Re: Variadic aggregates vs. project policy - Mailing list pgsql-hackers

From Tom Lane
Subject Re: Variadic aggregates vs. project policy
Date
Msg-id 23790.1377906986@sss.pgh.pa.us
Whole thread Raw
In response to Re: Variadic aggregates vs. project policy  (Andres Freund <andres@2ndquadrant.com>)
Responses Re: Variadic aggregates vs. project policy
List pgsql-hackers
Andres Freund <andres@2ndquadrant.com> writes:
> On 2013-08-29 18:29:34 -0400, Tom Lane wrote:
>> Andres Freund <andres@2ndquadrant.com> writes:
>>> I'd say we let the check in there but have a list of exceptions in it so
>>> that one has to explicitly think about the issue before adding the
>>> function.

>> That's pretty much how the tests in opr_sanity work now.

> I basically mean that we should adapt the paragraph you quoted upthread
> to roughly say something like:

Attached is a complete draft patch for this.  I modified the text about
the opr_sanity test a bit (though not exactly as you suggest) and also
added some text in xaggr.sgml pointing out the hazard, so that users can
make informed decisions about whether they want to use the feature.

My basic approach was to share the existing grammar and catalog support
for declaring variadic function arguments.  That made it practically free
to add support for storing argument names for aggregates, so I did that
too.  However, it was and remains true that aggregates don't support
default values for arguments, nor do we support writing calls in named or
mixed parameter style for them.  The same is true of window functions.
I felt that fixing those things was out of scope for this patch, but it
might be something somebody else wants to work on.  (I think that fixing
this might be relatively easy for window functions --- just need to get
the planner to apply its existing code for fixing up regular FuncExprs.
But it's less than trivial for aggregates because of our use of
TargetEntry list representation for aggregate parameter lists.)
Addition of default values for aggregates would run up against the same
number-of-arguments ambiguity we were discussing for VARIADIC, but I don't
see why we shouldn't adopt the same we-won't-do-this-but-users-can stance
as for VARIADIC.

Another point is that variadic window functions could stand some love.
I think it partially works, but ruleutils.c at least doesn't know how to
reverse-list such calls correctly.  Again, that seemed out of scope for
this patch.

Comments?

            regards, tom lane

diff --git a/doc/src/sgml/ref/alter_aggregate.sgml b/doc/src/sgml/ref/alter_aggregate.sgml
index 571a50a..aab5b2b 100644
*** a/doc/src/sgml/ref/alter_aggregate.sgml
--- b/doc/src/sgml/ref/alter_aggregate.sgml
*************** PostgreSQL documentation
*** 21,29 ****

   <refsynopsisdiv>
  <synopsis>
! ALTER AGGREGATE <replaceable>name</replaceable> ( <replaceable>argtype</replaceable> [ , ... ] ) RENAME TO
<replaceable>new_name</replaceable>
! ALTER AGGREGATE <replaceable>name</replaceable> ( <replaceable>argtype</replaceable> [ , ... ] ) OWNER TO
<replaceable>new_owner</replaceable>
! ALTER AGGREGATE <replaceable>name</replaceable> ( <replaceable>argtype</replaceable> [ , ... ] ) SET SCHEMA
<replaceable>new_schema</replaceable>
  </synopsis>
   </refsynopsisdiv>

--- 21,32 ----

   <refsynopsisdiv>
  <synopsis>
! ALTER AGGREGATE <replaceable>name</replaceable> ( [ <replaceable>argmode</replaceable> ] [
<replaceable>arg_name</replaceable>] <replaceable>arg_data_type</replaceable> [ , ... ] ) 
!   RENAME TO <replaceable>new_name</replaceable>
! ALTER AGGREGATE <replaceable>name</replaceable> ( [ <replaceable>argmode</replaceable> ] [
<replaceable>arg_name</replaceable>] <replaceable>arg_data_type</replaceable> [ , ... ] ) 
!   OWNER TO <replaceable>new_owner</replaceable>
! ALTER AGGREGATE <replaceable>name</replaceable> ( [ <replaceable>argmode</replaceable> ] [
<replaceable>arg_name</replaceable>] <replaceable>arg_data_type</replaceable> [ , ... ] ) 
!   SET SCHEMA <replaceable>new_schema</replaceable>
  </synopsis>
   </refsynopsisdiv>

*************** ALTER AGGREGATE <replaceable>name</repla
*** 62,73 ****
     </varlistentry>

     <varlistentry>
!     <term><replaceable class="parameter">argtype</replaceable></term>
      <listitem>
       <para>
        An input data type on which the aggregate function operates.
        To reference a zero-argument aggregate function, write <literal>*</>
!       in place of the list of input data types.
       </para>
      </listitem>
     </varlistentry>
--- 65,100 ----
     </varlistentry>

     <varlistentry>
!     <term><replaceable class="parameter">argmode</replaceable></term>
!
!     <listitem>
!      <para>
!       The mode of an argument: <literal>IN</> or <literal>VARIADIC</>.
!       If omitted, the default is <literal>IN</>.
!      </para>
!     </listitem>
!    </varlistentry>
!
!    <varlistentry>
!     <term><replaceable class="parameter">arg_name</replaceable></term>
!
!     <listitem>
!      <para>
!       The name of an argument.
!       Note that <command>ALTER AGGREGATE</command> does not actually pay
!       any attention to argument names, since only the argument data
!       types are needed to determine the aggregate function's identity.
!      </para>
!     </listitem>
!    </varlistentry>
!
!    <varlistentry>
!     <term><replaceable class="parameter">arg_data_type</replaceable></term>
      <listitem>
       <para>
        An input data type on which the aggregate function operates.
        To reference a zero-argument aggregate function, write <literal>*</>
!       in place of the list of argument specifications.
       </para>
      </listitem>
     </varlistentry>
diff --git a/doc/src/sgml/ref/alter_extension.sgml b/doc/src/sgml/ref/alter_extension.sgml
index 2dbba0c..a14fcb4 100644
*** a/doc/src/sgml/ref/alter_extension.sgml
--- b/doc/src/sgml/ref/alter_extension.sgml
*************** ALTER EXTENSION <replaceable class="PARA
*** 30,36 ****

  <phrase>where <replaceable class="PARAMETER">member_object</replaceable> is:</phrase>

!   AGGREGATE <replaceable class="PARAMETER">agg_name</replaceable> (<replaceable
class="PARAMETER">agg_type</replaceable>[, ...] ) | 
    CAST (<replaceable>source_type</replaceable> AS <replaceable>target_type</replaceable>) |
    COLLATION <replaceable class="PARAMETER">object_name</replaceable> |
    CONVERSION <replaceable class="PARAMETER">object_name</replaceable> |
--- 30,36 ----

  <phrase>where <replaceable class="PARAMETER">member_object</replaceable> is:</phrase>

!   AGGREGATE <replaceable class="PARAMETER">agg_name</replaceable> ( [ <replaceable
class="parameter">argmode</replaceable>] [ <replaceable class="parameter">argname</replaceable> ] <replaceable
class="parameter">agg_type</replaceable>[, ...] ) | 
    CAST (<replaceable>source_type</replaceable> AS <replaceable>target_type</replaceable>) |
    COLLATION <replaceable class="PARAMETER">object_name</replaceable> |
    CONVERSION <replaceable class="PARAMETER">object_name</replaceable> |
*************** ALTER EXTENSION <replaceable class="PARA
*** 179,185 ****
        <para>
         An input data type on which the aggregate function operates.
         To reference a zero-argument aggregate function, write <literal>*</>
!        in place of the list of input data types.
        </para>
       </listitem>
      </varlistentry>
--- 179,185 ----
        <para>
         An input data type on which the aggregate function operates.
         To reference a zero-argument aggregate function, write <literal>*</>
!        in place of the list of argument specifications.
        </para>
       </listitem>
      </varlistentry>
diff --git a/doc/src/sgml/ref/comment.sgml b/doc/src/sgml/ref/comment.sgml
index e94dd4b..e550500 100644
*** a/doc/src/sgml/ref/comment.sgml
--- b/doc/src/sgml/ref/comment.sgml
*************** PostgreSQL documentation
*** 23,29 ****
  <synopsis>
  COMMENT ON
  {
!   AGGREGATE <replaceable class="PARAMETER">agg_name</replaceable> (<replaceable
class="PARAMETER">agg_type</replaceable>[, ...] ) | 
    CAST (<replaceable>source_type</replaceable> AS <replaceable>target_type</replaceable>) |
    COLLATION <replaceable class="PARAMETER">object_name</replaceable> |
    COLUMN <replaceable class="PARAMETER">relation_name</replaceable>.<replaceable
class="PARAMETER">column_name</replaceable>| 
--- 23,29 ----
  <synopsis>
  COMMENT ON
  {
!   AGGREGATE <replaceable class="PARAMETER">agg_name</replaceable> ( [ <replaceable
class="parameter">argmode</replaceable>] [ <replaceable class="parameter">argname</replaceable> ] <replaceable
class="parameter">agg_type</replaceable>[, ...] ) | 
    CAST (<replaceable>source_type</replaceable> AS <replaceable>target_type</replaceable>) |
    COLLATION <replaceable class="PARAMETER">object_name</replaceable> |
    COLUMN <replaceable class="PARAMETER">relation_name</replaceable>.<replaceable
class="PARAMETER">column_name</replaceable>| 
*************** COMMENT ON
*** 126,132 ****
       <para>
        An input data type on which the aggregate function operates.
        To reference a zero-argument aggregate function, write <literal>*</>
!       in place of the list of input data types.
       </para>
      </listitem>
     </varlistentry>
--- 126,132 ----
       <para>
        An input data type on which the aggregate function operates.
        To reference a zero-argument aggregate function, write <literal>*</>
!       in place of the list of argument specifications.
       </para>
      </listitem>
     </varlistentry>
*************** COMMENT ON
*** 156,162 ****
        The mode of a function argument: <literal>IN</>, <literal>OUT</>,
        <literal>INOUT</>, or <literal>VARIADIC</>.
        If omitted, the default is <literal>IN</>.
!       Note that <command>COMMENT ON FUNCTION</command> does not actually pay
        any attention to <literal>OUT</> arguments, since only the input
        arguments are needed to determine the function's identity.
        So it is sufficient to list the <literal>IN</>, <literal>INOUT</>,
--- 156,162 ----
        The mode of a function argument: <literal>IN</>, <literal>OUT</>,
        <literal>INOUT</>, or <literal>VARIADIC</>.
        If omitted, the default is <literal>IN</>.
!       Note that <command>COMMENT</command> does not actually pay
        any attention to <literal>OUT</> arguments, since only the input
        arguments are needed to determine the function's identity.
        So it is sufficient to list the <literal>IN</>, <literal>INOUT</>,
*************** COMMENT ON
*** 170,176 ****
      <listitem>
       <para>
        The name of a function argument.
!       Note that <command>COMMENT ON FUNCTION</command> does not actually pay
        any attention to argument names, since only the argument data
        types are needed to determine the function's identity.
       </para>
--- 170,176 ----
      <listitem>
       <para>
        The name of a function argument.
!       Note that <command>COMMENT</command> does not actually pay
        any attention to argument names, since only the argument data
        types are needed to determine the function's identity.
       </para>
diff --git a/doc/src/sgml/ref/create_aggregate.sgml b/doc/src/sgml/ref/create_aggregate.sgml
index d5e4e27..2b35fa4 100644
*** a/doc/src/sgml/ref/create_aggregate.sgml
--- b/doc/src/sgml/ref/create_aggregate.sgml
*************** PostgreSQL documentation
*** 21,27 ****

