## 1.66. mergeset( integer, integer )

Function Properties
Language: PLPGSQL
Return Type: bigint

Generate MERGE_SET event to request that sets be merged together. Both sets must exist, and originate on the same node. They must be subscribed by the same set of nodes.

    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;

    	-- ----
    	-- 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, p_add_id);
    end;