransaction)
				{
					PrepareDecrAppendOnlyCommitWork(entry->gid);
				}

				if (Debug_persistent_print ||
					Debug_persistent_appendonly_commit_count_print)
					elog(Persistent_DebugPrintLevel(),
						 "Storage Manager: Append-Only Mirror Resync EOFs decrementing commit work for aborted transaction "
						 "(system count %d). "
						 "Relation %u/%u/%u, segment file #%d (persistent serial num " INT64_FORMAT ", TID %s)	",
						 systemAppendOnlyCommitWorkCount,
						 entry->key.relFileNode.spcNode,
						 entry->key.relFileNode.dbNode,
						 entry->key.relFileNode.relNode,
						 entry->key.segmentFileNum,
						 entry->persistentSerialNum,
						 ItemPointerToString(&entry->persistentTid));

				pendingAppendOnlyMirrorResyncIntentCount--;

				LWLockRelease(FileRepAppendOnlyCommitCountLock);
			}
		}

		if (Debug_persistent_print ||
			Debug_persistent_appendonly_commit_count_print)
			elog(Persistent_DebugPrintLevel(),
				 "Storage Manager: Append-Only mirror resync eofs list entry #%d: %u/%u/%u, segment file #%d, relation name '%s' "
				 "(forCommit %s, persistent TID %s, persistent serial number " INT64_FORMAT ", mirror catchup required %s,  mirror new EOF " INT64_FORMAT ")",
				 appendOnlyMirrorResyncEofsCount,
				 entry->key.relFileNode.spcNode,
				 entry->key.relFileNode.dbNode,
				 entry->key.relFileNode.relNode,
				 entry->key.segmentFileNum,
				 (entry->relationName == NULL ? "<null>" : entry->relationName),
				 (forCommit ? "true" : "false"),
				 ItemPointerToString(&entry->persistentTid),
				 entry->persistentSerialNum,
				 (entry->mirrorCatchupRequired ? "true" : "false"),
				 entry->mirrorNewEof);

		appendOnlyMirrorResyncEofsCount++;
	}
//.........这里部分代码省略.........

/*
 * Wait for synchronous replication, if requested by user.
 *
 * Initially backends start in state SYNC_REP_NOT_WAITING and then
 * change that state to SYNC_REP_WAITING before adding ourselves
 * to the wait queue. During SyncRepWakeQueue() a WALSender changes
 * the state to SYNC_REP_WAIT_COMPLETE once replication is confirmed.
 * This backend then resets its state to SYNC_REP_NOT_WAITING.
 */
void
SyncRepWaitForLSN(XLogRecPtr XactCommitLSN)
{
	char 		*new_status = NULL;
	const char *old_status;

	/*
	 * Fast exit if user has not requested sync replication, or
	 * there are no sync replication standby names defined.
	 * Note that those standbys don't need to be connected.
	 */
	if (!SyncRepRequested() || !SyncStandbysDefined())
		return;

	Assert(SHMQueueIsDetached(&(MyProc->syncRepLinks)));
	Assert(WalSndCtl != NULL);

	/* Reset the latch before adding ourselves to the queue. */
	ResetLatch(&MyProc->waitLatch);

	/*
	 * Set our waitLSN so WALSender will know when to wake us, and add
	 * ourselves to the queue.
	 */
	LWLockAcquire(SyncRepLock, LW_EXCLUSIVE);
	Assert(MyProc->syncRepState == SYNC_REP_NOT_WAITING);
	if (!WalSndCtl->sync_standbys_defined)
	{
		/*
		 * We don't wait for sync rep if WalSndCtl->sync_standbys_defined is
		 * not set.  See SyncRepUpdateSyncStandbysDefined.
		 */
		LWLockRelease(SyncRepLock);
		return;
	}
	MyProc->waitLSN = XactCommitLSN;
	MyProc->syncRepState = SYNC_REP_WAITING;
	SyncRepQueueInsert();
	Assert(SyncRepQueueIsOrderedByLSN());
	LWLockRelease(SyncRepLock);

	/* Alter ps display to show waiting for sync rep. */
	if (update_process_title)
	{
		int			len;

		old_status = get_ps_display(&len);
		new_status = (char *) palloc(len + 32 + 1);
		memcpy(new_status, old_status, len);
		sprintf(new_status + len, " waiting for %X/%X",
				XactCommitLSN.xlogid, XactCommitLSN.xrecoff);
		set_ps_display(new_status, false);
		new_status[len] = '\0'; /* truncate off " waiting ..." */
	}

