KIKIMR-19139 Delete TIndex fields from TPart

14 files changed, 158 insertions, 158 deletions

diff --git a/ydb/core/tablet_flat/benchmark/b_charge.cpp b/ydb/core/tablet_flat/benchmark/b_charge.cpp
index 203ca0b9027..793cbae77a7 100644
--- a/ydb/core/tablet_flat/benchmark/b_charge.cpp
+++ b/ydb/core/tablet_flat/benchmark/b_charge.cpp
@@ -63,9 +63,7 @@ namespace {
         TModel()
             : Tool(*Mass.Model->Scheme)
         {
-            auto pages = Eggs.At(0)->Index->End() - Eggs.At(0)->Index->Begin();
-
-            Y_VERIFY(pages > 120);
+            Y_VERIFY(NTest::IndexTools::CountMainPages(*Eggs.Lone()) > 120);
         }
 
         static NTest::TPartEggs MakeEggs() noexcept
diff --git a/ydb/core/tablet_flat/flat_page_index.h b/ydb/core/tablet_flat/flat_page_index.h
index 1151120cd8f..c1dae9b6e36 100644
--- a/ydb/core/tablet_flat/flat_page_index.h
+++ b/ydb/core/tablet_flat/flat_page_index.h
@@ -255,40 +255,16 @@ namespace NPage {
                 return 0; /* cannot estimate rows for one page part */
         }
 
-        TPageId UpperPage() const noexcept
-        {
-            return Page.Begin() ? (Page.End() - 1)->GetPageId() + 1 : 0;
-        }
-
-        const TRecord* GetFirstKeyRecord() const noexcept
-        {
-            return Page.Record(0);
-        }
-
         const TRecord* GetLastKeyRecord() const noexcept
         {
             return LastKey;
         }
 
-        const TRecord* At(TRecIdx index) const noexcept
-        {
-            Y_VERIFY(index <= Page.Count);
-            auto it = Page.Begin() + index;
-            return it
-                ? it.GetRecord()
-                : GetLastKeyRecord();
-        }
-
         TRowId GetEndRowId() const noexcept
         {
             return EndRowId;
         }
 
-        size_t RawSize() const noexcept
-        {
-            return Raw.size();
-        }
-
     private:
         TSharedData Raw;
         TBlock Page;
diff --git a/ydb/core/tablet_flat/flat_part_index_iter.h b/ydb/core/tablet_flat/flat_part_index_iter.h
index 07e886e497b..718ac87f67b 100644
--- a/ydb/core/tablet_flat/flat_part_index_iter.h
+++ b/ydb/core/tablet_flat/flat_part_index_iter.h
@@ -137,6 +137,13 @@ public:
         return Iter.GetRecord();
     }
 
+    // currently this method is needed for tests only, but it's worth to keep it for future optimizations
+    const TRecord * GetLastRecord() const {
+        Y_VERIFY(Index);
+        Y_VERIFY(Iter, "Should be called only after SeekLast call");
+        return Index->GetLastKeyRecord();
+    }
+
 private:
     EReady DataOrGone() const {
         return Iter ? EReady::Data : EReady::Gone;
diff --git a/ydb/core/tablet_flat/flat_part_loader.cpp b/ydb/core/tablet_flat/flat_part_loader.cpp
index 48b6f979ef4..e6f33820d06 100644
--- a/ydb/core/tablet_flat/flat_part_loader.cpp
+++ b/ydb/core/tablet_flat/flat_part_loader.cpp
@@ -162,23 +162,18 @@ TAutoPtr<NPageCollection::TFetch> TLoader::StageCreatePartView() noexcept
         Y_Fail("TPart has small blobs, " << Packs.size() << " page collections");
     }
 
-    TVector<TSharedData> groupIndexes;
-    groupIndexes.reserve(GroupIndexesIds.size());
+    // TODO: stop load indexes
     for (auto pageId : GroupIndexesIds) {
         auto* page = GetPage(pageId);
         if (!page) {
             Y_Fail("Missing group index page " << pageId);
         }
-        groupIndexes.emplace_back(*page);
     }
-
-    TVector<TSharedData> historicIndexes(Reserve(HistoricIndexesIds.size()));
     for (auto pageId : HistoricIndexesIds) {
         auto* page = GetPage(pageId);
         if (!page) {
             Y_Fail("Missing historic index page " << pageId);
         }
-        historicIndexes.emplace_back(*page);
     }
 
     const auto extra = BlobsLabelFor(Packs[0]->PageCollection->Label());
@@ -194,19 +189,25 @@ TAutoPtr<NPageCollection::TFetch> TLoader::StageCreatePartView() noexcept
         groupIndexesIds.push_back(pageId);
     }
 
