WriteBufferFromFileBase interface refactoring.

Disk->writeFile() returns WriteBufferFromFileBase.
DiskMemory read/write buffers refactoring.

dbms/src/Common/CounterInFile.h

@@ -99,8 +99,8 @@ public:
                 res += delta;
 
                 DB::WriteBufferFromFileDescriptor wb(fd, SMALL_READ_WRITE_BUFFER_SIZE);
-                wb.seek(0);
-                wb.truncate();
+                wb.seek(0, SEEK_SET);
+                wb.truncate(0);
                 DB::writeIntText(res, wb);
                 DB::writeChar('\n', wb);
                 wb.sync();
@@ -169,8 +169,8 @@ public:
             if (broken)
             {
                 DB::WriteBufferFromFileDescriptor wb(fd, SMALL_READ_WRITE_BUFFER_SIZE);
-                wb.seek(0);
-                wb.truncate();
+                wb.seek(0, SEEK_SET);
+                wb.truncate(0);
                 DB::writeIntText(value, wb);
                 DB::writeChar('\n', wb);
                 wb.sync();

dbms/src/Disks/DiskLocal.cpp

@@ -5,6 +5,9 @@
 #include <Common/filesystemHelpers.h>
 #include <Common/quoteString.h>
 
+#include <IO/createReadBufferFromFileBase.h>
+#include <IO/createWriteBufferFromFileBase.h>
+
 
 namespace DB
 {
@@ -46,8 +49,10 @@ private:
 class DiskLocalDirectoryIterator : public IDiskDirectoryIterator
 {
 public:
-    explicit DiskLocalDirectoryIterator(const String & disk_path_, const String & dir_path_) :
-        dir_path(dir_path_), iter(disk_path_ + dir_path_) {}
+    explicit DiskLocalDirectoryIterator(const String & disk_path_, const String & dir_path_)
+        : dir_path(dir_path_), iter(disk_path_ + dir_path_)
+    {
+    }
 
     void next() override { ++iter; }
 
@@ -200,15 +205,17 @@ void DiskLocal::copyFile(const String & from_path, const String & to_path)
     Poco::File(disk_path + from_path).copyTo(disk_path + to_path);
 }
 
-std::unique_ptr<ReadBufferFromFileBase> DiskLocal::readFile(const String & path, size_t buf_size) const
+std::unique_ptr<ReadBufferFromFileBase>
+DiskLocal::readFile(const String & path, size_t buf_size, size_t estimated_size, size_t aio_threshold, size_t mmap_threshold) const
 {
-    return std::make_unique<ReadBufferFromFile>(disk_path + path, buf_size);
+    return createReadBufferFromFileBase(disk_path + path, estimated_size, aio_threshold, mmap_threshold, buf_size);
 }
 
-std::unique_ptr<WriteBuffer> DiskLocal::writeFile(const String & path, size_t buf_size, WriteMode mode)
+std::unique_ptr<WriteBufferFromFileBase>
+DiskLocal::writeFile(const String & path, size_t buf_size, WriteMode mode, size_t estimated_size, size_t aio_threshold)
 {
     int flags = (mode == WriteMode::Append) ? (O_APPEND | O_CREAT | O_WRONLY) : -1;
-    return std::make_unique<WriteBufferFromFile>(disk_path + path, buf_size, flags);
+    return createWriteBufferFromFileBase(disk_path + path, estimated_size, aio_threshold, buf_size, flags);
 }
 
 void DiskLocal::remove(const String & path)

dbms/src/Disks/DiskLocal.h

@@ -1,8 +1,8 @@
 #pragma once
 
 #include <Disks/IDisk.h>
-#include <IO/ReadBufferFromFileBase.h>
 #include <IO/ReadBufferFromFile.h>
+#include <IO/ReadBufferFromFileBase.h>
 #include <IO/WriteBufferFromFile.h>
 
 #include <Poco/DirectoryIterator.h>
@@ -67,9 +67,19 @@ public:
 
     void copyFile(const String & from_path, const String & to_path) override;
 
