SERVER-48827 Implement limit in grammar

8 files changed, 348 insertions, 186 deletions

diff --git a/src/mongo/db/cst/bson_lexer.cpp b/src/mongo/db/cst/bson_lexer.cpp
index d1766c780e1..047f8ef4c95 100644
--- a/src/mongo/db/cst/bson_lexer.cpp
+++ b/src/mongo/db/cst/bson_lexer.cpp
@@ -45,6 +45,7 @@ const StringMap<PipelineParserGen::token_type> reservedKeyLookup = {
     {"coll", PipelineParserGen::token::COLL_ARG},
     {"pipeline", PipelineParserGen::token::PIPELINE_ARG},
     {"$skip", PipelineParserGen::token::STAGE_SKIP},
+    {"$limit", PipelineParserGen::token::STAGE_LIMIT},
 };
 bool isCompound(PipelineParserGen::symbol_type token) {
     return token.type_get() == static_cast<int>(PipelineParserGen::token::START_OBJECT) ||
diff --git a/src/mongo/db/cst/cst_pipeline_translation.cpp b/src/mongo/db/cst/cst_pipeline_translation.cpp
index 4b39ef388a7..5afcf8e70fd 100644
--- a/src/mongo/db/cst/cst_pipeline_translation.cpp
+++ b/src/mongo/db/cst/cst_pipeline_translation.cpp
@@ -38,6 +38,7 @@
 #include "mongo/db/cst/key_value.h"
 #include "mongo/db/exec/inclusion_projection_executor.h"
 #include "mongo/db/pipeline/document_source.h"
+#include "mongo/db/pipeline/document_source_limit.h"
 #include "mongo/db/pipeline/document_source_project.h"
 #include "mongo/db/pipeline/document_source_skip.h"
 #include "mongo/db/pipeline/expression_context.h"
@@ -45,6 +46,7 @@
 #include "mongo/db/query/projection_ast.h"
 #include "mongo/db/query/projection_parser.h"
 #include "mongo/util/intrusive_counter.h"
+#include "mongo/util/visit_helper.h"
 
 namespace mongo::cst_pipeline_translation {
 namespace {
@@ -107,6 +109,14 @@ auto translateSkip(const CNode& cst, const boost::intrusive_ptr<ExpressionContex
 }
 
 /**
+ * Unwrap a limit stage CNode and produce a DocumentSourceLimit.
+ */
+auto translateLimit(const CNode& cst, const boost::intrusive_ptr<ExpressionContext>& expCtx) {
+    UserLong limit = translateNumToLong(cst);
+    return DocumentSourceLimit::create(expCtx, limit);
+}
+
+/**
  * Walk an aggregation pipeline stage object CNode and produce a DocumentSource.
  */
 boost::intrusive_ptr<DocumentSource> translateSource(
@@ -116,6 +126,8 @@ boost::intrusive_ptr<DocumentSource> translateSource(
             return translateProject(cst.objectChildren()[0].second, expCtx);
         case KeyFieldname::skip:
             return translateSkip(cst.objectChildren()[0].second, expCtx);
+        case KeyFieldname::limit:
+            return translateLimit(cst.objectChildren()[0].second, expCtx);
         default:
             MONGO_UNREACHABLE;
     }
diff --git a/src/mongo/db/cst/cst_pipeline_translation_test.cpp b/src/mongo/db/cst/cst_pipeline_translation_test.cpp
index 90152227f91..6a7760b1bab 100644
--- a/src/mongo/db/cst/cst_pipeline_translation_test.cpp
+++ b/src/mongo/db/cst/cst_pipeline_translation_test.cpp
@@ -41,6 +41,7 @@
 #include "mongo/db/cst/key_value.h"
 #include "mongo/db/exec/document_value/document.h"
 #include "mongo/db/namespace_string.h"
+#include "mongo/db/pipeline/document_source_limit.h"
 #include "mongo/db/pipeline/document_source_single_document_transformation.h"
 #include "mongo/db/pipeline/document_source_skip.h"
 #include "mongo/db/pipeline/expression_context_for_test.h"
@@ -206,5 +207,44 @@ TEST(CstTest, TranslatesSkipWithLong) {
     ASSERT_EQ((dynamic_cast<DocumentSourceSkip&>(**iter).getSkip()), 8223372036854775807);
 }
 
+TEST(CstTest, TranslatesLimitWithInt) {
+    auto nss = NamespaceString{"db", "coll"};
+    const auto cst = CNode{CNode::ArrayChildren{
+        CNode{CNode::ObjectChildren{{KeyFieldname::limit, CNode{UserInt{10}}}}}}};
+    boost::intrusive_ptr<ExpressionContextForTest> expCtx(new ExpressionContextForTest(nss));
+    auto pipeline = cst_pipeline_translation::translatePipeline(cst, expCtx);
+    auto& sources = pipeline->getSources();
+    ASSERT_EQ(1u, sources.size());
+    auto iter = sources.begin();
+    ASSERT(typeid(DocumentSourceLimit) == typeid(**iter));
+    ASSERT_EQ(10ll, dynamic_cast<DocumentSourceLimit&>(**iter).getLimit());
+}
+
+TEST(CstTest, TranslatesLimitWithDouble) {
+    auto nss = NamespaceString{"db", "coll"};
+    const auto cst = CNode{CNode::ArrayChildren{
+        CNode{CNode::ObjectChildren{{KeyFieldname::limit, CNode{UserDouble{10.5}}}}}}};
+    boost::intrusive_ptr<ExpressionContextForTest> expCtx(new ExpressionContextForTest(nss));
+    auto pipeline = cst_pipeline_translation::translatePipeline(cst, expCtx);
+    auto& sources = pipeline->getSources();
+    ASSERT_EQ(1u, sources.size());
+    auto iter = sources.begin();
+    ASSERT(typeid(DocumentSourceLimit) == typeid(**iter));
+    ASSERT_EQ(10ll, dynamic_cast<DocumentSourceLimit&>(**iter).getLimit());
+}
+
+TEST(CstTest, TranslatesLimitWithLong) {
+    auto nss = NamespaceString{"db", "coll"};
+    const auto cst = CNode{CNode::ArrayChildren{
+        CNode{CNode::ObjectChildren{{KeyFieldname::limit, CNode{UserLong{123123123123}}}}}}};
+    boost::intrusive_ptr<ExpressionContextForTest> expCtx(new ExpressionContextForTest(nss));
+    auto pipeline = cst_pipeline_translation::translatePipeline(cst, expCtx);
+    auto& sources = pipeline->getSources();
+    ASSERT_EQ(1u, sources.size());
+    auto iter = sources.begin();
+    ASSERT(typeid(DocumentSourceLimit) == typeid(**iter));
+    ASSERT_EQ(123123123123, dynamic_cast<DocumentSourceLimit&>(**iter).getLimit());
+}
+
 }  // namespace
 }  // namespace mongo
diff --git a/src/mongo/db/cst/cst_test.cpp b/src/mongo/db/cst/cst_test.cpp
index 97dbf6ebc0c..4ed9b889f15 100644
--- a/src/mongo/db/cst/cst_test.cpp
+++ b/src/mongo/db/cst/cst_test.cpp
@@ -198,5 +198,64 @@ TEST(CstGrammarTest, InvalidParseSkipString) {
     ASSERT_THROWS_CODE(parseTree.parse(), AssertionException, ErrorCodes::FailedToParse);
 }
 
