SERVER-48464 Remove {$rand:{const:true}}

3 files changed, 7 insertions, 63 deletions

diff --git a/jstests/aggregation/expressions/rand.js b/jstests/aggregation/expressions/rand.js
index b87d9e58be6..d4d3559bc1a 100644
--- a/jstests/aggregation/expressions/rand.js
+++ b/jstests/aggregation/expressions/rand.js
@@ -29,26 +29,4 @@ print("Average: ", avg);
 const err = 10.0 / Math.sqrt(12.0 * N);
 assert.lte(0.5 - err, avg);
 assert.gte(0.5 + err, avg);
-
-const collConst = db.expression_rand_const;
-collConst.drop();
-assert.commandWorked(collConst.insert({_id: i, v: 0}));
-
-const randPipelineConst = [{$project: {r: {$rand: {const : true}}}}];
-let sum = 0.0;
-for (i = 0; i < N; i++) {
-    const resultArrayConst = collConst.aggregate(randPipelineConst).toArray();
-    assert.eq(1, resultArrayConst.length);
-
-    const r = resultArrayConst[0]["r"];
-    assert.lte(0.0, r);
-    assert.gte(1.0, r);
-
-    sum += r;
-}
-
-const avgConst = sum / N;
-print("Average Const: ", avgConst);
-assert.lte(0.5 - err, avgConst);
-assert.gte(0.5 + err, avgConst);
 }());
diff --git a/src/mongo/db/pipeline/expression.cpp b/src/mongo/db/pipeline/expression.cpp
index 42f95c7746f..80400576bf0 100644
--- a/src/mongo/db/pipeline/expression.cpp
+++ b/src/mongo/db/pipeline/expression.cpp
@@ -6439,34 +6439,11 @@ ExpressionRandom::ExpressionRandom(ExpressionContext* const expCtx) : Expression
 intrusive_ptr<Expression> ExpressionRandom::parse(ExpressionContext* const expCtx,
                                                   BSONElement exprElement,
                                                   const VariablesParseState& vps) {
-    bool hasConstField = false;
-    bool isConst = false;
-
     uassert(3040500,
-            str::stream() << "$rand not allowed inside collection validators",
+            "$rand not allowed inside collection validators",
             !expCtx->isParsingCollectionValidator);
 
-    for (const auto& elem : exprElement.Obj()) {
-        const auto fieldName = elem.fieldNameStringData();
-        if (fieldName == "const"_sd) {
-            uassert(
-                3040501, str::stream() << "'const' must be specified just once", !hasConstField);
-
-            uassert(3040502,
-                    str::stream() << "'const' argument must be a boolean, found "
-                                  << typeName(elem.type()),
-                    elem.type() == Bool);
-            isConst = elem.boolean();
-            hasConstField = true;
-        } else {
-            uasserted(3040503, str::stream() << "Unknown argument: " << fieldName);
-        }
-    }
-
-    if (isConst) {
-        ExpressionRandom exprRandom(expCtx);
-        return ExpressionConstant::create(expCtx, Value(exprRandom.getRandomValue()));
-    }
+    uassert(3040501, "$rand does not currently accept arguments", exprElement.Obj().isEmpty());
 
     return new ExpressionRandom(expCtx);
 }
@@ -6484,7 +6461,6 @@ Value ExpressionRandom::evaluate(const Document& root, Variables* variables) con
 }
 
 intrusive_ptr<Expression> ExpressionRandom::optimize() {
-    // Already optimized to ExpressionConstant if "const" option passed in.
     return intrusive_ptr<Expression>(this);
 }
 
@@ -6493,6 +6469,6 @@ void ExpressionRandom::_doAddDependencies(DepsTracker* deps) const {
 }
 
 Value ExpressionRandom::serialize(const bool explain) const {
-    return Value(DOC(getOpName() << DOC("const"_sd << Value(false))));
+    return Value(DOC(getOpName() << Document()));
 }
 }  // namespace mongo
diff --git a/src/mongo/db/pipeline/expression_test.cpp b/src/mongo/db/pipeline/expression_test.cpp
index 23150d4a1a3..99c1fe07648 100644
--- a/src/mongo/db/pipeline/expression_test.cpp
+++ b/src/mongo/db/pipeline/expression_test.cpp
@@ -2976,26 +2976,16 @@ TEST(ExpressionRandom, Basic) {
     auto expCtx = ExpressionContextForTest{};
     VariablesParseState vps = expCtx.variablesParseState;
 
-    // Test const = false case, we generate new random value on every call to evaluate().
+    // We generate a new random value on every call to evaluate().
     intrusive_ptr<Expression> expression =
         Expression::parseExpression(&expCtx, fromjson("{ $rand: {} }"), vps);
 
     const std::string& serialized = expression->serialize(false).getDocument().toString();
-    ASSERT_EQ("{$rand: {const: false}}", serialized);
+    ASSERT_EQ("{$rand: {}}", serialized);
 
-    const auto randFn1 = [&expression, &expCtx]() -> double {
+    const auto randFn = [&expression, &expCtx]() -> double {
         return expression->evaluate({}, &expCtx.variables).getDouble();
     };
-    assertRandomProperties(randFn1);
-
-    // Test const = true case, we optimize to a const.
-    const auto randFn2 = [&expression, &expCtx, &vps]() -> double {
-        expression =
-            Expression::parseExpression(&expCtx, fromjson("{ $rand: {const: true} }"), vps);
-        const std::string& serialized1 = expression->serialize(false).getDocument().toString();
-        ASSERT_TRUE(serialized1.find("{$const:") == 0);
-        return expression->evaluate({}, &expCtx.variables).getDouble();
-    };
-    assertRandomProperties(randFn2);
+    assertRandomProperties(randFn);
 }
 }  // namespace ExpressionTests