create string_agg in slony1_base.sql not slony1_funcs.sql

If the CREATE AGGREGATE is in slony1_funcs.sql it will fail on an update functions
since the aggregate already exists.  As part of the upgrade we will check
to see if we need to create the aggregate.

src/backend/slony1_base.sql

@@ -723,6 +723,39 @@ comment on column @NAMESPACE@.sl_components.co_eventtype is 'what kind of event
 comment on column @NAMESPACE@.sl_components.co_event is 'which event have I started processing?';
 
 
+
+--
+-- we create a function + aggregate for string_agg to aggregate strings
+-- some versions of PG (ie prior to 9.0) don't support this
+CREATE OR replace function @NAMESPACE@.agg_text_sum(txt_before TEXT, txt_new TEXT) RETURNS TEXT AS
+$BODY$
+DECLARE
+  c_delim text;
+BEGIN
+    c_delim = ',';
+	IF (txt_before IS NULL or txt_before='') THEN
+	   RETURN txt_new;
+	END IF;
+	RETURN txt_before || c_delim || txt_new;
+END;
+$BODY$
+LANGUAGE plpgsql;
+comment on function @NAMESPACE@.agg_text_sum(text,text) is 
+'An accumulator function used by the slony string_agg function to
+aggregate rows into a string';
+--
+-- create a string_agg function in the slony schema.
+-- PG 8.3 does not have this function so we make our own
+-- when slony stops supporting PG 8.3 we can switch to
+-- the PG 9.0+ provided version of string_agg
+--
+CREATE AGGREGATE @NAMESPACE@.string_agg(text) (
+SFUNC=@NAMESPACE@.agg_text_sum,
+STYPE=text,
+INITCOND=''
+);
+
+
 -- ----------------------------------------------------------------------
 -- Last but not least grant USAGE to the replication schema objects.
 -- ----------------------------------------------------------------------

src/backend/slony1_funcs.sql

@@ -5487,7 +5487,13 @@ create table @NAMESPACE@.sl_components (
 		alter table @NAMESPACE@.sl_log_2
 			enable replica trigger apply_trigger;
 	end if;
-
+	if not exists (select 1 from information_schema.routines where routine_schema = '_@CLUSTERNAME@' and routine_name = 'string_agg') then
+	       CREATE AGGREGATE @NAMESPACE@.string_agg(text) (
+	   	      SFUNC=@NAMESPACE@.agg_text_sum,
+		      STYPE=text,
+		      INITCOND=''
+		      );
+	end if;		    
 	return p_old;
 end;
 $$ language plpgsql;
@@ -6262,14 +6268,3 @@ LANGUAGE plpgsql;
 comment on function @NAMESPACE@.agg_text_sum(text,text) is 
 'An accumulator function used by the slony string_agg function to
 aggregate rows into a string';
---
--- create a string_agg function in the slony schema.
--- PG 8.3 does not have this function so we make our own
--- when slony stops supporting PG 8.3 we can switch to
--- the PG 9.0+ provided version of string_agg
---
-CREATE AGGREGATE @NAMESPACE@.string_agg(text) (
-SFUNC=@NAMESPACE@.agg_text_sum,
-STYPE=text,
-INITCOND=''
-);