From 352429486ac6707d802dc2b733eeccccacae7c83 Mon Sep 17 00:00:00 2001
From: Aliaksandr Valialkin <valyala@victoriametrics.com>
Date: Wed, 21 Jun 2023 20:40:01 -0700
Subject: [PATCH] Revert "app/vlselect/logsql: use buffered writer in order to
 save syscalls when sending big amounts of data to clients"

This reverts commit c19048dc13d2b49d3b7d901ba81f4d9dd172508b.

Reason for revert: it has been appeared that the net/http.ResponseWriter is already buffered,
so there in no need in double bufferring
---
 app/vlselect/logsql/buffered_writer.go | 70 --------------------------
 app/vlselect/logsql/sort_writer.go     | 30 +++++------
 2 files changed, 13 insertions(+), 87 deletions(-)
 delete mode 100644 app/vlselect/logsql/buffered_writer.go

diff --git a/app/vlselect/logsql/buffered_writer.go b/app/vlselect/logsql/buffered_writer.go
deleted file mode 100644
index cf539d1b01..0000000000
--- a/app/vlselect/logsql/buffered_writer.go
+++ /dev/null
@@ -1,70 +0,0 @@
-package logsql
-
-import (
-	"io"
-	"sync"
-)
-
-func getBufferedWriter() *bufferedWriter {
-	v := bufferedWriterPool.Get()
-	if v == nil {
-		return &bufferedWriter{}
-	}
-	return v.(*bufferedWriter)
-}
-
-func putBufferedWriter(bw *bufferedWriter) {
-	bw.reset()
-	bufferedWriterPool.Put(bw)
-}
-
-var bufferedWriterPool sync.Pool
-
-type bufferedWriter struct {
-	w   io.Writer
-	buf []byte
-}
-
-func (bw *bufferedWriter) reset() {
-	bw.w = nil
-	bw.buf = bw.buf[:0]
-}
-
-func (bw *bufferedWriter) Init(w io.Writer, bufLen int) {
-	bw.reset()
-	bw.w = w
-
-	buf := bw.buf
-	if n := bufLen - cap(buf); n > 0 {
-		buf = append(buf[:cap(buf)], make([]byte, n)...)
-	}
-	bw.buf = buf[:0]
-}
-
-func (bw *bufferedWriter) Write(p []byte) (int, error) {
-	buf := bw.buf
-	if len(buf)+len(p) <= cap(buf) {
-		bw.buf = append(buf, p...)
-		return len(p), nil
-	}
-	if len(buf) > 0 {
-		if _, err := bw.w.Write(buf); err != nil {
-			return 0, err
-		}
-		buf = buf[:0]
-	}
-	if len(p) <= cap(buf) {
-		bw.buf = append(buf, p...)
-		return len(p), nil
-	}
-	bw.buf = buf
-	return bw.w.Write(p)
-}
-
-func (bw *bufferedWriter) FlushIgnoreErrors() {
-	buf := bw.buf
-	if len(buf) > 0 {
-		_, _ = bw.w.Write(buf)
-		bw.buf = buf[:0]
-	}
-}
diff --git a/app/vlselect/logsql/sort_writer.go b/app/vlselect/logsql/sort_writer.go
index b26148f164..919fc8310b 100644
--- a/app/vlselect/logsql/sort_writer.go
+++ b/app/vlselect/logsql/sort_writer.go
@@ -37,7 +37,7 @@ var sortWriterPool sync.Pool
 // is sorted by _time field.
 type sortWriter struct {
 	mu         sync.Mutex
-	bw         *bufferedWriter
+	w          io.Writer
 	maxBufLen  int
 	buf        []byte
 	bufFlushed bool
@@ -46,10 +46,7 @@ type sortWriter struct {
 }
 
 func (sw *sortWriter) reset() {
-	if sw.bw != nil {
-		putBufferedWriter(sw.bw)
-		sw.bw = nil
-	}
+	sw.w = nil
 	sw.maxBufLen = 0
 	sw.buf = sw.buf[:0]
 	sw.bufFlushed = false
@@ -59,8 +56,7 @@ func (sw *sortWriter) reset() {
 func (sw *sortWriter) Init(w io.Writer, maxBufLen int) {
 	sw.reset()
 
-	sw.bw = getBufferedWriter()
-	sw.bw.Init(w, 64*1024)
+	sw.w = w
 	sw.maxBufLen = maxBufLen
 }
 
@@ -73,7 +69,7 @@ func (sw *sortWriter) MustWrite(p []byte) {
 	}
 
 	if sw.bufFlushed {
-		if _, err := sw.bw.Write(p); err != nil {
+		if _, err := sw.w.Write(p); err != nil {
 			sw.hasErr = true
 		}
 		return
@@ -84,26 +80,26 @@ func (sw *sortWriter) MustWrite(p []byte) {
 	}
 	sw.bufFlushed = true
 	if len(sw.buf) > 0 {
-		if _, err := sw.bw.Write(sw.buf); err != nil {
+		if _, err := sw.w.Write(sw.buf); err != nil {
 			sw.hasErr = true
 			return
 		}
 		sw.buf = sw.buf[:0]
 	}
-	if _, err := sw.bw.Write(p); err != nil {
+	if _, err := sw.w.Write(p); err != nil {
 		sw.hasErr = true
 	}
 }
 
 func (sw *sortWriter) FinalFlush() {
-	if !sw.hasErr && !sw.bufFlushed {
-		rs := getRowsSorter()
-		rs.parseRows(sw.buf)
-		rs.sort()
-		WriteJSONRows(sw.bw, rs.rows)
-		putRowsSorter(rs)
+	if sw.hasErr || sw.bufFlushed {
+		return
 	}
-	sw.bw.FlushIgnoreErrors()
+	rs := getRowsSorter()
+	rs.parseRows(sw.buf)
+	rs.sort()
+	WriteJSONRows(sw.w, rs.rows)
+	putRowsSorter(rs)
 }
 
 func getRowsSorter() *rowsSorter {