+TEST(CstGrammarTest, ParsesLimitInt) {
+    CNode output;
+    auto input = fromjson("{pipeline: [{$limit: 5}]}");
+    BSONLexer lexer(input["pipeline"].Array());
+    auto parseTree = PipelineParserGen(lexer, &output);
+    ASSERT_EQ(0, parseTree.parse());
+    auto stages = stdx::get<CNode::ArrayChildren>(output.payload);
+    ASSERT_EQ(1, stages.size());
+    ASSERT(KeyFieldname::limit == stages[0].firstKeyFieldname());
+    ASSERT_BSONOBJ_EQ(fromjson("{limit : \"<UserInt 5>\"}"), stages[0].toBson());
+}
+
+TEST(CstGrammarTest, ParsesLimitDouble) {
+    CNode output;
+    auto input = fromjson("{pipeline: [{$limit: 5.0}]}");
+    BSONLexer lexer(input["pipeline"].Array());
+    auto parseTree = PipelineParserGen(lexer, &output);
+    ASSERT_EQ(0, parseTree.parse());
+    auto stages = stdx::get<CNode::ArrayChildren>(output.payload);
+    ASSERT_EQ(1, stages.size());
+    ASSERT(KeyFieldname::limit == stages[0].firstKeyFieldname());
+    ASSERT_BSONOBJ_EQ(fromjson("{limit : \"<UserDouble 5.000000>\"}"), stages[0].toBson());
+}
+
+TEST(CstGrammarTest, ParsesLimitLong) {
+    CNode output;
+    auto input = fromjson("{pipeline: [{$limit: 123123123123}]}");
+    BSONLexer lexer(input["pipeline"].Array());
+    auto parseTree = PipelineParserGen(lexer, &output);
+    ASSERT_EQ(0, parseTree.parse());
+    auto stages = stdx::get<CNode::ArrayChildren>(output.payload);
+    ASSERT_EQ(1, stages.size());
+    ASSERT(KeyFieldname::limit == stages[0].firstKeyFieldname());
+    ASSERT_BSONOBJ_EQ(fromjson("{limit : \"<UserLong 123123123123>\"}"), stages[0].toBson());
+}
+
+TEST(CstGrammarTest, InvalidParseLimitString) {
+    CNode output;
+    auto input = fromjson("{pipeline: [{$limit: \"5\"}]}");
+    BSONLexer lexer(input["pipeline"].Array());
+    auto parseTree = PipelineParserGen(lexer, &output);
+    ASSERT_THROWS_CODE(parseTree.parse(), AssertionException, ErrorCodes::FailedToParse);
+}
+TEST(CstGrammarTest, InvalidParseLimitObject) {
+    CNode output;
+    auto input = fromjson("{pipeline: [{$limit: {}}]}");
+    BSONLexer lexer(input["pipeline"].Array());
+    auto parseTree = PipelineParserGen(lexer, &output);
+    ASSERT_THROWS_CODE(parseTree.parse(), AssertionException, ErrorCodes::FailedToParse);
+}
+
+TEST(CstGrammarTest, InvalidParseLimitArray) {
+    CNode output;
+    auto input = fromjson("{pipeline: [{$limit: [2]}]}");
+    BSONLexer lexer(input["pipeline"].Array());
+    auto parseTree = PipelineParserGen(lexer, &output);
+    ASSERT_THROWS_CODE(parseTree.parse(), AssertionException, ErrorCodes::FailedToParse);
+}
+
 }  // namespace
 }  // namespace mongo
diff --git a/src/mongo/db/cst/key_fieldname.h b/src/mongo/db/cst/key_fieldname.h
index e6c36bf49be..5659ed15846 100644
--- a/src/mongo/db/cst/key_fieldname.h
+++ b/src/mongo/db/cst/key_fieldname.h
@@ -41,8 +41,8 @@
     ENUMIFY(unionWith)           \
     ENUMIFY(collArg)             \
     ENUMIFY(pipelineArg)         \
-    ENUMIFY(limit)               \
-    ENUMIFY(skip)
+    ENUMIFY(skip)                \
+    ENUMIFY(limit)
 
 MAKE_PRINTABLE_ENUM(KeyFieldname, KEYFIELDNAMES);
 MAKE_PRINTABLE_ENUM_STRING_ARRAY(key_fieldname, KeyFieldname, KEYFIELDNAMES);
diff --git a/src/mongo/db/cst/pipeline_grammar.yy b/src/mongo/db/cst/pipeline_grammar.yy
index 9d6a1bbe906..824628e3a33 100644
--- a/src/mongo/db/cst/pipeline_grammar.yy
+++ b/src/mongo/db/cst/pipeline_grammar.yy
@@ -109,6 +109,7 @@
     STAGE_INHIBIT_OPTIMIZATION
     STAGE_UNION_WITH
     STAGE_SKIP
+    STAGE_LIMIT
 
