C++ pq_beginmessage函数代码示例

/* ----------------
 *		EndCommand - clean up the destination at end of command
 * ----------------
 */
void
EndCommand(const char *commandTag, CommandDest dest)
{
	StringInfoData buf;

	if (Gp_role == GP_ROLE_DISPATCH)
	{
		/*
		 * Just before a successful reply, let's see if the DTM has
		 * phase 2 retry work.
		 */
		doDtxPhase2Retry();
	}
	
	switch (dest)
	{
		case DestRemote:
		case DestRemoteExecute:
			if (Gp_role == GP_ROLE_EXECUTE && Gp_is_writer)
			{
				/*
				 * Extra information that indicates if the transaction made
				 * updates.
				 */
				sendQEDetails();

				pq_beginmessage(&buf, 'g');
				pq_sendstring(&buf, commandTag);

				AddQEWriterTransactionInfo(&buf);

				pq_endmessage(&buf);
			}
			else if (Gp_role == GP_ROLE_EXECUTE)
			{
				sendQEDetails();

				pq_beginmessage(&buf, 'C');
				pq_sendstring(&buf, commandTag);
				pq_endmessage(&buf);
			}
			else
				pq_puttextmessage('C', commandTag);
			break;
		case DestNone:
		case DestDebug:
		case DestSPI:
		case DestTuplestore:
		case DestIntoRel:
		case DestCopyOut:
			break;
	}
}

/*
 * IDENTIFY_SYSTEM
 */
static void
IdentifySystem(void)
{
	StringInfoData buf;
	char		sysid[32];
	char		tli[11];

	/*
	 * Reply with a result set with one row, two columns. First col is system
	 * ID, and second is timeline ID
	 */

	snprintf(sysid, sizeof(sysid), UINT64_FORMAT,
			 GetSystemIdentifier());
	snprintf(tli, sizeof(tli), "%u", ThisTimeLineID);

	/* Send a RowDescription message */
	pq_beginmessage(&buf, 'T');
	pq_sendint(&buf, 2, 2);		/* 2 fields */

	/* first field */
	pq_sendstring(&buf, "systemid");	/* col name */
	pq_sendint(&buf, 0, 4);		/* table oid */
	pq_sendint(&buf, 0, 2);		/* attnum */
	pq_sendint(&buf, TEXTOID, 4);		/* type oid */
	pq_sendint(&buf, -1, 2);	/* typlen */
	pq_sendint(&buf, 0, 4);		/* typmod */
	pq_sendint(&buf, 0, 2);		/* format code */

	/* second field */
	pq_sendstring(&buf, "timeline");	/* col name */
	pq_sendint(&buf, 0, 4);		/* table oid */
	pq_sendint(&buf, 0, 2);		/* attnum */
	pq_sendint(&buf, INT4OID, 4);		/* type oid */
	pq_sendint(&buf, 4, 2);		/* typlen */
	pq_sendint(&buf, 0, 4);		/* typmod */
	pq_sendint(&buf, 0, 2);		/* format code */
	pq_endmessage(&buf);

	/* Send a DataRow message */
	pq_beginmessage(&buf, 'D');
	pq_sendint(&buf, 2, 2);		/* # of columns */
	pq_sendint(&buf, strlen(sysid), 4); /* col1 len */
	pq_sendbytes(&buf, (char *) &sysid, strlen(sysid));
	pq_sendint(&buf, strlen(tli), 4);	/* col2 len */
	pq_sendbytes(&buf, (char *) tli, strlen(tli));
	pq_endmessage(&buf);

	/* Send CommandComplete and ReadyForQuery messages */
	EndCommand("SELECT", DestRemote);
	ReadyForQuery(DestRemote);
	/* ReadyForQuery did pq_flush for us */
}

/* ----------------
 *		EndCommand - clean up the destination at end of command
 * ----------------
 */
void
EndCommand(const char *commandTag, CommandDest dest)
{
    StringInfoData buf;

    switch (dest)
    {
    case DestRemote:
    case DestRemoteExecute:
        if (Gp_role == GP_ROLE_EXECUTE)
        {
            sendQEDetails();

            pq_beginmessage(&buf, 'C');
            pq_sendstring(&buf, commandTag);
            pq_endmessage(&buf);
        }
        else
            pq_puttextmessage('C', commandTag);
        break;
    case DestNone:
    case DestDebug:
    case DestSPI:
    case DestTuplestore:
    case DestIntoRel:
    case DestCopyOut:
        break;
    }
}

static void
SendResultDescriptionMessage(AttributeDefinition *attrs, int natts)
{
	int			proto = PG_PROTOCOL_MAJOR(FrontendProtocol);
	int			i;
	StringInfoData buf;