-    std::unique_ptr<ReadBufferFromFileBase> readFile(const String & path, size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE) const override;
+    std::unique_ptr<ReadBufferFromFileBase> readFile(
+        const String & path,
+        size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE,
+        size_t estimated_size = 0,
+        size_t aio_threshold = 0,
+        size_t mmap_threshold = 0) const override;
 
-    std::unique_ptr<WriteBuffer> writeFile(const String & path, size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE, WriteMode mode = WriteMode::Rewrite) override;
+    std::unique_ptr<WriteBufferFromFileBase> writeFile(
+        const String & path,
+        size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE,
+        WriteMode mode = WriteMode::Rewrite,
+        size_t estimated_size = 0,
+        size_t aio_threshold = 0) override;
 
     void remove(const String & path) override;
 

dbms/src/Disks/DiskMemory.cpp

@@ -1,8 +1,9 @@
 #include "DiskMemory.h"
 #include "DiskFactory.h"
 
+#include <IO/ReadBufferFromFileBase.h>
 #include <IO/ReadBufferFromString.h>
-#include <IO/SeekableReadBuffer.h>
+#include <IO/WriteBufferFromFileBase.h>
 #include <IO/WriteBufferFromString.h>
 #include <Interpreters/Context.h>
 
@@ -39,87 +40,100 @@ private:
     std::vector<String>::iterator iter;
 };
 
-ReadIndirectBuffer::ReadIndirectBuffer(String path_, const String & data_)
-    : ReadBufferFromFileBase(), buf(ReadBufferFromString(data_)), path(std::move(path_))
+/// Adapter with actual behaviour as ReadBufferFromString.
+class ReadIndirectBuffer : public ReadBufferFromFileBase
 {
-    internal_buffer = buf.buffer();
-    working_buffer = internal_buffer;
-    pos = working_buffer.begin();
-}
-
-off_t ReadIndirectBuffer::seek(off_t offset, int whence)
-{
-    if (whence == SEEK_SET)
+public:
+    ReadIndirectBuffer(String path_, const String & data_)
+        : ReadBufferFromFileBase(), impl(ReadBufferFromString(data_)), path(std::move(path_))
     {
-        if (offset >= 0 && working_buffer.begin() + offset < working_buffer.end())
+        internal_buffer = impl.buffer();
+        working_buffer = internal_buffer;
+        pos = working_buffer.begin();
+    }
+
+    std::string getFileName() const override { return path; }
+
+    off_t seek(off_t off, int whence) override
+    {
+        impl.swap(*this);
+        off_t result = impl.seek(off, whence);
+        impl.swap(*this);
+        return result;
+    }
+
+    off_t getPosition() override { return pos - working_buffer.begin(); }
+
+private:
+    ReadBufferFromString impl;
+    const String path;
+};
+
+/// This class is responsible to update files metadata after buffer is finalized.
+class WriteIndirectBuffer : public WriteBufferFromFileBase
+{
+public:
+    WriteIndirectBuffer(DiskMemory * disk_, String path_, WriteMode mode_, size_t buf_size)
+        : WriteBufferFromFileBase(buf_size, nullptr, 0), impl(), disk(disk_), path(std::move(path_)), mode(mode_)
+    {
+    }
+
+    ~WriteIndirectBuffer() override
+    {
+        try
         {
-            pos = working_buffer.begin() + offset;
-            return size_t(pos - working_buffer.begin());
+            finalize();
         }
-        else
-            throw Exception(
-                "Seek position is out of bounds. "
-                "Offset: "
-                    + std::to_string(offset) + ", Max: " + std::to_string(size_t(working_buffer.end() - working_buffer.begin())),
-                ErrorCodes::SEEK_POSITION_OUT_OF_BOUND);
-    }
-    else if (whence == SEEK_CUR)
-    {
-        Position new_pos = pos + offset;
-        if (new_pos >= working_buffer.begin() && new_pos < working_buffer.end())
+        catch (...)
         {
-            pos = new_pos;
-            return size_t(pos - working_buffer.begin());
+            tryLogCurrentException(__PRETTY_FUNCTION__);
         }
-        else
-            throw Exception(
-                "Seek position is out of bounds. "
-                "Offset: "
-                    + std::to_string(offset) + ", Max: " + std::to_string(size_t(working_buffer.end() - working_buffer.begin())),
-                ErrorCodes::SEEK_POSITION_OUT_OF_BOUND);
     }
-    else
-        throw Exception("Only SEEK_SET and SEEK_CUR seek modes allowed.", ErrorCodes::CANNOT_SEEK_THROUGH_FILE);
-}
 
