8.79. mergeset(integer, integer)

    declare
    	p_set_id			alias for $1;
    	p_add_id			alias for $2;
    	v_origin			int4;
    begin
    	-- ----
    	-- Grab the central configuration lock
    	-- ----
    	lock table sl_config_lock;
    	
    	-- ----
    	-- Check that both sets exist and originate here
    	-- ----
    	if p_set_id = p_add_id then
    		raise exception 'Slony-I: merged set ids cannot be identical';
    	end if;
    	select set_origin into v_origin from sl_set
    			where set_id = p_set_id;
    	if not found then
    		raise exception 'Slony-I: set % not found', p_set_id;
    	end if;
    	if v_origin != getLocalNodeId('_schemadoc') then
    		raise exception 'Slony-I: set % does not originate on local node',
    				p_set_id;
    	end if;
    
    	select set_origin into v_origin from sl_set
    			where set_id = p_add_id;
    	if not found then
    		raise exception 'Slony-I: set % not found', p_add_id;
    	end if;
    	if v_origin != getLocalNodeId('_schemadoc') then
    		raise exception 'Slony-I: set % does not originate on local node',
    				p_add_id;
    	end if;
    
    	-- ----
    	-- Check that both sets are subscribed by the same set of nodes
    	-- ----
    	if exists (select true from sl_subscribe SUB1
    				where SUB1.sub_set = p_set_id
    				and SUB1.sub_receiver not in (select SUB2.sub_receiver
    						from sl_subscribe SUB2
    						where SUB2.sub_set = p_add_id))
    	then
    		raise exception 'Slony-I: subscriber lists of set % and % are different',
    				p_set_id, p_add_id;
    	end if;
    
    	if exists (select true from sl_subscribe SUB1
    				where SUB1.sub_set = p_add_id
    				and SUB1.sub_receiver not in (select SUB2.sub_receiver
    						from sl_subscribe SUB2
    						where SUB2.sub_set = p_set_id))
    	then
    		raise exception 'Slony-I: subscriber lists of set % and % are different',
    				p_add_id, p_set_id;
    	end if;
    
    	-- ----
    	-- Check that all ENABLE_SUBSCRIPTION events for the set are confirmed
    	-- ----
    	if exists (select true from sl_event
    			where ev_type = 'ENABLE_SUBSCRIPTION'
    			and ev_data1 = p_add_id::text
    			and ev_seqno > (select max(con_seqno) from sl_confirm
    					where con_origin = ev_origin
    					and con_received::text = ev_data3))
    	then
    		raise exception 'Slony-I: set % has subscriptions in progress - cannot merge',
    				p_add_id;
    	end if;
    
    	-- ----
    	-- Create a SYNC event, merge the sets, create a MERGE_SET event
    	-- ----
    	perform createEvent('_schemadoc', 'SYNC', NULL);
    	perform mergeSet_int(p_set_id, p_add_id);
    	return  createEvent('_schemadoc', 'MERGE_SET', 
    			p_set_id::text, p_add_id::text);
    end;