Introduce "anycompatible" family of polymorphic types.

This patch adds the pseudo-types anycompatible, anycompatiblearray,
anycompatiblenonarray, and anycompatiblerange.  They work much like
anyelement, anyarray, anynonarray, and anyrange respectively, except
that the actual input values need not match precisely in type.
Instead, if we can find a common supertype (using the same rules
as for UNION/CASE type resolution), then the parser automatically
promotes the input values to that type.  For example,
"myfunc(anycompatible, anycompatible)" can match a call with one
integer and one bigint argument, with the integer automatically
promoted to bigint.  With anyelement in the definition, the user
would have had to cast the integer explicitly.

The new types also provide a second, independent set of type variables
for function matching; thus with "myfunc(anyelement, anyelement,
anycompatible) returns anycompatible" the first two arguments are
constrained to be the same type, but the third can be some other
type, and the result has the type of the third argument.  The need
for more than one set of type variables was foreseen back when we
first invented the polymorphic types, but we never did anything
about it.

Pavel Stehule, revised a bit by me

Discussion: https://postgr.es/m/CAFj8pRDna7VqNi8gR+Tt2Ktmz0cq5G93guc3Sbn_NVPLdXAkqA@mail.gmail.com

4 files changed, 224 insertions, 11 deletions

diff --git a/src/backend/utils/adt/json.c b/src/backend/utils/adt/json.c
index f78420e22dc..8bb00abb6b3 100644
--- a/src/backend/utils/adt/json.c
+++ b/src/backend/utils/adt/json.c
@@ -195,7 +195,7 @@ json_categorize_type(Oid typoid,
 		default:
 			/* Check for arrays and composites */
 			if (OidIsValid(get_element_type(typoid)) || typoid == ANYARRAYOID
-				|| typoid == RECORDARRAYOID)
+				|| typoid == ANYCOMPATIBLEARRAYOID || typoid == RECORDARRAYOID)
 				*tcategory = JSONTYPE_ARRAY;
 			else if (type_is_rowtype(typoid))	/* includes RECORDOID */
 				*tcategory = JSONTYPE_COMPOSITE;
diff --git a/src/backend/utils/adt/jsonb.c b/src/backend/utils/adt/jsonb.c
index b961d294723..1e9ca046c69 100644
--- a/src/backend/utils/adt/jsonb.c
+++ b/src/backend/utils/adt/jsonb.c
@@ -677,7 +677,7 @@ jsonb_categorize_type(Oid typoid,
 		default:
 			/* Check for arrays and composites */
 			if (OidIsValid(get_element_type(typoid)) || typoid == ANYARRAYOID
-				|| typoid == RECORDARRAYOID)
+				|| typoid == ANYCOMPATIBLEARRAYOID || typoid == RECORDARRAYOID)
 				*tcategory = JSONBTYPE_ARRAY;
 			else if (type_is_rowtype(typoid))	/* includes RECORDOID */
 				*tcategory = JSONBTYPE_COMPOSITE;
diff --git a/src/backend/utils/adt/pseudotypes.c b/src/backend/utils/adt/pseudotypes.c
index 9eee03c143a..3d6b2f90935 100644
--- a/src/backend/utils/adt/pseudotypes.c
+++ b/src/backend/utils/adt/pseudotypes.c
@@ -169,6 +169,26 @@ anyarray_send(PG_FUNCTION_ARGS)
 }
 
 /*
+ * anycompatiblearray
+ *
+ * We may as well allow output, since we do for anyarray.
+ */
+PSEUDOTYPE_DUMMY_INPUT_FUNC(anycompatiblearray);
+PSEUDOTYPE_DUMMY_RECEIVE_FUNC(anycompatiblearray);
+
+Datum
+anycompatiblearray_out(PG_FUNCTION_ARGS)
+{
+	return array_out(fcinfo);
+}
+
+Datum
+anycompatiblearray_send(PG_FUNCTION_ARGS)
+{
+	return array_send(fcinfo);
+}
+
+/*
  * anyenum
  *
  * We may as well allow output, since enum_out will in fact work.
@@ -195,6 +215,19 @@ anyrange_out(PG_FUNCTION_ARGS)
 }
 