	pq_beginmessage(&buf, 'T'); /* tuple descriptor message type */
	pq_sendint(&buf, natts, 2);	/* # of attrs in tuples */

	for (i = 0; i < natts; ++i)
	{
		pq_sendstring(&buf, attrs[i].name);
		/* column ID info appears in protocol 3.0 and up */
		if (proto >= 3)
		{
			pq_sendint(&buf, 0, 4);
			pq_sendint(&buf, 0, 2);
		}
		/* If column is a domain, send the base type and typmod instead */
		pq_sendint(&buf, attrs[i].typid, sizeof(Oid));
		pq_sendint(&buf, attrs[i].typlen, sizeof(int16));
		/* typmod appears in protocol 2.0 and up */
		if (proto >= 2)
			pq_sendint(&buf, attrs[i].typmod, sizeof(int32));
		/* format info appears in protocol 3.0 and up */
		if (proto >= 3)
			pq_sendint(&buf, 0, 2);
	}

	pq_endmessage(&buf);
}

static Source *
CreateRemoteSource(const char *path, TupleDesc desc)
{
	RemoteSource *self = (RemoteSource *) palloc0(sizeof(RemoteSource));
	self->base.close = (SourceCloseProc) RemoteSourceClose;

	if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 3)
	{
		/* new way */
		StringInfoData	buf;
		int16			format;
		int				nattrs;
		int				i;

		self->base.read = (SourceReadProc) RemoteSourceRead;

		/* count valid fields */
		for (nattrs = 0, i = 0; i < desc->natts; i++)
		{
			if (desc->attrs[i]->attisdropped)
				continue;
			nattrs++;
		}

		format = (IsBinaryCopy() ? 1 : 0);
		pq_beginmessage(&buf, 'G');
		pq_sendbyte(&buf, format);		/* overall format */
		pq_sendint(&buf, nattrs, 2);
		for (i = 0; i < nattrs; i++)
			pq_sendint(&buf, format, 2);		/* per-column formats */
		pq_endmessage(&buf);
		self->buffer = makeStringInfo();
	}
	else if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 2)
	{
		self->base.read = (SourceReadProc) RemoteSourceReadOld;

		/* old way */
		if (IsBinaryCopy())
			ereport(ERROR,
					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
			errmsg("COPY BINARY is not supported to stdout or from stdin")));
		pq_putemptymessage('G');
	}
	else
	{
		self->base.read = (SourceReadProc) RemoteSourceReadOld;

		/* very old way */
		if (IsBinaryCopy())
			ereport(ERROR,
					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
			errmsg("COPY BINARY is not supported to stdout or from stdin")));
		pq_putemptymessage('D');
	}
	/* We *must* flush here to ensure FE knows it can send. */
	pq_flush();

	return (Source *) self;
}

/*
 * Send NOTIFY message to my front end.
 */
static void
NotifyMyFrontEnd(char *relname, int32 listenerPID)
{
	if (whereToSendOutput == DestRemote)
	{
		StringInfoData buf;

		pq_beginmessage(&buf, 'A');
		pq_sendint(&buf, listenerPID, sizeof(int32));
		pq_sendstring(&buf, relname);
		if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 3)
		{
			/* XXX Add parameter string here later */
			pq_sendstring(&buf, "");
		}
		pq_endmessage(&buf);

		/*
		 * NOTE: we do not do pq_flush() here.	For a self-notify, it will
		 * happen at the end of the transaction, and for incoming notifies
		 * ProcessIncomingNotify will do it after finding all the notifies.
		 */
	}
	else
		elog(INFO, "NOTIFY for %s", relname);
}

/* ----------------
 *		ReadyForQuery - tell dest that we are ready for a new query
 *
 *		The ReadyForQuery message is sent in protocol versions 2.0 and up
 *		so that the FE can tell when we are done processing a query string.
 *		In versions 3.0 and up, it also carries a transaction state indicator.
 *
 *		Note that by flushing the stdio buffer here, we can avoid doing it
 *		most other places and thus reduce the number of separate packets sent.
 * ----------------
 */
void
ReadyForQuery(CommandDest dest)
{
	switch (dest)
	{
		case DestRemote:
		case DestRemoteExecute:
			if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 3)
			{
				StringInfoData buf;

				pq_beginmessage(&buf, 'Z');
				pq_sendbyte(&buf, TransactionBlockStatusCode());
				pq_endmessage(&buf);
			}
			else if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 2)
				pq_putemptymessage('Z');
			/* Flush output at end of cycle in any case. */
			pq_flush();
			break;

		case DestNone:
		case DestDebug:
		case DestSPI:
		case DestTuplestore:
		case DestIntoRel:
		case DestCopyOut:
			break;
	}
}

