added RemoveColumnsBlockInputStream

dbms/src/DataStreams/RemoveColumnsBlockInputStream.h

@@ -0,0 +1,56 @@
+#pragma once
+
+#include <DataStreams/IProfilingBlockInputStream.h>
+#include <Columns/ColumnConst.h>
+
+
+
+namespace DB
+{
+
+/** Removes the specified columns from the block.
+    */
+class RemoveColumnsBlockInputStream : public IProfilingBlockInputStream
+{
+public:
+    RemoveColumnsBlockInputStream(
+        BlockInputStreamPtr input_,
+        const Names & columns_to_remove_)
+    : columns_to_remove(columns_to_remove_)
+    {
+        children.push_back(input_);
+    }
+
+    String getName() const override { return "RemoveColumns"; }
+
+    String getID() const override
+    {
+        std::stringstream res;
+        res << "RemoveColumns(" << children.back()->getID();
+
+        for (const auto & it : columns_to_remove)
+            res << ", " << it;
+
+        res << ")";
+        return res.str();
+    }
+
+protected:
+    Block readImpl() override
+    {
+        Block res = children.back()->read();
+        if (!res)
+            return res;
+
+        for (const auto & it : columns_to_remove)
+            if (res.has(it))
+                res.erase(it);
+
+        return res;
+    }
+
+private:
+    Names columns_to_remove;
+};
+
+}