Shrink to fit compressed redo log

8 files changed, 55 insertions, 0 deletions

diff --git a/ydb/core/tablet_flat/flat_executor_txloglogic.cpp b/ydb/core/tablet_flat/flat_executor_txloglogic.cpp
index d5197d8466d..2e1973b229f 100644
--- a/ydb/core/tablet_flat/flat_executor_txloglogic.cpp
+++ b/ydb/core/tablet_flat/flat_executor_txloglogic.cpp
@@ -7,6 +7,7 @@
 #include "logic_redo_entry.h"
 #include "logic_redo_queue.h"
 #include "probes.h"
+#include "util_string.h"
 #include <ydb/core/tablet_flat/flat_executor.pb.h>
 #include <util/system/sanitizers.h>
 
@@ -207,6 +208,9 @@ void TLogicRedo::MakeLogEntry(TLogCommit &commit, TString redo, TArrayRef<const
         Counters->Cumulative()[TMonCo::LOG_REDO_WRITTEN].Increment(coded.size());
 
         if (embed && coded.size() <= MaxSizeToEmbedInLog) {
+            // Note: Encode reserves MaxCompressedLength bytes
+            NUtil::ShrinkToFit(coded);
+
             commit.Embedded = std::move(coded);
             Queue->Push({ Cookies->Gen, commit.Step }, affects, commit.Embedded);
         } else {
diff --git a/ydb/core/tablet_flat/ut_util/CMakeLists.darwin-x86_64.txt b/ydb/core/tablet_flat/ut_util/CMakeLists.darwin-x86_64.txt
index 56f770b9f18..ef00170d4bf 100644
--- a/ydb/core/tablet_flat/ut_util/CMakeLists.darwin-x86_64.txt
+++ b/ydb/core/tablet_flat/ut_util/CMakeLists.darwin-x86_64.txt
@@ -27,6 +27,7 @@ target_link_options(ydb-core-tablet_flat-ut_util PRIVATE
 )
 target_sources(ydb-core-tablet_flat-ut_util PRIVATE
   ${CMAKE_SOURCE_DIR}/ydb/core/tablet_flat/util_pool_ut.cpp
+  ${CMAKE_SOURCE_DIR}/ydb/core/tablet_flat/util_string_ut.cpp
 )
 set_property(
   TARGET
diff --git a/ydb/core/tablet_flat/ut_util/CMakeLists.linux-aarch64.txt b/ydb/core/tablet_flat/ut_util/CMakeLists.linux-aarch64.txt
index 0a4c093f79e..1db598c5ea4 100644
--- a/ydb/core/tablet_flat/ut_util/CMakeLists.linux-aarch64.txt
+++ b/ydb/core/tablet_flat/ut_util/CMakeLists.linux-aarch64.txt
@@ -30,6 +30,7 @@ target_link_options(ydb-core-tablet_flat-ut_util PRIVATE
 )
 target_sources(ydb-core-tablet_flat-ut_util PRIVATE
   ${CMAKE_SOURCE_DIR}/ydb/core/tablet_flat/util_pool_ut.cpp
+  ${CMAKE_SOURCE_DIR}/ydb/core/tablet_flat/util_string_ut.cpp
 )
 set_property(
   TARGET
diff --git a/ydb/core/tablet_flat/ut_util/CMakeLists.linux-x86_64.txt b/ydb/core/tablet_flat/ut_util/CMakeLists.linux-x86_64.txt
index 07e40c35d5d..71b81b4ee60 100644
--- a/ydb/core/tablet_flat/ut_util/CMakeLists.linux-x86_64.txt
+++ b/ydb/core/tablet_flat/ut_util/CMakeLists.linux-x86_64.txt
@@ -31,6 +31,7 @@ target_link_options(ydb-core-tablet_flat-ut_util PRIVATE
 )
 target_sources(ydb-core-tablet_flat-ut_util PRIVATE
   ${CMAKE_SOURCE_DIR}/ydb/core/tablet_flat/util_pool_ut.cpp
+  ${CMAKE_SOURCE_DIR}/ydb/core/tablet_flat/util_string_ut.cpp
 )
 set_property(
   TARGET
diff --git a/ydb/core/tablet_flat/ut_util/CMakeLists.windows-x86_64.txt b/ydb/core/tablet_flat/ut_util/CMakeLists.windows-x86_64.txt
index 71591f2c8d5..3865b70295f 100644
--- a/ydb/core/tablet_flat/ut_util/CMakeLists.windows-x86_64.txt
+++ b/ydb/core/tablet_flat/ut_util/CMakeLists.windows-x86_64.txt
@@ -20,6 +20,7 @@ target_link_libraries(ydb-core-tablet_flat-ut_util PUBLIC
 )
 target_sources(ydb-core-tablet_flat-ut_util PRIVATE
   ${CMAKE_SOURCE_DIR}/ydb/core/tablet_flat/util_pool_ut.cpp
+  ${CMAKE_SOURCE_DIR}/ydb/core/tablet_flat/util_string_ut.cpp
 )
 set_property(
   TARGET
diff --git a/ydb/core/tablet_flat/ut_util/ya.make b/ydb/core/tablet_flat/ut_util/ya.make
index c06ae56fd2b..36aa1a0273d 100644
--- a/ydb/core/tablet_flat/ut_util/ya.make
+++ b/ydb/core/tablet_flat/ut_util/ya.make
@@ -5,6 +5,7 @@ SIZE(MEDIUM)
 
 SRCS(
     util_pool_ut.cpp
+    util_string_ut.cpp
 )
 
 END()
diff --git a/ydb/core/tablet_flat/util_string.h b/ydb/core/tablet_flat/util_string.h
new file mode 100644
index 00000000000..ceb618abf5f
--- /dev/null
+++ b/ydb/core/tablet_flat/util_string.h
@@ -0,0 +1,14 @@
+#pragma once
+
+#include "defs.h"
+
+namespace NKikimr::NUtil {
+
+inline void ShrinkToFit(TString& input) {
+    // capacity / size > 1.5
+    if (input.capacity() * 2 > input.size() * 3) {
+        input = input.copy();
+    }
+}
+
+}
diff --git a/ydb/core/tablet_flat/util_string_ut.cpp b/ydb/core/tablet_flat/util_string_ut.cpp
new file mode 100644
index 00000000000..c26c60e34a4
--- /dev/null
+++ b/ydb/core/tablet_flat/util_string_ut.cpp
@@ -0,0 +1,32 @@
+#include <library/cpp/testing/unittest/registar.h>
+#include "util_string.h"
+
+namespace NKikimr::NUtil {
+
+Y_UNIT_TEST_SUITE(UtilString) {
+    Y_UNIT_TEST(ShrinkToFit) {
+        { // don't shrink if not much changes
+            TString s;
+            s.reserve(150);
+            s += std::string(120, 'x');
+            auto before = s.data();
+            ShrinkToFit(s);
+            UNIT_ASSERT_GE(s.capacity(), 150);
+            UNIT_ASSERT_VALUES_EQUAL((size_t)s.data(), (size_t)before);
+        }
+
+        { // shrink if much changes
+            TString s, copy;
+            s.reserve(150);
+            s += std::string(80, 'x');
+            copy = s.copy();
+            auto before = s.data();
+            ShrinkToFit(s);
+            UNIT_ASSERT_LE(s.capacity(), 100);
+            UNIT_ASSERT_VALUES_UNEQUAL((size_t)s.data(), (size_t)before);
+            UNIT_ASSERT_VALUES_EQUAL(copy, s);
+        }
+    }
+}
+
+}