     // $unionWith arguments.
     COLL_ARG
@@ -126,7 +127,7 @@
 //
 // Semantic values (aka the C++ types produced by the actions).
 //
-%nterm <CNode> stageList stage inhibitOptimization unionWith num skip
+%nterm <CNode> stageList stage inhibitOptimization unionWith num skip limit
 
 //
 // Grammar rules
@@ -151,7 +152,7 @@ stageList[result]:
 START_ORDERED_OBJECT: { lexer.sortObjTokens(); } START_OBJECT;
 
 stage:
-    inhibitOptimization | unionWith | skip
+    inhibitOptimization | unionWith | skip | limit
 ;
 
 inhibitOptimization:
@@ -188,4 +189,9 @@ skip:
         $skip = CNode{CNode::ObjectChildren{std::pair{KeyFieldname::skip, $num}}};
 };
 
+limit:
+    STAGE_LIMIT num {
+        $limit = CNode{CNode::ObjectChildren{std::pair{KeyFieldname::limit, $num}}};
+};
+
 %%
diff --git a/src/mongo/db/cst/pipeline_parser_gen.cpp b/src/mongo/db/cst/pipeline_parser_gen.cpp
index 159de24c602..1767319051f 100644
--- a/src/mongo/db/cst/pipeline_parser_gen.cpp
+++ b/src/mongo/db/cst/pipeline_parser_gen.cpp
@@ -204,32 +204,33 @@ PipelineParserGen::stack_symbol_type::stack_symbol_type() {}
 PipelineParserGen::stack_symbol_type::stack_symbol_type(YY_RVREF(stack_symbol_type) that)
     : super_type(YY_MOVE(that.state), YY_MOVE(that.location)) {
     switch (that.kind()) {
-        case 18:  // stageList
-        case 19:  // stage
-        case 20:  // inhibitOptimization
-        case 21:  // unionWith
-        case 22:  // num
-        case 23:  // skip
+        case 19:  // stageList
+        case 20:  // stage
+        case 21:  // inhibitOptimization
+        case 22:  // unionWith
+        case 23:  // num
+        case 24:  // skip
+        case 25:  // limit
             value.YY_MOVE_OR_COPY<CNode>(YY_MOVE(that.value));
             break;
 
-        case 16:  // BOOL
+        case 17:  // BOOL
             value.YY_MOVE_OR_COPY<bool>(YY_MOVE(that.value));
             break;
 
-        case 15:  // NUMBER_DOUBLE
+        case 16:  // NUMBER_DOUBLE
             value.YY_MOVE_OR_COPY<double>(YY_MOVE(that.value));
             break;
 
-        case 13:  // NUMBER_INT
+        case 14:  // NUMBER_INT
             value.YY_MOVE_OR_COPY<int>(YY_MOVE(that.value));
             break;
 
-        case 14:  // NUMBER_LONG
+        case 15:  // NUMBER_LONG
             value.YY_MOVE_OR_COPY<long long>(YY_MOVE(that.value));
             break;
 
-        case 12:  // STRING
+        case 13:  // STRING
             value.YY_MOVE_OR_COPY<std::string>(YY_MOVE(that.value));
             break;
 
@@ -246,32 +247,33 @@ PipelineParserGen::stack_symbol_type::stack_symbol_type(YY_RVREF(stack_symbol_ty
 PipelineParserGen::stack_symbol_type::stack_symbol_type(state_type s, YY_MOVE_REF(symbol_type) that)
     : super_type(s, YY_MOVE(that.location)) {
     switch (that.kind()) {
-        case 18:  // stageList
-        case 19:  // stage
-        case 20:  // inhibitOptimization
-        case 21:  // unionWith
-        case 22:  // num
-        case 23:  // skip
+        case 19:  // stageList
+        case 20:  // stage
+        case 21:  // inhibitOptimization
+        case 22:  // unionWith
+        case 23:  // num
+        case 24:  // skip
+        case 25:  // limit
             value.move<CNode>(YY_MOVE(that.value));
             break;
 
-        case 16:  // BOOL
+        case 17:  // BOOL
             value.move<bool>(YY_MOVE(that.value));
             break;
 
-        case 15:  // NUMBER_DOUBLE
+        case 16:  // NUMBER_DOUBLE
             value.move<double>(YY_MOVE(that.value));
             break;
 
-        case 13:  // NUMBER_INT
+        case 14:  // NUMBER_INT
             value.move<int>(YY_MOVE(that.value));
             break;
 
-        case 14:  // NUMBER_LONG
+        case 15:  // NUMBER_LONG
             value.move<long long>(YY_MOVE(that.value));
             break;
 
-        case 12:  // STRING
+        case 13:  // STRING
             value.move<std::string>(YY_MOVE(that.value));
             break;
 
@@ -288,32 +290,33 @@ PipelineParserGen::stack_symbol_type& PipelineParserGen::stack_symbol_type::oper
     const stack_symbol_type& that) {
     state = that.state;
     switch (that.kind()) {
-        case 18:  // stageList
-        case 19:  // stage
-        case 20:  // inhibitOptimization
-        case 21:  // unionWith
-        case 22:  // num
-        case 23:  // skip
+        case 19:  // stageList
+        case 20:  // stage
+        case 21:  // inhibitOptimization
+        case 22:  // unionWith
+        case 23:  // num
+        case 24:  // skip
+        case 25:  // limit
             value.copy<CNode>(that.value);
             break;
 
-        case 16:  // BOOL
+        case 17:  // BOOL
             value.copy<bool>(that.value);
             break;
 
-        case 15:  // NUMBER_DOUBLE
+        case 16:  // NUMBER_DOUBLE
             value.copy<double>(that.value);
             break;
 
-        case 13:  // NUMBER_INT
+        case 14:  // NUMBER_INT
             value.copy<int>(that.value);
             break;
 