-off_t ReadIndirectBuffer::getPosition()
-{
-    return pos - working_buffer.begin();
-}
-
-void WriteIndirectBuffer::finalize()
-{
-    if (isFinished())
-        return;
-
-    next();
-    WriteBufferFromVector::finalize();
-
-    auto iter = disk->files.find(path);
-
-    if (iter == disk->files.end())
-        throw Exception("File '" + path + "' does not exist", ErrorCodes::FILE_DOESNT_EXIST);
-
-    // Resize to the actual number of bytes written to string.
-    value.resize(count());
-
-    if (mode == WriteMode::Rewrite)
-        disk->files.insert_or_assign(path, DiskMemory::FileData{iter->second.type, value});
-    else if (mode == WriteMode::Append)
-        disk->files.insert_or_assign(path, DiskMemory::FileData{iter->second.type, iter->second.data + value});
-}
-
-WriteIndirectBuffer::~WriteIndirectBuffer()
-{
-    try
+    void finalize() override
     {
-        finalize();
+        if (impl.isFinished())
+            return;
+
+        next();
+
+        /// str() finalizes buffer.
+        String value = impl.str();
+
+        auto iter = disk->files.find(path);
+
+        if (iter == disk->files.end())
+            throw Exception("File '" + path + "' does not exist", ErrorCodes::FILE_DOESNT_EXIST);
+
+        /// Resize to the actual number of bytes written to string.
+        value.resize(count());
+
+        if (mode == WriteMode::Rewrite)
+            disk->files.insert_or_assign(path, DiskMemory::FileData{iter->second.type, value});
+        else if (mode == WriteMode::Append)
+            disk->files.insert_or_assign(path, DiskMemory::FileData{iter->second.type, iter->second.data + value});
     }
-    catch (...)
+
+    std::string getFileName() const override { return path; }
+
+    void sync() override {}
+
+private:
+    void nextImpl() override
     {
-        tryLogCurrentException(__PRETTY_FUNCTION__);
+        if (!offset())
+            return;
+
+        impl.write(working_buffer.begin(), offset());
     }
-}
+
+private:
+    WriteBufferFromOwnString impl;
+    DiskMemory * disk;
+    const String path;
+    const WriteMode mode;
+};
+
 
 ReservationPtr DiskMemory::reserve(UInt64 /*bytes*/)
 {
@@ -302,7 +316,7 @@ void DiskMemory::copyFile(const String & /*from_path*/, const String & /*to_path
     throw Exception("Method copyFile is not implemented for memory disks", ErrorCodes::NOT_IMPLEMENTED);
 }
 
-std::unique_ptr<ReadBufferFromFileBase> DiskMemory::readFile(const String & path, size_t /*buf_size*/) const
+std::unique_ptr<ReadBufferFromFileBase> DiskMemory::readFile(const String & path, size_t /*buf_size*/, size_t, size_t, size_t) const
 {
     std::lock_guard lock(mutex);
 
@@ -313,7 +327,7 @@ std::unique_ptr<ReadBufferFromFileBase> DiskMemory::readFile(const String & path
     return std::make_unique<ReadIndirectBuffer>(path, iter->second.data);
 }
 
-std::unique_ptr<WriteBuffer> DiskMemory::writeFile(const String & path, size_t /*buf_size*/, WriteMode mode)
+std::unique_ptr<WriteBufferFromFileBase> DiskMemory::writeFile(const String & path, size_t buf_size, WriteMode mode, size_t, size_t)
 {
     std::lock_guard lock(mutex);
 