   <refsynopsisdiv>
  <synopsis>
! CREATE AGGREGATE <replaceable class="PARAMETER">name</replaceable> ( <replaceable
class="PARAMETER">input_data_type</replaceable>[ , ... ] ) ( 
      SFUNC = <replaceable class="PARAMETER">sfunc</replaceable>,
      STYPE = <replaceable class="PARAMETER">state_data_type</replaceable>
      [ , FINALFUNC = <replaceable class="PARAMETER">ffunc</replaceable> ]
--- 21,27 ----

   <refsynopsisdiv>
  <synopsis>
! CREATE AGGREGATE <replaceable class="parameter">name</replaceable> ( [ <replaceable
class="parameter">argmode</replaceable>] [ <replaceable class="parameter">arg_name</replaceable> ] <replaceable
class="parameter">arg_data_type</replaceable>[ , ... ] ) ( 
      SFUNC = <replaceable class="PARAMETER">sfunc</replaceable>,
      STYPE = <replaceable class="PARAMETER">state_data_type</replaceable>
      [ , FINALFUNC = <replaceable class="PARAMETER">ffunc</replaceable> ]
*************** CREATE AGGREGATE <replaceable class="PAR
*** 118,124 ****
     Note that this behavior is only available when
     <replaceable class="PARAMETER">state_data_type</replaceable>
     is the same as the first
!    <replaceable class="PARAMETER">input_data_type</replaceable>.
     When these types are different, you must supply a nonnull initial
     condition or use a nonstrict transition function.
    </para>
--- 118,124 ----
     Note that this behavior is only available when
     <replaceable class="PARAMETER">state_data_type</replaceable>
     is the same as the first
!    <replaceable class="PARAMETER">arg_data_type</replaceable>.
     When these types are different, you must supply a nonnull initial
     condition or use a nonstrict transition function.
    </para>
*************** SELECT col FROM tab ORDER BY col USING s
*** 187,198 ****
     </varlistentry>

     <varlistentry>
!     <term><replaceable class="PARAMETER">input_data_type</replaceable></term>
      <listitem>
       <para>
        An input data type on which this aggregate function operates.
        To create a zero-argument aggregate function, write <literal>*</>
!       in place of the list of input data types.  (An example of such an
        aggregate is <function>count(*)</function>.)
       </para>
      </listitem>
--- 187,222 ----
     </varlistentry>

     <varlistentry>
!     <term><replaceable class="parameter">argmode</replaceable></term>
!
!     <listitem>
!      <para>
!       The mode of an argument: <literal>IN</> or <literal>VARIADIC</>.
!       (Aggregate functions do not support <literal>OUT</> arguments.)
!       If omitted, the default is <literal>IN</>.  Only the last argument
!       can be marked <literal>VARIADIC</>.
!      </para>
!     </listitem>
!    </varlistentry>
!
!    <varlistentry>
!     <term><replaceable class="parameter">arg_name</replaceable></term>
!
!     <listitem>
!      <para>
!       The name of an argument.  This is currently only useful for
!       documentation purposes.  If omitted, the argument has no name.
!      </para>
!     </listitem>
!    </varlistentry>
!
!    <varlistentry>
!     <term><replaceable class="PARAMETER">arg_data_type</replaceable></term>
      <listitem>
       <para>
        An input data type on which this aggregate function operates.
        To create a zero-argument aggregate function, write <literal>*</>
!       in place of the list of argument specifications.  (An example of such an
        aggregate is <function>count(*)</function>.)
       </para>
      </listitem>
*************** SELECT col FROM tab ORDER BY col USING s
*** 205,212 ****
        In the old syntax for <command>CREATE AGGREGATE</>, the input data type
        is specified by a <literal>basetype</> parameter rather than being
        written next to the aggregate name.  Note that this syntax allows
!       only one input parameter.  To define a zero-argument aggregate function,
!       specify the <literal>basetype</> as
        <literal>"ANY"</> (not <literal>*</>).
       </para>
      </listitem>
--- 229,236 ----
        In the old syntax for <command>CREATE AGGREGATE</>, the input data type
        is specified by a <literal>basetype</> parameter rather than being
        written next to the aggregate name.  Note that this syntax allows
!       only one input parameter.  To define a zero-argument aggregate function
!       with this syntax, specify the <literal>basetype</> as
        <literal>"ANY"</> (not <literal>*</>).
       </para>
      </listitem>
diff --git a/doc/src/sgml/ref/drop_aggregate.sgml b/doc/src/sgml/ref/drop_aggregate.sgml
index 1ed152f..06060fb 100644
*** a/doc/src/sgml/ref/drop_aggregate.sgml
--- b/doc/src/sgml/ref/drop_aggregate.sgml
*************** PostgreSQL documentation
*** 21,27 ****

   <refsynopsisdiv>
  <synopsis>
! DROP AGGREGATE [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable> ( <replaceable
class="PARAMETER">argtype</replaceable>[ , ... ] ) [ CASCADE | RESTRICT ] 
  </synopsis>
   </refsynopsisdiv>

--- 21,29 ----

   <refsynopsisdiv>
  <synopsis>
! DROP AGGREGATE [ IF EXISTS ]
!   <replaceable class="parameter">name</replaceable> ( [ <replaceable class="parameter">argmode</replaceable> ] [
<replaceableclass="parameter">arg_name</replaceable> ] <replaceable class="parameter">arg_data_type</replaceable> [ ,
...] ) 
!   [ CASCADE | RESTRICT ]
  </synopsis>
   </refsynopsisdiv>

*************** DROP AGGREGATE [ IF EXISTS ] <replaceabl
*** 60,71 ****
     </varlistentry>

     <varlistentry>
!     <term><replaceable class="parameter">argtype</replaceable></term>
      <listitem>
       <para>
        An input data type on which the aggregate function operates.
        To reference a zero-argument aggregate function, write <literal>*</>
!       in place of the list of input data types.
       </para>
      </listitem>
     </varlistentry>
--- 62,97 ----
     </varlistentry>

     <varlistentry>
!     <term><replaceable class="parameter">argmode</replaceable></term>
!
!     <listitem>
!      <para>
!       The mode of an argument: <literal>IN</> or <literal>VARIADIC</>.
!       If omitted, the default is <literal>IN</>.
!      </para>
!     </listitem>
!    </varlistentry>
!
!    <varlistentry>
!     <term><replaceable class="parameter">arg_name</replaceable></term>
!
!     <listitem>
!      <para>
!       The name of an argument.
!       Note that <command>DROP AGGREGATE</command> does not actually pay
!       any attention to argument names, since only the argument data
!       types are needed to determine the aggregate function's identity.
!      </para>
!     </listitem>
!    </varlistentry>
!
!    <varlistentry>
!     <term><replaceable class="parameter">arg_data_type</replaceable></term>
      <listitem>
       <para>
        An input data type on which the aggregate function operates.
        To reference a zero-argument aggregate function, write <literal>*</>
!       in place of the list of argument specifications.
       </para>
      </listitem>
     </varlistentry>
diff --git a/doc/src/sgml/ref/security_label.sgml b/doc/src/sgml/ref/security_label.sgml
index 52cb1d1..76c131f 100644
*** a/doc/src/sgml/ref/security_label.sgml
--- b/doc/src/sgml/ref/security_label.sgml
*************** SECURITY LABEL [ FOR <replaceable class=
*** 25,31 ****
  {
    TABLE <replaceable class="PARAMETER">object_name</replaceable> |
    COLUMN <replaceable class="PARAMETER">table_name</replaceable>.<replaceable
class="PARAMETER">column_name</replaceable>| 
!   AGGREGATE <replaceable class="PARAMETER">agg_name</replaceable> (<replaceable
class="PARAMETER">agg_type</replaceable>[, ...] ) | 
    DATABASE <replaceable class="PARAMETER">object_name</replaceable> |
    DOMAIN <replaceable class="PARAMETER">object_name</replaceable> |
    EVENT TRIGGER <replaceable class="PARAMETER">object_name</replaceable> |
--- 25,31 ----
  {
    TABLE <replaceable class="PARAMETER">object_name</replaceable> |
    COLUMN <replaceable class="PARAMETER">table_name</replaceable>.<replaceable
class="PARAMETER">column_name</replaceable>| 
!   AGGREGATE <replaceable class="PARAMETER">agg_name</replaceable> ( [ <replaceable
class="parameter">argmode</replaceable>] [ <replaceable class="parameter">argname</replaceable> ] <replaceable
class="parameter">agg_type</replaceable>[, ...] ) | 
    DATABASE <replaceable class="PARAMETER">object_name</replaceable> |
    DOMAIN <replaceable class="PARAMETER">object_name</replaceable> |
    EVENT TRIGGER <replaceable class="PARAMETER">object_name</replaceable> |
*************** SECURITY LABEL [ FOR <replaceable class=
*** 107,118 ****
     </varlistentry>

