Merge pull request #11749 from vespa-engine/balder/compact-buffer-after-compression

Balder/compact buffer after compression

3 files changed, 28 insertions, 9 deletions

diff --git a/searchlib/src/tests/docstore/document_store/document_store_test.cpp b/searchlib/src/tests/docstore/document_store/document_store_test.cpp
index f950377be4b..04ec18aacc4 100644
--- a/searchlib/src/tests/docstore/document_store/document_store_test.cpp
+++ b/searchlib/src/tests/docstore/document_store/document_store_test.cpp
@@ -142,6 +142,15 @@ TEST("require that Value can store zstd compressed data") {
     verifyValue(S1, v);
 }
 
+TEST("require that Value is shrunk to fit compressed data") {
+    Value v = createValue(S1, CompressionConfig::ZSTD);
+    EXPECT_EQUAL(CompressionConfig::ZSTD, v.getCompression());
+    EXPECT_EQUAL(128u, v.size());
+    EXPECT_EQUAL(128u, v.capacity());
+    EXPECT_EQUAL(297u, v.getUncompressedSize());
+    verifyValue(S1, v);
+}
+
 TEST("require that Value can detect if output not equal to input") {
     Value v = createValue(S1, CompressionConfig::NONE);
     const_cast<uint8_t *>(static_cast<const uint8_t *>(v.get()))[8] ^= 0xff;
diff --git a/searchlib/src/vespa/searchlib/docstore/value.cpp b/searchlib/src/vespa/searchlib/docstore/value.cpp
index ea29c894cba..09725b447cd 100644
--- a/searchlib/src/vespa/searchlib/docstore/value.cpp
+++ b/searchlib/src/vespa/searchlib/docstore/value.cpp
@@ -42,6 +42,19 @@ Value::set(vespalib::DataBuffer &&buf, ssize_t len) {
     set(std::move(buf), len, CompressionConfig());
 }
 
+namespace {
+
+vespalib::alloc::Alloc
+compact(size_t sz, vespalib::alloc::Alloc buf) {
+    if (vespalib::roundUp2inN(sz) < vespalib::roundUp2inN(buf.size())) {
+        vespalib::alloc::Alloc shrunk = buf.create(sz);
+        memcpy(shrunk.get(), buf.get(), sz);
+        return shrunk;
+    }
+    return buf;
+}
+
+}
 void
 Value::set(vespalib::DataBuffer &&buf, ssize_t len, const CompressionConfig &compression) {
     assert(len < std::numeric_limits<uint32_t>::max());
@@ -50,20 +63,16 @@ Value::set(vespalib::DataBuffer &&buf, ssize_t len, const CompressionConfig &com
     vespalib::ConstBufferRef input(buf.getData(), len);
     CompressionConfig::Type type = compress(compression, input, compressed, true);
     _compressedSize = compressed.getDataLen();
+    _compression = type;
+    _uncompressedSize = len;
+    _uncompressedCrc = XXH64(input.c_str(), input.size(), 0);
+    _buf = std::make_shared<Alloc>(compact(_compressedSize,
+            (buf.getData() == compressed.getData()) ? buf.stealBuffer() : compressed.stealBuffer()));
 
-    if (buf.getData() == compressed.getData()) {
-        // Uncompressed so we can just steal the underlying buffer.
-        _buf = std::make_shared<Alloc>(buf.stealBuffer());
-    } else {
-        _buf = std::make_shared<Alloc>(compressed.stealBuffer());
-    }
     assert(((type == CompressionConfig::NONE) &&
             (len == ssize_t(_compressedSize))) ||
            ((type != CompressionConfig::NONE) &&
             (len > ssize_t(_compressedSize))));
-    _compression = type;
-    _uncompressedSize = len;
-    _uncompressedCrc = XXH64(input.c_str(), input.size(), 0);
 }
 
 Value::Result
diff --git a/searchlib/src/vespa/searchlib/docstore/value.h b/searchlib/src/vespa/searchlib/docstore/value.h
index f58d96e3e77..fb377abb2fb 100644
--- a/searchlib/src/vespa/searchlib/docstore/value.h
+++ b/searchlib/src/vespa/searchlib/docstore/value.h
@@ -42,6 +42,7 @@ public:
     Result decompressed() const;
 
     size_t size() const { return _compressedSize; }
+    size_t capacity() const { return _buf ? _buf->size() : 0; }
     bool empty() const { return size() == 0; }
     operator const void *() const { return get(); }
     const void *get() const;