@@ -328,7 +342,7 @@ std::unique_ptr<WriteBuffer> DiskMemory::writeFile(const String & path, size_t /
         files.emplace(path, FileData{FileType::File});
     }
 
-    return std::make_unique<WriteIndirectBuffer>(this, path, mode);
+    return std::make_unique<WriteIndirectBuffer>(this, path, mode, buf_size);
 }
 
 void DiskMemory::remove(const String & path)

dbms/src/Disks/DiskMemory.h

@@ -5,46 +5,13 @@
 #include <unordered_map>
 #include <utility>
 #include <Disks/IDisk.h>
-#include <IO/ReadBufferFromFileBase.h>
-#include <IO/ReadBufferFromString.h>
-#include <IO/WriteBufferFromString.h>
 
 namespace DB
 {
 class DiskMemory;
-class ReadBuffer;
-class WriteBuffer;
+class ReadBufferFromFileBase;
+class WriteBufferFromFileBase;
 
-/// Adapter with actual behaviour as ReadBufferFromString.
-class ReadIndirectBuffer : public ReadBufferFromFileBase
-{
-public:
-    ReadIndirectBuffer(String path_, const String & data_);
-
-    std::string getFileName() const override { return path; }
-    off_t seek(off_t off, int whence) override;
-    off_t getPosition() override;
-
-private:
-    ReadBufferFromString buf;
-    String path;
-};
-
-/// This class is responsible to update files metadata after buffer is finalized.
-class WriteIndirectBuffer : public WriteBufferFromOwnString
-{
-public:
-    WriteIndirectBuffer(DiskMemory * disk_, String path_, WriteMode mode_) : disk(disk_), path(std::move(path_)), mode(mode_) {}
-
-    ~WriteIndirectBuffer() override;
-
-    void finalize() override;
-
-private:
-    DiskMemory * disk;
-    String path;
-    WriteMode mode;
-};
 
 /** Implementation of Disk intended only for testing purposes.
   * All filesystem objects are stored in memory and lost on server restart.
@@ -93,10 +60,19 @@ public:
 
     void copyFile(const String & from_path, const String & to_path) override;
 
-    std::unique_ptr<ReadBufferFromFileBase> readFile(const String & path, size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE) const override;
+    std::unique_ptr<ReadBufferFromFileBase> readFile(
+        const String & path,
+        size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE,
+        size_t estimated_size = 0,
+        size_t aio_threshold = 0,
+        size_t mmap_threshold = 0) const override;
 
-    std::unique_ptr<WriteBuffer>
-    writeFile(const String & path, size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE, WriteMode mode = WriteMode::Rewrite) override;
+    std::unique_ptr<WriteBufferFromFileBase> writeFile(
+        const String & path,
+        size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE,
+        WriteMode mode = WriteMode::Rewrite,
+        size_t estimated_size = 0,
+        size_t aio_threshold = 0) override;
 
     void remove(const String & path) override;
 

dbms/src/Disks/DiskS3.cpp

@@ -52,25 +52,28 @@ namespace
      */
     struct Metadata
     {
-        // Metadata file version.
+        /// Metadata file version.
         const UInt32 VERSION = 1;
 
         using PathAndSize = std::pair<String, size_t>;
 
-        // Path to metadata file on local FS.
+        /// Path to metadata file on local FS.
         String metadata_file_path;
-        // S3 object references count.
+        /// S3 object references count.
         UInt32 s3_objects_count;
-        // Total size of all S3 objects.
+        /// Total size of all S3 objects.
         size_t total_size;
-        // S3 objects paths and their sizes.
+        /// S3 objects paths and their sizes.
         std::vector<PathAndSize> s3_objects;
 
         explicit Metadata(const Poco::File & file) : Metadata(file.path(), false) {}
 
-        // Load metadata by path or create empty if `create` flag is set.
+        /// Load metadata by path or create empty if `create` flag is set.
         explicit Metadata(const String & file_path, bool create = false)
-            : metadata_file_path(file_path), s3_objects_count(0), total_size(0), s3_objects(0)
+            : metadata_file_path(file_path)
+            , s3_objects_count(0)
+            , total_size(0)
+            , s3_objects(0)
         {
             if (create)
                 return;
@@ -112,10 +115,11 @@ namespace
             s3_objects.emplace_back(path, size);
         }
 