     <varlistentry>
!     <term><replaceable class="parameter">arg_type</replaceable></term>
      <listitem>
       <para>
        An input data type on which the aggregate function operates.
        To reference a zero-argument aggregate function, write <literal>*</>
!       in place of the list of input data types.
       </para>
      </listitem>
     </varlistentry>
--- 107,118 ----
     </varlistentry>

     <varlistentry>
!     <term><replaceable class="parameter">agg_type</replaceable></term>
      <listitem>
       <para>
        An input data type on which the aggregate function operates.
        To reference a zero-argument aggregate function, write <literal>*</>
!       in place of the list of argument specifications.
       </para>
      </listitem>
     </varlistentry>
*************** SECURITY LABEL [ FOR <replaceable class=
*** 125,131 ****
        The mode of a function argument: <literal>IN</>, <literal>OUT</>,
        <literal>INOUT</>, or <literal>VARIADIC</>.
        If omitted, the default is <literal>IN</>.
!       Note that <command>SECURITY LABEL ON FUNCTION</command> does not actually
        pay any attention to <literal>OUT</> arguments, since only the input
        arguments are needed to determine the function's identity.
        So it is sufficient to list the <literal>IN</>, <literal>INOUT</>,
--- 125,131 ----
        The mode of a function argument: <literal>IN</>, <literal>OUT</>,
        <literal>INOUT</>, or <literal>VARIADIC</>.
        If omitted, the default is <literal>IN</>.
!       Note that <command>SECURITY LABEL</command> does not actually
        pay any attention to <literal>OUT</> arguments, since only the input
        arguments are needed to determine the function's identity.
        So it is sufficient to list the <literal>IN</>, <literal>INOUT</>,
*************** SECURITY LABEL [ FOR <replaceable class=
*** 140,146 ****
      <listitem>
       <para>
        The name of a function argument.
!       Note that <command>SECURITY LABEL ON FUNCTION</command> does not actually
        pay any attention to argument names, since only the argument data
        types are needed to determine the function's identity.
       </para>
--- 140,146 ----
      <listitem>
       <para>
        The name of a function argument.
!       Note that <command>SECURITY LABEL</command> does not actually
        pay any attention to argument names, since only the argument data
        types are needed to determine the function's identity.
       </para>
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index 803ed85..e3dbc4b 100644
*** a/doc/src/sgml/syntax.sgml
--- b/doc/src/sgml/syntax.sgml
*************** SELECT concat_lower_or_upper('Hello', 'W
*** 2524,2529 ****
--- 2524,2536 ----
      having numerous parameters that have default values, named or mixed
      notation can save a great deal of writing and reduce chances for error.
     </para>
+
+    <note>
+     <para>
+      Named and mixed call notations can currently be used only with regular
+      functions, not with aggregate functions or window functions.
+     </para>
+    </note>
    </sect2>
   </sect1>

diff --git a/doc/src/sgml/xaggr.sgml b/doc/src/sgml/xaggr.sgml
index 1822f6d..9ed7d99 100644
*** a/doc/src/sgml/xaggr.sgml
--- b/doc/src/sgml/xaggr.sgml
*************** SELECT attrelid::regclass, array_accum(a
*** 170,175 ****
--- 170,211 ----
    </para>

    <para>
+    An aggregate function can be made to accept a varying number of arguments
+    by declaring its last argument as a <literal>VARIADIC</> array, in much
+    the same fashion as for regular functions; see
+    <xref linkend="xfunc-sql-variadic-functions">.  The aggregate's transition
+    function must have the same array type as its last argument.  The
+    transition function typically would also be marked <literal>VARIADIC</>,
+    but this is not strictly required.
+   </para>
+
+   <note>
+    <para>
+     Variadic aggregates are easily misused in connection with
+     the <literal>ORDER BY</> option (see <xref linkend="syntax-aggregates">),
+     since the parser cannot tell whether the wrong number of actual arguments
+     have been given in such a combination.  Keep in mind that everything to
+     the right of <literal>ORDER BY</> is a sort key, not an argument to the
+     aggregate.  For example, in
+ <programlisting>
+ SELECT myaggregate(a ORDER BY a, b, c) FROM ...
+ </programlisting>
+     the parser will see this as a single aggregate function argument and
+     three sort keys.  However, the user might have intended
+ <programlisting>
+ SELECT myaggregate(a, b, c ORDER BY a) FROM ...
+ </programlisting>
+     If <literal>myaggregate</> is variadic, both these calls could be
+     perfectly valid.
+    </para>
+
+    <para>
+     For the same reason, it's wise to think twice before creating aggregate
+     functions with the same names and different numbers of regular arguments.
+    </para>
+   </note>
+
+   <para>
     A function written in C can detect that it is being called as an
     aggregate transition or final function by calling
     <function>AggCheckCallContext</>, for example:
diff --git a/src/backend/catalog/pg_aggregate.c b/src/backend/catalog/pg_aggregate.c
index 480c17c..d9e961e 100644
*** a/src/backend/catalog/pg_aggregate.c
--- b/src/backend/catalog/pg_aggregate.c
*************** static Oid lookup_agg_function(List *fnN
*** 45,52 ****
  Oid
  AggregateCreate(const char *aggName,
                  Oid aggNamespace,
-                 Oid *aggArgTypes,
                  int numArgs,
                  List *aggtransfnName,
                  List *aggfinalfnName,
                  List *aggsortopName,
--- 45,56 ----
  Oid
  AggregateCreate(const char *aggName,
                  Oid aggNamespace,
                  int numArgs,
+                 oidvector *parameterTypes,
+                 Datum allParameterTypes,
+                 Datum parameterModes,
+                 Datum parameterNames,
+                 List *parameterDefaults,
                  List *aggtransfnName,
                  List *aggfinalfnName,
                  List *aggsortopName,
*************** AggregateCreate(const char *aggName,
*** 61,66 ****
--- 65,71 ----
      Oid            transfn;
      Oid            finalfn = InvalidOid;    /* can be omitted */
      Oid            sortop = InvalidOid;    /* can be omitted */
+     Oid           *aggArgTypes = parameterTypes->values;
      bool        hasPolyArg;
      bool        hasInternalArg;
      Oid            rettype;
*************** AggregateCreate(const char *aggName,
*** 244,255 ****
                                false,    /* isStrict (not needed for agg) */
                                PROVOLATILE_IMMUTABLE,    /* volatility (not
                                                           * needed for agg) */
!                               buildoidvector(aggArgTypes,
!                                              numArgs),    /* paramTypes */
!                               PointerGetDatum(NULL),    /* allParamTypes */
!                               PointerGetDatum(NULL),    /* parameterModes */
!                               PointerGetDatum(NULL),    /* parameterNames */
!                               NIL,        /* parameterDefaults */
                                PointerGetDatum(NULL),    /* proconfig */
                                1,    /* procost */
                                0);        /* prorows */
--- 249,259 ----
                                false,    /* isStrict (not needed for agg) */
                                PROVOLATILE_IMMUTABLE,    /* volatility (not
                                                           * needed for agg) */
!                               parameterTypes,    /* paramTypes */
!                               allParameterTypes,        /* allParamTypes */
!                               parameterModes,    /* parameterModes */
!                               parameterNames,    /* parameterNames */
!                               parameterDefaults,        /* parameterDefaults */
                                PointerGetDatum(NULL),    /* proconfig */
                                1,    /* procost */
                                0);        /* prorows */
diff --git a/src/backend/commands/aggregatecmds.c b/src/backend/commands/aggregatecmds.c
index 4a03786..78af092 100644
*** a/src/backend/commands/aggregatecmds.c
--- b/src/backend/commands/aggregatecmds.c
***************
*** 45,54 ****
   *
   * "oldstyle" signals the old (pre-8.2) style where the aggregate input type
   * is specified by a BASETYPE element in the parameters.  Otherwise,
!  * "args" defines the input type(s).
   */
  Oid
! DefineAggregate(List *name, List *args, bool oldstyle, List *parameters)
  {
      char       *aggName;
      Oid            aggNamespace;
--- 45,56 ----
   *
   * "oldstyle" signals the old (pre-8.2) style where the aggregate input type
   * is specified by a BASETYPE element in the parameters.  Otherwise,
!  * "args" is a list of FunctionParameter structs defining the agg's arguments.
!  * "parameters" is a list of DefElem representing the agg's definition clauses.
   */
  Oid
! DefineAggregate(List *name, List *args, bool oldstyle, List *parameters,
!                 const char *queryString)
  {
      char       *aggName;
      Oid            aggNamespace;
*************** DefineAggregate(List *name, List *args,
*** 59,66 ****
      TypeName   *baseType = NULL;
      TypeName   *transType = NULL;
      char       *initval = NULL;
-     Oid           *aggArgTypes;
      int            numArgs;
      Oid            transTypeId;
      char        transTypeType;
      ListCell   *pl;
--- 61,72 ----
      TypeName   *baseType = NULL;
      TypeName   *transType = NULL;
      char       *initval = NULL;
      int            numArgs;
+     oidvector  *parameterTypes;
+     ArrayType  *allParameterTypes;
+     ArrayType  *parameterModes;
+     ArrayType  *parameterNames;
+     List       *parameterDefaults;
      Oid            transTypeId;
      char        transTypeType;
      ListCell   *pl;
*************** DefineAggregate(List *name, List *args,
*** 131,136 ****
--- 137,144 ----
           * Historically we allowed the command to look like basetype = 'ANY'
           * so we must do a case-insensitive comparison for the name ANY. Ugh.
           */
+         Oid            aggArgTypes[1];
+
          if (baseType == NULL)
              ereport(ERROR,
                      (errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
*************** DefineAggregate(List *name, List *args,
*** 139,160 ****
          if (pg_strcasecmp(TypeNameToString(baseType), "ANY") == 0)
          {
              numArgs = 0;
!             aggArgTypes = NULL;
          }
          else
          {
              numArgs = 1;
-             aggArgTypes = (Oid *) palloc(sizeof(Oid));
              aggArgTypes[0] = typenameTypeId(NULL, baseType);
          }
      }
      else
      {
          /*
!          * New style: args is a list of TypeNames (possibly zero of 'em).
           */
!         ListCell   *lc;
!         int            i = 0;