 /*
+ * anycompatiblerange
+ *
+ * We may as well allow output, since range_out will in fact work.
+ */
+PSEUDOTYPE_DUMMY_INPUT_FUNC(anycompatiblerange);
+
+Datum
+anycompatiblerange_out(PG_FUNCTION_ARGS)
+{
+	return range_out(fcinfo);
+}
+
+/*
  * void
  *
  * We support void_in so that PL functions can return VOID without any
@@ -316,3 +349,5 @@ PSEUDOTYPE_DUMMY_IO_FUNCS(tsm_handler);
 PSEUDOTYPE_DUMMY_IO_FUNCS(internal);
 PSEUDOTYPE_DUMMY_IO_FUNCS(anyelement);
 PSEUDOTYPE_DUMMY_IO_FUNCS(anynonarray);
+PSEUDOTYPE_DUMMY_IO_FUNCS(anycompatible);
+PSEUDOTYPE_DUMMY_IO_FUNCS(anycompatiblenonarray);
diff --git a/src/backend/utils/fmgr/funcapi.c b/src/backend/utils/fmgr/funcapi.c
index 4e9d21bd541..78ed8572038 100644
--- a/src/backend/utils/fmgr/funcapi.c
+++ b/src/backend/utils/fmgr/funcapi.c
@@ -552,7 +552,9 @@ resolve_anyrange_from_others(polymorphic_actuals *actuals)
  * with concrete data types deduced from the input arguments.
  * declared_args is an oidvector of the function's declared input arg types
  * (showing which are polymorphic), and call_expr is the call expression.
- * Returns true if able to deduce all types, false if not.
+ *
+ * Returns true if able to deduce all types, false if necessary information
+ * is not provided (call_expr is NULL or arg types aren't identifiable).
  */
 static bool
 resolve_polymorphic_tupdesc(TupleDesc tupdesc, oidvector *declared_args,
@@ -564,8 +566,13 @@ resolve_polymorphic_tupdesc(TupleDesc tupdesc, oidvector *declared_args,
 	bool		have_anyelement_result = false;
 	bool		have_anyarray_result = false;
 	bool		have_anyrange_result = false;
+	bool		have_anycompatible_result = false;
+	bool		have_anycompatible_array_result = false;
+	bool		have_anycompatible_range_result = false;
 	polymorphic_actuals poly_actuals;
+	polymorphic_actuals anyc_actuals;
 	Oid			anycollation = InvalidOid;
+	Oid			anycompatcollation = InvalidOid;
 	int			i;
 
 	/* See if there are any polymorphic outputs; quick out if not */
@@ -587,6 +594,19 @@ resolve_polymorphic_tupdesc(TupleDesc tupdesc, oidvector *declared_args,
 				have_polymorphic_result = true;
 				have_anyrange_result = true;
 				break;
+			case ANYCOMPATIBLEOID:
+			case ANYCOMPATIBLENONARRAYOID:
+				have_polymorphic_result = true;
+				have_anycompatible_result = true;
+				break;
+			case ANYCOMPATIBLEARRAYOID:
+				have_polymorphic_result = true;
+				have_anycompatible_array_result = true;
+				break;
+			case ANYCOMPATIBLERANGEOID:
+				have_polymorphic_result = true;
+				have_anycompatible_range_result = true;
+				break;
 			default:
 				break;
 		}
@@ -596,12 +616,16 @@ resolve_polymorphic_tupdesc(TupleDesc tupdesc, oidvector *declared_args,
 
 	/*
 	 * Otherwise, extract actual datatype(s) from input arguments.  (We assume
-	 * the parser already validated consistency of the arguments.)
+	 * the parser already validated consistency of the arguments.  Also, for
+	 * the ANYCOMPATIBLE pseudotype family, we expect that all matching
+	 * arguments were coerced to the selected common supertype, so that it
+	 * doesn't matter which one's exposed type we look at.)
 	 */
 	if (!call_expr)
 		return false;			/* no hope */
 
 	memset(&poly_actuals, 0, sizeof(poly_actuals));
+	memset(&anyc_actuals, 0, sizeof(anyc_actuals));
 
 	for (i = 0; i < nargs; i++)
 	{
@@ -636,6 +660,34 @@ resolve_polymorphic_tupdesc(TupleDesc tupdesc, oidvector *declared_args,
 						return false;
 				}
 				break;
+			case ANYCOMPATIBLEOID:
+			case ANYCOMPATIBLENONARRAYOID:
+				if (!OidIsValid(anyc_actuals.anyelement_type))
+				{
+					anyc_actuals.anyelement_type =
+						get_call_expr_argtype(call_expr, i);
+					if (!OidIsValid(anyc_actuals.anyelement_type))
+						return false;
+				}
+				break;
+			case ANYCOMPATIBLEARRAYOID:
+				if (!OidIsValid(anyc_actuals.anyarray_type))
+				{
+					anyc_actuals.anyarray_type =
+						get_call_expr_argtype(call_expr, i);
+					if (!OidIsValid(anyc_actuals.anyarray_type))
+						return false;
+				}
+				break;
+			case ANYCOMPATIBLERANGEOID:
+				if (!OidIsValid(anyc_actuals.anyrange_type))
+				{
+					anyc_actuals.anyrange_type =
+						get_call_expr_argtype(call_expr, i);
+					if (!OidIsValid(anyc_actuals.anyrange_type))
+						return false;
+				}
+				break;
 			default:
 				break;
 		}
@@ -651,18 +703,33 @@ resolve_polymorphic_tupdesc(TupleDesc tupdesc, oidvector *declared_args,
 	if (have_anyrange_result && !OidIsValid(poly_actuals.anyrange_type))
 		resolve_anyrange_from_others(&poly_actuals);
 