-        void save()
+        /// Fsync metadata file if 'sync' flag is set.
+        void save(bool sync = false)
         {
             WriteBufferFromFile buf(metadata_file_path, 1024);
-
+            
             writeIntText(VERSION, buf);
             writeChar('\n', buf);
 
@@ -132,11 +136,12 @@ namespace
                 writeChar('\n', buf);
             }
             buf.finalize();
+            if (sync)
+                buf.sync();
         }
     };
 
-    // Reads data from S3.
-    // It supports reading from multiple S3 paths that resides in Metadata.
+    /// Reads data from S3 using stored paths in metadata.
     class ReadIndirectBufferFromS3 : public ReadBufferFromFileBase
     {
     public:
@@ -148,7 +153,6 @@ namespace
             , metadata(std::move(metadata_))
             , buf_size(buf_size_)
             , absolute_position(0)
-            , initialized(false)
             , current_buf_idx(0)
             , current_buf(nullptr)
         {
@@ -196,19 +200,16 @@ namespace
                 }
                 offset -= size;
             }
-            initialized = true;
             return nullptr;
         }
 
         bool nextImpl() override
         {
-            // Find first available buffer that fits to given offset.
-            if (!initialized)
-            {
+            /// Find first available buffer that fits to given offset.
+            if (!current_buf)
                 current_buf = initialize();
-            }
 
-            // If current buffer has remaining data - use it.
+            /// If current buffer has remaining data - use it.
             if (current_buf && current_buf->next())
             {
                 working_buffer = current_buf->buffer();
@@ -216,7 +217,7 @@ namespace
                 return true;
             }
 
-            // If there is no available buffers - nothing to read.
+            /// If there is no available buffers - nothing to read.
             if (current_buf_idx + 1 >= metadata.s3_objects_count)
                 return false;
 
@@ -237,13 +238,12 @@ namespace
         size_t buf_size;
 
         size_t absolute_position = 0;
-        bool initialized;
         UInt32 current_buf_idx;
         std::unique_ptr<ReadBufferFromS3> current_buf;
     };
 
     /// Stores data in S3 and adds the object key (S3 path) and object size to metadata file on local FS.
-    class WriteIndirectBufferFromS3 : public WriteBufferFromS3
+    class WriteIndirectBufferFromS3 : public WriteBufferFromFileBase
     {
     public:
         WriteIndirectBufferFromS3(
@@ -253,25 +253,15 @@ namespace
             const String & s3_path_,
             size_t min_upload_part_size,
             size_t buf_size_)
-            : WriteBufferFromS3(client_ptr_, bucket_, s3_path_, min_upload_part_size, buf_size_)
+            : WriteBufferFromFileBase(buf_size_, nullptr, 0)
+            , impl(WriteBufferFromS3(client_ptr_, bucket_, s3_path_, min_upload_part_size, buf_size_))
             , metadata(std::move(metadata_))
             , s3_path(s3_path_)
         {
         }
 
-        void finalize() override
-        {
-            WriteBufferFromS3::finalize();
-            metadata.addObject(s3_path, total_size);
-            metadata.save();
-            finalized = true;
-        }
-
         ~WriteIndirectBufferFromS3() override
         {
-            if (finalized)
-                return;
-
             try
             {
                 finalize();
@@ -282,7 +272,38 @@ namespace
             }
         }
 
+        void finalize() override
+        {
+            if (finalized)
+                return;
+
+            next();
+            impl.finalize();
+
+            metadata.addObject(s3_path, count());
+            metadata.save();
+
+            finalized = true;
+        }
+
+        void sync() override { metadata.save(true); }
+        std::string getFileName() const override { return metadata.metadata_file_path; }
+
     private:
+        void nextImpl() override
+        {
+            /// Transfer current working buffer to WriteBufferFromS3.
+            impl.swap(*this);
+
+            /// Write actual data to S3.
+            impl.next();
+
+            /// Return back working buffer.
+            impl.swap(*this);
+        }
+
+    private:
+        WriteBufferFromS3 impl;
         bool finalized = false;
         Metadata metadata;
         String s3_path;
@@ -457,7 +478,7 @@ void DiskS3::copyFile(const String & from_path, const String & to_path)
     to.save();
 }
 