          if (baseType != NULL)
              ereport(ERROR,
--- 147,172 ----
          if (pg_strcasecmp(TypeNameToString(baseType), "ANY") == 0)
          {
              numArgs = 0;
!             aggArgTypes[0] = InvalidOid;
          }
          else
          {
              numArgs = 1;
              aggArgTypes[0] = typenameTypeId(NULL, baseType);
          }
+         parameterTypes = buildoidvector(aggArgTypes, numArgs);
+         allParameterTypes = NULL;
+         parameterModes = NULL;
+         parameterNames = NULL;
+         parameterDefaults = NIL;
      }
      else
      {
          /*
!          * New style: args is a list of FunctionParameters (possibly zero of
!          * 'em).  We share functioncmds.c's code for processing them.
           */
!         Oid            requiredResultType;

          if (baseType != NULL)
              ereport(ERROR,
*************** DefineAggregate(List *name, List *args,
*** 162,174 ****
                       errmsg("basetype is redundant with aggregate input type specification")));

          numArgs = list_length(args);
!         aggArgTypes = (Oid *) palloc(sizeof(Oid) * numArgs);
!         foreach(lc, args)
!         {
!             TypeName   *curTypeName = (TypeName *) lfirst(lc);
!
!             aggArgTypes[i++] = typenameTypeId(NULL, curTypeName);
!         }
      }

      /*
--- 174,193 ----
                       errmsg("basetype is redundant with aggregate input type specification")));

          numArgs = list_length(args);
!         interpret_function_parameter_list(args,
!                                           InvalidOid,
!                                           true, /* is an aggregate */
!                                           queryString,
!                                           ¶meterTypes,
!                                           &allParameterTypes,
!                                           ¶meterModes,
!                                           ¶meterNames,
!                                           ¶meterDefaults,
!                                           &requiredResultType);
!         /* Parameter defaults are not currently allowed by the grammar */
!         Assert(parameterDefaults == NIL);
!         /* There shouldn't have been any OUT parameters, either */
!         Assert(requiredResultType == InvalidOid);
      }

      /*
*************** DefineAggregate(List *name, List *args,
*** 219,226 ****
       */
      return AggregateCreate(aggName,        /* aggregate name */
                             aggNamespace,        /* namespace */
-                            aggArgTypes, /* input data type(s) */
                             numArgs,
                             transfuncName,        /* step function name */
                             finalfuncName,        /* final function name */
                             sortoperatorName,    /* sort operator name */
--- 238,249 ----
       */
      return AggregateCreate(aggName,        /* aggregate name */
                             aggNamespace,        /* namespace */
                             numArgs,
+                            parameterTypes,
+                            PointerGetDatum(allParameterTypes),
+                            PointerGetDatum(parameterModes),
+                            PointerGetDatum(parameterNames),
+                            parameterDefaults,
                             transfuncName,        /* step function name */
                             finalfuncName,        /* final function name */
                             sortoperatorName,    /* sort operator name */
diff --git a/src/backend/commands/functioncmds.c b/src/backend/commands/functioncmds.c
index 0a9facf..ca754b4 100644
*** a/src/backend/commands/functioncmds.c
--- b/src/backend/commands/functioncmds.c
*************** compute_return_type(TypeName *returnType
*** 88,94 ****

      typtup = LookupTypeName(NULL, returnType, NULL);

-
      if (typtup)
      {
          if (!((Form_pg_type) GETSTRUCT(typtup))->typisdefined)
--- 88,93 ----
*************** compute_return_type(TypeName *returnType
*** 158,179 ****
  }

  /*
!  * Interpret the parameter list of the CREATE FUNCTION statement.
   *
   * Results are stored into output parameters.  parameterTypes must always
   * be created, but the other arrays are set to NULL if not needed.
   * requiredResultType is set to InvalidOid if there are no OUT parameters,
   * else it is set to the OID of the implied result type.
   */
! static void
! examine_parameter_list(List *parameters, Oid languageOid,
!                        const char *queryString,
!                        oidvector **parameterTypes,
!                        ArrayType **allParameterTypes,
!                        ArrayType **parameterModes,
!                        ArrayType **parameterNames,
!                        List **parameterDefaults,
!                        Oid *requiredResultType)
  {
      int            parameterCount = list_length(parameters);
      Oid           *inTypes;
--- 157,187 ----
  }

  /*
!  * Interpret the function parameter list of a CREATE FUNCTION or
!  * CREATE AGGREGATE statement.
!  *
!  * Input parameters:
!  * parameters: list of FunctionParameter structs
!  * languageOid: OID of function language (InvalidOid if it's CREATE AGGREGATE)
!  * is_aggregate: needed only to determine error handling
!  * queryString: likewise, needed only for error handling
   *
   * Results are stored into output parameters.  parameterTypes must always
   * be created, but the other arrays are set to NULL if not needed.
   * requiredResultType is set to InvalidOid if there are no OUT parameters,
   * else it is set to the OID of the implied result type.
   */
! void
! interpret_function_parameter_list(List *parameters,
!                                   Oid languageOid,
!                                   bool is_aggregate,
!                                   const char *queryString,
!                                   oidvector **parameterTypes,
!                                   ArrayType **allParameterTypes,
!                                   ArrayType **parameterModes,
!                                   ArrayType **parameterNames,
!                                   List **parameterDefaults,
!                                   Oid *requiredResultType)
  {
      int            parameterCount = list_length(parameters);
      Oid           *inTypes;
*************** examine_parameter_list(List *parameters,
*** 223,228 ****
--- 231,242 ----
                              (errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
                             errmsg("SQL function cannot accept shell type %s",
                                    TypeNameToString(t))));
+                 /* We don't allow creating aggregates on shell types either */
+                 else if (is_aggregate)
+                     ereport(ERROR,
+                             (errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
+                              errmsg("aggregate cannot accept shell type %s",
+                                     TypeNameToString(t))));
                  else
                      ereport(NOTICE,
                              (errcode(ERRCODE_WRONG_OBJECT_TYPE),
*************** examine_parameter_list(List *parameters,
*** 246,254 ****
              aclcheck_error_type(aclresult, toid);

          if (t->setof)
!             ereport(ERROR,
!                     (errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
!                      errmsg("functions cannot accept set arguments")));

          /* handle input parameters */
          if (fp->mode != FUNC_PARAM_OUT && fp->mode != FUNC_PARAM_TABLE)
--- 260,275 ----
              aclcheck_error_type(aclresult, toid);

          if (t->setof)
!         {
!             if (is_aggregate)
!                 ereport(ERROR,
!                         (errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
!                          errmsg("aggregates cannot accept set arguments")));
!             else
!                 ereport(ERROR,
!                         (errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
!                          errmsg("functions cannot accept set arguments")));
!         }

          /* handle input parameters */
          if (fp->mode != FUNC_PARAM_OUT && fp->mode != FUNC_PARAM_TABLE)
*************** CreateFunction(CreateFunctionStmt *stmt,
*** 890,902 ****
       * Convert remaining parameters of CREATE to form wanted by
       * ProcedureCreate.
       */
!     examine_parameter_list(stmt->parameters, languageOid, queryString,
!                            ¶meterTypes,
!                            &allParameterTypes,
!                            ¶meterModes,
!                            ¶meterNames,
!                            ¶meterDefaults,
!                            &requiredResultType);

      if (stmt->returnType)
      {
--- 911,926 ----
       * Convert remaining parameters of CREATE to form wanted by
       * ProcedureCreate.
       */
!     interpret_function_parameter_list(stmt->parameters,
!                                       languageOid,
!                                       false,    /* not an aggregate */
!                                       queryString,
!                                       ¶meterTypes,
!                                       &allParameterTypes,
!                                       ¶meterModes,
!                                       ¶meterNames,
!                                       ¶meterDefaults,
!                                       &requiredResultType);

