DDLWorkerQueueTable - add intial scaffolding

src/Interpreters/DDLWorker.cpp

@@ -1128,6 +1128,13 @@ String DDLWorker::enqueueQuery(DDLLogEntry & entry)
     return node_path;
 }
 
+std::vector<String> DDLWorker::dumpQueriesInQueue()
+{
+    std::vector<String> queries;
+    // TODO:
+    return queries;
+}
+
 
 void DDLWorker::runMainThread()
 {
@@ -1517,6 +1524,7 @@ BlockIO executeDDLQueryOnCluster(const ASTPtr & query_ptr_, const Context & cont
     else
         context.checkAccess(query_requires_access);
 
+    // enqueue the queries into the DDL worker queue
     DDLLogEntry entry;
     entry.hosts = std::move(hosts);
     entry.query = queryToString(query_ptr);

src/Interpreters/DDLWorker.h

@@ -45,6 +45,9 @@ public:
     /// Pushes query into DDL queue, returns path to created node
     String enqueueQuery(DDLLogEntry & entry);
 
+    /// Fetches the queries that are currently in the DDL queue
+    std::vector<String> dumpQueriesInQueue();
+
     /// Host ID (name:port) for logging purposes
     /// Note that in each task hosts are identified individually by name:port from initiator server cluster config
     std::string getCommonHostID() const

src/Storages/System/StorageSystemDDLWorkerQueue.cpp

@@ -0,0 +1,20 @@
+#include "StorageSystemDDLWorkerQueue.h"
+
+#include <algorithm>
+#include <DataTypes/DataTypeString.h>
+
+
+namespace DB
+{
+NamesAndTypesList StorageSystemDDLWorkerQueue::getNamesAndTypes()
+{
+    return {
+        {"query", std::make_shared<DataTypeString>()},
+    };
+}
+
+void StorageSystemDDLWorkerQueue::fillData(MutableColumns & res_columns, const Context &, const SelectQueryInfo &) const
+{
+    // TODO: insert into table
+}
+}

src/Storages/System/StorageSystemDDLWorkerQueue.h

@@ -0,0 +1,29 @@
+#pragma once
+
+#include <Storages/System/IStorageSystemOneBlock.h>
+#include <ext/shared_ptr_helper.h>
+
+
+namespace DB
+{
+class Context;
+
+
+/** System table "ddl_worker_queue" with list of queries that are currently in the DDL worker queue.
+  */
+class StorageSystemDDLWorkerQueue final : public ext::shared_ptr_helper<StorageSystemDDLWorkerQueue>,
+                                          public IStorageSystemOneBlock<StorageSystemDDLWorkerQueue>
+{
+    friend struct ext::shared_ptr_helper<StorageSystemDDLWorkerQueue>;
+
+protected:
+    void fillData(MutableColumns & res_columns, const Context & context, const SelectQueryInfo & query_info) const override;
+
+    using IStorageSystemOneBlock::IStorageSystemOneBlock;
+
+public:
+    std::string getName() const override { return "SystemDDLWorkerQueue"; }
+
+    static NamesAndTypesList getNamesAndTypes();
+};
+}

src/Storages/System/attachSystemTables.cpp

@@ -39,6 +39,8 @@
 #include <Storages/System/StorageSystemZooKeeper.h>
 #include <Storages/System/StorageSystemContributors.h>
 #include <Storages/System/StorageSystemErrors.h>
+#include <Storages/System/StorageSystemDDLWorkerQueue.h>
+
 #if !defined(ARCADIA_BUILD)
     #include <Storages/System/StorageSystemLicenses.h>
     #include <Storages/System/StorageSystemTimeZones.h>
@@ -134,6 +136,7 @@ void attachSystemTablesServer(IDatabase & system_database, bool has_zookeeper)
     attach<StorageSystemMutations>(system_database, "mutations");
     attach<StorageSystemReplicas>(system_database, "replicas");
     attach<StorageSystemReplicationQueue>(system_database, "replication_queue");
+    attach<StorageSystemDDLWorkerQueue>(system_database, "ddl_worker_queue");
     attach<StorageSystemDistributionQueue>(system_database, "distribution_queue");
     attach<StorageSystemDictionaries>(system_database, "dictionaries");
     attach<StorageSystemModels>(system_database, "models");

src/Storages/ya.make

@@ -147,6 +147,7 @@ SRCS(
     System/StorageSystemContributors.cpp
     System/StorageSystemContributors.generated.cpp
     System/StorageSystemCurrentRoles.cpp
+    System/StorageSystemDDLWorkerQueue.cpp
     System/StorageSystemDataTypeFamilies.cpp
     System/StorageSystemDatabases.cpp
     System/StorageSystemDetachedParts.cpp