+    // TODO: put index size to stat?
+    // TODO: include history indexes bytes
+    size_t indexesRawSize = 0;
+    for (auto indexPage : groupIndexesIds) {
+        indexesRawSize += GetPageSize(indexPage);
+    }
+
     auto *partStore = new TPartStore(
         Packs.front()->PageCollection->Label(),
         {
             epoch,
             TPartScheme::Parse(*scheme, Rooted),
-            { groupIndexesIds, HistoricIndexesIds },
+            { std::move(groupIndexesIds), HistoricIndexesIds },
             *index,
             blobs ? new NPage::TExtBlobs(*blobs, extra) : nullptr,
             byKey ? new NPage::TBloom(*byKey) : nullptr,
             large ? new NPage::TFrames(*large) : nullptr,
             small ? new NPage::TFrames(*small) : nullptr,
-            std::move(groupIndexes),
-            std::move(historicIndexes),
+            indexesRawSize,
             MinRowVersion,
             MaxRowVersion,
             garbageStats ? new NPage::TGarbageStats(*garbageStats) : nullptr,
diff --git a/ydb/core/tablet_flat/flat_part_loader.h b/ydb/core/tablet_flat/flat_part_loader.h
index 32ee5de7f3b..1d6d2c7fa20 100644
--- a/ydb/core/tablet_flat/flat_part_loader.h
+++ b/ydb/core/tablet_flat/flat_part_loader.h
@@ -145,6 +145,11 @@ namespace NTable {
             return page == Max<TPageId>() ? nullptr : Packs[0]->Lookup(page);
         }
 
+        size_t GetPageSize(TPageId page) noexcept
+        {
+            return Packs[0]->PageCollection->Page(page).Size;
+        }
+
         void ParseMeta(TArrayRef<const char> plain) noexcept
         {
             TMemoryInput stream(plain.data(), plain.size());
diff --git a/ydb/core/tablet_flat/flat_stat_part.h b/ydb/core/tablet_flat/flat_stat_part.h
index b0e036768b6..89e518e6778 100644
--- a/ydb/core/tablet_flat/flat_stat_part.h
+++ b/ydb/core/tablet_flat/flat_stat_part.h
@@ -52,7 +52,7 @@ public:
         for (ui32 group : xrange(size_t(1), Part->GroupsCount)) {
             AltGroups.emplace_back(Part.Get(), env, NPage::TGroupId(group));
         }
-        for (ui32 group : xrange(Part->HistoricIndexes.size())) {
+        for (ui32 group : xrange(Part->HistoricGroupsCount)) {
             HistoryGroups.emplace_back(Part.Get(), env, NPage::TGroupId(group, true));
         }
     }
@@ -158,7 +158,7 @@ private:
         if (IsValid()) {
             return Pos.GetRowId();
         }
-        if (TRowId endRowId = Part->Index.GetEndRowId(); endRowId != Max<TRowId>()) {
+        if (TRowId endRowId = Pos.GetEndRowId(); endRowId != Max<TRowId>()) {
             // This would include the last page rows when known
             return endRowId;
         }
diff --git a/ydb/core/tablet_flat/flat_table_part.h b/ydb/core/tablet_flat/flat_table_part.h
index 6aeb6f15a55..51c1a998402 100644
--- a/ydb/core/tablet_flat/flat_table_part.h
+++ b/ydb/core/tablet_flat/flat_table_part.h
@@ -61,8 +61,7 @@ namespace NTable {
             TIntrusiveConstPtr<NPage::TBloom> ByKey;
             TIntrusiveConstPtr<NPage::TFrames> Large;
             TIntrusiveConstPtr<NPage::TFrames> Small;
-            TVector<TSharedData> GroupIndexes;
-            TVector<TSharedData> HistoricIndexes;
+            size_t IndexesRawSize;
             TRowVersion MinRowVersion;
             TRowVersion MaxRowVersion;
             TIntrusiveConstPtr<NPage::TGarbageStats> GarbageStats;
@@ -87,29 +86,19 @@ namespace NTable {
             , Small(std::move(params.Small))
             , IndexPages(std::move(params.IndexPages))
             , Index(std::move(params.Index))
-            , GroupIndexes(
-                std::make_move_iterator(params.GroupIndexes.begin()),
-                std::make_move_iterator(params.GroupIndexes.end()))
-            , HistoricIndexes(
-                std::make_move_iterator(params.HistoricIndexes.begin()),
-                std::make_move_iterator(params.HistoricIndexes.end()))
             , ByKey(std::move(params.ByKey))
             , GarbageStats(std::move(params.GarbageStats))
             , TxIdStats(std::move(params.TxIdStats))
             , Stat(stat)
             , GroupsCount(IndexPages.Groups.size())
             , HistoricGroupsCount(IndexPages.Historic.size())
-            , IndexesRawSize(Index.RawSize() + SumRawSize(GroupIndexes))
+            , IndexesRawSize(params.IndexesRawSize)
             , MinRowVersion(params.MinRowVersion)
             , MaxRowVersion(params.MaxRowVersion)
         {
             Y_VERIFY(Scheme->Groups.size() == GroupsCount,
                 "Part has scheme with %" PRISZT " groups, but %" PRISZT " indexes",
                 Scheme->Groups.size(), GroupsCount);
-            Y_VERIFY(HistoricIndexes.empty() || HistoricIndexes.size() == GroupsCount,
-                "Part has %" PRISZT " indexes, but %" PRISZT " historic indexes",
-                GroupsCount, HistoricIndexes.size());
-
             Y_VERIFY(!HistoricGroupsCount || HistoricGroupsCount == GroupsCount,
                 "Part has %" PRISZT " indexes, but %" PRISZT " historic indexes",
                 GroupsCount, HistoricGroupsCount);
@@ -141,24 +130,6 @@ namespace NTable {
         virtual ui8 GetPageChannel(NPage::TPageId id, NPage::TGroupId groupId = { }) const = 0;
         virtual ui8 GetPageChannel(ELargeObj lob, ui64 ref) const = 0;
 