      if (stmt->returnType)
      {
diff --git a/src/backend/executor/nodeAgg.c b/src/backend/executor/nodeAgg.c
index 7a0c254..e02a6ff 100644
*** a/src/backend/executor/nodeAgg.c
--- b/src/backend/executor/nodeAgg.c
*************** ExecInitAgg(Agg *node, EState *estate, i
*** 1696,1701 ****
--- 1696,1702 ----
          /* build expression trees using actual argument & result types */
          build_aggregate_fnexprs(inputTypes,
                                  numArguments,
+                                 aggref->aggvariadic,
                                  aggtranstype,
                                  aggref->aggtype,
                                  aggref->inputcollid,
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index bbc5336..544ba98 100644
*** a/src/backend/executor/nodeWindowAgg.c
--- b/src/backend/executor/nodeWindowAgg.c
*************** initialize_peragg(WindowAggState *winsta
*** 1817,1822 ****
--- 1817,1823 ----
      /* build expression trees using actual argument & result types */
      build_aggregate_fnexprs(inputTypes,
                              numArguments,
+                             false,        /* no variadic window functions yet */
                              aggtranstype,
                              wfunc->wintype,
                              wfunc->inputcollid,
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 788907e..65f3b98 100644
*** a/src/backend/nodes/copyfuncs.c
--- b/src/backend/nodes/copyfuncs.c
*************** _copyAggref(const Aggref *from)
*** 1141,1146 ****
--- 1141,1147 ----
      COPY_NODE_FIELD(aggdistinct);
      COPY_NODE_FIELD(aggfilter);
      COPY_SCALAR_FIELD(aggstar);
+     COPY_SCALAR_FIELD(aggvariadic);
      COPY_SCALAR_FIELD(agglevelsup);
      COPY_LOCATION_FIELD(location);

diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 496e31d..4c9b05e 100644
*** a/src/backend/nodes/equalfuncs.c
--- b/src/backend/nodes/equalfuncs.c
*************** _equalAggref(const Aggref *a, const Aggr
*** 198,203 ****
--- 198,204 ----
      COMPARE_NODE_FIELD(aggdistinct);
      COMPARE_NODE_FIELD(aggfilter);
      COMPARE_SCALAR_FIELD(aggstar);
+     COMPARE_SCALAR_FIELD(aggvariadic);
      COMPARE_SCALAR_FIELD(agglevelsup);
      COMPARE_LOCATION_FIELD(location);

diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index cff4734..a2903f9 100644
*** a/src/backend/nodes/outfuncs.c
--- b/src/backend/nodes/outfuncs.c
*************** _outAggref(StringInfo str, const Aggref
*** 962,967 ****
--- 962,968 ----
      WRITE_NODE_FIELD(aggdistinct);
      WRITE_NODE_FIELD(aggfilter);
      WRITE_BOOL_FIELD(aggstar);
+     WRITE_BOOL_FIELD(aggvariadic);
      WRITE_UINT_FIELD(agglevelsup);
      WRITE_LOCATION_FIELD(location);
  }
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index aad63e5..d325bb3 100644
*** a/src/backend/nodes/readfuncs.c
--- b/src/backend/nodes/readfuncs.c
*************** _readAggref(void)
*** 497,502 ****
--- 497,503 ----
      READ_NODE_FIELD(aggdistinct);
      READ_NODE_FIELD(aggfilter);
      READ_BOOL_FIELD(aggstar);
+     READ_BOOL_FIELD(aggvariadic);
      READ_UINT_FIELD(agglevelsup);
      READ_LOCATION_FIELD(location);

diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 22e82ba..a9812af 100644
*** a/src/backend/parser/gram.y
--- b/src/backend/parser/gram.y
*************** static Node *makeRecursiveViewSelect(cha
*** 324,331 ****
                  reloptions opt_reloptions
                  OptWith opt_distinct opt_definition func_args func_args_list
                  func_args_with_defaults func_args_with_defaults_list
                  func_as createfunc_opt_list alterfunc_opt_list
!                 aggr_args old_aggr_definition old_aggr_list
                  oper_argtypes RuleActionList RuleActionMulti
                  opt_column_list columnList opt_name_list
                  sort_clause opt_sort_clause sortby_list index_params
--- 324,332 ----
                  reloptions opt_reloptions
                  OptWith opt_distinct opt_definition func_args func_args_list
                  func_args_with_defaults func_args_with_defaults_list
+                 aggr_args aggr_args_list
                  func_as createfunc_opt_list alterfunc_opt_list
!                 old_aggr_definition old_aggr_list
                  oper_argtypes RuleActionList RuleActionMulti
                  opt_column_list columnList opt_name_list
                  sort_clause opt_sort_clause sortby_list index_params
*************** static Node *makeRecursiveViewSelect(cha
*** 352,358 ****
  %type <into>    into_clause create_as_target create_mv_target

  %type <defelt>    createfunc_opt_item common_func_opt_item dostmt_opt_item
! %type <fun_param> func_arg func_arg_with_default table_func_column
  %type <fun_param_mode> arg_class
  %type <typnam>    func_return func_type

--- 353,359 ----
  %type <into>    into_clause create_as_target create_mv_target

  %type <defelt>    createfunc_opt_item common_func_opt_item dostmt_opt_item
! %type <fun_param> func_arg func_arg_with_default table_func_column aggr_arg
  %type <fun_param_mode> arg_class
  %type <typnam>    func_return func_type

*************** AlterExtensionContentsStmt:
*** 3659,3665 ****
                      n->action = $4;
                      n->objtype = OBJECT_AGGREGATE;
                      n->objname = $6;
!                     n->objargs = $7;
                      $$ = (Node *)n;
                  }
              | ALTER EXTENSION name add_drop CAST '(' Typename AS Typename ')'
--- 3660,3666 ----
                      n->action = $4;
                      n->objtype = OBJECT_AGGREGATE;
                      n->objname = $6;
!                     n->objargs = extractArgTypes($7);
                      $$ = (Node *)n;
                  }
              | ALTER EXTENSION name add_drop CAST '(' Typename AS Typename ')'
*************** def_arg:    func_type                        { $$ = (Node *)$
*** 4760,4769 ****
              | Sconst                        { $$ = (Node *)makeString($1); }
          ;

- aggr_args:    '(' type_list ')'                        { $$ = $2; }
-             | '(' '*' ')'                            { $$ = NIL; }
-         ;
-
  old_aggr_definition: '(' old_aggr_list ')'            { $$ = $2; }
          ;

--- 4761,4766 ----
*************** CommentStmt:
*** 5242,5248 ****
                      CommentStmt *n = makeNode(CommentStmt);
                      n->objtype = OBJECT_AGGREGATE;
                      n->objname = $4;
!                     n->objargs = $5;
                      n->comment = $7;
                      $$ = (Node *) n;
                  }
--- 5239,5245 ----
                      CommentStmt *n = makeNode(CommentStmt);
                      n->objtype = OBJECT_AGGREGATE;
                      n->objname = $4;
!                     n->objargs = extractArgTypes($5);
                      n->comment = $7;
                      $$ = (Node *) n;
                  }
*************** SecLabelStmt:
*** 5408,5414 ****
                      n->provider = $3;
                      n->objtype = OBJECT_AGGREGATE;
                      n->objname = $6;
!                     n->objargs = $7;
                      n->label = $9;
                      $$ = (Node *) n;
                  }
--- 5405,5411 ----
                      n->provider = $3;
                      n->objtype = OBJECT_AGGREGATE;
                      n->objname = $6;
!                     n->objargs = extractArgTypes($7);
                      n->label = $9;
                      $$ = (Node *) n;
                  }
*************** func_arg_with_default:
*** 6395,6400 ****
--- 6392,6419 ----
                  }
          ;

+ /* Aggregate args can be most things that function args can be */
+ aggr_arg:    func_arg
+                 {
+                     if (!($1->mode == FUNC_PARAM_IN ||
+                           $1->mode == FUNC_PARAM_VARIADIC))
+                         ereport(ERROR,
+                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+                                  errmsg("aggregates cannot have output arguments"),
+                                  parser_errposition(@1)));
+                     $$ = $1;
+                 }
+         ;
+
+ /* Zero-argument aggregates are named with * for consistency with COUNT(*) */
+ aggr_args:    '(' aggr_args_list ')'                    { $$ = $2; }
+             | '(' '*' ')'                            { $$ = NIL; }
+         ;
+
+ aggr_args_list:
+             aggr_arg                                { $$ = list_make1($1); }
+             | aggr_args_list ',' aggr_arg            { $$ = lappend($1, $3); }
+         ;

