Add array_agg as alias of groupArray for PostgreSQL compatibility

docs/en/sql-reference/aggregate-functions/reference/grouparray.md

@@ -44,3 +44,5 @@ Result:
 ```
 
 The groupArray function will remove ᴺᵁᴸᴸ value based on the above results.
+
+- Alias: `array_agg`.

src/AggregateFunctions/AggregateFunctionGroupArray.cpp

@@ -125,6 +125,7 @@ void registerAggregateFunctionGroupArray(AggregateFunctionFactory & factory)
     AggregateFunctionProperties properties = { .returns_default_when_only_null = false, .is_order_dependent = true };
 
     factory.registerFunction("groupArray", { createAggregateFunctionGroupArray<false>, properties });
+    factory.registerAlias("array_agg", "groupArray", AggregateFunctionFactory::CaseInsensitive);
     factory.registerFunction("groupArraySample", { createAggregateFunctionGroupArraySample, properties });
     factory.registerFunction("groupArrayLast", { createAggregateFunctionGroupArray<true>, properties });
 }

tests/queries/0_stateless/02813_array_agg.reference

@@ -0,0 +1,6 @@
+['hello, world!','hello, world!','hello, world!','hello, world!','hello, world!']
+['hello, world!']
+['hello, world!']
+['hello, world!']
+['hello, world!']
+['hello, world!']

tests/queries/0_stateless/02813_array_agg.sql

@@ -0,0 +1,10 @@
+drop table if exists t;
+create table t (n Int32, s String) engine=MergeTree order by n;
+
+insert into t select number, 'hello, world!' from numbers (5);
+
+select array_agg(s) from t;
+
+select aRray_Agg(s) from t group by n;
+
+drop table t;