-std::unique_ptr<ReadBufferFromFileBase> DiskS3::readFile(const String & path, size_t buf_size) const
+std::unique_ptr<ReadBufferFromFileBase> DiskS3::readFile(const String & path, size_t buf_size, size_t, size_t, size_t) const
 {
     Metadata metadata(metadata_path + path);
 
@@ -468,19 +489,19 @@ std::unique_ptr<ReadBufferFromFileBase> DiskS3::readFile(const String & path, si
     return std::make_unique<ReadIndirectBufferFromS3>(client, bucket, metadata, buf_size);
 }
 
-std::unique_ptr<WriteBuffer> DiskS3::writeFile(const String & path, size_t buf_size, WriteMode mode)
+std::unique_ptr<WriteBufferFromFileBase> DiskS3::writeFile(const String & path, size_t buf_size, WriteMode mode, size_t, size_t)
 {
     bool exist = exists(path);
-    // Reference to store new S3 object.
+    /// Path to store new S3 object.
     auto s3_path = s3_root_path + getRandomName();
     if (!exist || mode == WriteMode::Rewrite)
     {
-        // If metadata file exists - remove and create new.
+        /// If metadata file exists - remove and create new.
         if (exist)
             remove(path);
 
         Metadata metadata(metadata_path + path, true);
-        // Save empty metadata to disk to have ability to get file size while buffer is not finalized.
+        /// Save empty metadata to disk to have ability to get file size while buffer is not finalized.
         metadata.save();
 
         LOG_DEBUG(&Logger::get("DiskS3"), "Write to file by path: " << backQuote(metadata_path + path) << " New S3 path: " << s3_path);
@@ -512,7 +533,7 @@ void DiskS3::remove(const String & path)
         {
             auto s3_path = metadata.s3_objects[i].first;
 
-            // TODO: Make operation idempotent. Do not throw exception if key is already deleted.
+            /// TODO: Make operation idempotent. Do not throw exception if key is already deleted.
             Aws::S3::Model::DeleteObjectRequest request;
             request.SetBucket(bucket);
             request.SetKey(s3_path);

dbms/src/Disks/DiskS3.h

@@ -21,8 +21,13 @@ class DiskS3 : public IDisk
 public:
     friend class DiskS3Reservation;
 
-    DiskS3(String name_, std::shared_ptr<Aws::S3::S3Client> client_, String bucket_, String s3_root_path_,
-           String metadata_path_, size_t min_upload_part_size_);
+    DiskS3(
+        String name_,
+        std::shared_ptr<Aws::S3::S3Client> client_,
+        String bucket_,
+        String s3_root_path_,
+        String metadata_path_,
+        size_t min_upload_part_size_);
 
     const String & getName() const override { return name; }
 
@@ -62,9 +67,19 @@ public:
 
     void copyFile(const String & from_path, const String & to_path) override;
 
-    std::unique_ptr<ReadBufferFromFileBase> readFile(const String & path, size_t buf_size) const override;
+    std::unique_ptr<ReadBufferFromFileBase> readFile(
+        const String & path,
+        size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE,
+        size_t estimated_size = 0,
+        size_t aio_threshold = 0,
+        size_t mmap_threshold = 0) const override;
 
-    std::unique_ptr<WriteBuffer> writeFile(const String & path, size_t buf_size, WriteMode mode) override;
+    std::unique_ptr<WriteBufferFromFileBase> writeFile(
+        const String & path,
+        size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE,
+        WriteMode mode = WriteMode::Rewrite,
+        size_t estimated_size = 0,
+        size_t aio_threshold = 0) override;
 
     void remove(const String & path) override;
 

dbms/src/Disks/IDisk.h

@@ -26,7 +26,7 @@ class IReservation;
 using ReservationPtr = std::unique_ptr<IReservation>;
 
 class ReadBufferFromFileBase;
-class WriteBuffer;
+class WriteBufferFromFileBase;
 