  createfunc_opt_list:
              /* Must be at least one to prevent conflict */
*************** RemoveAggrStmt:
*** 6594,6600 ****
                      DropStmt *n = makeNode(DropStmt);
                      n->removeType = OBJECT_AGGREGATE;
                      n->objects = list_make1($3);
!                     n->arguments = list_make1($4);
                      n->behavior = $5;
                      n->missing_ok = false;
                      n->concurrent = false;
--- 6613,6619 ----
                      DropStmt *n = makeNode(DropStmt);
                      n->removeType = OBJECT_AGGREGATE;
                      n->objects = list_make1($3);
!                     n->arguments = list_make1(extractArgTypes($4));
                      n->behavior = $5;
                      n->missing_ok = false;
                      n->concurrent = false;
*************** RemoveAggrStmt:
*** 6605,6611 ****
                      DropStmt *n = makeNode(DropStmt);
                      n->removeType = OBJECT_AGGREGATE;
                      n->objects = list_make1($5);
!                     n->arguments = list_make1($6);
                      n->behavior = $7;
                      n->missing_ok = true;
                      n->concurrent = false;
--- 6624,6630 ----
                      DropStmt *n = makeNode(DropStmt);
                      n->removeType = OBJECT_AGGREGATE;
                      n->objects = list_make1($5);
!                     n->arguments = list_make1(extractArgTypes($6));
                      n->behavior = $7;
                      n->missing_ok = true;
                      n->concurrent = false;
*************** RenameStmt: ALTER AGGREGATE func_name ag
*** 6821,6827 ****
                      RenameStmt *n = makeNode(RenameStmt);
                      n->renameType = OBJECT_AGGREGATE;
                      n->object = $3;
!                     n->objarg = $4;
                      n->newname = $7;
                      n->missing_ok = false;
                      $$ = (Node *)n;
--- 6840,6846 ----
                      RenameStmt *n = makeNode(RenameStmt);
                      n->renameType = OBJECT_AGGREGATE;
                      n->object = $3;
!                     n->objarg = extractArgTypes($4);
                      n->newname = $7;
                      n->missing_ok = false;
                      $$ = (Node *)n;
*************** AlterObjectSchemaStmt:
*** 7295,7301 ****
                      AlterObjectSchemaStmt *n = makeNode(AlterObjectSchemaStmt);
                      n->objectType = OBJECT_AGGREGATE;
                      n->object = $3;
!                     n->objarg = $4;
                      n->newschema = $7;
                      n->missing_ok = false;
                      $$ = (Node *)n;
--- 7314,7320 ----
                      AlterObjectSchemaStmt *n = makeNode(AlterObjectSchemaStmt);
                      n->objectType = OBJECT_AGGREGATE;
                      n->object = $3;
!                     n->objarg = extractArgTypes($4);
                      n->newschema = $7;
                      n->missing_ok = false;
                      $$ = (Node *)n;
*************** AlterOwnerStmt: ALTER AGGREGATE func_nam
*** 7524,7530 ****
                      AlterOwnerStmt *n = makeNode(AlterOwnerStmt);
                      n->objectType = OBJECT_AGGREGATE;
                      n->object = $3;
!                     n->objarg = $4;
                      n->newowner = $7;
                      $$ = (Node *)n;
                  }
--- 7543,7549 ----
                      AlterOwnerStmt *n = makeNode(AlterOwnerStmt);
                      n->objectType = OBJECT_AGGREGATE;
                      n->object = $3;
!                     n->objarg = extractArgTypes($4);
                      n->newowner = $7;
                      $$ = (Node *)n;
                  }
diff --git a/src/backend/parser/parse_agg.c b/src/backend/parser/parse_agg.c
index 4e4e1cd..98cb58a 100644
*** a/src/backend/parser/parse_agg.c
--- b/src/backend/parser/parse_agg.c
*************** check_ungrouped_columns_walker(Node *nod
*** 965,970 ****
--- 965,971 ----
  void
  build_aggregate_fnexprs(Oid *agg_input_types,
                          int agg_num_inputs,
+                         bool agg_variadic,
                          Oid agg_state_type,
                          Oid agg_result_type,
                          Oid agg_input_collation,
*************** build_aggregate_fnexprs(Oid *agg_input_t
*** 975,980 ****
--- 976,982 ----
  {
      Param       *argp;
      List       *args;
+     FuncExpr   *fexpr;
      int            i;

      /*
*************** build_aggregate_fnexprs(Oid *agg_input_t
*** 1005,1016 ****
          args = lappend(args, argp);
      }

!     *transfnexpr = (Expr *) makeFuncExpr(transfn_oid,
!                                          agg_state_type,
!                                          args,
!                                          InvalidOid,
!                                          agg_input_collation,
!                                          COERCE_EXPLICIT_CALL);

      /* see if we have a final function */
      if (!OidIsValid(finalfn_oid))
--- 1007,1020 ----
          args = lappend(args, argp);
      }

!     fexpr = makeFuncExpr(transfn_oid,
!                          agg_state_type,
!                          args,
!                          InvalidOid,
!                          agg_input_collation,
!                          COERCE_EXPLICIT_CALL);
!     fexpr->funcvariadic = agg_variadic;
!     *transfnexpr = (Expr *) fexpr;

      /* see if we have a final function */
      if (!OidIsValid(finalfn_oid))
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 1f02c9a..2bd24c8 100644
*** a/src/backend/parser/parse_func.c
--- b/src/backend/parser/parse_func.c
*************** ParseFuncOrColumn(ParseState *pstate, Li
*** 385,391 ****
      }

      /*
!      * When function is called an explicit VARIADIC labeled parameter,
       * and the declared_arg_type is "any", then sanity check the actual
       * parameter type now - it must be an array.
       */
--- 385,391 ----
      }

      /*
!      * When function is called with an explicit VARIADIC labeled parameter,
       * and the declared_arg_type is "any", then sanity check the actual
       * parameter type now - it must be an array.
       */
*************** ParseFuncOrColumn(ParseState *pstate, Li
*** 425,432 ****
          aggref->aggtype = rettype;
          /* aggcollid and inputcollid will be set by parse_collate.c */
          /* args, aggorder, aggdistinct will be set by transformAggregateCall */
-         aggref->aggstar = agg_star;
          aggref->aggfilter = agg_filter;
          /* agglevelsup will be set by transformAggregateCall */
          aggref->location = location;

--- 425,433 ----
          aggref->aggtype = rettype;
          /* aggcollid and inputcollid will be set by parse_collate.c */
          /* args, aggorder, aggdistinct will be set by transformAggregateCall */
          aggref->aggfilter = agg_filter;
+         aggref->aggstar = agg_star;
+         aggref->aggvariadic = func_variadic;
          /* agglevelsup will be set by transformAggregateCall */
          aggref->location = location;

*************** ParseFuncOrColumn(ParseState *pstate, Li
*** 448,457 ****
                       parser_errposition(pstate, location)));

          /*
!          * Currently it's not possible to define an aggregate with named
!          * arguments, so this case should be impossible.  Check anyway because
!          * the planner and executor wouldn't cope with NamedArgExprs in an
!          * Aggref node.
           */
          if (argnames != NIL)
              ereport(ERROR,
--- 449,461 ----
                       parser_errposition(pstate, location)));

          /*
!          * We might want to support named arguments later, but disallow it for
!          * now.  We'd need to figure out the parsed representation (should the
!          * NamedArgExprs go above or below the TargetEntry nodes?) and then
!          * teach the planner to reorder the list properly.    Or maybe we could
!          * make transformAggregateCall do that?  However, if you'd also like
!          * to allow default arguments for aggregates, we'd need to do it in
!          * planning to avoid semantic problems.
           */
          if (argnames != NIL)
              ereport(ERROR,
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index c940897..b1023c4 100644
*** a/src/backend/tcop/utility.c
--- b/src/backend/tcop/utility.c
*************** ProcessUtilitySlow(Node *parsetree,
*** 1103,1109 ****
                      {
                          case OBJECT_AGGREGATE:
                              DefineAggregate(stmt->defnames, stmt->args,
!                                             stmt->oldstyle, stmt->definition);
                              break;
                          case OBJECT_OPERATOR:
                              Assert(stmt->args == NIL);
--- 1103,1110 ----
                      {
                          case OBJECT_AGGREGATE:
                              DefineAggregate(stmt->defnames, stmt->args,
!                                             stmt->oldstyle, stmt->definition,
!                                             queryString);
                              break;
                          case OBJECT_OPERATOR:
                              Assert(stmt->args == NIL);
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 2b005d6..37d66e1 100644
*** a/src/backend/utils/adt/ruleutils.c
--- b/src/backend/utils/adt/ruleutils.c
*************** get_agg_expr(Aggref *aggref, deparse_con
*** 7405,7410 ****
--- 7405,7411 ----
      Oid            argtypes[FUNC_MAX_ARGS];
      List       *arglist;
      int            nargs;
+     bool        use_variadic;
      ListCell   *l;

      /* Extract the regular arguments, ignoring resjunk stuff for the moment */
*************** get_agg_expr(Aggref *aggref, deparse_con
*** 7430,7442 ****
      appendStringInfo(buf, "%s(%s",
                       generate_function_name(aggref->aggfnoid, nargs,
                                              NIL, argtypes,
!                                             false, NULL),
                       (aggref->aggdistinct != NIL) ? "DISTINCT " : "");
      /* aggstar can be set only in zero-argument aggregates */
      if (aggref->aggstar)
          appendStringInfoChar(buf, '*');
      else
!         get_rule_expr((Node *) arglist, context, true);
      if (aggref->aggorder != NIL)
      {
          appendStringInfoString(buf, " ORDER BY ");
--- 7431,7456 ----
      appendStringInfo(buf, "%s(%s",
                       generate_function_name(aggref->aggfnoid, nargs,
                                              NIL, argtypes,
!                                             aggref->aggvariadic,
!                                             &use_variadic),
                       (aggref->aggdistinct != NIL) ? "DISTINCT " : "");
+
      /* aggstar can be set only in zero-argument aggregates */
      if (aggref->aggstar)
          appendStringInfoChar(buf, '*');
      else
!     {
!         nargs = 0;
!         foreach(l, arglist)
!         {
!             if (nargs++ > 0)
!                 appendStringInfoString(buf, ", ");
!             if (use_variadic && lnext(l) == NULL)
!                 appendStringInfoString(buf, "VARIADIC ");
!             get_rule_expr((Node *) lfirst(l), context, true);
!         }
!     }
!
      if (aggref->aggorder != NIL)
      {
          appendStringInfoString(buf, " ORDER BY ");
*************** generate_relation_name(Oid relid, List *
*** 8581,8587 ****
   *        types.    (Those matter because of ambiguous-function resolution rules.)
   *
   * If we're dealing with a potentially variadic function (in practice, this
!  * means a FuncExpr and not some other way of calling the function), then
   * was_variadic must specify whether VARIADIC appeared in the original call,
   * and *use_variadic_p will be set to indicate whether to print VARIADIC in
   * the output.    For non-FuncExpr cases, was_variadic should be FALSE and
--- 8595,8601 ----
   *        types.    (Those matter because of ambiguous-function resolution rules.)
   *
   * If we're dealing with a potentially variadic function (in practice, this
!  * means a FuncExpr or Aggref, not some other way of calling a function), then
   * was_variadic must specify whether VARIADIC appeared in the original call,
   * and *use_variadic_p will be set to indicate whether to print VARIADIC in
   * the output.    For non-FuncExpr cases, was_variadic should be FALSE and
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index e1ef55f..57320cc 100644
*** a/src/bin/pg_dump/pg_dump.c
--- b/src/bin/pg_dump/pg_dump.c
*************** static void getTableData(TableInfo *tbli
*** 229,235 ****
  static void makeTableDataInfo(TableInfo *tbinfo, bool oids);
  static void buildMatViewRefreshDependencies(Archive *fout);
  static void getTableDataFKConstraints(void);
! static char *format_function_arguments(FuncInfo *finfo, char *funcargs);
  static char *format_function_arguments_old(Archive *fout,
                                FuncInfo *finfo, int nallargs,
                                char **allargtypes,
--- 229,236 ----
  static void makeTableDataInfo(TableInfo *tbinfo, bool oids);
  static void buildMatViewRefreshDependencies(Archive *fout);
  static void getTableDataFKConstraints(void);
! static char *format_function_arguments(FuncInfo *finfo, char *funcargs,
!                                        bool is_agg);
  static char *format_function_arguments_old(Archive *fout,
                                FuncInfo *finfo, int nallargs,
                                char **allargtypes,
*************** dumpProcLang(Archive *fout, ProcLangInfo
*** 9365,9379 ****
   * format_function_arguments: generate function name and argument list
   *
   * This is used when we can rely on pg_get_function_arguments to format
!  * the argument list.
   */
  static char *
! format_function_arguments(FuncInfo *finfo, char *funcargs)
  {
      PQExpBufferData fn;

      initPQExpBuffer(&fn);
!     appendPQExpBuffer(&fn, "%s(%s)", fmtId(finfo->dobj.name), funcargs);
      return fn.data;
  }