-        const NPage::TIndex& GetGroupIndex(NPage::TGroupId groupId) const noexcept {
-            if (!groupId.Historic) {
-                if (groupId.Index == 0) {
-                    return Index;
-                } else {
-                    Y_VERIFY(groupId.Index <= GroupIndexes.size(),
-                        "Group index %" PRIu32 " is missing",
-                        groupId.Index);
-                    return GroupIndexes[groupId.Index - 1];
-                }
-            } else {
-                Y_VERIFY(groupId.Index < HistoricIndexes.size(),
-                    "Historic index %" PRIu32 " is missing",
-                    groupId.Index);
-                return HistoricIndexes[groupId.Index];
-            }
-        }
-
     protected:
         // Helper for CloneWithEpoch
         TPart(const TPart& src, TEpoch epoch)
@@ -170,8 +141,6 @@ namespace NTable {
             , Small(src.Small)
             , IndexPages(src.IndexPages)
             , Index(src.Index)
-            , GroupIndexes(src.GroupIndexes)
-            , HistoricIndexes(src.HistoricIndexes)
             , ByKey(src.ByKey)
             , GarbageStats(src.GarbageStats)
             , Stat(src.Stat)
@@ -182,15 +151,6 @@ namespace NTable {
             , MaxRowVersion(src.MaxRowVersion)
         { }
 
-    private:
-        static size_t SumRawSize(const TVector<NPage::TIndex>& indexes) {
-            size_t ret = 0;
-            for (auto& index : indexes) {
-                ret += index.RawSize();
-            }
-            return ret;
-        }
-
     public:
         const TLogoBlobID Label;
         const TEpoch Epoch;
@@ -200,8 +160,6 @@ namespace NTable {
         const TIntrusiveConstPtr<NPage::TFrames> Small;
         const TIndexPages IndexPages;
         const NPage::TIndex Index;
-        const TVector<NPage::TIndex> GroupIndexes;
-        const TVector<NPage::TIndex> HistoricIndexes;
         const TIntrusiveConstPtr<NPage::TBloom> ByKey;
         const TIntrusiveConstPtr<NPage::TGarbageStats> GarbageStats;
         const TIntrusiveConstPtr<NPage::TTxIdStatsPage> TxIdStats;
diff --git a/ydb/core/tablet_flat/test/libs/table/test_part.h b/ydb/core/tablet_flat/test/libs/table/test_part.h
index 1690af9a9a3..6050408aa2a 100644
--- a/ydb/core/tablet_flat/test/libs/table/test_part.h
+++ b/ydb/core/tablet_flat/test/libs/table/test_part.h
@@ -48,7 +48,7 @@ namespace NTest {
 
         ui64 GetPageSize(NPage::TPageId id, NPage::TGroupId groupId) const override
         {
-            return Store->GetPage(groupId.Index, id)->size();
+            return Store->GetPageSize(groupId.Index, id);
         }
 
