Add string_agg aggregate functions. The one argument version concatenates

the input values into a string. The two argument version also does the same
thing, but inserts delimiters between elements.

Original patch by Pavel Stehule, reviewed by David E. Wheeler and me.

2 files changed, 38 insertions, 0 deletions

diff --git a/src/test/regress/expected/aggregates.out b/src/test/regress/expected/aggregates.out
index 9669a52fbe..2460d9dfd6 100644
--- a/src/test/regress/expected/aggregates.out
+++ b/src/test/regress/expected/aggregates.out
@@ -799,3 +799,34 @@ select aggfns(distinct a,a,c order by a,b)
 ERROR:  in an aggregate with DISTINCT, ORDER BY expressions must appear in argument list
 LINE 1: select aggfns(distinct a,a,c order by a,b)
                                                 ^
+-- string_agg tests
+select string_agg(a) from (values('aaaa'),('bbbb'),('cccc')) g(a);
+  string_agg  
+--------------
+ aaaabbbbcccc
+(1 row)
+
+select string_agg(a,',') from (values('aaaa'),('bbbb'),('cccc')) g(a);
+   string_agg   
+----------------
+ aaaa,bbbb,cccc
+(1 row)
+
+select string_agg(a,',') from (values('aaaa'),(null),('bbbb'),('cccc')) g(a);
+   string_agg   
+----------------
+ aaaa,bbbb,cccc
+(1 row)
+
+select string_agg(a,',') from (values(null),(null),('bbbb'),('cccc')) g(a);
+ string_agg 
+------------
+ bbbb,cccc
+(1 row)
+
+select string_agg(a,',') from (values(null),(null)) g(a);
+ string_agg 
+------------
+ 
+(1 row)
+
diff --git a/src/test/regress/sql/aggregates.sql b/src/test/regress/sql/aggregates.sql
index 18f2e57b72..daa89167a2 100644
--- a/src/test/regress/sql/aggregates.sql
+++ b/src/test/regress/sql/aggregates.sql
@@ -355,3 +355,10 @@ select aggfns(distinct a,b,c order by a,b,i,c)
   from (values (1,1,'foo')) v(a,b,c), generate_series(1,2) i;
 select aggfns(distinct a,a,c order by a,b)
   from (values (1,1,'foo')) v(a,b,c), generate_series(1,2) i;
+
+-- string_agg tests
+select string_agg(a) from (values('aaaa'),('bbbb'),('cccc')) g(a);
+select string_agg(a,',') from (values('aaaa'),('bbbb'),('cccc')) g(a);
+select string_agg(a,',') from (values('aaaa'),(null),('bbbb'),('cccc')) g(a);
+select string_agg(a,',') from (values(null),(null),('bbbb'),('cccc')) g(a);
+select string_agg(a,',') from (values(null),(null)) g(a);