--- 9366,9385 ----
   * format_function_arguments: generate function name and argument list
   *
   * This is used when we can rely on pg_get_function_arguments to format
!  * the argument list.  Note, however, that pg_get_function_arguments
!  * does not special-case zero-argument aggregates.
   */
  static char *
! format_function_arguments(FuncInfo *finfo, char *funcargs, bool is_agg)
  {
      PQExpBufferData fn;

      initPQExpBuffer(&fn);
!     appendPQExpBuffer(&fn, "%s", fmtId(finfo->dobj.name));
!     if (is_agg && finfo->nargs == 0)
!         appendPQExpBuffer(&fn, "(*)");
!     else
!         appendPQExpBuffer(&fn, "(%s)", funcargs);
      return fn.data;
  }

*************** dumpFunc(Archive *fout, FuncInfo *finfo)
*** 9804,9811 ****
      if (funcargs)
      {
          /* 8.4 or later; we rely on server-side code for most of the work */
!         funcfullsig = format_function_arguments(finfo, funcargs);
!         funcsig = format_function_arguments(finfo, funciargs);
      }
      else
      {
--- 9810,9817 ----
      if (funcargs)
      {
          /* 8.4 or later; we rely on server-side code for most of the work */
!         funcfullsig = format_function_arguments(finfo, funcargs, false);
!         funcsig = format_function_arguments(finfo, funciargs, false);
      }
      else
      {
*************** dumpAgg(Archive *fout, AggInfo *agginfo)
*** 11405,11411 ****
      PQExpBuffer delq;
      PQExpBuffer labelq;
      PQExpBuffer details;
!     char       *aggsig;
      char       *aggsig_tag;
      PGresult   *res;
      int            i_aggtransfn;
--- 11411,11418 ----
      PQExpBuffer delq;
      PQExpBuffer labelq;
      PQExpBuffer details;
!     char       *aggsig;            /* identity signature */
!     char       *aggfullsig;        /* full signature */
      char       *aggsig_tag;
      PGresult   *res;
      int            i_aggtransfn;
*************** dumpAgg(Archive *fout, AggInfo *agginfo)
*** 11435,11452 ****
      selectSourceSchema(fout, agginfo->aggfn.dobj.namespace->dobj.name);

      /* Get aggregate-specific details */
!     if (fout->remoteVersion >= 80100)
      {
          appendPQExpBuffer(query, "SELECT aggtransfn, "
                            "aggfinalfn, aggtranstype::pg_catalog.regtype, "
                            "aggsortop::pg_catalog.regoperator, "
                            "agginitval, "
!                           "'t'::boolean AS convertok "
                        "FROM pg_catalog.pg_aggregate a, pg_catalog.pg_proc p "
                            "WHERE a.aggfnoid = p.oid "
                            "AND p.oid = '%u'::pg_catalog.oid",
                            agginfo->aggfn.dobj.catId.oid);
      }
      else if (fout->remoteVersion >= 70300)
      {
          appendPQExpBuffer(query, "SELECT aggtransfn, "
--- 11442,11473 ----
      selectSourceSchema(fout, agginfo->aggfn.dobj.namespace->dobj.name);

      /* Get aggregate-specific details */
!     if (fout->remoteVersion >= 80400)
      {
          appendPQExpBuffer(query, "SELECT aggtransfn, "
                            "aggfinalfn, aggtranstype::pg_catalog.regtype, "
                            "aggsortop::pg_catalog.regoperator, "
                            "agginitval, "
!                           "'t'::boolean AS convertok, "
!                           "pg_catalog.pg_get_function_arguments(p.oid) AS funcargs, "
!                           "pg_catalog.pg_get_function_identity_arguments(p.oid) AS funciargs "
                        "FROM pg_catalog.pg_aggregate a, pg_catalog.pg_proc p "
                            "WHERE a.aggfnoid = p.oid "
                            "AND p.oid = '%u'::pg_catalog.oid",
                            agginfo->aggfn.dobj.catId.oid);
      }
+     else if (fout->remoteVersion >= 80100)
+     {
+         appendPQExpBuffer(query, "SELECT aggtransfn, "
+                           "aggfinalfn, aggtranstype::pg_catalog.regtype, "
+                           "aggsortop::pg_catalog.regoperator, "
+                           "agginitval, "
+                           "'t'::boolean AS convertok "
+                           "FROM pg_catalog.pg_aggregate a, pg_catalog.pg_proc p "
+                           "WHERE a.aggfnoid = p.oid "
+                           "AND p.oid = '%u'::pg_catalog.oid",
+                           agginfo->aggfn.dobj.catId.oid);
+     }
      else if (fout->remoteVersion >= 70300)
      {
          appendPQExpBuffer(query, "SELECT aggtransfn, "
*************** dumpAgg(Archive *fout, AggInfo *agginfo)
*** 11499,11505 ****
      agginitval = PQgetvalue(res, 0, i_agginitval);
      convertok = (PQgetvalue(res, 0, i_convertok)[0] == 't');

!     aggsig = format_aggregate_signature(agginfo, fout, true);
      aggsig_tag = format_aggregate_signature(agginfo, fout, false);

      if (!convertok)
--- 11520,11543 ----
      agginitval = PQgetvalue(res, 0, i_agginitval);
      convertok = (PQgetvalue(res, 0, i_convertok)[0] == 't');

!     if (fout->remoteVersion >= 80400)
!     {
!         /* 8.4 or later; we rely on server-side code for most of the work */
!         char       *funcargs;
!         char       *funciargs;
!
!         funcargs = PQgetvalue(res, 0, PQfnumber(res, "funcargs"));
!         funciargs = PQgetvalue(res, 0, PQfnumber(res, "funciargs"));
!         aggfullsig = format_function_arguments(&agginfo->aggfn, funcargs, true);
!         aggsig = format_function_arguments(&agginfo->aggfn, funciargs, true);
!     }
!     else
!     {
!         /* pre-8.4, do it ourselves */
!         aggsig = format_aggregate_signature(agginfo, fout, true);
!         aggfullsig = aggsig;
!     }
!
      aggsig_tag = format_aggregate_signature(agginfo, fout, false);

      if (!convertok)
*************** dumpAgg(Archive *fout, AggInfo *agginfo)
*** 11559,11565 ****
                        aggsig);

      appendPQExpBuffer(q, "CREATE AGGREGATE %s (\n%s\n);\n",
!                       aggsig, details->data);

      appendPQExpBuffer(labelq, "AGGREGATE %s", aggsig);

--- 11597,11603 ----
                        aggsig);

      appendPQExpBuffer(q, "CREATE AGGREGATE %s (\n%s\n);\n",
!                       aggfullsig, details->data);

      appendPQExpBuffer(labelq, "AGGREGATE %s", aggsig);

diff --git a/src/bin/psql/describe.c b/src/bin/psql/describe.c
index dad1d5a..ed1c5fd 100644
*** a/src/bin/psql/describe.c
--- b/src/bin/psql/describe.c
*************** describeAggregates(const char *pattern,
*** 72,78 ****
                        gettext_noop("Name"),
                        gettext_noop("Result data type"));

!     if (pset.sversion >= 80200)
          appendPQExpBuffer(&buf,
                            "  CASE WHEN p.pronargs = 0\n"
                            "    THEN CAST('*' AS pg_catalog.text)\n"
--- 72,85 ----
                        gettext_noop("Name"),
                        gettext_noop("Result data type"));

!     if (pset.sversion >= 80400)
!         appendPQExpBuffer(&buf,
!                           "  CASE WHEN p.pronargs = 0\n"
!                           "    THEN CAST('*' AS pg_catalog.text)\n"
!                      "    ELSE pg_catalog.pg_get_function_arguments(p.oid)\n"
!                           "  END AS \"%s\",\n",
!                           gettext_noop("Argument data types"));
!     else if (pset.sversion >= 80200)
          appendPQExpBuffer(&buf,
                            "  CASE WHEN p.pronargs = 0\n"
                            "    THEN CAST('*' AS pg_catalog.text)\n"
diff --git a/src/include/catalog/pg_aggregate.h b/src/include/catalog/pg_aggregate.h
index 6fb10a9..5ad6ea6 100644
*** a/src/include/catalog/pg_aggregate.h
--- b/src/include/catalog/pg_aggregate.h
*************** DATA(insert ( 3175    json_agg_transfn    json
*** 240,247 ****
   */
  extern Oid AggregateCreate(const char *aggName,
                  Oid aggNamespace,
-                 Oid *aggArgTypes,
                  int numArgs,
                  List *aggtransfnName,
                  List *aggfinalfnName,
                  List *aggsortopName,
--- 240,251 ----
   */
  extern Oid AggregateCreate(const char *aggName,
                  Oid aggNamespace,
                  int numArgs,
+                 oidvector *parameterTypes,
+                 Datum allParameterTypes,
+                 Datum parameterModes,
+                 Datum parameterNames,
+                 List *parameterDefaults,
                  List *aggtransfnName,
                  List *aggfinalfnName,
                  List *aggsortopName,
diff --git a/src/include/commands/defrem.h b/src/include/commands/defrem.h
index fa9f41f..836c99e 100644
*** a/src/include/commands/defrem.h
--- b/src/include/commands/defrem.h
***************
*** 15,20 ****
--- 15,21 ----
  #define DEFREM_H

