Drafted HashOutputFormat

src/Formats/registerFormats.cpp

@@ -94,6 +94,7 @@ void registerOutputFormatMarkdown(FormatFactory & factory);
 void registerOutputFormatPostgreSQLWire(FormatFactory & factory);
 void registerOutputFormatPrometheus(FormatFactory & factory);
 void registerOutputFormatSQLInsert(FormatFactory & factory);
+void registerOutputFormatHash(FormatFactory & factory);
 
 /// Input only formats.
 
@@ -240,6 +241,7 @@ void registerFormats()
     registerOutputFormatCapnProto(factory);
     registerOutputFormatPrometheus(factory);
     registerOutputFormatSQLInsert(factory);
+    registerOutputFormatHash(factory);
 
     registerInputFormatRegexp(factory);
     registerInputFormatJSONAsString(factory);

src/Processors/Formats/Impl/HashOutputFormat.cpp

@@ -0,0 +1,47 @@
+#include <Processors/Formats/Impl/HashOutputFormat.h>
+#include <Columns/IColumn.h>
+#include <Formats/FormatFactory.h>
+#include <IO/WriteBuffer.h>
+#include <Processors/Port.h>
+
+
+namespace DB
+{
+
+HashOutputFormat::HashOutputFormat(WriteBuffer & out_, SharedHeader header_)
+    : IOutputFormat(header_, out_) 
+{
+}
+
+String HashOutputFormat::getName() const
+{
+    return "HashOutputFormat";
+}
+
+void HashOutputFormat::consume(Chunk chunk)
+{
+    for (const auto & column : chunk.getColumns())
+    {
+        for (size_t i = 0; i < column->size(); ++i)
+            column->updateHashWithValue(i, hash);
+    }
+}
+
+void HashOutputFormat::finalizeImpl()
+{
+    std::string hashString = getSipHash128AsHexString(hash);
+    out.write(hashString.data(), hashString.size());
+    out.write("\n", 1);
+    out.next();
+}
+
+void registerOutputFormatHash(FormatFactory & factory)
+{
+    factory.registerOutputFormat("Hash",
+        [](WriteBuffer & buf, const Block & header, const FormatSettings &)
+        {
+            return std::make_shared<HashOutputFormat>(buf, std::make_shared<const Block>(header));
+        });
+}
+
+}

src/Processors/Formats/Impl/HashOutputFormat.h

@@ -0,0 +1,22 @@
+#pragma once
+
+#include <Common/SipHash.h>
+#include <Processors/Formats/IOutputFormat.h>
+
+namespace DB
+{
+
+class HashOutputFormat final  : public IOutputFormat
+{
+public:
+    HashOutputFormat(WriteBuffer & out_, SharedHeader header_);
+    String getName() const override;
+
+private:
+    void consume(Chunk chunk) override;
+    void finalizeImpl() override;
+
+    SipHash hash;
+};
+
+}

tests/queries/0_stateless/03577_hash_format.reference

@@ -0,0 +1,3 @@
+75b419a3aa739a211291e7cc119bd3c9
+d3b90098d049660862d6dc53ac7505e5
+92d47ccfb2950a8e10ac9ddf4314f1bf

tests/queries/0_stateless/03577_hash_format.sql

@@ -0,0 +1,3 @@
+SELECT number FROM system.numbers LIMIT 1 FORMAT Hash;
+SELECT number FROM system.numbers LIMIT 20 FORMAT Hash;
+SELECT number AS hello, toString(number) AS world, (hello, world) AS tuple, nullIf(hello % 3, 0) AS sometimes_nulls FROM system.numbers LIMIT 20 FORMAT Hash;