 /**
  * Mode of opening a file for write.
@@ -121,11 +121,21 @@ public:
     /// Copy the file from `from_path` to `to_path`.
     virtual void copyFile(const String & from_path, const String & to_path) = 0;
 
-    /// Open the file for read and return SeekableReadBuffer object.
-    virtual std::unique_ptr<ReadBufferFromFileBase> readFile(const String & path, size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE) const = 0;
+    /// Open the file for read and return ReadBufferFromFileBase object.
+    virtual std::unique_ptr<ReadBufferFromFileBase> readFile(
+        const String & path,
+        size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE,
+        size_t estimated_size = 0,
+        size_t aio_threshold = 0,
+        size_t mmap_threshold = 0) const = 0;
 
-    /// Open the file for write and return WriteBuffer object.
-    virtual std::unique_ptr<WriteBuffer> writeFile(const String & path, size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE, WriteMode mode = WriteMode::Rewrite) = 0;
+    /// Open the file for write and return WriteBufferFromFileBase object.
+    virtual std::unique_ptr<WriteBufferFromFileBase> writeFile(
+        const String & path,
+        size_t buf_size = DBMS_DEFAULT_BUFFER_SIZE,
+        WriteMode mode = WriteMode::Rewrite,
+        size_t estimated_size = 0,
+        size_t aio_threshold = 0) = 0;
 
     /// Remove file or directory. Throws exception if file doesn't exists or if directory is not empty.
     virtual void remove(const String & path) = 0;

dbms/src/IO/WriteBufferAIO.cpp

@@ -139,7 +139,7 @@ void WriteBufferAIO::nextImpl()
     is_pending_write = true;
 }
 
-off_t WriteBufferAIO::doSeek(off_t off, int whence)
+off_t WriteBufferAIO::seek(off_t off, int whence)
 {
     flush();
 
@@ -169,7 +169,7 @@ off_t WriteBufferAIO::doSeek(off_t off, int whence)
     return pos_in_file;
 }
 
-void WriteBufferAIO::doTruncate(off_t length)
+void WriteBufferAIO::truncate(off_t length)
 {
     flush();
 

dbms/src/IO/WriteBufferAIO.h

@@ -34,15 +34,15 @@ public:
     WriteBufferAIO(const WriteBufferAIO &) = delete;
     WriteBufferAIO & operator=(const WriteBufferAIO &) = delete;
 
-    off_t getPositionInFile() override;
+    off_t getPositionInFile();
+    off_t seek(off_t off, int whence);
+    void truncate(off_t length);
     void sync() override;
     std::string getFileName() const override { return filename; }
-    int getFD() const override { return fd; }
+    int getFD() const { return fd; }
 
 private:
     void nextImpl() override;
-    off_t doSeek(off_t off, int whence) override;
-    void doTruncate(off_t length) override;
 
     /// If there's still data in the buffer, we'll write them.
     void flush();

dbms/src/IO/WriteBufferFromFileBase.cpp

@@ -8,14 +8,4 @@ WriteBufferFromFileBase::WriteBufferFromFileBase(size_t buf_size, char * existin
 {
 }
 
-off_t WriteBufferFromFileBase::seek(off_t off, int whence)
-{
-    return doSeek(off, whence);
-}
-
-void WriteBufferFromFileBase::truncate(off_t length)
-{
-    return doTruncate(length);
-}
-
 }

dbms/src/IO/WriteBufferFromFileBase.h

@@ -15,16 +15,8 @@ public:
     WriteBufferFromFileBase(size_t buf_size, char * existing_memory, size_t alignment);
     ~WriteBufferFromFileBase() override = default;
 