/*
 * Execute the CREATE BARRIER command. Write a BARRIER WAL record and flush the
 * WAL buffers to disk before returning to the caller. Writing the WAL record
 * does not guarantee successful completion of the barrier command.
 */
void
ProcessCreateBarrierExecute(const char *id)
{
	StringInfoData buf;

	if (!IsConnFromCoord())
		ereport(ERROR,
				(errcode(ERRCODE_INTERNAL_ERROR),
				 errmsg("The CREATE BARRIER EXECUTE message is expected to "
						"arrive from a Coordinator")));
	{
		XLogRecData rdata[1];
		XLogRecPtr recptr;

		rdata[0].data = (char *) id;
		rdata[0].len = strlen(id) + 1;
		rdata[0].buffer = InvalidBuffer;
		rdata[0].next = NULL;

		recptr = XLogInsert(RM_BARRIER_ID, XLOG_BARRIER_CREATE, rdata);
		XLogFlush(recptr);
	}

	pq_beginmessage(&buf, 'b');
	pq_sendstring(&buf, id);
	pq_endmessage(&buf);
	pq_flush();
}

/*
 * SendRowDescriptionMessage --- send a RowDescription message to the frontend
 *
 * Notes: the TupleDesc has typically been manufactured by ExecTypeFromTL()
 * or some similar function; it does not contain a full set of fields.
 * The targetlist will be NIL when executing a utility function that does
 * not have a plan.  If the targetlist isn't NIL then it is a Query node's
 * targetlist; it is up to us to ignore resjunk columns in it.  The formats[]
 * array pointer might be NULL (if we are doing Describe on a prepared stmt);
 * send zeroes for the format codes in that case.
 */
void
SendRowDescriptionMessage(TupleDesc typeinfo, List *targetlist, int16 *formats)
{
	Form_pg_attribute *attrs = typeinfo->attrs;
	int			natts = typeinfo->natts;
	int			proto = PG_PROTOCOL_MAJOR(FrontendProtocol);
	int			i;
	StringInfoData buf;
	ListCell   *tlist_item = list_head(targetlist);

	pq_beginmessage(&buf, 'T'); /* tuple descriptor message type */
	pq_sendint(&buf, natts, 2); /* # of attrs in tuples */

	for (i = 0; i < natts; ++i)
	{
		Oid			atttypid = attrs[i]->atttypid;
		int32		atttypmod = attrs[i]->atttypmod;

		pq_sendstring(&buf, NameStr(attrs[i]->attname));
		/* column ID info appears in protocol 3.0 and up */
		if (proto >= 3)
		{
			/* Do we have a non-resjunk tlist item? */
			while (tlist_item &&
				   ((TargetEntry *) lfirst(tlist_item))->resjunk)
				tlist_item = lnext(tlist_item);
			if (tlist_item)
			{
				TargetEntry *tle = (TargetEntry *) lfirst(tlist_item);

				pq_sendint(&buf, tle->resorigtbl, 4);
				pq_sendint(&buf, tle->resorigcol, 2);
				tlist_item = lnext(tlist_item);
			}
			else
			{
				/* No info available, so send zeroes */
				pq_sendint(&buf, 0, 4);
				pq_sendint(&buf, 0, 2);
			}
		}
		/* If column is a domain, send the base type and typmod instead */
		atttypid = getBaseTypeAndTypmod(atttypid, &atttypmod);
		pq_sendint(&buf, (int) atttypid, sizeof(atttypid));
		pq_sendint(&buf, attrs[i]->attlen, sizeof(attrs[i]->attlen));
		/* typmod appears in protocol 2.0 and up */
		if (proto >= 2)
			pq_sendint(&buf, atttypmod, sizeof(atttypmod));
		/* format info appears in protocol 3.0 and up */
		if (proto >= 3)
		{
			if (formats)
				pq_sendint(&buf, formats[i], 2);
			else
				pq_sendint(&buf, 0, 2);
		}
	}
	pq_endmessage(&buf);
}

/*
 * SendNumRowsRejected
 *
 * Using this function the QE sends back to the client QD the number 
 * of rows that were rejected in this last data load in SREH mode.
 */
void SendNumRowsRejected(int numrejected)
{
	StringInfoData buf;
	
	if (Gp_role != GP_ROLE_EXECUTE)
		elog(FATAL, "SendNumRowsRejected: called outside of execute context.");

	pq_beginmessage(&buf, 'j'); /* 'j' is the msg code for rejected records */
	pq_sendint(&buf, numrejected, 4);
	pq_endmessage(&buf);	
}

static void
putEndLocationReply(XLogRecPtr *endLocation)
{
	StringInfoData buf;
	
	pq_beginmessage(&buf, 's');
	pq_sendint(&buf, endLocation->xlogid, 4);
	pq_sendint(&buf, endLocation->xrecoff, 4);
	pq_endmessage(&buf);
	pq_flush();
}