         NPage::EPage GetPageType(NPage::TPageId id, NPage::TGroupId groupId) const override
@@ -145,4 +145,49 @@ namespace NTest {
 
     TString DumpPart(const TPartStore&, ui32 depth = 10) noexcept;
 
+    namespace IndexTools {
+        inline size_t CountMainPages(const TPartStore& part) {
+            size_t result = 0;
+
+            TTestEnv env;
+            TPartIndexIt index(&part, &env, { });
+            for (size_t i = 0; ; i++) {
+                auto ready = i == 0 ? index.Seek(0) : index.Next();
+                if (ready != EReady::Data) {
+                    Y_VERIFY(ready != EReady::Page, "Unexpected page fault");
+                    break;
+                }
+                result++;
+            }
+
+            return result;
+        }
+
+        inline TRowId GetEndRowId(const TPartStore& part) {
+            TTestEnv env;
+            TPartIndexIt index(&part, &env, { });
+            return index.GetEndRowId();
+        }
+
+        inline const TPartIndexIt::TRecord * GetLastRecord(const TPartStore& part) {
+            TTestEnv env;
+            TPartIndexIt index(&part, &env, { });
+            Y_VERIFY(index.SeekLast() == EReady::Data);
+            return index.GetLastRecord();
+        }
+
+        inline const TPartIndexIt::TRecord * GetRecord(const TPartStore& part, TPageId pageId) {
+            TTestEnv env;
+            TPartIndexIt index(&part, &env, { });
+
+            Y_VERIFY(index.Seek(0) == EReady::Data);
+            for (TPageId p = 0; p < pageId; p++) {
+                Y_VERIFY(index.Next() == EReady::Data);
+            }
+
+            Y_VERIFY(index.GetPageId() == pageId);
+            return index.GetRecord();
+        }
+    }
+
 }}}
diff --git a/ydb/core/tablet_flat/test/libs/table/test_store.h b/ydb/core/tablet_flat/test/libs/table/test_store.h
index 9bcc2bd6148..0b6f6c9c555 100644
--- a/ydb/core/tablet_flat/test/libs/table/test_store.h
+++ b/ydb/core/tablet_flat/test/libs/table/test_store.h
@@ -32,8 +32,6 @@ namespace NTest {
             TData *ByKey;
             TData *Large;
             TData *Small;
-            TVector<TSharedData> GroupIndexes;
-            TVector<TSharedData> HistoricIndexes;
             TData *GarbageStats;
             TData *TxIdStats;
         };
@@ -63,6 +61,13 @@ namespace NTest {
             return &PageCollections.at(room).at(page);
         }
 
+        size_t GetPageSize(ui32 room, ui32 page) const noexcept
+        {
+            Y_VERIFY(room < PageCollections.size(), "Room is out of bounds");
+
+            return PageCollections.at(room).at(page).size();
+        }
+
         NPage::EPage GetPageType(ui32 room, ui32 page) const noexcept
         {
             Y_VERIFY(room < PageCollections.size(), "Room is out of bounds");
@@ -129,8 +134,6 @@ namespace NTest {
                 GetPage(MainPageCollection, ByKey),
                 GetPage(MainPageCollection, Large),
                 nullptr,
-                { },
-                { },
                 nullptr,
                 nullptr,
             };
diff --git a/ydb/core/tablet_flat/test/libs/table/test_writer.h b/ydb/core/tablet_flat/test/libs/table/test_writer.h
index e5d6171fae8..e57925312a1 100644
--- a/ydb/core/tablet_flat/test/libs/table/test_writer.h
+++ b/ydb/core/tablet_flat/test/libs/table/test_writer.h
@@ -73,6 +73,11 @@ namespace NTest {
 
             TEpoch epoch = TEpoch(root.GetEpoch());
 
