io: Fix checksum seek at end

dbms/src/Common/ProfileEvents.cpp

@@ -138,6 +138,7 @@
     M(S3PutObjectRetry)                        \
     M(S3IORead)                                \
     M(S3IOSeek)                                \
+    M(S3IOSeekBackward)                        \
     M(FileCacheHit)                            \
     M(FileCacheMiss)                           \
     M(FileCacheEvict)                          \

dbms/src/IO/Checksum/ChecksumBuffer.cpp

@@ -18,6 +18,80 @@ namespace DB
 {
 using namespace DB::Digest;
 
+template <typename Backend>
+off_t FramedChecksumReadBuffer<Backend>::doSeek(off_t offset, int whence)
+{
+    auto & frame = reinterpret_cast<ChecksumFrame<Backend> &>(
+        *(this->working_buffer.begin() - sizeof(ChecksumFrame<Backend>))); // align should not fail
+
+    if (whence == SEEK_CUR)
+    {
+        offset = getPositionInFile() + offset;
+    }
+    else if (whence != SEEK_SET)
+    {
+        throw TiFlashException(
+            "FramedChecksumReadBuffer::seek expects SEEK_SET or SEEK_CUR as whence",
+            Errors::Checksum::Internal);
+    }
+    auto target_frame = offset / frame_size;
+    auto target_offset = offset % frame_size;
+
+    // If we have already seek to EOF, then working_buffer was cleared
+    if (target_frame == current_frame && working_buffer.size() > 0)
+    {
+        if (unlikely(target_offset > working_buffer.size()))
+            pos = working_buffer.end();
+        else
+            pos = working_buffer.begin() + target_offset;
+        return offset;
+    }
+
+    // Seek according to `target_frame` and `target_offset`
+    // read the header and the body
+    auto header_offset = target_frame * (sizeof(ChecksumFrame<Backend>) + frame_size);
+    auto result = in->seek(static_cast<off_t>(header_offset), SEEK_SET);
+    if (result == -1)
+    {
+        throw TiFlashException(
+            Errors::Checksum::IOFailure,
+            "checksum framed file {} is not seekable",
+            in->getFileName());
+    }
+    auto length = expectRead(
+        working_buffer.begin() - sizeof(ChecksumFrame<Backend>),
+        sizeof(ChecksumFrame<Backend>) + frame_size);
+    if (length == 0)
+    {
+        current_frame = target_frame;
+        pos = working_buffer.begin();
+        working_buffer.resize(0);
+        return offset; // EOF
+    }
+    if (unlikely(length != sizeof(ChecksumFrame<Backend>) + frame.bytes))
+    {
+        throw TiFlashException(
+            Errors::Checksum::DataCorruption,
+            "frame length (header = {}, body = {}, read = {}) mismatch for {}",
+            sizeof(ChecksumFrame<Backend>),
+            frame.bytes,
+            length,
+            in->getFileName());
+    }
+
+    // body checksum examination
+    checkBody();
+
+    // update statistics
+    current_frame = target_frame;
+    if (unlikely(target_offset > working_buffer.size()))
+        pos = working_buffer.end();
+    else
+        pos = working_buffer.begin() + target_offset;
+
+    return offset;
+}
+
 template class FramedChecksumReadBuffer<None>;
 template class FramedChecksumReadBuffer<CRC32>;
 template class FramedChecksumReadBuffer<CRC64>;

dbms/src/IO/Checksum/ChecksumBuffer.h

@@ -423,72 +423,7 @@ class FramedChecksumReadBuffer : public ReadBufferFromFileDescriptor
         return true;
     }
 
