Add virtual column _headers for url table engine

base/poco/Net/include/Poco/Net/HTTPResponse.h

@@ -18,7 +18,9 @@
 #define Net_HTTPResponse_INCLUDED
 
 
+#include <map>
 #include <vector>
+
 #include "Poco/Net/HTTPCookie.h"
 #include "Poco/Net/HTTPMessage.h"
 #include "Poco/Net/Net.h"
@@ -180,6 +182,8 @@ namespace Net
         /// May throw an exception in case of a malformed
         /// Set-Cookie header.
 
+        void getHeaders(std::map<std::string, std::string> & headers) const;
+
         void write(std::ostream & ostr) const;
         /// Writes the HTTP response to the given
         /// output stream.

base/poco/Net/src/HTTPResponse.cpp

@@ -209,6 +209,15 @@ void HTTPResponse::getCookies(std::vector<HTTPCookie>& cookies) const
 	}
 }
 
+void HTTPResponse::getHeaders(std::map<std::string, std::string> & headers) const
+{
+    headers.clear();
+    for (const auto & it : *this)
+    {
+        headers.emplace(it.first, it.second);
+    }
+}
+
 
 void HTTPResponse::write(std::ostream& ostr) const
 {

src/IO/ReadWriteBufferFromHTTP.cpp

@@ -443,6 +443,7 @@ std::unique_ptr<ReadBuffer> ReadWriteBufferFromHTTP::initialize()
     }
 
     response.getCookies(cookies);
+    response.getHeaders(response_headers);
     content_encoding = response.get("Content-Encoding", "");
 
     // Remember file size. It'll be used to report eof in next nextImpl() call.
@@ -680,6 +681,19 @@ std::string ReadWriteBufferFromHTTP::getResponseCookie(const std::string & name,
     return def;
 }
 
+Map ReadWriteBufferFromHTTP::getResponseHeaders() const
+{
+    Map map;
+    for (const auto & header : response_headers)
+    {
+        Tuple elem;
+        elem.emplace_back(header.first);
+        elem.emplace_back(header.second);
+        map.emplace_back(elem);
+    }
+    return map;
+}
+
 void ReadWriteBufferFromHTTP::setNextCallback(NextCallback next_callback_)
 {
     next_callback = next_callback_;

src/IO/ReadWriteBufferFromHTTP.h

@@ -90,6 +90,9 @@ private:
     std::unique_ptr<ReadBuffer> impl;
 
     std::vector<Poco::Net::HTTPCookie> cookies;
+
+    std::map<String, String> response_headers;
+
     HTTPHeaderEntries http_header_entries;
     std::function<void(size_t)> next_callback;
 
@@ -187,6 +190,8 @@ public:
 
     HTTPFileInfo getFileInfo();
     static HTTPFileInfo parseFileInfo(const Poco::Net::HTTPResponse & response, size_t requested_range_begin);
+
+    Map getResponseHeaders() const;
 };
 
 using ReadWriteBufferFromHTTPPtr = std::unique_ptr<ReadWriteBufferFromHTTP>;

src/Storages/StorageURL.cpp

@@ -44,10 +44,11 @@
 #include <IO/HTTPHeaderEntries.h>
 
 #include <algorithm>
+#include <DataTypes/DataTypeLowCardinality.h>
+#include <DataTypes/DataTypeMap.h>
+#include <DataTypes/DataTypeString.h>
 #include <QueryPipeline/QueryPipelineBuilder.h>
 #include <Poco/Net/HTTPRequest.h>
-#include <DataTypes/DataTypeString.h>
-#include <DataTypes/DataTypeLowCardinality.h>
 
 namespace ProfileEvents
 {
@@ -167,7 +168,19 @@ IStorageURLBase::IStorageURLBase(
     storage_metadata.setComment(comment);
     setInMemoryMetadata(storage_metadata);
 
