Receiving columns metadata

Author: den818

clickhouse/client.cpp

@@ -430,6 +430,22 @@ bool Client::Impl::ReceivePacket(uint64_t* server_packet) {
         return false;
     }
 
+    case ServerCodes::TableColumns: {
+        // external table name
+        if (!WireFormat::SkipString(*input_)) {
+            return false;
+        }
+
+        std::string columns_metadata;
+        if (!WireFormat::ReadString(*input_, &columns_metadata)) {
+            return false;
+        }
+        if (events_) {
+            events_->OnColumnsMetadata(columns_metadata);
+        }
+        return true;
+    }
+
     default:
         throw UnimplementedError("unimplemented " + std::to_string((int)packet_type));
         break;

clickhouse/protocol.h

@@ -16,14 +16,15 @@ namespace clickhouse {
             Extremes             = 8,    /// Block of mins and maxs, may be compressed.
             TablesStatusResponse = 9,    /// Response to TableStatus.
             Log                  = 10,   /// Query execution log.
+            TableColumns         = 11,   /// Columns' description for default values calculation
         };
     }
 
     /// Types of packets sent by client.
     namespace ClientCodes {
         enum {
             Hello       = 0,    /// Name, version, default database name.
-            Query       = 1,    /** Query id, query settings, query processing stage, 
+            Query       = 1,    /** Query id, query settings, query processing stage,
                                   * compression status, and query text (no INSERT data).
                                   */
             Data        = 2,    /// Data `Block` (e.g. INSERT data), may be compressed.
@@ -32,7 +33,7 @@ namespace clickhouse {
         };
     }
 
-    /// Should we compress `Block`s of data 
+    /// Should we compress `Block`s of data
     namespace CompressionState {
         enum {
             Disable     = 0,

clickhouse/query.h

@@ -66,6 +66,8 @@ class QueryEvents {
 
     virtual void OnProgress(const Progress& progress) = 0;
 
+    virtual void OnColumnsMetadata(const std::string& columns_metadata) = 0;
+
     virtual void OnFinish() = 0;
 };
 
@@ -74,6 +76,7 @@ using ExceptionCallback        = std::function<void(const Exception& e)>;
 using ProgressCallback         = std::function<void(const Progress& progress)>;
 using SelectCallback           = std::function<void(const Block& block)>;
 using SelectCancelableCallback = std::function<bool(const Block& block)>;
+using ColumnsMetadataCallback  = std::function<bool(const std::string& columns_metadata)>;
 
 
 class Query : public QueryEvents {
@@ -116,6 +119,12 @@ class Query : public QueryEvents {
         return *this;
     }
 
+    /// Set handler for receiving a metedata of column of query.
+    inline Query& OnColumnsMetadata(ColumnsMetadataCallback cb) {
+        columns_metadata_cb_ = std::move(cb);
+        return *this;
+    }
+
     static const std::string default_query_id;
 
 private:
@@ -149,6 +158,12 @@ class Query : public QueryEvents {
         }
     }
 
+    void OnColumnsMetadata(const std::string& columns_metadata) override {
+        if (columns_metadata_cb_) {
+            columns_metadata_cb_(columns_metadata);
+        }
+    }
+
     void OnFinish() override {
     }
 
@@ -159,6 +174,7 @@ class Query : public QueryEvents {
     ProgressCallback progress_cb_;
     SelectCallback select_cb_;
     SelectCancelableCallback select_cancelable_cb_;
+    ColumnsMetadataCallback columns_metadata_cb_;
 };
 
 }