SERVER-62006 add listCatalog aggregation stage

4 files changed, 235 insertions, 0 deletions

diff --git a/src/mongo/db/pipeline/SConscript b/src/mongo/db/pipeline/SConscript
index 84ffd9cca7c..6a67e39b95d 100644
--- a/src/mongo/db/pipeline/SConscript
+++ b/src/mongo/db/pipeline/SConscript
@@ -291,6 +291,7 @@ pipelineEnv.Library(
         'document_source_internal_split_pipeline.cpp',
         'document_source_limit.cpp',
         'document_source_list_cached_and_active_users.cpp',
+        'document_source_list_catalog.cpp',
         'document_source_list_local_sessions.cpp',
         'document_source_list_sessions.cpp',
         'document_source_lookup.cpp',
diff --git a/src/mongo/db/pipeline/document_source_list_catalog.cpp b/src/mongo/db/pipeline/document_source_list_catalog.cpp
new file mode 100644
index 00000000000..fc29a777360
--- /dev/null
+++ b/src/mongo/db/pipeline/document_source_list_catalog.cpp
@@ -0,0 +1,123 @@
+/**
+ *    Copyright (C) 2022-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the Server Side Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#include "mongo/db/pipeline/document_source_list_catalog.h"
+
+#include <fmt/format.h>
+
+#include "mongo/db/commands/feature_compatibility_version_documentation.h"
+#include "mongo/db/namespace_string.h"
+#include "mongo/db/pipeline/expression_context.h"
+#include "mongo/db/pipeline/process_interface/mongo_process_interface.h"
+#include "mongo/db/server_options.h"
+#include "mongo/db/storage/storage_parameters_gen.h"
+#include "mongo/util/version/releases.h"
+
+namespace mongo {
+
+using boost::intrusive_ptr;
+
+REGISTER_DOCUMENT_SOURCE_WITH_MIN_VERSION(listCatalog,
+                                          DocumentSourceListCatalog::LiteParsed::parse,
+                                          DocumentSourceListCatalog::createFromBson,
+                                          AllowedWithApiStrict::kNeverInVersion1,
+                                          multiversion::FeatureCompatibilityVersion::kVersion_5_3);
+
+const char* DocumentSourceListCatalog::getSourceName() const {
+    return kStageName.rawData();
+}
+
+PrivilegeVector DocumentSourceListCatalog::LiteParsed::requiredPrivileges(
+    bool isMongos, bool bypassDocumentValidation) const {
+
+    // Refer to privileges for the readAnyDatabase role in addReadOnlyAnyDbPrivileges().
+    // See builtin_roles.cpp.
+    // TODO(SERVER-63748): Change privileges to a combination of listDatabases, listCollections,
+    // and listIndexes.
+    return {Privilege(ResourcePattern::forDatabaseName("admin"), ActionType::find)};
+}
+
+DocumentSource::GetNextResult DocumentSourceListCatalog::doGetNext() {
+    if (!_catalogDocsInitialized) {
+        _catalogDocs = pExpCtx->mongoProcessInterface->listCatalog(pExpCtx->opCtx);
+        _catalogDocsInitialized = true;
+    }
+
+    if (!_catalogDocs.empty()) {
+        Document doc{_catalogDocs.front()};
+        _catalogDocs.pop_front();
+        return doc;
+    }
+
+    return GetNextResult::makeEOF();
+}
+
+DocumentSourceListCatalog::DocumentSourceListCatalog(
+    const intrusive_ptr<ExpressionContext>& pExpCtx)
+    : DocumentSource(kStageName, pExpCtx) {}
+
+intrusive_ptr<DocumentSource> DocumentSourceListCatalog::createFromBson(
+    BSONElement elem, const intrusive_ptr<ExpressionContext>& pExpCtx) {
+    uassert(6200600,
+            "The $listCatalog stage specification must be an empty object",
+            elem.type() == Object && elem.Obj().isEmpty());
+
+    const NamespaceString& nss = pExpCtx->ns;
+
+    uassert(ErrorCodes::InvalidNamespace,
+            "$listCatalog must be run against the 'admin' database with {aggregate: 1}",
+            nss.db() == NamespaceString::kAdminDb && nss.isCollectionlessAggregateNS());
+
+    uassert(ErrorCodes::QueryFeatureNotAllowed,
+            fmt::format("The {} aggregation stage is not enabled", kStageName),
+            feature_flags::gDocumentSourceListCatalog.isEnabled(
+                serverGlobalParams.featureCompatibility));
+
+    // We declare this stage with a min version but the base class DocumentSource checks the
+    // minimum version only if pExpCtx->maxFeatureCompatibilityVersion is provided.