-    setVirtuals(VirtualColumnUtils::getVirtualsForFileLikeStorage(storage_metadata.getColumns(), context_, getSampleURI(uri, context_), format_settings));
+    auto virtual_columns_desc = VirtualColumnUtils::getVirtualsForFileLikeStorage(
+        storage_metadata.getColumns(), context_, getSampleURI(uri, context_), format_settings);
+    if (!storage_metadata.getColumns().has("_headers"))
+    {
+        virtual_columns_desc.addEphemeral(
+            "_headers",
+            std::make_shared<DataTypeMap>(
+                std::make_shared<DataTypeLowCardinality>(std::make_shared<DataTypeString>()),
+                std::make_shared<DataTypeLowCardinality>(std::make_shared<DataTypeString>())),
+            "");
+    }
+
+    setVirtuals(virtual_columns_desc);
 }
 
 
@@ -292,11 +305,13 @@ StorageURLSource::StorageURLSource(
     const URIParams & params,
     bool glob_url,
     bool need_only_count_)
-    : SourceWithKeyCondition(info.source_header, false), WithContext(context_)
+    : SourceWithKeyCondition(info.source_header, false)
+    , WithContext(context_)
     , name(std::move(name_))
     , columns_description(info.columns_description)
     , requested_columns(info.requested_columns)
-    , requested_virtual_columns(info.requested_virtual_columns)
+    , need_headers_virtual_column(info.requested_virtual_columns.contains("_headers"))
+    , requested_virtual_columns(info.requested_virtual_columns.eraseNames({"_headers"}))
     , block_for_format(info.format_header)
     , uri_iterator(uri_iterator_)
     , format(format_)
@@ -436,6 +451,20 @@ Chunk StorageURLSource::generate()
                     .path = curr_uri.getPath(),
                     .size = current_file_size,
                 }, getContext(), columns_description);
+            if (need_headers_virtual_column)
+            {
+                if (!http_response_headers_initialized)
+                {
+                    http_response_headers = dynamic_cast<ReadWriteBufferFromHTTP *>(read_buf.get())->getResponseHeaders();
+                    http_response_headers_initialized = true;
+                }
+
+                auto type = std::make_shared<DataTypeMap>(
+                    std::make_shared<DataTypeLowCardinality>(std::make_shared<DataTypeString>()),
+                    std::make_shared<DataTypeLowCardinality>(std::make_shared<DataTypeString>()));
+
+                chunk.addColumn(type->createColumnConst(chunk.getNumRows(), http_response_headers));
+            }
             return chunk;
         }
 
@@ -446,6 +475,7 @@ Chunk StorageURLSource::generate()
         reader.reset();
         input_format.reset();
         read_buf.reset();
+        http_response_headers_initialized = false;
         total_rows_in_file = 0;
     }
     return {};

src/Storages/StorageURL.h

@@ -220,6 +220,7 @@ private:
     String name;
     ColumnsDescription columns_description;
     NamesAndTypesList requested_columns;
+    bool need_headers_virtual_column;
     NamesAndTypesList requested_virtual_columns;
     Block block_for_format;
     std::shared_ptr<IteratorWrapper> uri_iterator;
@@ -233,6 +234,9 @@ private:
 
     Poco::Net::HTTPBasicCredentials credentials;
 
+    Map http_response_headers;
+    bool http_response_headers_initialized = false;
+
     std::unique_ptr<ReadBuffer> read_buf;
     std::shared_ptr<IInputFormat> input_format;
     std::unique_ptr<QueryPipeline> pipeline;

tests/queries/0_stateless/03228_url_engine_response_headers.reference

@@ -0,0 +1,2 @@
+Map(LowCardinality(String), LowCardinality(String))
+1	1

tests/queries/0_stateless/03228_url_engine_response_headers.sql

@@ -0,0 +1,7 @@
+SELECT toTypeName(_headers)
+FROM url('http://127.0.0.1:8123/?query=select+1&user=default', LineAsString, 's String');
+
+SELECT
+    *,
+    mapFromString(_headers['X-ClickHouse-Summary'])['read_rows']
+FROM url('http://127.0.0.1:8123/?query=select+1&user=default', LineAsString, 's String');