-    off_t doSeek(off_t offset, int whence) override
-    {
-        auto & frame = reinterpret_cast<ChecksumFrame<Backend> &>(
-            *(this->working_buffer.begin() - sizeof(ChecksumFrame<Backend>))); // align should not fail
-
-        if (whence == SEEK_CUR)
-        {
-            offset = getPositionInFile() + offset;
-        }
-        else if (whence != SEEK_SET)
-        {
-            throw TiFlashException(
-                "FramedChecksumReadBuffer::seek expects SEEK_SET or SEEK_CUR as whence",
-                Errors::Checksum::Internal);
-        }
-        auto target_frame = offset / frame_size;
-        auto target_offset = offset % frame_size;
-
-        if (target_frame == current_frame)
-        {
-            pos = working_buffer.begin() + target_offset;
-            return offset;
-        }
-        else
-        {
-            // read the header and the body
-            auto header_offset = target_frame * (sizeof(ChecksumFrame<Backend>) + frame_size);
-            auto result = in->seek(static_cast<off_t>(header_offset), SEEK_SET);
-            if (result == -1)
-            {
-                throw TiFlashException(
-                    "checksum framed file " + in->getFileName() + " is not seekable",
-                    Errors::Checksum::IOFailure);
-            }
-            auto length = expectRead(
-                working_buffer.begin() - sizeof(ChecksumFrame<Backend>),
-                sizeof(ChecksumFrame<Backend>) + frame_size);
-            if (length == 0)
-            {
-                current_frame = target_frame;
-                pos = working_buffer.begin();
-                working_buffer.resize(0);
-                return offset; // EOF
-            }
-            if (unlikely(length != sizeof(ChecksumFrame<Backend>) + frame.bytes))
-            {
-                throw TiFlashException(
-                    fmt::format(
-                        "frame length (header = {}, body = {}, read = {}) mismatch for {}",
-                        sizeof(ChecksumFrame<Backend>),
-                        frame.bytes,
-                        length,
-                        in->getFileName()),
-                    Errors::Checksum::DataCorruption);
-            }
-
-            // body checksum examination
-            checkBody();
-
-            // update statistics
-            current_frame = target_frame;
-            pos = working_buffer.begin() + target_offset;
-        }
-
-        return offset;
-    }
+    off_t doSeek(off_t offset, int whence) override;
 };
 
 } // namespace DB

dbms/src/IO/Checksum/tests/gtest_dm_checksum_buffer.cpp

@@ -12,10 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wsign-compare"
-#include <gtest/gtest.h>
-#pragma GCC diagnostic pop
+#include <Common/Logger.h>
 #include <IO/BaseFile/PosixRandomAccessFile.h>
 #include <IO/BaseFile/PosixWritableFile.h>
 #include <IO/BaseFile/RateLimiter.h>
@@ -28,14 +25,15 @@
 #include <Poco/File.h>
 #include <Storages/DeltaMerge/DMChecksumConfig.h>
 #include <Storages/Page/PageUtil.h>
+#include <TestUtils/TiFlashTestBasic.h>
 #include <fmt/format.h>
 