/*
 * Send a gpdb libpq message.
 */
void
sendQEDetails(void)
{
	StringInfoData buf;

	pq_beginmessage(&buf, 'w');
	pq_sendint(&buf, (int32) ICListenerPort, sizeof(int32));
	pq_sendint(&buf, sizeof(PG_VERSION_STR), sizeof(int32));
	pq_sendbytes(&buf, PG_VERSION_STR, sizeof(PG_VERSION_STR));
	pq_endmessage(&buf);
}

/*
 * Send a gpdb libpq message.
 */
void
sendQEDetails(void)
{
	StringInfoData buf;

	pq_beginmessage(&buf, 'w');
	pq_sendint(&buf, (int32) Gp_listener_port, sizeof(int32));			
	pq_sendint64(&buf, VmemTracker_GetMaxReservedVmemBytes());
	pq_sendint(&buf, sizeof(PG_VERSION_STR), sizeof(int32));
	pq_sendbytes(&buf, PG_VERSION_STR, sizeof(PG_VERSION_STR));
	pq_endmessage(&buf);
}

/*
 * START_REPLICATION
 */
static void
StartReplication(StartReplicationCmd *cmd)
{
    StringInfoData buf;

    /*
     * Let postmaster know that we're streaming. Once we've declared us as a
     * WAL sender process, postmaster will let us outlive the bgwriter and
     * kill us last in the shutdown sequence, so we get a chance to stream all
     * remaining WAL at shutdown, including the shutdown checkpoint. Note that
     * there's no going back, and we mustn't write any WAL records after this.
     */
    MarkPostmasterChildWalSender();
    SendPostmasterSignal(PMSIGNAL_ADVANCE_STATE_MACHINE);

    /*
     * Check that we're logging enough information in the WAL for
     * log-shipping.
     *
     * NOTE: This only checks the current value of wal_level. Even if the
     * current setting is not 'minimal', there can be old WAL in the pg_xlog
     * directory that was created with 'minimal'. So this is not bulletproof,
     * the purpose is just to give a user-friendly error message that hints
     * how to configure the system correctly.
     */
    if (wal_level == WAL_LEVEL_MINIMAL)
        ereport(FATAL,
                (errcode(ERRCODE_CANNOT_CONNECT_NOW),
                 errmsg("standby connections not allowed because wal_level=minimal")));

    /*
     * When we first start replication the standby will be behind the primary.
     * For some applications, for example, synchronous replication, it is
     * important to have a clear state for this initial catchup mode, so we
     * can trigger actions when we change streaming state later. We may stay
     * in this state for a long time, which is exactly why we want to be able
     * to monitor whether or not we are still here.
     */
    WalSndSetState(WALSNDSTATE_CATCHUP);

    /* Send a CopyBothResponse message, and start streaming */
    pq_beginmessage(&buf, 'W');
    pq_sendbyte(&buf, 0);
    pq_sendint(&buf, 0, 2);
    pq_endmessage(&buf);
    pq_flush();

    /*
     * Initialize position to the received one, then the xlog records begin to
     * be shipped from that position
     */
    sentPtr = cmd->startpoint;
}

/*
 * START_REPLICATION
 */
static void
StartReplication(StartReplicationCmd * cmd)
{
	StringInfoData buf;

	/*
	 * Let postmaster know that we're streaming. Once we've declared us as
	 * a WAL sender process, postmaster will let us outlive the bgwriter and
	 * kill us last in the shutdown sequence, so we get a chance to stream
	 * all remaining WAL at shutdown, including the shutdown checkpoint.
	 * Note that there's no going back, and we mustn't write any WAL records
	 * after this.
	 */
	MarkPostmasterChildWalSender();

	/*
	 * Check that we're logging enough information in the WAL for
	 * log-shipping.
	 *
	 * NOTE: This only checks the current value of wal_level. Even if the
	 * current setting is not 'minimal', there can be old WAL in the pg_xlog
	 * directory that was created with 'minimal'. So this is not bulletproof,
	 * the purpose is just to give a user-friendly error message that hints
	 * how to configure the system correctly.
	 */
	if (wal_level == WAL_LEVEL_MINIMAL)
		ereport(FATAL,
				(errcode(ERRCODE_CANNOT_CONNECT_NOW),
		errmsg("standby connections not allowed because wal_level=minimal")));

	/* Send a CopyBothResponse message, and start streaming */
	pq_beginmessage(&buf, 'W');
	pq_sendbyte(&buf, 0);
	pq_sendint(&buf, 0, 2);
	pq_endmessage(&buf);
	pq_flush();

	/*
	 * Initialize position to the received one, then the xlog records begin to
	 * be shipped from that position
	 */
	sentPtr = cmd->startpoint;
}