  #include "nodes/parsenodes.h"
+ #include "utils/array.h"

  /* commands/dropcmds.c */
  extern void RemoveObjects(DropStmt *stmt);
*************** extern void IsThereFunctionInNamespace(c
*** 53,58 ****
--- 54,69 ----
                             oidvector *proargtypes, Oid nspOid);
  extern void ExecuteDoStmt(DoStmt *stmt);
  extern Oid    get_cast_oid(Oid sourcetypeid, Oid targettypeid, bool missing_ok);
+ extern void interpret_function_parameter_list(List *parameters,
+                                   Oid languageOid,
+                                   bool is_aggregate,
+                                   const char *queryString,
+                                   oidvector **parameterTypes,
+                                   ArrayType **allParameterTypes,
+                                   ArrayType **parameterModes,
+                                   ArrayType **parameterNames,
+                                   List **parameterDefaults,
+                                   Oid *requiredResultType);

  /* commands/operatorcmds.c */
  extern Oid    DefineOperator(List *names, List *parameters);
*************** extern void RemoveOperatorById(Oid operO
*** 60,66 ****

  /* commands/aggregatecmds.c */
  extern Oid DefineAggregate(List *name, List *args, bool oldstyle,
!                 List *parameters);

  /* commands/opclasscmds.c */
  extern Oid    DefineOpClass(CreateOpClassStmt *stmt);
--- 71,77 ----

  /* commands/aggregatecmds.c */
  extern Oid DefineAggregate(List *name, List *args, bool oldstyle,
!                 List *parameters, const char *queryString);

  /* commands/opclasscmds.c */
  extern Oid    DefineOpClass(CreateOpClassStmt *stmt);
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index a778951..7918537 100644
*** a/src/include/nodes/primnodes.h
--- b/src/include/nodes/primnodes.h
*************** typedef struct Aggref
*** 249,254 ****
--- 249,255 ----
      List       *aggdistinct;    /* DISTINCT (list of SortGroupClause) */
      Expr       *aggfilter;        /* FILTER expression */
      bool        aggstar;        /* TRUE if argument list was really '*' */
+     bool        aggvariadic;    /* TRUE if VARIADIC was used in call */
      Index        agglevelsup;    /* > 0 if agg belongs to outer query */
      int            location;        /* token location, or -1 if unknown */
  } Aggref;
diff --git a/src/include/parser/parse_agg.h b/src/include/parser/parse_agg.h
index 8fa0ca7..b6d9dd3 100644
*** a/src/include/parser/parse_agg.h
--- b/src/include/parser/parse_agg.h
*************** extern void parseCheckAggregates(ParseSt
*** 25,30 ****
--- 25,31 ----

  extern void build_aggregate_fnexprs(Oid *agg_input_types,
                          int agg_num_inputs,
+                         bool agg_variadic,
                          Oid agg_state_type,
                          Oid agg_result_type,
                          Oid agg_input_collation,
diff --git a/src/test/regress/expected/aggregates.out b/src/test/regress/expected/aggregates.out
index 7fa9005..1af79e5 100644
*** a/src/test/regress/expected/aggregates.out
--- b/src/test/regress/expected/aggregates.out
*************** select aggfns(distinct a,b,c order by a,
*** 1249,1251 ****
--- 1249,1264 ----
   {"(2,2,bar)","(3,1,baz)"}
  (1 row)

+ -- variadic aggregates
+ select least_agg(q1,q2) from int8_tbl;
+      least_agg
+ -------------------
+  -4567890123456789
+ (1 row)
+
+ select least_agg(variadic array[q1,q2]) from int8_tbl;
+      least_agg
+ -------------------
+  -4567890123456789
+ (1 row)
+
diff --git a/src/test/regress/expected/create_aggregate.out b/src/test/regress/expected/create_aggregate.out
index ad14594..6c7566f 100644
*** a/src/test/regress/expected/create_aggregate.out
--- b/src/test/regress/expected/create_aggregate.out
*************** create aggregate aggfns(integer,integer,
*** 59,61 ****
--- 59,68 ----
     sfunc = aggfns_trans, stype = aggtype[],
     initcond = '{}'
  );
+ -- variadic aggregate
+ create function least_accum(anyelement, variadic anyarray)
+ returns anyelement language sql as
+   'select least($1, min($2[i])) from generate_subscripts($2,1) g(i)';
+ create aggregate least_agg(variadic items anyarray) (
+   stype = anyelement, sfunc = least_accum
+ );
diff --git a/src/test/regress/expected/opr_sanity.out b/src/test/regress/expected/opr_sanity.out
index 256b719..515cd9d 100644
*** a/src/test/regress/expected/opr_sanity.out
--- b/src/test/regress/expected/opr_sanity.out
*************** ORDER BY 1, 2;
*** 843,848 ****
--- 843,850 ----
  -- to avoid this because it opens the door for confusion in connection with
  -- ORDER BY: novices frequently put the ORDER BY in the wrong place.
  -- See the fate of the single-argument form of string_agg() for history.
+ -- (Note: we don't forbid users from creating such aggregates; the policy is
+ -- just to think twice before creating built-in aggregates like this.)
  -- The only aggregates that should show up here are count(x) and count(*).
  SELECT p1.oid::regprocedure, p2.oid::regprocedure
  FROM pg_proc AS p1, pg_proc AS p2
*************** ORDER BY 1;
*** 855,861 ****
   count("any") | count()
  (1 row)

! -- For the same reason, aggregates with default arguments are no good.
  SELECT oid, proname
  FROM pg_proc AS p
  WHERE proisagg AND proargdefaults IS NOT NULL;
--- 857,871 ----
   count("any") | count()
  (1 row)

! -- For the same reason, we avoid creating built-in variadic aggregates.
! SELECT oid, proname
! FROM pg_proc AS p
! WHERE proisagg AND provariadic != 0;
!  oid | proname
! -----+---------
! (0 rows)
!
! -- For the same reason, built-in aggregates with default arguments are no good.
  SELECT oid, proname
  FROM pg_proc AS p
  WHERE proisagg AND proargdefaults IS NOT NULL;
diff --git a/src/test/regress/sql/aggregates.sql b/src/test/regress/sql/aggregates.sql
index 5c0196f..397edff 100644
*** a/src/test/regress/sql/aggregates.sql
--- b/src/test/regress/sql/aggregates.sql
*************** select sum(unique1) FILTER (WHERE
*** 480,482 ****
--- 480,486 ----
  select aggfns(distinct a,b,c order by a,c using ~<~,b) filter (where a > 1)
      from (values (1,3,'foo'),(0,null,null),(2,2,'bar'),(3,1,'baz')) v(a,b,c),
      generate_series(1,2) i;
+
+ -- variadic aggregates
+ select least_agg(q1,q2) from int8_tbl;
+ select least_agg(variadic array[q1,q2]) from int8_tbl;
diff --git a/src/test/regress/sql/create_aggregate.sql b/src/test/regress/sql/create_aggregate.sql
index 84f9a4f..3c7d330 100644
*** a/src/test/regress/sql/create_aggregate.sql
--- b/src/test/regress/sql/create_aggregate.sql
*************** create aggregate aggfns(integer,integer,
*** 71,73 ****
--- 71,82 ----
     sfunc = aggfns_trans, stype = aggtype[],
     initcond = '{}'
  );
+
+ -- variadic aggregate
+ create function least_accum(anyelement, variadic anyarray)
+ returns anyelement language sql as
+   'select least($1, min($2[i])) from generate_subscripts($2,1) g(i)';
+
+ create aggregate least_agg(variadic items anyarray) (
+   stype = anyelement, sfunc = least_accum
+ );
diff --git a/src/test/regress/sql/opr_sanity.sql b/src/test/regress/sql/opr_sanity.sql
index a3be0c1..efcd70f 100644
*** a/src/test/regress/sql/opr_sanity.sql
--- b/src/test/regress/sql/opr_sanity.sql
*************** ORDER BY 1, 2;
*** 674,679 ****
--- 674,681 ----
  -- to avoid this because it opens the door for confusion in connection with
  -- ORDER BY: novices frequently put the ORDER BY in the wrong place.
  -- See the fate of the single-argument form of string_agg() for history.
+ -- (Note: we don't forbid users from creating such aggregates; the policy is
+ -- just to think twice before creating built-in aggregates like this.)
  -- The only aggregates that should show up here are count(x) and count(*).

  SELECT p1.oid::regprocedure, p2.oid::regprocedure
*************** WHERE p1.oid < p2.oid AND p1.proname = p
*** 683,689 ****
      array_dims(p1.proargtypes) != array_dims(p2.proargtypes)
  ORDER BY 1;

! -- For the same reason, aggregates with default arguments are no good.

  SELECT oid, proname
  FROM pg_proc AS p
--- 685,697 ----
      array_dims(p1.proargtypes) != array_dims(p2.proargtypes)
  ORDER BY 1;

! -- For the same reason, we avoid creating built-in variadic aggregates.
!
! SELECT oid, proname
! FROM pg_proc AS p
! WHERE proisagg AND provariadic != 0;
!
! -- For the same reason, built-in aggregates with default arguments are no good.

  SELECT oid, proname
  FROM pg_proc AS p

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