Fixed #36293 -- Avoided buffering streaming responses in GZipMiddleware.

This avoids latency and/or blocking.

The example of streaming a CSV file was rewritten to employ batching for
greater efficiency in all layers (db, HTTP, etc.). The improved
performance from batching should outweigh the drag introduced by an
additional byte for each flush.

Co-authored-by: huoyinghui <huoyinghui@users.noreply.github.com>

1 files changed, 10 insertions, 2 deletions

diff --git a/docs/howto/outputting-csv.txt b/docs/howto/outputting-csv.txt
index c5ae7094d2..10de00503e 100644
--- a/docs/howto/outputting-csv.txt
+++ b/docs/howto/outputting-csv.txt
@@ -67,9 +67,12 @@ avoid a load balancer dropping a connection that might have otherwise timed out
 while the server was generating the response.
 
 In this example, we make full use of Python generators to efficiently handle
-the assembly and transmission of a large CSV file::
+the assembly and transmission of a large CSV file. Rows are batched together
+to reduce HTTP overhead and improve compression efficiency when used with
+:class:`~django.middleware.gzip.GZipMiddleware`::
 
     import csv
+    from itertools import batched
 
     from django.http import StreamingHttpResponse
 
@@ -92,8 +95,13 @@ the assembly and transmission of a large CSV file::
         rows = (["Row {}".format(idx), str(idx)] for idx in range(65536))
         pseudo_buffer = Echo()
         writer = csv.writer(pseudo_buffer)
+
+        def stream_batched_rows():
+            for batch in batched(rows, 100):
+                yield "".join(writer.writerow(row) for row in batch)
+
         return StreamingHttpResponse(
-            (writer.writerow(row) for row in rows),
+            stream_batched_rows(),
             content_type="text/csv",
             headers={"Content-Disposition": 'attachment; filename="somefilename.csv"'},
         )