-        case 14:  // NUMBER_LONG
+        case 15:  // NUMBER_LONG
             value.copy<long long>(that.value);
             break;
 
-        case 12:  // STRING
+        case 13:  // STRING
             value.copy<std::string>(that.value);
             break;
 
@@ -329,32 +332,33 @@ PipelineParserGen::stack_symbol_type& PipelineParserGen::stack_symbol_type::oper
     stack_symbol_type& that) {
     state = that.state;
     switch (that.kind()) {
-        case 18:  // stageList
-        case 19:  // stage
-        case 20:  // inhibitOptimization
-        case 21:  // unionWith
-        case 22:  // num
-        case 23:  // skip
+        case 19:  // stageList
+        case 20:  // stage
+        case 21:  // inhibitOptimization
+        case 22:  // unionWith
+        case 23:  // num
+        case 24:  // skip
+        case 25:  // limit
             value.move<CNode>(that.value);
             break;
 
-        case 16:  // BOOL
+        case 17:  // BOOL
             value.move<bool>(that.value);
             break;
 
-        case 15:  // NUMBER_DOUBLE
+        case 16:  // NUMBER_DOUBLE
             value.move<double>(that.value);
             break;
 
-        case 13:  // NUMBER_INT
+        case 14:  // NUMBER_INT
             value.move<int>(that.value);
             break;
 
-        case 14:  // NUMBER_LONG
+        case 15:  // NUMBER_LONG
             value.move<long long>(that.value);
             break;
 
-        case 12:  // STRING
+        case 13:  // STRING
             value.move<std::string>(that.value);
             break;
 
@@ -581,32 +585,33 @@ int PipelineParserGen::parse() {
                correct type. The default '$$ = $1' action is NOT applied
                when using variants.  */
             switch (yyr1_[yyn]) {
-                case 18:  // stageList
-                case 19:  // stage
-                case 20:  // inhibitOptimization
-                case 21:  // unionWith
-                case 22:  // num
-                case 23:  // skip
+                case 19:  // stageList
+                case 20:  // stage
+                case 21:  // inhibitOptimization
+                case 22:  // unionWith
+                case 23:  // num
+                case 24:  // skip
+                case 25:  // limit
                     yylhs.value.emplace<CNode>();
                     break;
 
-                case 16:  // BOOL
+                case 17:  // BOOL
                     yylhs.value.emplace<bool>();
                     break;
 
-                case 15:  // NUMBER_DOUBLE
+                case 16:  // NUMBER_DOUBLE
                     yylhs.value.emplace<double>();
                     break;
 
-                case 13:  // NUMBER_INT
+                case 14:  // NUMBER_INT
                     yylhs.value.emplace<int>();
                     break;
 
-                case 14:  // NUMBER_LONG
+                case 15:  // NUMBER_LONG
                     yylhs.value.emplace<long long>();
                     break;
 
-                case 12:  // STRING
+                case 13:  // STRING
                     yylhs.value.emplace<std::string>();
                     break;
 
@@ -630,72 +635,80 @@ int PipelineParserGen::parse() {
             {
                 switch (yyn) {
                     case 2:
-#line 137 "src/mongo/db/cst/pipeline_grammar.yy"
+#line 138 "src/mongo/db/cst/pipeline_grammar.yy"
                     {
                         *cst = std::move(yystack_[1].value.as<CNode>());
                     }
-#line 706 "src/mongo/db/cst/pipeline_parser_gen.cpp"
+#line 711 "src/mongo/db/cst/pipeline_parser_gen.cpp"
                     break;
 
                     case 3:
-#line 142 "src/mongo/db/cst/pipeline_grammar.yy"
+#line 143 "src/mongo/db/cst/pipeline_grammar.yy"
                     {
                     }
-#line 712 "src/mongo/db/cst/pipeline_parser_gen.cpp"
+#line 717 "src/mongo/db/cst/pipeline_parser_gen.cpp"
                     break;
 
                     case 4:
-#line 143 "src/mongo/db/cst/pipeline_grammar.yy"
+#line 144 "src/mongo/db/cst/pipeline_grammar.yy"
                     {
                         yylhs.value.as<CNode>() =
                             CNode{CNode::ArrayChildren{yystack_[2].value.as<CNode>()}};
                     }
-#line 720 "src/mongo/db/cst/pipeline_parser_gen.cpp"
+#line 725 "src/mongo/db/cst/pipeline_parser_gen.cpp"
                     break;
 
                     case 5:
-#line 151 "src/mongo/db/cst/pipeline_grammar.yy"
+#line 152 "src/mongo/db/cst/pipeline_grammar.yy"
                     {
                         lexer.sortObjTokens();
                     }
-#line 726 "src/mongo/db/cst/pipeline_parser_gen.cpp"
+#line 731 "src/mongo/db/cst/pipeline_parser_gen.cpp"
                     break;
 
                     case 7:
-#line 154 "src/mongo/db/cst/pipeline_grammar.yy"
+#line 155 "src/mongo/db/cst/pipeline_grammar.yy"
                     {
                         yylhs.value.as<CNode>() = yystack_[0].value.as<CNode>();
                     }
-#line 732 "src/mongo/db/cst/pipeline_parser_gen.cpp"
+#line 737 "src/mongo/db/cst/pipeline_parser_gen.cpp"
                     break;
 
                     case 8:
-#line 154 "src/mongo/db/cst/pipeline_grammar.yy"
+#line 155 "src/mongo/db/cst/pipeline_grammar.yy"
                     {
                         yylhs.value.as<CNode>() = yystack_[0].value.as<CNode>();
                     }
-#line 738 "src/mongo/db/cst/pipeline_parser_gen.cpp"
+#line 743 "src/mongo/db/cst/pipeline_parser_gen.cpp"
                     break;
 
                     case 9:
-#line 154 "src/mongo/db/cst/pipeline_grammar.yy"
+#line 155 "src/mongo/db/cst/pipeline_grammar.yy"
                     {
                         yylhs.value.as<CNode>() = yystack_[0].value.as<CNode>();
                     }
-#line 744 "src/mongo/db/cst/pipeline_parser_gen.cpp"
+#line 749 "src/mongo/db/cst/pipeline_parser_gen.cpp"
                     break;
 