+#include <ext/scope_guard.h>
 #include <random>
 
-namespace DB
-{
-namespace tests
+namespace DB::tests
 {
+
 namespace
 {
 std::random_device dev; // NOLINT(cert-err58-cpp)
@@ -372,5 +370,129 @@ TEST_STACKED_SEEKING(CRC32)
 TEST_STACKED_SEEKING(CRC64)
 TEST_STACKED_SEEKING(City128)
 TEST_STACKED_SEEKING(XXH3)
-} // namespace tests
-} // namespace DB
+
+template <ChecksumAlgo D>
+void runCompressedSeekableReaderBufferTest()
+try
+{
+    auto log = Logger::get();
+    // Create a temporary file for testing
+    const std::string temp_file_path = "/tmp/tiflash_compressed_seek_test.dat";
+    SCOPE_EXIT({
+        Poco::File file(temp_file_path);
+        if (file.exists())
+            file.remove();
+    });
+    // Test data - create multiple blocks with different patterns
+    std::vector<std::string> test_blocks;
+
+    test_blocks = {
+        std::string(1500, 'A') + "BLOCK0_END",
+        std::string(800, 'B') + "BLOCK1_END",
+        "", // Block 2 is empty
+        "", // Block 3 is empty
+    };
+
+    std::vector<size_t> block_compressed_offsets;
+    std::vector<size_t> block_decompressed_sizes;
+
+    auto [limiter, provider] = prepareIO();
+    auto config = DM::DMChecksumConfig{{}, TIFLASH_DEFAULT_CHECKSUM_FRAME_SIZE, D};
+
+    // Write compressed data to file
+    {
+        auto plain_file = ChecksumWriteBufferBuilder::build(
+            true,
+            provider,
+            temp_file_path,
+            EncryptionPath(temp_file_path, temp_file_path),
+            false,
+            limiter->getWriteLimiter(),
+            config.getChecksumAlgorithm(),
+            config.getChecksumFrameLength(),
+            /*flags*/
+            -1,
+            /*mode*/ 0666,
+            1048576);
+        auto compressed_buf
+            = CompressedWriteBuffer<>::build(*plain_file, CompressionSettings(CompressionMethod::LZ4), false);
+
+        for (const auto & block_data : test_blocks)
+        {
+            // Record the compressed file offset before writing this block
+            block_compressed_offsets.push_back(plain_file->count());
+            block_decompressed_sizes.push_back(block_data.size());
+
+            // Write the block data
+            compressed_buf->write(block_data.data(), block_data.size());
+            compressed_buf->next(); // Force compression of this block
+        }
+    }
+
+    LOG_INFO(log, "Created compressed file with {} blocks", test_blocks.size());
+    for (size_t i = 0; i < block_compressed_offsets.size(); ++i)
+    {
+        LOG_INFO(
+            log,
+            "Block {}: compressed_offset={}, decompressed_size={}",
+            i,
+            block_compressed_offsets[i],
+            block_decompressed_sizes[i]);
+    }
+
+
+    auto compressed_in = CompressedReadBufferFromFileBuilder::build(
+        provider,
+        temp_file_path,
+        EncryptionPath(temp_file_path, temp_file_path),
+        config.getChecksumFrameLength(),
+        limiter->getReadLimiter(),
+        config.getChecksumAlgorithm(),
+        config.getChecksumFrameLength());
+
+    // 1. Check seek + read
+    for (size_t i = 0; i < test_blocks.size(); ++i)
+    {
+        // Seek to the start of each block
+        LOG_INFO(log, "Seeking to block {} at offset {}", i, block_compressed_offsets[i]);
+        compressed_in->seek(block_compressed_offsets[i], 0);
+
+        // Read the data
+        std::string read_data;
+        read_data.resize(block_decompressed_sizes[i]);
+        compressed_in->readBig(read_data.data(), block_decompressed_sizes[i]);
+
+        // Verify the data matches
+        ASSERT_EQ(read_data, test_blocks[i]) << "Block " << i << " data mismatch";
+    }
+
+    // Seek in inverse order to test seek again
+    for (size_t i = 0; i < test_blocks.size(); ++i)
+    {
+        assert(i + 1 <= test_blocks.size());
+        const size_t target_block = test_blocks.size() - i - 1;
+        compressed_in->seek(block_compressed_offsets[target_block], 0);
+        std::string read_data;
+        read_data.resize(block_decompressed_sizes[target_block]);
+        size_t num_read = compressed_in->readBig(read_data.data(), test_blocks[target_block].size());
+        ASSERT_EQ(num_read, test_blocks[target_block].size());
+        read_data.resize(num_read);
+        ASSERT_EQ(read_data, test_blocks[target_block])
+            << "Block " << target_block << " data mismatch after seek again";
+    }
+}
+CATCH
+
+#define TEST_COMPRESSEDSEEKABLE(ALGO)                                \
+    TEST(DMChecksumBuffer##ALGO, CompressedSeekable)                 \
+    {                                                                \
+        runCompressedSeekableReaderBufferTest<ChecksumAlgo::ALGO>(); \
+    } // NOLINT(cert-err58-cpp)
+
+TEST_COMPRESSEDSEEKABLE(None)
+TEST_COMPRESSEDSEEKABLE(CRC32)
+TEST_COMPRESSEDSEEKABLE(CRC64)
+TEST_COMPRESSEDSEEKABLE(City128)
+TEST_COMPRESSEDSEEKABLE(XXH3)
+
+} // namespace DB::tests