+    if (!pExpCtx->maxFeatureCompatibilityVersion) {
+        const auto& globalFcv = serverGlobalParams.featureCompatibility;
+        using FCV = multiversion::FeatureCompatibilityVersion;
+        uassert(ErrorCodes::QueryFeatureNotAllowed,
+                fmt::format("The {} aggregation stage is not allowed in the current feature "
+                            "compatibility version. See {} for more information.",
+                            kStageName,
+                            feature_compatibility_version_documentation::kCompatibilityLink),
+                !globalFcv.isVersionInitialized() ||
+                    globalFcv.isGreaterThanOrEqualTo(FCV::kVersion_5_3));
+    }
+
+    return new DocumentSourceListCatalog(pExpCtx);
+}
+
+Value DocumentSourceListCatalog::serialize(
+    boost::optional<ExplainOptions::Verbosity> explain) const {
+    return Value(DOC(getSourceName() << Document()));
+}
+}  // namespace mongo
diff --git a/src/mongo/db/pipeline/document_source_list_catalog.h b/src/mongo/db/pipeline/document_source_list_catalog.h
new file mode 100644
index 00000000000..c0cb3829a00
--- /dev/null
+++ b/src/mongo/db/pipeline/document_source_list_catalog.h
@@ -0,0 +1,107 @@
+/**
+ *    Copyright (C) 2022-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the Server Side Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#pragma once
+
+#include <deque>
+
+#include "mongo/bson/bsonobj.h"
+#include "mongo/db/pipeline/document_source.h"
+#include "mongo/db/pipeline/lite_parsed_document_source.h"
+
+namespace mongo {
+
+/**
+ * Provides a document source interface to retrieve catalog metadata for collections and views.
+ * Each document returned represents either:
+ * - a single collection with its indexes; or
+ * - a view instance.
+ */
+class DocumentSourceListCatalog final : public DocumentSource {
+public:
+    static constexpr StringData kStageName = "$listCatalog"_sd;
+
+    class LiteParsed final : public LiteParsedDocumentSource {
+    public:
+        static std::unique_ptr<LiteParsed> parse(const NamespaceString& nss,
+                                                 const BSONElement& spec) {
+            return std::make_unique<LiteParsed>(spec.fieldName());
+        }
+
+        explicit LiteParsed(std::string parseTimeName)
+            : LiteParsedDocumentSource(std::move(parseTimeName)) {}
+
+        stdx::unordered_set<NamespaceString> getInvolvedNamespaces() const final {
+            return stdx::unordered_set<NamespaceString>();
+        }
+
+
+        PrivilegeVector requiredPrivileges(bool isMongos,
+                                           bool bypassDocumentValidation) const final;
+
+        bool isInitialSource() const final {
+            return true;
+        }
+    };
+
+    // virtuals from DocumentSource
+    const char* getSourceName() const final;
+    Value serialize(boost::optional<ExplainOptions::Verbosity> explain = boost::none) const final;
+
+    StageConstraints constraints(Pipeline::SplitState pipeState) const final {
+        StageConstraints constraints(StreamType::kStreaming,
+                                     PositionRequirement::kFirst,
+                                     HostTypeRequirement::kAnyShard,
+                                     DiskUseRequirement::kNoDiskUse,
+                                     FacetRequirement::kNotAllowed,
+                                     TransactionRequirement::kNotAllowed,
+                                     LookupRequirement::kAllowed,
+                                     UnionRequirement::kAllowed);
+
+        constraints.isIndependentOfAnyCollection = true;
+        constraints.requiresInputDocSource = false;
+        return constraints;
+    }
+
+    boost::optional<DistributedPlanLogic> distributedPlanLogic() final {
+        return boost::none;
+    }
+
+    static boost::intrusive_ptr<DocumentSource> createFromBson(
+        BSONElement elem, const boost::intrusive_ptr<ExpressionContext>& pExpCtx);
+
+private:
+    DocumentSourceListCatalog(const boost::intrusive_ptr<ExpressionContext>& pExpCtx);
+    GetNextResult doGetNext() final;
+
+    bool _catalogDocsInitialized = false;
+    std::deque<BSONObj> _catalogDocs;
+};
+
+}  // namespace mongo
diff --git a/src/mongo/db/storage/storage_parameters.idl b/src/mongo/db/storage/storage_parameters.idl
index f306417a6da..871ce5e09b4 100644
--- a/src/mongo/db/storage/storage_parameters.idl
+++ b/src/mongo/db/storage/storage_parameters.idl
@@ -152,3 +152,7 @@ feature_flags:
         description: "When enabled, support batching multi-document deletions"
         cpp_varname: feature_flags::gBatchMultiDeletes
         default: false
+    featureFlagDocumentSourceListCatalog:
+        description: "When enabled, allow the use of the $listCatalog aggregation stage"
+        cpp_varname: feature_flags::gDocumentSourceListCatalog
+        default: false