                     case 10:
-#line 158 "src/mongo/db/cst/pipeline_grammar.yy"
+#line 155 "src/mongo/db/cst/pipeline_grammar.yy"
+                    {
+                        yylhs.value.as<CNode>() = yystack_[0].value.as<CNode>();
+                    }
+#line 755 "src/mongo/db/cst/pipeline_parser_gen.cpp"
+                    break;
+
+                    case 11:
+#line 159 "src/mongo/db/cst/pipeline_grammar.yy"
                     {
                         yylhs.value.as<CNode>() = CNode{CNode::ObjectChildren{
                             std::pair{KeyFieldname::inhibitOptimization, CNode::noopLeaf()}}};
                     }
-#line 753 "src/mongo/db/cst/pipeline_parser_gen.cpp"
+#line 764 "src/mongo/db/cst/pipeline_parser_gen.cpp"
                     break;
 
-                    case 11:
-#line 164 "src/mongo/db/cst/pipeline_grammar.yy"
+                    case 12:
+#line 165 "src/mongo/db/cst/pipeline_grammar.yy"
                     {
                         auto coll = CNode{UserString(yystack_[3].value.as<std::string>())};
                         auto pipeline = CNode{UserDouble(yystack_[1].value.as<double>())};
@@ -705,45 +718,54 @@ int PipelineParserGen::parse() {
                                           {KeyFieldname::collArg, std::move(coll)},
                                           {KeyFieldname::pipelineArg, std::move(pipeline)}}}}}};
                     }
-#line 767 "src/mongo/db/cst/pipeline_parser_gen.cpp"
+#line 778 "src/mongo/db/cst/pipeline_parser_gen.cpp"
                     break;
 
-                    case 12:
-#line 175 "src/mongo/db/cst/pipeline_grammar.yy"
+                    case 13:
+#line 176 "src/mongo/db/cst/pipeline_grammar.yy"
                     {
                         yylhs.value.as<CNode>() = CNode{UserInt(yystack_[0].value.as<int>())};
                     }
-#line 775 "src/mongo/db/cst/pipeline_parser_gen.cpp"
+#line 786 "src/mongo/db/cst/pipeline_parser_gen.cpp"
                     break;
 
-                    case 13:
-#line 178 "src/mongo/db/cst/pipeline_grammar.yy"
+                    case 14:
+#line 179 "src/mongo/db/cst/pipeline_grammar.yy"
                     {
                         yylhs.value.as<CNode>() =
                             CNode{UserLong(yystack_[0].value.as<long long>())};
                     }
-#line 783 "src/mongo/db/cst/pipeline_parser_gen.cpp"
+#line 794 "src/mongo/db/cst/pipeline_parser_gen.cpp"
                     break;
 
-                    case 14:
-#line 181 "src/mongo/db/cst/pipeline_grammar.yy"
+                    case 15:
+#line 182 "src/mongo/db/cst/pipeline_grammar.yy"
                     {
                         yylhs.value.as<CNode>() = CNode{UserDouble(yystack_[0].value.as<double>())};
                     }
-#line 791 "src/mongo/db/cst/pipeline_parser_gen.cpp"
+#line 802 "src/mongo/db/cst/pipeline_parser_gen.cpp"
                     break;
 
-                    case 15:
-#line 187 "src/mongo/db/cst/pipeline_grammar.yy"
+                    case 16:
+#line 188 "src/mongo/db/cst/pipeline_grammar.yy"
                     {
                         yylhs.value.as<CNode>() = CNode{CNode::ObjectChildren{
                             std::pair{KeyFieldname::skip, yystack_[0].value.as<CNode>()}}};
                     }
-#line 799 "src/mongo/db/cst/pipeline_parser_gen.cpp"
+#line 810 "src/mongo/db/cst/pipeline_parser_gen.cpp"
+                    break;
+
+                    case 17:
+#line 193 "src/mongo/db/cst/pipeline_grammar.yy"
+                    {
+                        yylhs.value.as<CNode>() = CNode{CNode::ObjectChildren{
+                            std::pair{KeyFieldname::limit, yystack_[0].value.as<CNode>()}}};
+                    }
+#line 818 "src/mongo/db/cst/pipeline_parser_gen.cpp"
                     break;
 
 
-#line 803 "src/mongo/db/cst/pipeline_parser_gen.cpp"
+#line 822 "src/mongo/db/cst/pipeline_parser_gen.cpp"
 
                     default:
                         break;
@@ -912,31 +934,34 @@ const signed char PipelineParserGen::yypact_ninf_ = -11;
 
 const signed char PipelineParserGen::yytable_ninf_ = -1;
 
-const signed char PipelineParserGen::yypact_[] = {1,   4,   8,   -7,  3,   -11, 7,  -11, -10, 9,
-                                                  -11, -11, -11, -11, 10,  2,   12, -11, -11, -11,
-                                                  -11, 4,   -11, -1,  -11, -11, 5,  6,   13,  -11};
+const signed char PipelineParserGen::yypact_[] = {
+    2, 5,  9,   -7,  4,   -11, 8,   -11, -10, -10, 10,  -11, -11, -11, -11, -11, 11,
+    1, 13, -11, -11, -11, -11, -11, 5,   -11, 0,   -11, -11, 6,   3,   16,  -11};
 
-const signed char PipelineParserGen::yydefact_[] = {
-    0, 3, 0, 0, 0, 1, 0, 5, 0, 0, 7, 8, 9, 2, 0, 0, 0, 12, 13, 14, 15, 3, 10, 0, 6, 4, 0, 0, 0, 11};
+const signed char PipelineParserGen::yydefact_[] = {0,  3,  0, 0,  0, 1, 0, 5, 0,  0,  0,
+                                                    7,  8,  9, 10, 2, 0, 0, 0, 13, 14, 15,
+                                                    16, 17, 3, 11, 0, 6, 4, 0, 0,  0,  12};
 