+	if (have_anycompatible_result && !OidIsValid(anyc_actuals.anyelement_type))
+		resolve_anyelement_from_others(&anyc_actuals);
+
+	if (have_anycompatible_array_result && !OidIsValid(anyc_actuals.anyarray_type))
+		resolve_anyarray_from_others(&anyc_actuals);
+
+	if (have_anycompatible_range_result && !OidIsValid(anyc_actuals.anyrange_type))
+		resolve_anyrange_from_others(&anyc_actuals);
+
 	/*
 	 * Identify the collation to use for polymorphic OUT parameters. (It'll
-	 * necessarily be the same for both anyelement and anyarray.)  Note that
-	 * range types are not collatable, so any possible internal collation of a
-	 * range type is not considered here.
+	 * necessarily be the same for both anyelement and anyarray, likewise for
+	 * anycompatible and anycompatiblearray.)  Note that range types are not
+	 * collatable, so any possible internal collation of a range type is not
+	 * considered here.
 	 */
 	if (OidIsValid(poly_actuals.anyelement_type))
 		anycollation = get_typcollation(poly_actuals.anyelement_type);
 	else if (OidIsValid(poly_actuals.anyarray_type))
 		anycollation = get_typcollation(poly_actuals.anyarray_type);
 
-	if (OidIsValid(anycollation))
+	if (OidIsValid(anyc_actuals.anyelement_type))
+		anycompatcollation = get_typcollation(anyc_actuals.anyelement_type);
+	else if (OidIsValid(anyc_actuals.anyarray_type))
+		anycompatcollation = get_typcollation(anyc_actuals.anyarray_type);
+
+	if (OidIsValid(anycollation) || OidIsValid(anycompatcollation))
 	{
 		/*
 		 * The types are collatable, so consider whether to use a nondefault
@@ -672,7 +739,12 @@ resolve_polymorphic_tupdesc(TupleDesc tupdesc, oidvector *declared_args,
 		Oid			inputcollation = exprInputCollation(call_expr);
 
 		if (OidIsValid(inputcollation))
-			anycollation = inputcollation;
+		{
+			if (OidIsValid(anycollation))
+				anycollation = inputcollation;
+			if (OidIsValid(anycompatcollation))
+				anycompatcollation = inputcollation;
+		}
 	}
 
 	/* And finally replace the tuple column types as needed */
@@ -708,6 +780,31 @@ resolve_polymorphic_tupdesc(TupleDesc tupdesc, oidvector *declared_args,
 								   0);
 				/* no collation should be attached to a range type */
 				break;
+			case ANYCOMPATIBLEOID:
+			case ANYCOMPATIBLENONARRAYOID:
+				TupleDescInitEntry(tupdesc, i + 1,
+								   NameStr(att->attname),
+								   anyc_actuals.anyelement_type,
+								   -1,
+								   0);
+				TupleDescInitEntryCollation(tupdesc, i + 1, anycompatcollation);
+				break;
+			case ANYCOMPATIBLEARRAYOID:
+				TupleDescInitEntry(tupdesc, i + 1,
+								   NameStr(att->attname),
+								   anyc_actuals.anyarray_type,
+								   -1,
+								   0);
+				TupleDescInitEntryCollation(tupdesc, i + 1, anycompatcollation);
+				break;
+			case ANYCOMPATIBLERANGEOID:
+				TupleDescInitEntry(tupdesc, i + 1,
+								   NameStr(att->attname),
+								   anyc_actuals.anyrange_type,
+								   -1,
+								   0);
+				/* no collation should be attached to a range type */
+				break;
 			default:
 				break;
 		}
@@ -720,7 +817,9 @@ resolve_polymorphic_tupdesc(TupleDesc tupdesc, oidvector *declared_args,
  * Given the declared argument types and modes for a function, replace any
  * polymorphic types (ANYELEMENT etc) in argtypes[] with concrete data types
  * deduced from the input arguments found in call_expr.
- * Returns true if able to deduce all types, false if not.
+ *
+ * Returns true if able to deduce all types, false if necessary information
+ * is not provided (call_expr is NULL or arg types aren't identifiable).
  *
  * This is the same logic as resolve_polymorphic_tupdesc, but with a different
  * argument representation, and slightly different output responsibilities.
@@ -735,16 +834,21 @@ resolve_polymorphic_argtypes(int numargs, Oid *argtypes, char *argmodes,
 	bool		have_anyelement_result = false;
 	bool		have_anyarray_result = false;
 	bool		have_anyrange_result = false;
+	bool		have_anycompatible_result = false;
+	bool		have_anycompatible_array_result = false;
+	bool		have_anycompatible_range_result = false;
 	polymorphic_actuals poly_actuals;
+	polymorphic_actuals anyc_actuals;
 	int			inargno;
 	int			i;
 
