Merge pull request #12803 from man-group/perf-optimize-extraction

PERF: extract files from wheel in 1MB blocks + skip decoding for 0 bytes files

Author: pfmoore

news/12803.bugfix.rst

@@ -0,0 +1,4 @@
+Improve pip install performance. Files are now extracted in 1MB blocks,
+or in one block matching the file size for smaller files.
+A decompressor is no longer instantiated when extracting 0 bytes files,
+it is not necessary because there is no data to decompress.

src/pip/_internal/operations/install/wheel.py

@@ -371,9 +371,13 @@ def save(self) -> None:
 
         zipinfo = self._getinfo()
 
-        with self._zip_file.open(zipinfo) as f:
-            with open(self.dest_path, "wb") as dest:
-                shutil.copyfileobj(f, dest)
+        # optimization: the file is created by open(),
+        # skip the decompression when there is 0 bytes to decompress.
+        with open(self.dest_path, "wb") as dest:
+            if zipinfo.file_size > 0:
+                with self._zip_file.open(zipinfo) as f:
+                    blocksize = min(zipinfo.file_size, 1024 * 1024)
+                    shutil.copyfileobj(f, dest, blocksize)
 
         if zip_item_is_executable(zipinfo):
             set_extracted_file_to_default_mode_plus_executable(self.dest_path)