-const signed char PipelineParserGen::yypgoto_[] = {-11, -3, -11, -11, -11, -11, -11, -11, -11, -11};
+const signed char PipelineParserGen::yypgoto_[] = {
+    -11, -3, -11, -11, -11, 14, -11, -11, -11, -11, -11};
 
-const signed char PipelineParserGen::yydefgoto_[] = {-1, 4, 9, 10, 11, 20, 12, 2, 15, 16};
+const signed char PipelineParserGen::yydefgoto_[] = {-1, 4, 10, 11, 12, 22, 13, 14, 2, 17, 18};
 
-const signed char PipelineParserGen::yytable_[] = {6,  7,  8,  17, 18, 19, 1,  3,  5, 13, 14,
-                                                   26, 23, 21, 22, 24, 27, 29, 25, 0, 0,  28};
+const signed char PipelineParserGen::yytable_[] = {6,  7,  8,  9,  19, 20, 21, 1,  3,  5,  15, 16,
+                                                   26, 29, 24, 25, 27, 0,  30, 31, 32, 28, 0,  23};
 
-const signed char PipelineParserGen::yycheck_[] = {7,  8,  9, 13, 14, 15, 5, 3,  0,  6,  3,
-                                                   12, 10, 4, 4,  3,  11, 4, 21, -1, -1, 15};
+const signed char PipelineParserGen::yycheck_[] = {7,  8,  9, 10, 14, 15, 16, 5,  3, 0,  6,  3,
+                                                   11, 13, 4, 4,  3,  -1, 12, 16, 4, 24, -1, 9};
 
-const signed char PipelineParserGen::yystos_[] = {0,  5,  24, 3,  18, 0,  7,  8,  9,  19,
-                                                  20, 21, 23, 6,  3,  25, 26, 13, 14, 15,
-                                                  22, 4,  4,  10, 3,  18, 12, 11, 15, 4};
+const signed char PipelineParserGen::yystos_[] = {0,  5,  26, 3,  19, 0, 7,  8,  9,  10, 20,
+                                                  21, 22, 24, 25, 6,  3, 27, 28, 14, 15, 16,
+                                                  23, 23, 4,  4,  11, 3, 19, 13, 12, 16, 4};
 
 const signed char PipelineParserGen::yyr1_[] = {
-    0, 17, 24, 18, 18, 26, 25, 19, 19, 19, 20, 21, 22, 22, 22, 23};
+    0, 18, 26, 19, 19, 28, 27, 20, 20, 20, 20, 21, 22, 23, 23, 23, 24, 25};
 
-const signed char PipelineParserGen::yyr2_[] = {0, 2, 3, 0, 4, 0, 2, 1, 1, 1, 3, 7, 1, 1, 1, 2};
+const signed char PipelineParserGen::yyr2_[] = {
+    0, 2, 3, 0, 4, 0, 2, 1, 1, 1, 1, 3, 7, 1, 1, 1, 2, 2};
 
 
 #if YYDEBUG
@@ -952,6 +977,7 @@ const char* const PipelineParserGen::yytname_[] = {"\"EOF\"",
                                                    "STAGE_INHIBIT_OPTIMIZATION",
                                                    "STAGE_UNION_WITH",
                                                    "STAGE_SKIP",
+                                                   "STAGE_LIMIT",
                                                    "COLL_ARG",
                                                    "PIPELINE_ARG",
                                                    "STRING",
@@ -966,6 +992,7 @@ const char* const PipelineParserGen::yytname_[] = {"\"EOF\"",
                                                    "unionWith",
                                                    "num",
                                                    "skip",
+                                                   "limit",
                                                    "pipeline",
                                                    "START_ORDERED_OBJECT",
                                                    "$@1",
@@ -975,7 +1002,7 @@ const char* const PipelineParserGen::yytname_[] = {"\"EOF\"",
 
 #if YYDEBUG
 const unsigned char PipelineParserGen::yyrline_[] = {
-    0, 137, 137, 142, 143, 151, 151, 154, 154, 154, 158, 164, 175, 178, 181, 187};
+    0, 138, 138, 143, 144, 152, 152, 155, 155, 155, 155, 159, 165, 176, 179, 182, 188, 193};
 
 void PipelineParserGen::yy_stack_print_() const {
     *yycdebug_ << "Stack now";
@@ -998,6 +1025,6 @@ void PipelineParserGen::yy_reduce_print_(int yyrule) const {
 
 #line 52 "src/mongo/db/cst/pipeline_grammar.yy"
 }  // namespace mongo
-#line 1106 "src/mongo/db/cst/pipeline_parser_gen.cpp"
+#line 1131 "src/mongo/db/cst/pipeline_parser_gen.cpp"
 
-#line 191 "src/mongo/db/cst/pipeline_grammar.yy"
+#line 197 "src/mongo/db/cst/pipeline_grammar.yy"
diff --git a/src/mongo/db/cst/pipeline_parser_gen.hpp b/src/mongo/db/cst/pipeline_parser_gen.hpp
index 4c1a36754c0..c742e600bca 100644
--- a/src/mongo/db/cst/pipeline_parser_gen.hpp
+++ b/src/mongo/db/cst/pipeline_parser_gen.hpp
@@ -373,6 +373,7 @@ public:
             // unionWith
             // num
             // skip
+            // limit
             char dummy1[sizeof(CNode)];
 
