Function exec_replication_command

src/backend/replication/walsender.c:1558–1763

* Execute an incoming replication command. * * Returns true if the cmd_string was recognized as WalSender command, false * if not. */

 * if not.
 */
bool
exec_replication_command(const char *cmd_string)
{
	int			parse_rc;
	Node	   *cmd_node;
	const char *cmdtag;
	MemoryContext cmd_context;
	MemoryContext old_context;

	/*
	 * If WAL sender has been told that shutdown is getting close, switch its
	 * status accordingly to handle the next replication commands correctly.
	 */
	if (got_STOPPING)
		WalSndSetState(WALSNDSTATE_STOPPING);

	/*
	 * Throw error if in stopping mode.  We need prevent commands that could
	 * generate WAL while the shutdown checkpoint is being written.  To be
	 * safe, we just prohibit all new commands.
	 */
	if (MyWalSnd->state == WALSNDSTATE_STOPPING)
		ereport(ERROR,
				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				 errmsg("cannot execute new commands while WAL sender is in stopping mode")));

	/*
	 * CREATE_REPLICATION_SLOT ... LOGICAL exports a snapshot until the next
	 * command arrives. Clean up the old stuff if there's anything.
	 */
	SnapBuildClearExportedSnapshot();

	CHECK_FOR_INTERRUPTS();

	/*
	 * Prepare to parse and execute the command.
	 */
	cmd_context = AllocSetContextCreate(CurrentMemoryContext,
										"Replication command context",
										ALLOCSET_DEFAULT_SIZES);
	old_context = MemoryContextSwitchTo(cmd_context);

	replication_scanner_init(cmd_string);

	/*
	 * Is it a WalSender command?
	 */
	if (!replication_scanner_is_replication_command())
	{
		/* Nope; clean up and get out. */
		replication_scanner_finish();

		MemoryContextSwitchTo(old_context);
		MemoryContextDelete(cmd_context);

		/* XXX this is a pretty random place to make this check */
		if (MyDatabaseId == InvalidOid)
			ereport(ERROR,