	/*
	 * Wait for specified LSN to be confirmed.
	 *
	 * Each proc has its own wait latch, so we perform a normal latch
	 * check/wait loop here.
	 */
	for (;;)
	{
		int syncRepState;

		/*
		 * Wait on latch for up to 60 seconds. This allows us to
		 * check for postmaster death regularly while waiting.
		 * Note that timeout here does not necessarily release from loop.
		 */
		WaitLatch(&MyProc->waitLatch, 60000000L);

		/* Must reset the latch before testing state. */
		ResetLatch(&MyProc->waitLatch);

		/*
		 * Try checking the state without the lock first.  There's no guarantee
		 * that we'll read the most up-to-date value, so if it looks like we're
		 * still waiting, recheck while holding the lock.  But if it looks like
		 * we're done, we must really be done, because once walsender changes
		 * the state to SYNC_REP_WAIT_COMPLETE, it will never update it again,
		 * so we can't be seeing a stale value in that case.
		 */
		syncRepState = MyProc->syncRepState;
		if (syncRepState == SYNC_REP_WAITING)
		{
			LWLockAcquire(SyncRepLock, LW_SHARED);
			syncRepState = MyProc->syncRepState;
			LWLockRelease(SyncRepLock);
		}
		if (syncRepState == SYNC_REP_WAIT_COMPLETE)
//.........这里部分代码省略.........

Datum
dbms_alert_defered_signal(PG_FUNCTION_ARGS)
{
	TriggerData *trigdata = (TriggerData *) fcinfo->context;
	TupleDesc tupdesc;
	HeapTuple rettuple;
	char *relname;
	text *name;
	text *message;
	int event_col;
	int message_col;

	Datum datum;
	bool isnull;
	int cycle = 0;
	float8 endtime;
	float8 timeout = 2;

	if (!CALLED_AS_TRIGGER(fcinfo))
		ereport(ERROR,
			(errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
			 errmsg("not called by trigger manager")));

	if (!TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
		ereport(ERROR,
			(errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
			 errmsg("not called on valid event")));

	if (SPI_connect() < 0)
		ereport(ERROR,
			(errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
			 errmsg("SPI_connect failed")));

	if (strcmp((relname = SPI_getrelname(trigdata->tg_relation)), "ora_alerts") != 0)
		ereport(ERROR,
			(errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
			 errmsg("not called with valid relation")));

	rettuple = trigdata->tg_trigtuple;
	tupdesc = trigdata->tg_relation->rd_att;

	if (SPI_ERROR_NOATTRIBUTE == (event_col = SPI_fnumber(tupdesc, "event")))
		ereport(ERROR,
			(errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
			 errmsg("attribute event not found")));


	if (SPI_ERROR_NOATTRIBUTE == (message_col = SPI_fnumber(tupdesc, "message")))
		ereport(ERROR,
			(errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
			 errmsg("attribute message not found")));

	datum = SPI_getbinval(rettuple, tupdesc, event_col, &isnull);
	if (isnull)
		ereport(ERROR,
    			(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
        		 errmsg("event name is NULL"),
			 errdetail("Eventname may not be NULL.")));
	name = DatumGetTextP(datum);

	datum = SPI_getbinval(rettuple, tupdesc, message_col, &isnull);
	if (isnull)
		message = NULL;
	else
		message = DatumGetTextP(datum);

	WATCH_PRE(timeout, endtime, cycle);
	if (ora_lock_shmem(SHMEMMSGSZ, MAX_PIPES, MAX_EVENTS, MAX_LOCKS, false))
	{
		ItemPointer tid;
		Oid argtypes[1] = {TIDOID};
		char nulls[1] = {' '};
		Datum values[1];
		void *plan;

		create_message(name, message);
		LWLockRelease(shmem_lock);

		tid = &rettuple->t_data->t_ctid;

		if (!(plan = SPI_prepare("DELETE FROM ora_alerts WHERE ctid = $1", 1, argtypes)))
			ereport(ERROR,
				(errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
				 errmsg("SPI_prepare failed")));

		values[0] = ItemPointerGetDatum(tid);

		if (SPI_OK_DELETE != SPI_execute_plan(plan, values, nulls, false, 1))
			ereport(ERROR,
				(errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
				errmsg("can't execute sql")));

