Format ODBCDriver2 with NULL support (#2834)

* Format ODBCDriver2 with NULL support

* Fix comment

* Update ODBCDriver2BlockOutputStream.cpp

* clean

dbms/src/Formats/FormatFactory.cpp

@@ -120,6 +120,7 @@ void registerOutputFormatJSON(FormatFactory & factory);
 void registerOutputFormatJSONCompact(FormatFactory & factory);
 void registerOutputFormatXML(FormatFactory & factory);
 void registerOutputFormatODBCDriver(FormatFactory & factory);
+void registerOutputFormatODBCDriver2(FormatFactory & factory);
 void registerOutputFormatNull(FormatFactory & factory);
 
 /// Input only formats.
@@ -153,6 +154,7 @@ FormatFactory::FormatFactory()
     registerOutputFormatJSONCompact(*this);
     registerOutputFormatXML(*this);
     registerOutputFormatODBCDriver(*this);
+    registerOutputFormatODBCDriver2(*this);
     registerOutputFormatNull(*this);
 }
 

dbms/src/Formats/ODBCDriver2BlockOutputStream.cpp

@@ -0,0 +1,95 @@
+#include <Core/Block.h>
+#include <Formats/FormatFactory.h>
+#include <Formats/ODBCDriver2BlockOutputStream.h>
+#include <IO/WriteBuffer.h>
+#include <IO/WriteHelpers.h>
+
+
+#include <Core/iostream_debug_helpers.h>
+
+
+namespace DB
+{
+ODBCDriver2BlockOutputStream::ODBCDriver2BlockOutputStream(
+    WriteBuffer & out_, const Block & header_, const FormatSettings & format_settings)
+    : out(out_), header(header_), format_settings(format_settings)
+{
+}
+
+void ODBCDriver2BlockOutputStream::flush()
+{
+    out.next();
+}
+
+void writeODBCString(WriteBuffer & out, const std::string & str)
+{
+    writeIntBinary(Int32(str.size()), out);
+    out.write(str.data(), str.size());
+}
+
+void ODBCDriver2BlockOutputStream::write(const Block & block)
+{
+    const size_t rows = block.rows();
+    const size_t columns = block.columns();
+    String text_value;
+
+    for (size_t i = 0; i < rows; ++i)
+    {
+        for (size_t j = 0; j < columns; ++j)
+        {
+            text_value.resize(0);
+            const ColumnWithTypeAndName & col = block.getByPosition(j);
+
+            if (col.column->isNullAt(i))
+            {
+                writeIntBinary(Int32(-1), out);
+            }
+            else
+            {
+                {
+                    WriteBufferFromString text_out(text_value);
+                    col.type->serializeText(*col.column, i, text_out, format_settings);
+                }
+                writeODBCString(out, text_value);
+            }
+        }
+    }
+}
+
+void ODBCDriver2BlockOutputStream::writePrefix()
+{
+    const size_t columns = header.columns();
+
+    /// Number of header rows.
+    writeIntBinary(Int32(2), out);
+
+    /// Names of columns.
+    /// Number of columns + 1 for first name column.
+    writeIntBinary(Int32(columns + 1), out);
+    writeODBCString(out, "name");
+    for (size_t i = 0; i < columns; ++i)
+    {
+        const ColumnWithTypeAndName & col = header.getByPosition(i);
+        writeODBCString(out, col.name);
+    }
+
+    /// Types of columns.
+    writeIntBinary(Int32(columns + 1), out);
+    writeODBCString(out, "type");
+    for (size_t i = 0; i < columns; ++i)
+    {
+        const ColumnWithTypeAndName & col = header.getByPosition(i);
+        writeODBCString(out, col.type->getName());
+    }
+}
+
+
+void registerOutputFormatODBCDriver2(FormatFactory & factory)
+{
+    factory.registerOutputFormat(
+        "ODBCDriver2", [](WriteBuffer & buf, const Block & sample, const Context &, const FormatSettings & format_settings) {
+            return std::make_shared<ODBCDriver2BlockOutputStream>(buf, sample, format_settings);
+        });
+}
+
+}

dbms/src/Formats/ODBCDriver2BlockOutputStream.h

@@ -0,0 +1,44 @@
+#pragma once
+
+#include <string>
+#include <Core/Block.h>
+#include <DataStreams/IBlockOutputStream.h>
+#include <Formats/FormatSettings.h>
+
+
+namespace DB
+{
+class WriteBuffer;
+
+
+/** A data format designed to simplify the implementation of the ODBC driver.
+  * ODBC driver is designed to be build for different platforms without dependencies from the main code,
+  *  so the format is made that way so that it can be as easy as possible to parse it.
+  * A header is displayed with the required information.
+  * The data is then output in the order of the rows. Each value is displayed as follows: length in Int32 format (-1 for NULL), then data in text form.
+  */
+class ODBCDriver2BlockOutputStream : public IBlockOutputStream
+{
+public:
+    ODBCDriver2BlockOutputStream(WriteBuffer & out_, const Block & header_, const FormatSettings & format_settings);
+
+    Block getHeader() const override
+    {
+        return header;
+    }
+    void write(const Block & block) override;
+    void writePrefix() override;
+
+    void flush() override;
+    std::string getContentType() const override
+    {
+        return "application/octet-stream";
+    }
+
+private:
+    WriteBuffer & out;
+    const Block header;
+    const FormatSettings format_settings;
+};
+
+}