+            size_t indexesRawSize = 0;
+            for (auto indexPage : eggs.IndexGroupsPages) {
+                indexesRawSize += Store->GetPageSize(0, indexPage);
+            }
+
             return
                 new TPartStore(
                     std::move(Store),
@@ -86,8 +91,7 @@ namespace NTest {
                         eggs.ByKey ? new TBloom(*eggs.ByKey) : nullptr,
                         eggs.Large ? new TFrames(*eggs.Large) : nullptr,
                         eggs.Small ? new TFrames(*eggs.Small) : nullptr,
-                        std::move(eggs.GroupIndexes),
-                        std::move(eggs.HistoricIndexes),
+                        indexesRawSize,
                         TRowVersion(minRowVersion.GetStep(), minRowVersion.GetTxId()),
                         TRowVersion(maxRowVersion.GetStep(), maxRowVersion.GetTxId()),
                         eggs.GarbageStats ? new NPage::TGarbageStats(*eggs.GarbageStats) : nullptr,
@@ -115,30 +119,23 @@ namespace NTest {
                 indexGroupsPages.push_back(lay.GetIndex());
             }
 
-            TVector<TSharedData> groupIndexes;
             for (ui32 pageId : lay.GetGroupIndexes()) {
                 indexGroupsPages.push_back(pageId);
-                groupIndexes.emplace_back(*Store->GetPage(0, pageId));
             }
-
-            TVector<TSharedData> historicIndexes;
             for (ui32 pageId : lay.GetHistoricIndexes()) {
                 indexHistoricPages.push_back(pageId);
-                historicIndexes.emplace_back(*Store->GetPage(0, pageId));
             }
 
             return {
                 true /* rooted page collection */,
-                indexGroupsPages, 
-                indexHistoricPages,
+                std::move(indexGroupsPages), 
+                std::move(indexHistoricPages),
                 Store->GetPage(0, lay.HasIndex() ? lay.GetIndex() : undef),
                 Store->GetPage(0, lay.HasScheme() ? lay.GetScheme() : undef),
                 Store->GetPage(0, lay.HasGlobs() ? lay.GetGlobs() : undef),
                 Store->GetPage(0, lay.HasByKey() ? lay.GetByKey() : undef),
                 Store->GetPage(0, lay.HasLarge() ? lay.GetLarge() : undef),
                 Store->GetPage(0, lay.HasSmall() ? lay.GetSmall() : undef),
-                std::move(groupIndexes),
-                std::move(historicIndexes),
                 Store->GetPage(0, lay.HasGarbageStats() ? lay.GetGarbageStats() : undef),
                 Store->GetPage(0, lay.HasTxIdStats() ? lay.GetTxIdStats() : undef),
             };
diff --git a/ydb/core/tablet_flat/ut/ut_charge.cpp b/ydb/core/tablet_flat/ut/ut_charge.cpp
index fceb7152b09..af2f98755a0 100644
--- a/ydb/core/tablet_flat/ut/ut_charge.cpp
+++ b/ydb/core/tablet_flat/ut/ut_charge.cpp
@@ -104,9 +104,7 @@ namespace {
             , Eggs(MakeEggs(groups, history))
             , Tool(*Mass.Model->Scheme)
         {
-            auto pages = Eggs.Lone()->Index->End() - Eggs.Lone()->Index->Begin();
-
-            UNIT_ASSERT(pages == 9);
+            UNIT_ASSERT(NTest::IndexTools::CountMainPages(*Eggs.Lone()) == 9);
         }
 
         NTest::TPartEggs MakeEggs(bool groups, bool history) noexcept
@@ -335,9 +333,15 @@ namespace {
                 }
 
                 TMap<ui64, ui64> absoluteId;
-                auto groupIndex = Eggs.Lone()->GetGroupIndex(groupId);
-                for (auto it = groupIndex->Begin(); it != groupIndex->End(); it++) {
-                    absoluteId[absoluteId.size()] = it->GetPageId();
+                NTest::TTestEnv env;
+                TPartIndexIt groupIndex(Eggs.Lone().Get(), &env, groupId);
+                for (size_t i = 0; ; i++) {
+                    auto ready = i == 0 ? groupIndex.Seek(0) : groupIndex.Next();
+                    if (ready != EReady::Data) {
+                        Y_VERIFY(ready != EReady::Page);
+                        break;
+                    }
+                    absoluteId[absoluteId.size()] = groupIndex.GetPageId();
                 }
 
                 TSet<TPageId> actualValue;
diff --git a/ydb/core/tablet_flat/ut/ut_compaction_multi.cpp b/ydb/core/tablet_flat/ut/ut_compaction_multi.cpp
index beb115c5c02..27617afa4b8 100644
--- a/ydb/core/tablet_flat/ut/ut_compaction_multi.cpp
+++ b/ydb/core/tablet_flat/ut/ut_compaction_multi.cpp
@@ -55,9 +55,10 @@ Y_UNIT_TEST_SUITE(TCompactionMulti) {
             UNIT_ASSERT_VALUES_EQUAL(fullPageSize, initialConf.Groups[0].PageSize);
 
