From 8603807b57f911766710fbde70d06897625fee50 Mon Sep 17 00:00:00 2001
From: Igor Nikonov <igor@clickhouse.com>
Date: Sat, 15 Apr 2023 12:33:21 +0000
Subject: [PATCH] Use generic way to parallelize output for file()

+ disable parallelization for storage Null
---
 src/Storages/StorageFile.cpp | 10 +---------
 src/Storages/StorageNull.h   |  2 ++
 2 files changed, 3 insertions(+), 9 deletions(-)

diff --git a/src/Storages/StorageFile.cpp b/src/Storages/StorageFile.cpp
index 1b195d2eb47..7e5a93c13c1 100644
--- a/src/Storages/StorageFile.cpp
+++ b/src/Storages/StorageFile.cpp
@@ -791,15 +791,7 @@ Pipe StorageFile::read(
             std::move(read_buffer)));
     }
 
-    Pipe pipe = Pipe::unitePipes(std::move(pipes));
-    /// Parallelize output as much as possible
-    /// Note: number of streams can be 0 if paths is empty
-    ///       It happens if globs in file(path, ...) expands to empty set i.e. no files to process
-    if (num_streams > 0 && num_streams < max_num_streams)
-    {
-        pipe.resize(max_num_streams);
-    }
-    return pipe;
+    return Pipe::unitePipes(std::move(pipes));
 }
 
 
diff --git a/src/Storages/StorageNull.h b/src/Storages/StorageNull.h
index 2270731c0e3..24ddb311b65 100644
--- a/src/Storages/StorageNull.h
+++ b/src/Storages/StorageNull.h
@@ -42,6 +42,8 @@ public:
             std::make_shared<NullSource>(storage_snapshot->getSampleBlockForColumns(column_names)));
     }
 
+    bool parallelizeOutputAfterReading() const override { return false; }
+
     bool supportsParallelInsert() const override { return true; }
 
     SinkToStoragePtr write(const ASTPtr &, const StorageMetadataPtr & metadata_snapshot, ContextPtr) override