-    off_t seek(off_t off, int whence = SEEK_SET);
-    void truncate(off_t length = 0);
-    virtual off_t getPositionInFile() = 0;
     void sync() override = 0;
     virtual std::string getFileName() const = 0;
-    virtual int getFD() const = 0;
-
-protected:
-    virtual off_t doSeek(off_t off, int whence) = 0;
-    virtual void doTruncate(off_t length) = 0;
 };
 
 }

dbms/src/IO/WriteBufferFromFileDescriptor.cpp

@@ -98,12 +98,6 @@ WriteBufferFromFileDescriptor::~WriteBufferFromFileDescriptor()
 }
 
 
-off_t WriteBufferFromFileDescriptor::getPositionInFile()
-{
-    return seek(0, SEEK_CUR);
-}
-
-
 void WriteBufferFromFileDescriptor::sync()
 {
     /// If buffer has pending data - write it.
@@ -116,7 +110,7 @@ void WriteBufferFromFileDescriptor::sync()
 }
 
 
-off_t WriteBufferFromFileDescriptor::doSeek(off_t offset, int whence)
+off_t WriteBufferFromFileDescriptor::seek(off_t offset, int whence)
 {
     off_t res = lseek(fd, offset, whence);
     if (-1 == res)
@@ -126,7 +120,7 @@ off_t WriteBufferFromFileDescriptor::doSeek(off_t offset, int whence)
 }
 
 
-void WriteBufferFromFileDescriptor::doTruncate(off_t length)
+void WriteBufferFromFileDescriptor::truncate(off_t length)
 {
     int res = ftruncate(fd, length);
     if (-1 == res)

dbms/src/IO/WriteBufferFromFileDescriptor.h

@@ -35,19 +35,15 @@ public:
 
     ~WriteBufferFromFileDescriptor() override;
 
-    int getFD() const override
+    int getFD() const
     {
         return fd;
     }
 
-    off_t getPositionInFile() override;
-
     void sync() override;
 
-private:
-    off_t doSeek(off_t offset, int whence) override;
-
-    void doTruncate(off_t length) override;
+    off_t seek(off_t offset, int whence);
+    void truncate(off_t length);
 };
 
 }

dbms/src/IO/WriteBufferFromS3.cpp

@@ -136,7 +136,6 @@ void WriteBufferFromS3::writePart(const String & data)
     {
         auto etag = outcome.GetResult().GetETag();
         part_tags.push_back(etag);
-        total_size += data.size();
         LOG_DEBUG(
             log,
             "Writing part finished. "

dbms/src/IO/WriteBufferFromS3.h

@@ -38,10 +38,6 @@ private:
 
     Logger * log = &Logger::get("WriteBufferFromS3");
 
-protected:
-    // Total size of all uploaded parts.
-    size_t total_size = 0;
-
 public:
     explicit WriteBufferFromS3(
         std::shared_ptr<Aws::S3::S3Client> client_ptr_,

dbms/src/Storages/StorageLog.cpp

@@ -8,6 +8,7 @@
 #include <Interpreters/evaluateConstantExpression.h>
 
 #include <IO/ReadBufferFromFileBase.h>
+#include <IO/WriteBufferFromFileBase.h>
 #include <Compression/CompressedReadBuffer.h>
 #include <Compression/CompressedWriteBuffer.h>
 #include <IO/ReadHelpers.h>

dbms/src/Storages/StorageStripeLog.cpp

@@ -8,6 +8,7 @@
 #include <Common/escapeForFileName.h>
 #include <Common/Exception.h>
 
+#include <IO/WriteBufferFromFileBase.h>
 #include <Compression/CompressedReadBufferFromFile.h>
 #include <Compression/CompressedWriteBuffer.h>
 #include <IO/ReadHelpers.h>

dbms/src/Storages/StorageTinyLog.cpp

@@ -11,6 +11,7 @@
 #include <Common/typeid_cast.h>
 
 #include <IO/ReadBufferFromFileBase.h>
+#include <IO/WriteBufferFromFileBase.h>
 #include <Compression/CompressionFactory.h>
 #include <Compression/CompressedReadBuffer.h>
 #include <Compression/CompressedWriteBuffer.h>