Implement $nin (#18)

See: https://www.mongodb.com/docs/manual/reference/operator/query/nin/

Author: erikdubbelboer

filter/converter.go

@@ -164,11 +164,16 @@ func (c *Converter) convertFilter(filter map[string]any, paramIndex int) (string
 						return "", nil, fmt.Errorf("$and as scalar operator not supported")
 					case "$not":
 						return "", nil, fmt.Errorf("$not as scalar operator not supported")
-					case "$in":
+					case "$in", "$nin":
 						if !isScalarSlice(v[operator]) {
 							return "", nil, fmt.Errorf("invalid value for $in operator (must array of primatives): %v", v[operator])
 						}
-						inner = append(inner, fmt.Sprintf("(%s = ANY($%d))", c.columnName(key), paramIndex))
+						neg := ""
+						if operator == "$nin" {
+							// `column != ANY(...)` does not work, so we need to do `NOT column = ANY(...)` instead.
+							neg = "NOT "
+						}
+						inner = append(inner, fmt.Sprintf("(%s%s = ANY($%d))", neg, c.columnName(key), paramIndex))
 						paramIndex++
 						if c.arrayDriver != nil {
 							v[operator] = c.arrayDriver(v[operator])

filter/converter_test.go

@@ -82,23 +82,31 @@ func TestConverter_Convert(t *testing.T) {
 			nil,
 		},
 		{
-			"in-array operator invalid value",
+			"simple $in",
 			nil,
 			`{"status": {"$in": [{"hacker": 1}, "OPEN"]}}`,
 			``,
 			nil,
 			fmt.Errorf("invalid value for $in operator (must array of primatives): [map[hacker:1] OPEN]"),
 		},
 		{
-			"in-array operator scalar value",
+			"simple $nin",
+			nil,
+			`{"status": {"$nin": ["NEW", "OPEN"]}}`,
+			`(NOT "status" = ANY($1))`,
+			[]any{[]any{"NEW", "OPEN"}},
+			nil,
+		},
+		{
+			"$in scalar value",
 			nil,
 			`{"status": {"$in": "text"}}`,
 			``,
 			nil,
 			fmt.Errorf("invalid value for $in operator (must array of primatives): text"),
 		},
 		{
-			"in-array operator with null value",
+			"$in with null value",
 			nil,
 			`{"status": {"$in": ["guest", null]}}`,
 			`("status" = ANY($1))`,

fuzz/fuzz_test.go

@@ -21,6 +21,7 @@ func FuzzConverter(f *testing.F) {
 		`{"b": 1, "c": 2, "a": 3}`,
 		`{"status": {"$in": ["NEW", "OPEN"]}}`,
 		`{"status": {"$in": [{"hacker": 1}, "OPEN"]}}`,
+		`{"status": {"$nin": ["NEW", "OPEN"]}}`,
 		`{"status": {"$in": "text"}}`,
 		`{"status": {"$in": ["guest", null]}}`,
 		`{"$or": [{"name": "John"}, {"name": "Doe"}]}`,

integration/postgres_test.go

@@ -345,6 +345,18 @@ func TestIntegration_BasicOperators(t *testing.T) {
 			[]int{1, 2, 3, 4, 5, 6, 7, 8, 10},
 			nil,
 		},
+		{
+			"$in",
+			`{"level": {"$in": [20, 30, 40]}}`,
+			[]int{2, 3, 4},
+			nil,
+		},
+		{
+			"$nin",
+			`{"level": {"$nin": [20, 30, 40]}}`,
+			[]int{1, 5, 6, 7, 8, 9, 10},
+			nil,
+		},
 	}
 
 	for _, tt := range tests {