added system.macros table [#CLICKHOUSE-3591]

dbms/src/Common/Macros.h

@@ -21,9 +21,10 @@ public:
       */
     String expand(const String & s, size_t level = 0) const;
 
-private:
     using MacroMap = std::map<String, String>;
+    const MacroMap getMacroMap() const { return macros; }
 
+private:
     MacroMap macros;
 };
 

dbms/src/Storages/System/StorageSystemMacros.cpp

@@ -0,0 +1,48 @@
+#include <Common/Macros.h>
+#include <Columns/ColumnString.h>
+#include <DataTypes/DataTypeString.h>
+#include <DataStreams/OneBlockInputStream.h>
+#include <Storages/System/StorageSystemMacros.h>
+#include <Interpreters/Context.h>
+
+
+namespace DB
+{
+
+
+StorageSystemMacros::StorageSystemMacros(const std::string & name_)
+        : name(name_)
+{
+    columns = NamesAndTypesList{
+            {"macro", std::make_shared<DataTypeString>()},
+            {"substitution", std::make_shared<DataTypeString>()},
+    };
+}
+
+
+BlockInputStreams StorageSystemMacros::read(
+        const Names & column_names,
+        const SelectQueryInfo &,
+        const Context & context,
+        QueryProcessingStage::Enum & processed_stage,
+        const size_t /*max_block_size*/,
+        const unsigned /*num_streams*/)
+{
+    check(column_names);
+    processed_stage = QueryProcessingStage::FetchColumns;
+
+    MutableColumns res_columns = getSampleBlock().cloneEmptyColumns();
+
+    auto macros = context.getMacros();
+
+    for (const auto & macro : macros->getMacroMap())
+    {
+        res_columns[0]->insert(macro.first);
+        res_columns[1]->insert(macro.second);
+    }
+
+    return BlockInputStreams(1, std::make_shared<OneBlockInputStream>(getSampleBlock().cloneWithColumns(std::move(res_columns))));
+}
+
+
+}

dbms/src/Storages/System/StorageSystemMacros.h

@@ -0,0 +1,36 @@
+#pragma once
+
+#include <ext/shared_ptr_helper.h>
+#include <Storages/IStorage.h>
+
+
+namespace DB
+{
+
+class Context;
+
+
+/** Implements `databases` system table, which allows you to get information about all databases.
+  */
+class StorageSystemMacros : public ext::shared_ptr_helper<StorageSystemMacros>, public IStorage
+{
+public:
+    std::string getName() const override { return "SystemMacros"; }
+    std::string getTableName() const override { return name; }
+
+    BlockInputStreams read(
+            const Names & column_names,
+            const SelectQueryInfo & query_info,
+            const Context & context,
+            QueryProcessingStage::Enum & processed_stage,
+            size_t max_block_size,
+            unsigned num_streams) override;
+
+private:
+    const std::string name;
+
+protected:
+    StorageSystemMacros(const std::string & name_);
+};
+
+}

dbms/src/Storages/System/attachSystemTables.cpp

@@ -10,6 +10,7 @@
 #include <Storages/System/StorageSystemEvents.h>
 #include <Storages/System/StorageSystemFunctions.h>
 #include <Storages/System/StorageSystemGraphite.h>
+#include <Storages/System/StorageSystemMacros.h>
 #include <Storages/System/StorageSystemMerges.h>
 #include <Storages/System/StorageSystemMetrics.h>
 #include <Storages/System/StorageSystemModels.h>
@@ -56,6 +57,7 @@ void attachSystemTablesServer(IDatabase & system_database, bool has_zookeeper)
     system_database.attachTable("models", StorageSystemModels::create("models"));
     system_database.attachTable("clusters", StorageSystemClusters::create("clusters"));
     system_database.attachTable("graphite_retentions", StorageSystemGraphite::create("graphite_retentions"));
+    system_database.attachTable("macros", StorageSystemMacros::create("macros"));
 
     if (has_zookeeper)
         system_database.attachTable("zookeeper", StorageSystemZooKeeper::create("zookeeper"));