             // BOOL
@@ -438,13 +439,14 @@ public:
             STAGE_INHIBIT_OPTIMIZATION = 7,  // STAGE_INHIBIT_OPTIMIZATION
             STAGE_UNION_WITH = 8,            // STAGE_UNION_WITH
             STAGE_SKIP = 9,                  // STAGE_SKIP
-            COLL_ARG = 10,                   // COLL_ARG
-            PIPELINE_ARG = 11,               // PIPELINE_ARG
-            STRING = 12,                     // STRING
-            NUMBER_INT = 13,                 // NUMBER_INT
-            NUMBER_LONG = 14,                // NUMBER_LONG
-            NUMBER_DOUBLE = 15,              // NUMBER_DOUBLE
-            BOOL = 16                        // BOOL
+            STAGE_LIMIT = 10,                // STAGE_LIMIT
+            COLL_ARG = 11,                   // COLL_ARG
+            PIPELINE_ARG = 12,               // PIPELINE_ARG
+            STRING = 13,                     // STRING
+            NUMBER_INT = 14,                 // NUMBER_INT
+            NUMBER_LONG = 15,                // NUMBER_LONG
+            NUMBER_DOUBLE = 16,              // NUMBER_DOUBLE
+            BOOL = 17                        // BOOL
         };
         /// Backward compatibility alias (Bison 3.6).
         typedef token_kind_type yytokentype;
@@ -459,7 +461,7 @@ public:
     /// Symbol kinds.
     struct symbol_kind {
         enum symbol_kind_type {
-            YYNTOKENS = 17,  ///< Number of tokens.
+            YYNTOKENS = 18,  ///< Number of tokens.
             S_YYEMPTY = -2,
             S_YYEOF = 0,                       // "EOF"
             S_YYerror = 1,                     // error
@@ -471,23 +473,25 @@ public:
             S_STAGE_INHIBIT_OPTIMIZATION = 7,  // STAGE_INHIBIT_OPTIMIZATION
             S_STAGE_UNION_WITH = 8,            // STAGE_UNION_WITH
             S_STAGE_SKIP = 9,                  // STAGE_SKIP
-            S_COLL_ARG = 10,                   // COLL_ARG
-            S_PIPELINE_ARG = 11,               // PIPELINE_ARG
-            S_STRING = 12,                     // STRING
-            S_NUMBER_INT = 13,                 // NUMBER_INT
-            S_NUMBER_LONG = 14,                // NUMBER_LONG
-            S_NUMBER_DOUBLE = 15,              // NUMBER_DOUBLE
-            S_BOOL = 16,                       // BOOL
-            S_YYACCEPT = 17,                   // $accept
-            S_stageList = 18,                  // stageList
-            S_stage = 19,                      // stage
-            S_inhibitOptimization = 20,        // inhibitOptimization
-            S_unionWith = 21,                  // unionWith
-            S_num = 22,                        // num
-            S_skip = 23,                       // skip
-            S_pipeline = 24,                   // pipeline
-            S_START_ORDERED_OBJECT = 25,       // START_ORDERED_OBJECT
-            S_26_1 = 26                        // $@1
+            S_STAGE_LIMIT = 10,                // STAGE_LIMIT
+            S_COLL_ARG = 11,                   // COLL_ARG
+            S_PIPELINE_ARG = 12,               // PIPELINE_ARG
+            S_STRING = 13,                     // STRING
+            S_NUMBER_INT = 14,                 // NUMBER_INT
+            S_NUMBER_LONG = 15,                // NUMBER_LONG
+            S_NUMBER_DOUBLE = 16,              // NUMBER_DOUBLE
+            S_BOOL = 17,                       // BOOL
+            S_YYACCEPT = 18,                   // $accept
+            S_stageList = 19,                  // stageList
+            S_stage = 20,                      // stage
+            S_inhibitOptimization = 21,        // inhibitOptimization
+            S_unionWith = 22,                  // unionWith
+            S_num = 23,                        // num
+            S_skip = 24,                       // skip
+            S_limit = 25,                      // limit
+            S_pipeline = 26,                   // pipeline
+            S_START_ORDERED_OBJECT = 27,       // START_ORDERED_OBJECT
+            S_28_1 = 28                        // $@1
         };
     };
 
@@ -516,32 +520,33 @@ public:
         basic_symbol(basic_symbol&& that)
             : Base(std::move(that)), value(), location(std::move(that.location)) {
             switch (this->kind()) {
-                case 18:  // stageList
-                case 19:  // stage
-                case 20:  // inhibitOptimization
-                case 21:  // unionWith
-                case 22:  // num
-                case 23:  // skip
+                case 19:  // stageList
+                case 20:  // stage
+                case 21:  // inhibitOptimization
+                case 22:  // unionWith
+                case 23:  // num
+                case 24:  // skip
+                case 25:  // limit
                     value.move<CNode>(std::move(that.value));
                     break;
 
-                case 16:  // BOOL
+                case 17:  // BOOL
                     value.move<bool>(std::move(that.value));
                     break;
 
-                case 15:  // NUMBER_DOUBLE
+                case 16:  // NUMBER_DOUBLE
                     value.move<double>(std::move(that.value));
                     break;
 
-                case 13:  // NUMBER_INT
+                case 14:  // NUMBER_INT
                     value.move<int>(std::move(that.value));
                     break;
 
-                case 14:  // NUMBER_LONG
+                case 15:  // NUMBER_LONG
                     value.move<long long>(std::move(that.value));
                     break;
 
-                case 12:  // STRING
+                case 13:  // STRING
                     value.move<std::string>(std::move(that.value));
                     break;
 
@@ -622,32 +627,33 @@ public:
 
             // Value type destructor.
             switch (yykind) {
-                case 18:  // stageList
-                case 19:  // stage
-                case 20:  // inhibitOptimization
-                case 21:  // unionWith
-                case 22:  // num
-                case 23:  // skip
+                case 19:  // stageList
+                case 20:  // stage
+                case 21:  // inhibitOptimization
+                case 22:  // unionWith
+                case 23:  // num
+                case 24:  // skip
+                case 25:  // limit
                     value.template destroy<CNode>();
                     break;
 
-                case 16:  // BOOL
+                case 17:  // BOOL
                     value.template destroy<bool>();
                     break;
 
-                case 15:  // NUMBER_DOUBLE
+                case 16:  // NUMBER_DOUBLE
                     value.template destroy<double>();
                     break;
 
-                case 13:  // NUMBER_INT
+                case 14:  // NUMBER_INT
                     value.template destroy<int>();
                     break;
 
-                case 14:  // NUMBER_LONG
+                case 15:  // NUMBER_LONG
                     value.template destroy<long long>();
                     break;
 
