Add JSON_ARRAY() transformation

Author: Nikita Glukhov

src/backend/nodes/copyfuncs.c

@@ -2358,6 +2358,22 @@ _copyJsonOutput(const JsonOutput *from)
 	return newnode;
 }
 
+/*
+ * _copyJsonArrayCtor
+ */
+static JsonArrayCtor *
+_copyJsonArrayCtor(const JsonArrayCtor *from)
+{
+	JsonArrayCtor *newnode = makeNode(JsonArrayCtor);
+
+	COPY_NODE_FIELD(exprs);
+	COPY_NODE_FIELD(output);
+	COPY_SCALAR_FIELD(absent_on_null);
+	COPY_LOCATION_FIELD(location);
+
+	return newnode;
+}
+
 /* ****************************************************************
  *						pathnodes.h copy functions
  *
@@ -5276,6 +5292,9 @@ copyObjectImpl(const void *from)
 		case T_JsonOutput:
 			retval = _copyJsonOutput(from);
 			break;
+		case T_JsonArrayCtor:
+			retval = _copyJsonArrayCtor(from);
+			break;
 
 			/*
 			 * RELATION NODES

src/backend/nodes/nodeFuncs.c

@@ -4010,6 +4010,16 @@ raw_expression_tree_walker(Node *node,
 					return true;
 			}
 			break;
+		case T_JsonArrayCtor:
+			{
+				JsonArrayCtor *jac = (JsonArrayCtor *) node;
+
+				if (walker(jac->output, context))
+					return true;
+				if (walker(jac->exprs, context))
+					return true;
+			}
+			break;
 		default:
 			elog(ERROR, "unrecognized node type: %d",
 				 (int) nodeTag(node));

src/backend/parser/parse_expr.c

@@ -122,6 +122,7 @@ static Node *transformIndirection(ParseState *pstate, A_Indirection *ind);
 static Node *transformTypeCast(ParseState *pstate, TypeCast *tc);
 static Node *transformCollateClause(ParseState *pstate, CollateClause *c);
 static Node *transformJsonObjectCtor(ParseState *pstate, JsonObjectCtor *ctor);
+static Node *transformJsonArrayCtor(ParseState *pstate, JsonArrayCtor *ctor);
 static Node *make_row_comparison_op(ParseState *pstate, List *opname,
 									List *largs, List *rargs, int location);
 static Node *make_row_distinct_op(ParseState *pstate, List *opname,
@@ -374,6 +375,10 @@ transformExprRecurse(ParseState *pstate, Node *expr)
 			result = transformJsonObjectCtor(pstate, (JsonObjectCtor *) expr);
 			break;
 
+		case T_JsonArrayCtor:
+			result = transformJsonArrayCtor(pstate, (JsonArrayCtor *) expr);
+			break;
+
 		default:
 			/* should not reach here */
 			elog(ERROR, "unrecognized node type: %d", (int) nodeTag(expr));
@@ -3995,3 +4000,68 @@ transformJsonObjectCtor(ParseState *pstate, JsonObjectCtor *ctor)
 