 	/*
 	 * First pass: resolve polymorphic inputs, check for outputs.  As in
 	 * resolve_polymorphic_tupdesc, we rely on the parser to have enforced
-	 * type consistency.
+	 * type consistency and coerced ANYCOMPATIBLE args to a common supertype.
 	 */
 	memset(&poly_actuals, 0, sizeof(poly_actuals));
+	memset(&anyc_actuals, 0, sizeof(anyc_actuals));
 	inargno = 0;
 	for (i = 0; i < numargs; i++)
 	{
@@ -808,6 +912,61 @@ resolve_polymorphic_argtypes(int numargs, Oid *argtypes, char *argmodes,
 					argtypes[i] = poly_actuals.anyrange_type;
 				}
 				break;
+			case ANYCOMPATIBLEOID:
+			case ANYCOMPATIBLENONARRAYOID:
+				if (argmode == PROARGMODE_OUT || argmode == PROARGMODE_TABLE)
+				{
+					have_polymorphic_result = true;
+					have_anycompatible_result = true;
+				}
+				else
+				{
+					if (!OidIsValid(anyc_actuals.anyelement_type))
+					{
+						anyc_actuals.anyelement_type =
+							get_call_expr_argtype(call_expr, inargno);
+						if (!OidIsValid(anyc_actuals.anyelement_type))
+							return false;
+					}
+					argtypes[i] = anyc_actuals.anyelement_type;
+				}
+				break;
+			case ANYCOMPATIBLEARRAYOID:
+				if (argmode == PROARGMODE_OUT || argmode == PROARGMODE_TABLE)
+				{
+					have_polymorphic_result = true;
+					have_anycompatible_array_result = true;
+				}
+				else
+				{
+					if (!OidIsValid(anyc_actuals.anyarray_type))
+					{
+						anyc_actuals.anyarray_type =
+							get_call_expr_argtype(call_expr, inargno);
+						if (!OidIsValid(anyc_actuals.anyarray_type))
+							return false;
+					}
+					argtypes[i] = anyc_actuals.anyarray_type;
+				}
+				break;
+			case ANYCOMPATIBLERANGEOID:
+				if (argmode == PROARGMODE_OUT || argmode == PROARGMODE_TABLE)
+				{
+					have_polymorphic_result = true;
+					have_anycompatible_range_result = true;
+				}
+				else
+				{
+					if (!OidIsValid(anyc_actuals.anyrange_type))
+					{
+						anyc_actuals.anyrange_type =
+							get_call_expr_argtype(call_expr, inargno);
+						if (!OidIsValid(anyc_actuals.anyrange_type))
+							return false;
+					}
+					argtypes[i] = anyc_actuals.anyrange_type;
+				}
+				break;
 			default:
 				break;
 		}
@@ -829,6 +988,15 @@ resolve_polymorphic_argtypes(int numargs, Oid *argtypes, char *argmodes,
 	if (have_anyrange_result && !OidIsValid(poly_actuals.anyrange_type))
 		resolve_anyrange_from_others(&poly_actuals);
 
+	if (have_anycompatible_result && !OidIsValid(anyc_actuals.anyelement_type))
+		resolve_anyelement_from_others(&anyc_actuals);
+
+	if (have_anycompatible_array_result && !OidIsValid(anyc_actuals.anyarray_type))
+		resolve_anyarray_from_others(&anyc_actuals);
+
+	if (have_anycompatible_range_result && !OidIsValid(anyc_actuals.anyrange_type))
+		resolve_anyrange_from_others(&anyc_actuals);
+
 	/* And finally replace the output column types as needed */
 	for (i = 0; i < numargs; i++)
 	{
@@ -845,6 +1013,16 @@ resolve_polymorphic_argtypes(int numargs, Oid *argtypes, char *argmodes,
 			case ANYRANGEOID:
 				argtypes[i] = poly_actuals.anyrange_type;
 				break;
+			case ANYCOMPATIBLEOID:
+			case ANYCOMPATIBLENONARRAYOID:
+				argtypes[i] = anyc_actuals.anyelement_type;
+				break;
+			case ANYCOMPATIBLEARRAYOID:
+				argtypes[i] = anyc_actuals.anyarray_type;
+				break;
+			case ANYCOMPATIBLERANGEOID:
+				argtypes[i] = anyc_actuals.anyrange_type;
+				break;
 			default:
 				break;
 		}