-                case 12:  // STRING
+                case 13:  // STRING
                     value.template destroy<std::string>();
                     break;
 
@@ -735,8 +741,8 @@ public:
                       tok == token::START_OBJECT || tok == token::END_OBJECT ||
                       tok == token::START_ARRAY || tok == token::END_ARRAY ||
                       tok == token::STAGE_INHIBIT_OPTIMIZATION || tok == token::STAGE_UNION_WITH ||
-                      tok == token::STAGE_SKIP || tok == token::COLL_ARG ||
-                      tok == token::PIPELINE_ARG);
+                      tok == token::STAGE_SKIP || tok == token::STAGE_LIMIT ||
+                      tok == token::COLL_ARG || tok == token::PIPELINE_ARG);
         }
 #else
         symbol_type(int tok, const location_type& l) : super_type(token_type(tok), l) {
@@ -744,8 +750,8 @@ public:
                       tok == token::START_OBJECT || tok == token::END_OBJECT ||
                       tok == token::START_ARRAY || tok == token::END_ARRAY ||
                       tok == token::STAGE_INHIBIT_OPTIMIZATION || tok == token::STAGE_UNION_WITH ||
-                      tok == token::STAGE_SKIP || tok == token::COLL_ARG ||
-                      tok == token::PIPELINE_ARG);
+                      tok == token::STAGE_SKIP || tok == token::STAGE_LIMIT ||
+                      tok == token::COLL_ARG || tok == token::PIPELINE_ARG);
         }
 #endif
 #if 201103L <= YY_CPLUSPLUS
@@ -938,6 +944,15 @@ public:
     }
 #endif
 #if 201103L <= YY_CPLUSPLUS
+    static symbol_type make_STAGE_LIMIT(location_type l) {
+        return symbol_type(token::STAGE_LIMIT, std::move(l));
+    }
+#else
+    static symbol_type make_STAGE_LIMIT(const location_type& l) {
+        return symbol_type(token::STAGE_LIMIT, l);
+    }
+#endif
+#if 201103L <= YY_CPLUSPLUS
     static symbol_type make_COLL_ARG(location_type l) {
         return symbol_type(token::COLL_ARG, std::move(l));
     }
@@ -1280,8 +1295,8 @@ private:
 
     /// Constants.
     enum {
-        yylast_ = 21,  ///< Last index in yytable_.
-        yynnts_ = 10,  ///< Number of nonterminal symbols.
+        yylast_ = 23,  ///< Last index in yytable_.
+        yynnts_ = 11,  ///< Number of nonterminal symbols.
         yyfinal_ = 5   ///< Termination state number.
     };
 
@@ -1300,32 +1315,33 @@ template <typename Base>
 PipelineParserGen::basic_symbol<Base>::basic_symbol(const basic_symbol& that)
     : Base(that), value(), location(that.location) {
     switch (this->kind()) {
-        case 18:  // stageList
-        case 19:  // stage
-        case 20:  // inhibitOptimization
-        case 21:  // unionWith
-        case 22:  // num
-        case 23:  // skip
+        case 19:  // stageList
+        case 20:  // stage
+        case 21:  // inhibitOptimization
+        case 22:  // unionWith
+        case 23:  // num
+        case 24:  // skip
+        case 25:  // limit
             value.copy<CNode>(YY_MOVE(that.value));
             break;
 
-        case 16:  // BOOL
+        case 17:  // BOOL
             value.copy<bool>(YY_MOVE(that.value));
             break;
 
-        case 15:  // NUMBER_DOUBLE
+        case 16:  // NUMBER_DOUBLE
             value.copy<double>(YY_MOVE(that.value));
             break;
 
-        case 13:  // NUMBER_INT
+        case 14:  // NUMBER_INT
             value.copy<int>(YY_MOVE(that.value));
             break;
 
-        case 14:  // NUMBER_LONG
+        case 15:  // NUMBER_LONG
             value.copy<long long>(YY_MOVE(that.value));
             break;
 
-        case 12:  // STRING
+        case 13:  // STRING
             value.copy<std::string>(YY_MOVE(that.value));
             break;
 
@@ -1350,32 +1366,33 @@ template <typename Base>
 void PipelineParserGen::basic_symbol<Base>::move(basic_symbol& s) {
     super_type::move(s);
     switch (this->kind()) {
-        case 18:  // stageList
-        case 19:  // stage
-        case 20:  // inhibitOptimization
-        case 21:  // unionWith
-        case 22:  // num
-        case 23:  // skip
+        case 19:  // stageList
+        case 20:  // stage
+        case 21:  // inhibitOptimization
+        case 22:  // unionWith
+        case 23:  // num
+        case 24:  // skip
+        case 25:  // limit
             value.move<CNode>(YY_MOVE(s.value));
             break;
 
-        case 16:  // BOOL
+        case 17:  // BOOL
             value.move<bool>(YY_MOVE(s.value));
             break;
 
-        case 15:  // NUMBER_DOUBLE
+        case 16:  // NUMBER_DOUBLE
             value.move<double>(YY_MOVE(s.value));
             break;
 
-        case 13:  // NUMBER_INT
+        case 14:  // NUMBER_INT
             value.move<int>(YY_MOVE(s.value));
             break;
 
-        case 14:  // NUMBER_LONG
+        case 15:  // NUMBER_LONG
             value.move<long long>(YY_MOVE(s.value));
             break;
 
-        case 12:  // STRING
+        case 13:  // STRING
             value.move<std::string>(YY_MOVE(s.value));
             break;
 
@@ -1419,7 +1436,7 @@ inline PipelineParserGen::symbol_kind_type PipelineParserGen::by_kind::type_get(
 
 #line 52 "src/mongo/db/cst/pipeline_grammar.yy"
 }  // namespace mongo
-#line 1705 "src/mongo/db/cst/pipeline_parser_gen.hpp"
+#line 1728 "src/mongo/db/cst/pipeline_parser_gen.hpp"
 
 
 #endif  // !YY_YY_SRC_MONGO_DB_CST_PIPELINE_PARSER_GEN_HPP_INCLUDED