1 files changed, 38 insertions, 0 deletions
diff --git a/src/mongo/db/pipeline/expression_trigonometric.h b/src/mongo/db/pipeline/expression_trigonometric.h
index 1c4236e7ccc..b015f97da78 100644
--- a/src/mongo/db/pipeline/expression_trigonometric.h
+++ b/src/mongo/db/pipeline/expression_trigonometric.h
@@ -230,4 +230,42 @@ public:
      */
     virtual const char* getOpName() const = 0;
 };
+
+class ExpressionArcTangent2 final : public ExpressionTwoNumericArgs<ExpressionArcTangent2> {
+public:
+    explicit ExpressionArcTangent2(ExpressionContext* const expCtx)
+        : ExpressionTwoNumericArgs(expCtx) {}
+
+    ExpressionArcTangent2(ExpressionContext* const expCtx, ExpressionVector&& children)
+        : ExpressionTwoNumericArgs(expCtx, std::move(children)) {}
+
+    Value evaluateNumericArgs(const Value& numericArg1, const Value& numericArg2) const final {
+        auto totalType = BSONType::NumberDouble;
+        // If the type of either argument is NumberDecimal, we promote to Decimal128.
+        if (numericArg1.getType() == BSONType::NumberDecimal ||
+            numericArg2.getType() == BSONType::NumberDecimal) {
+            totalType = BSONType::NumberDecimal;
+        }
+        switch (totalType) {
+            case BSONType::NumberDecimal: {
+                auto dec = numericArg1.coerceToDecimal();
+                return Value(dec.atan2(numericArg2.coerceToDecimal()));
+            }
+            case BSONType::NumberDouble: {
+                return Value(
+                    std::atan2(numericArg1.coerceToDouble(), numericArg2.coerceToDouble()));
+            }
+            default:
+                MONGO_UNREACHABLE;
+        }
+    }
+
+    const char* getOpName() const final {
+        return "$atan2";
+    }
+
+    void acceptVisitor(ExpressionVisitor* visitor) final {
+        return visitor->visit(this);
+    }
+};
 }  // namespace mongo