 	return coerceJsonFuncExpr(pstate, (Node *) jsctor, jsctor->returning, true);
 }
+
+/*
+ * Transform JSON_ARRAY() constructor.
+ *
+ * JSON_ARRAY() is transformed into json[b]_build_array[_ext]() call
+ * depending on the output JSON format. The first argument of
+ * json[b]_build_array_ext() is absent_on_null.
+ *
+ * Then function call result is coerced to the target type.
+ */
+static Node *
+transformJsonArrayCtor(ParseState *pstate, JsonArrayCtor *ctor)
+{
+	JsonReturning returning;
+	JsonCtorExpr *jsctor;
+	FuncExpr   *fexpr;
+	List	   *args = NIL;
+	Oid			funcid;
+	Oid			funcrettype;
+
+	/* transform element expressions, if any */
+	if (ctor->exprs)
+	{
+		ListCell   *lc;
+
+		/* append the first absent_on_null argument */
+		args = lappend(args, makeBoolConst(ctor->absent_on_null, false));
+
+		/* transform and append element arguments */
+		foreach(lc, ctor->exprs)
+		{
+			JsonValueExpr *jsval = castNode(JsonValueExpr, lfirst(lc));
+			Node	   *val = transformJsonValueExpr(pstate, jsval,
+													 JS_FORMAT_DEFAULT);
+
+			args = lappend(args, val);
+		}
+	}
+
+	transformJsonOutput(pstate, ctor->output, true, &returning);
+
+	if (returning.format.type == JS_FORMAT_JSONB)
+	{
+		funcid = args ? F_JSONB_BUILD_ARRAY_EXT : F_JSONB_BUILD_ARRAY_NOARGS;
+		funcrettype = JSONBOID;
+	}
+	else
+	{
+		funcid = args ? F_JSON_BUILD_ARRAY_EXT : F_JSON_BUILD_ARRAY_NOARGS;
+		funcrettype = JSONOID;
+	}
+
+	fexpr = makeFuncExpr(funcid, funcrettype, args,
+						 InvalidOid, InvalidOid, COERCE_EXPLICIT_CALL);
+	fexpr->location = ctor->location;
+
+	jsctor = makeNode(JsonCtorExpr);
+	jsctor->func = fexpr;
+	jsctor->type = JSCTOR_JSON_ARRAY;
+	jsctor->returning = returning;
+	jsctor->unique = false;
+	jsctor->absent_on_null = ctor->absent_on_null;
+
+	return coerceJsonFuncExpr(pstate, (Node *) jsctor, &returning, true);
+}

src/backend/parser/parse_target.c

@@ -1934,6 +1934,9 @@ FigureColnameInternal(Node *node, char **name)
 		case T_JsonObjectCtor:
 			*name = "json_object";
 			return 2;
+		case T_JsonArrayCtor:
+			*name = "json_array";
+			return 2;
 		default:
 			break;
 	}

src/backend/utils/adt/json.c

@@ -1237,11 +1237,9 @@ json_build_object_noargs(PG_FUNCTION_ARGS)
 	PG_RETURN_TEXT_P(cstring_to_text_with_len("{}", 2));
 }
 
-/*
- * SQL function json_build_array(variadic "any")
- */
-Datum
-json_build_array(PG_FUNCTION_ARGS)
+static Datum
+json_build_array_worker(FunctionCallInfo fcinfo, int first_vararg,
+						bool absent_on_null)
 {
 	int			nargs;
 	int			i;
@@ -1252,7 +1250,8 @@ json_build_array(PG_FUNCTION_ARGS)
 	Oid		   *types;
 
 	/* fetch argument values to build the array */
-	nargs = extract_variadic_args(fcinfo, 0, false, &args, &types, &nulls);
+	nargs = extract_variadic_args(fcinfo, first_vararg, false,
+								  &args, &types, &nulls);
 
 	if (nargs < 0)
 		PG_RETURN_NULL();
@@ -1263,6 +1262,9 @@ json_build_array(PG_FUNCTION_ARGS)
 
 	for (i = 0; i < nargs; i++)
 	{
+		if (absent_on_null && nulls[i])
+			continue;
+
 		appendStringInfoString(result, sep);
 		sep = ", ";
 		add_json(args[i], nulls[i], result, types[i], false);
@@ -1273,6 +1275,24 @@ json_build_array(PG_FUNCTION_ARGS)
 	PG_RETURN_TEXT_P(cstring_to_text_with_len(result->data, result->len));
 }
 
+/*
+ * SQL function json_build_array(variadic "any")
+ */
+Datum
+json_build_array(PG_FUNCTION_ARGS)
+{
+	return json_build_array_worker(fcinfo, 0, false);
+}
+
+/*
+ * SQL function json_build_array_ext(absent_on_null bool, variadic "any")
+ */
+Datum
+json_build_array_ext(PG_FUNCTION_ARGS)
+{
+	return json_build_array_worker(fcinfo, 1, PG_GETARG_BOOL(0));
+}
+
 /*
  * degenerate case of json_build_array where it gets 0 arguments.
  */

src/backend/utils/adt/jsonb.c

@@ -1237,11 +1237,9 @@ jsonb_build_object_noargs(PG_FUNCTION_ARGS)
 	PG_RETURN_POINTER(JsonbValueToJsonb(result.res));
 }
 