		SPI_finish();
		return PointerGetDatum(rettuple);
	}
	WATCH_POST(timeout, endtime, cycle);
	LOCK_ERROR();

	PG_RETURN_NULL();
}

/*
 * Update the LSNs on each queue based upon our latest state. This
 * implements a simple policy of first-valid-standby-releases-waiter.
 *
 * Other policies are possible, which would change what we do here and what
 * perhaps also which information we store as well.
 */
void
SyncRepReleaseWaiters(void)
{
	volatile WalSndCtlData *walsndctl = WalSndCtl;
	volatile WalSnd *syncWalSnd = NULL;
	int 		numprocs = 0;
	int			priority = 0;
	int			i;

	/*
	 * If this WALSender is serving a standby that is not on the list of
	 * potential standbys then we have nothing to do. If we are still
	 * starting up or still running base backup, then leave quickly also.
	 */
	if (MyWalSnd->sync_standby_priority == 0 ||
		MyWalSnd->state < WALSNDSTATE_STREAMING)
		return;

	/*
	 * We're a potential sync standby. Release waiters if we are the
	 * highest priority standby. If there are multiple standbys with
	 * same priorities then we use the first mentioned standby.
	 * If you change this, also change pg_stat_get_wal_senders().
	 */
	LWLockAcquire(SyncRepLock, LW_EXCLUSIVE);

	for (i = 0; i < max_wal_senders; i++)
	{
		/* use volatile pointer to prevent code rearrangement */
		volatile WalSnd *walsnd = &walsndctl->walsnds[i];

		if (walsnd->pid != 0 &&
			walsnd->sync_standby_priority > 0 &&
			(priority == 0 ||
			 priority > walsnd->sync_standby_priority))
		{
			 priority = walsnd->sync_standby_priority;
			 syncWalSnd = walsnd;
		}
	}

	/*
	 * We should have found ourselves at least.
	 */
	Assert(syncWalSnd);

	/*
	 * If we aren't managing the highest priority standby then just leave.
	 */
	if (syncWalSnd != MyWalSnd)
	{
		LWLockRelease(SyncRepLock);
		announce_next_takeover = true;
		return;
	}

	if (XLByteLT(walsndctl->lsn, MyWalSnd->flush))
	{
		/*
		 * Set the lsn first so that when we wake backends they will
		 * release up to this location.
		 */
		walsndctl->lsn = MyWalSnd->flush;
		numprocs = SyncRepWakeQueue(false);
	}

	LWLockRelease(SyncRepLock);

	elog(DEBUG3, "released %d procs up to %X/%X",
					numprocs,
					MyWalSnd->flush.xlogid,
					MyWalSnd->flush.xrecoff);

	/*
	 * If we are managing the highest priority standby, though we weren't
	 * prior to this, then announce we are now the sync standby.
	 */
	if (announce_next_takeover)
	{
		announce_next_takeover = false;
		ereport(LOG,
				(errmsg("standby \"%s\" is now the synchronous standby with priority %u",
						application_name, MyWalSnd->sync_standby_priority)));
	}
}

/*
 * ShmemInitStruct -- Create/attach to a structure in shared memory.
 *
 *		This is called during initialization to find or allocate
 *		a data structure in shared memory.  If no other process
 *		has created the structure, this routine allocates space
 *		for it.  If it exists already, a pointer to the existing
 *		structure is returned.
 *
 *	Returns: pointer to the object.  *foundPtr is set TRUE if the object was
 *		already in the shmem index (hence, already initialized).
 *
 *	Note: before Postgres 9.0, this function returned NULL for some failure
 *	cases.  Now, it always throws error instead, so callers need not check
 *	for NULL.
 */
void *
ShmemInitStruct(const char *name, Size size, bool *foundPtr)
{
	ShmemIndexEnt *result;
	void	   *structPtr;

	LWLockAcquire(ShmemIndexLock, LW_EXCLUSIVE);

	if (!ShmemIndex)
	{
		PGShmemHeader *shmemseghdr = ShmemSegHdr;

