Fix(bigquery)!: recognize ARRAY_CONCAT_AGG as an aggregate function (#5141)

Author: georgesittas

sqlglot/expressions.py

@@ -5539,6 +5539,10 @@ class ArrayConcat(Func):
     is_var_len_args = True
 
 
+class ArrayConcatAgg(AggFunc):
+    pass
+
+
 class ArrayConstructCompact(Func):
     arg_types = {"expressions": True}
     is_var_len_args = True

tests/dialects/test_bigquery.py

@@ -55,6 +55,10 @@ def test_bigquery(self):
         select_with_quoted_udf = self.validate_identity("SELECT `p.d.UdF`(data) FROM `p.d.t`")
         self.assertEqual(select_with_quoted_udf.selects[0].name, "p.d.UdF")
 
+        self.validate_identity("ARRAY_CONCAT_AGG(x ORDER BY ARRAY_LENGTH(x) LIMIT 2)")
+        self.validate_identity("ARRAY_CONCAT_AGG(x LIMIT 2)")
+        self.validate_identity("ARRAY_CONCAT_AGG(x ORDER BY ARRAY_LENGTH(x))")
+        self.validate_identity("ARRAY_CONCAT_AGG(x)")
         self.validate_identity("PARSE_TIMESTAMP('%Y-%m-%dT%H:%M:%E*S%z', x)")
         self.validate_identity("SELECT ARRAY_CONCAT([1])")
         self.validate_identity("SELECT * FROM READ_CSV('bla.csv')")