Added support for gzip compression of request body

Usefull for massive data load to ClickHouse

conn.go

@@ -1,6 +1,7 @@
 package clickhouse
 
 import (
+	"compress/gzip"
 	"context"
 	"database/sql"
 	"database/sql/driver"
@@ -13,7 +14,6 @@ import (
 	"net/http"
 	"net/url"
 	"os"
-	"strings"
 	"sync/atomic"
 	"time"
 
@@ -302,7 +302,21 @@ func (c *conn) buildRequest(ctx context.Context, query string, params []driver.V
 		method = http.MethodPost
 	}
 	c.log("query: ", query)
-	req, err := http.NewRequest(method, c.url.String(), strings.NewReader(query))
+
+	bodyReader, bodyWriter := io.Pipe()
+	go func() {
+		if c.useGzipCompression {
+			gz := gzip.NewWriter(bodyWriter)
+			_, err := gz.Write([]byte(query))
+			gz.Close()
+			bodyWriter.CloseWithError(err)
+		} else {
+			bodyWriter.Write([]byte(query))
+			bodyWriter.Close()
+		}
+	}()
+
+	req, err := http.NewRequest(method, c.url.String(), bodyReader)
 	if err != nil {
 		return nil, err
 	}
@@ -335,6 +349,10 @@ func (c *conn) buildRequest(ctx context.Context, query string, params []driver.V
 	}
 	req.URL.RawQuery = reqQuery.Encode()
 
+	if c.useGzipCompression {
+		req.Header.Set("Content-Encoding", "gzip")
+	}
+
 	return req, nil
 }
 

conn_test.go

@@ -1,6 +1,7 @@
 package clickhouse
 
 import (
+	"compress/gzip"
 	"context"
 	"database/sql"
 	"database/sql/driver"
@@ -380,6 +381,24 @@ func (s *connSuite) TestBuildRequestParamsInterpolation() {
 	}
 }
 
+func (s *connSuite) TestRequestBodyGzipCompression() {
+	query := `INSERT INTO test (str) VALUES ("Question?")`
+	cn := newConn(NewConfig())
+	cn.useGzipCompression = true
+	req, err := cn.buildRequest(context.Background(), query, make([]driver.Value, 0), false)
+	if s.NoError(err) {
+		s.Contains(req.Header, "Content-Encoding")
+		gz, err := gzip.NewReader(req.Body)
+		if s.NoError(err) {
+			defer gz.Close()
+			body, e := ioutil.ReadAll(gz)
+			if s.NoError(e) {
+				s.Equal(query, string(body))
+			}
+		}
+	}
+}
+
 func TestConn(t *testing.T) {
 	suite.Run(t, new(connSuite))
 }