-/*
- * SQL function jsonb_build_array(variadic "any")
- */
-Datum
-jsonb_build_array(PG_FUNCTION_ARGS)
+static Datum
+jsonb_build_array_worker(FunctionCallInfo fcinfo, int first_vararg,
+						 bool absent_on_null)
 {
 	int			nargs;
 	int			i;
@@ -1251,7 +1249,8 @@ jsonb_build_array(PG_FUNCTION_ARGS)
 	Oid		   *types;
 
 	/* build argument values to build the array */
-	nargs = extract_variadic_args(fcinfo, 0, true, &args, &types, &nulls);
+	nargs = extract_variadic_args(fcinfo, first_vararg, true,
+								  &args, &types, &nulls);
 
 	if (nargs < 0)
 		PG_RETURN_NULL();
@@ -1261,13 +1260,36 @@ jsonb_build_array(PG_FUNCTION_ARGS)
 	result.res = pushJsonbValue(&result.parseState, WJB_BEGIN_ARRAY, NULL);
 
 	for (i = 0; i < nargs; i++)
+	{
+		if (absent_on_null && nulls[i])
+			continue;
+
 		add_jsonb(args[i], nulls[i], &result, types[i], false);
+	}
 
 	result.res = pushJsonbValue(&result.parseState, WJB_END_ARRAY, NULL);
 
 	PG_RETURN_POINTER(JsonbValueToJsonb(result.res));
 }
 
+/*
+ * SQL function jsonb_build_array(variadic "any")
+ */
+Datum
+jsonb_build_array(PG_FUNCTION_ARGS)
+{
+	return jsonb_build_array_worker(fcinfo, 0, false);
+}
+
+/*
+ * SQL function jsonb_build_array_ext(absent_on_null bool, variadic "any")
+ */
+Datum
+jsonb_build_array_ext(PG_FUNCTION_ARGS)
+{
+	return jsonb_build_array_worker(fcinfo, 1, PG_GETARG_BOOL(0));
+}
+
 /*
  * degenerate case of jsonb_build_array where it gets 0 arguments.
  */

src/include/catalog/pg_proc.dat

@@ -8397,6 +8397,11 @@
   proname => 'json_build_array', proisstrict => 'f', provolatile => 's',
   prorettype => 'json', proargtypes => '',
   prosrc => 'json_build_array_noargs' },
+{ oid => '2228', descr => 'build a json array from any inputs',
+  proname => 'json_build_array_ext', provariadic => 'any', proisstrict => 'f',
+  provolatile => 's', prorettype => 'json', proargtypes => 'bool any',
+  proallargtypes => '{bool,any}', proargmodes => '{i,v}',
+  prosrc => 'json_build_array_ext' },
 { oid => '3200',
   descr => 'build a json object from pairwise key/value inputs',
   proname => 'json_build_object', provariadic => 'any', proisstrict => 'f',
@@ -9272,6 +9277,11 @@
   proname => 'jsonb_build_array', proisstrict => 'f', provolatile => 's',
   prorettype => 'jsonb', proargtypes => '',
   prosrc => 'jsonb_build_array_noargs' },
+{ oid => '6068', descr => 'build a jsonb array from any inputs',
+  proname => 'jsonb_build_array_ext', provariadic => 'any', proisstrict => 'f',
+  provolatile => 's', prorettype => 'jsonb', proargtypes => 'bool any',
+  proallargtypes => '{bool,any}', proargmodes => '{i,v}',
+  prosrc => 'jsonb_build_array_ext' },
 { oid => '3273',
   descr => 'build a jsonb object from pairwise key/value inputs',
   proname => 'jsonb_build_object', provariadic => 'any', proisstrict => 'f',