		/* Must be trying to create/attach to ShmemIndex itself */
		Assert(strcmp(name, "ShmemIndex") == 0);

		if (IsUnderPostmaster)
		{
			/* Must be initializing a (non-standalone) backend */
			Assert(shmemseghdr->index != NULL);
			structPtr = shmemseghdr->index;
			*foundPtr = TRUE;
		}
		else
		{
			/*
			 * If the shmem index doesn't exist, we are bootstrapping: we must
			 * be trying to init the shmem index itself.
			 *
			 * Notice that the ShmemIndexLock is released before the shmem
			 * index has been initialized.  This should be OK because no other
			 * process can be accessing shared memory yet.
			 */
			Assert(shmemseghdr->index == NULL);
			structPtr = ShmemAlloc(size);
			shmemseghdr->index = structPtr;
			*foundPtr = FALSE;
		}
		LWLockRelease(ShmemIndexLock);
		return structPtr;
	}

	/* look it up in the shmem index */
	result = (ShmemIndexEnt *)
		hash_search(ShmemIndex, name, HASH_ENTER_NULL, foundPtr);

	if (!result)
	{
		LWLockRelease(ShmemIndexLock);
		ereport(ERROR,
				(errcode(ERRCODE_OUT_OF_MEMORY),
		errmsg("could not create ShmemIndex entry for data structure \"%s\"",
			   name)));
	}

	if (*foundPtr)
	{
		/*
		 * Structure is in the shmem index so someone else has allocated it
		 * already.  The size better be the same as the size we are trying to
		 * initialize to, or there is a name conflict (or worse).
		 */
		if (result->size != size)
		{
			LWLockRelease(ShmemIndexLock);
			ereport(ERROR,
				  (errmsg("ShmemIndex entry size is wrong for data structure"
						  " \"%s\": expected %zu, actual %zu",
						  name, size, result->size)));
		}
		structPtr = result->location;
	}
	else
	{
		/* It isn't in the table yet. allocate and initialize it */
		structPtr = ShmemAllocNoError(size);
		if (structPtr == NULL)
		{
			/* out of memory; remove the failed ShmemIndex entry */
			hash_search(ShmemIndex, name, HASH_REMOVE, NULL);
			LWLockRelease(ShmemIndexLock);
			ereport(ERROR,
					(errcode(ERRCODE_OUT_OF_MEMORY),
					 errmsg("not enough shared memory for data structure"
							" \"%s\" (%zu bytes requested)",
//.........这里部分代码省略.........

/*
 * Write a page from a shared buffer, if necessary.
 * Does nothing if the specified slot is not dirty.
 *
 * NOTE: only one write attempt is made here.  Hence, it is possible that
 * the page is still dirty at exit (if someone else re-dirtied it during
 * the write).	However, we *do* attempt a fresh write even if the page
 * is already being written; this is for checkpoints.
 *
 * Control lock must be held at entry, and will be held at exit.
 */
static void
SlruInternalWritePage(SlruCtl ctl, int slotno, SlruFlush fdata)
{
	SlruShared	shared = ctl->shared;
	int			pageno = shared->page_number[slotno];
	bool		ok;

	/* If a write is in progress, wait for it to finish */
	while (shared->page_status[slotno] == SLRU_PAGE_WRITE_IN_PROGRESS &&
		   shared->page_number[slotno] == pageno)
	{
		SimpleLruWaitIO(ctl, slotno);
	}

	/*
	 * Do nothing if page is not dirty, or if buffer no longer contains the
	 * same page we were called for.
	 */
	if (!shared->page_dirty[slotno] ||
		shared->page_status[slotno] != SLRU_PAGE_VALID ||
		shared->page_number[slotno] != pageno)
		return;

	/*
	 * Mark the slot write-busy, and clear the dirtybit.  After this point, a
	 * transaction status update on this page will mark it dirty again.
	 */
	shared->page_status[slotno] = SLRU_PAGE_WRITE_IN_PROGRESS;
	shared->page_dirty[slotno] = false;

	/* Acquire per-buffer lock (cannot deadlock, see notes at top) */
	LWLockAcquire(shared->buffer_locks[slotno], LW_EXCLUSIVE);

	/* Release control lock while doing I/O */
	LWLockRelease(shared->ControlLock);

	/* Do the write */
	ok = SlruPhysicalWritePage(ctl, pageno, slotno, fdata);

	/* If we failed, and we're in a flush, better close the files */
	if (!ok && fdata)
	{
		int			i;

		for (i = 0; i < fdata->num_files; i++)
			close(fdata->fd[i]);
	}

	/* Re-acquire control lock and update page state */
	LWLockAcquire(shared->ControlLock, LW_EXCLUSIVE);

	Assert(shared->page_number[slotno] == pageno &&
		   shared->page_status[slotno] == SLRU_PAGE_WRITE_IN_PROGRESS);

	/* If we failed to write, mark the page dirty again */
	if (!ok)
		shared->page_dirty[slotno] = true;

	shared->page_status[slotno] = SLRU_PAGE_VALID;

	LWLockRelease(shared->buffer_locks[slotno]);

	/* Now it's okay to ereport if we failed */
	if (!ok)
		SlruReportIOError(ctl, pageno, InvalidTransactionId);
}

/*
 * Returns activity of walsenders, including pids and xlog locations sent to
 * standby servers.
 */
Datum
pg_stat_get_wal_senders(PG_FUNCTION_ARGS)
{
#define PG_STAT_GET_WAL_SENDERS_COLS	8
	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
	TupleDesc	tupdesc;
	Tuplestorestate *tupstore;
	MemoryContext per_query_ctx;
	MemoryContext oldcontext;
	int		   *sync_priority;
	int			priority = 0;
	int			sync_standby = -1;
	int			i;

	/* check to see if caller supports us returning a tuplestore */
	if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("set-valued function called in context that cannot accept a set")));
	if (!(rsinfo->allowedModes & SFRM_Materialize))
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("materialize mode required, but it is not " \
						"allowed in this context")));

	/* Build a tuple descriptor for our result type */
	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
		elog(ERROR, "return type must be a row type");

	per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
	oldcontext = MemoryContextSwitchTo(per_query_ctx);

	tupstore = tuplestore_begin_heap(true, false, work_mem);
	rsinfo->returnMode = SFRM_Materialize;
	rsinfo->setResult = tupstore;
	rsinfo->setDesc = tupdesc;

	MemoryContextSwitchTo(oldcontext);

	/*
	 * Get the priorities of sync standbys all in one go, to minimise lock
	 * acquisitions and to allow us to evaluate who is the current sync
	 * standby. This code must match the code in SyncRepReleaseWaiters().
	 */
	sync_priority = palloc(sizeof(int) * max_wal_senders);
	LWLockAcquire(SyncRepLock, LW_SHARED);
	for (i = 0; i < max_wal_senders; i++)
	{
		/* use volatile pointer to prevent code rearrangement */
		volatile WalSnd *walsnd = &WalSndCtl->walsnds[i];

		if (walsnd->pid != 0)
		{
			sync_priority[i] = walsnd->sync_standby_priority;

			if (walsnd->state == WALSNDSTATE_STREAMING &&
				walsnd->sync_standby_priority > 0 &&
				(priority == 0 ||
				 priority > walsnd->sync_standby_priority))
			{
				priority = walsnd->sync_standby_priority;
				sync_standby = i;
			}
		}
	}
	LWLockRelease(SyncRepLock);

	for (i = 0; i < max_wal_senders; i++)
	{
		/* use volatile pointer to prevent code rearrangement */
		volatile WalSnd *walsnd = &WalSndCtl->walsnds[i];
		char		location[MAXFNAMELEN];
		XLogRecPtr	sentPtr;
		XLogRecPtr	write;
		XLogRecPtr	flush;
		XLogRecPtr	apply;
		WalSndState state;
		Datum		values[PG_STAT_GET_WAL_SENDERS_COLS];
		bool		nulls[PG_STAT_GET_WAL_SENDERS_COLS];

		if (walsnd->pid == 0)
			continue;

		SpinLockAcquire(&walsnd->mutex);
		sentPtr = walsnd->sentPtr;
		state = walsnd->state;
		write = walsnd->write;
		flush = walsnd->flush;
		apply = walsnd->apply;
		SpinLockRelease(&walsnd->mutex);

		memset(nulls, 0, sizeof(nulls));
		values[0] = Int32GetDatum(walsnd->pid);

		if (!superuser())
		{
//.........这里部分代码省略.........