             // Verify the last page contains a single row
-            auto lastPage = initialPart->Index->End();
-            UNIT_ASSERT_C(--lastPage, "Unexpected failure to find the last index page");
-            auto count = initialPart->Index.GetEndRowId() - lastPage->GetRowId();
+            TTestEnv env;
+            TPartIndexIt iter(initialPart, &env, { });
+            Y_VERIFY(iter.SeekLast() == EReady::Data, "Unexpected failure to find the last index page");
+            auto count = iter.GetEndRowId() - iter.GetRowId();
             UNIT_ASSERT_C(count == 1, "Unexpected " << count << " rows on the last page");
         }
 
diff --git a/ydb/core/tablet_flat/ut/ut_part.cpp b/ydb/core/tablet_flat/ut/ut_part.cpp
index 7eaac59bf97..2e45cd1f420 100644
--- a/ydb/core/tablet_flat/ut/ut_part.cpp
+++ b/ydb/core/tablet_flat/ut/ut_part.cpp
@@ -182,10 +182,10 @@ Y_UNIT_TEST_SUITE(TPart) {
         /* Verify part has correct first and last key in the index */
 
         const auto part = (*wrap).Eggs.Lone();
-        UNIT_ASSERT_VALUES_EQUAL(part->Index.Rows(), 2u);
+        UNIT_ASSERT_VALUES_EQUAL(IndexTools::GetEndRowId(*part), 2u);
         const NPage::TCompare<NPage::TIndex::TRecord> cmp(part->Scheme->Groups[0].ColsKeyIdx, *(*lay).Keys);
-        UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*part->Index.GetFirstKeyRecord(), TRowTool(*lay).KeyCells(foo)), 0);
-        UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*part->Index.GetLastKeyRecord(), TRowTool(*lay).KeyCells(bar)), 0);
+        UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*IndexTools::GetRecord(*part, 0), TRowTool(*lay).KeyCells(foo)), 0);
+        UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*IndexTools::GetLastRecord(*part), TRowTool(*lay).KeyCells(bar)), 0);
 
         DumpPart(*(*wrap).Eggs.Lone(), 10);
     }
@@ -380,7 +380,7 @@ Y_UNIT_TEST_SUITE(TPart) {
         UNIT_ASSERT_C(Eggs0().Parts.size() == 1, "Eggs0 has " << Eggs0().Parts.size() << "p");
 
         auto &part = *Eggs0().Lone();
-        auto pages = part.Index->End() - part.Index->Begin();
+        auto pages = IndexTools::CountMainPages(part);
         auto minIndex = PageConf().Groups.at(0).IndexMin * 8;
 
         auto cWidth = [](const NPage::TFrames *frames, ui32 span) -> ui32 {
@@ -401,7 +401,7 @@ Y_UNIT_TEST_SUITE(TPart) {
         /*_ Ensure that produced part has enough pages for code coverage and
             index grow algorithm in data pages writer has been triggered. */
 
-        UNIT_ASSERT(pages > 100 && part.Index.RawSize() >= minIndex);
+        UNIT_ASSERT(pages > 100 && part.GetPageSize(part.IndexPages.Groups[0], { }) >= minIndex);
 
         { /*_ Ensure that part has some external blobs written to room 1 */
             auto one = Eggs0().Lone()->Blobs->Total();
@@ -426,10 +426,10 @@ Y_UNIT_TEST_SUITE(TPart) {
         }
 
         { /*_  Check that the last key matches in the index */
-            UNIT_ASSERT_VALUES_EQUAL(part.Index.Rows(), Mass0().Saved.Size());
+            UNIT_ASSERT_VALUES_EQUAL(IndexTools::GetEndRowId(part), Mass0().Saved.Size());
             const NPage::TCompare<NPage::TIndex::TRecord> cmp(part.Scheme->Groups[0].ColsKeyIdx, *Eggs0().Scheme->Keys);
             auto lastKey = TRowTool(*Eggs0().Scheme).KeyCells(Mass0().Saved[Mass0().Saved.Size()-1]);
-            UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*part.Index.GetLastKeyRecord(), lastKey), 0);
+            UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*IndexTools::GetLastRecord(part), lastKey), 0);
         }
 
         { /*_  Check that part has correct number of slices */
@@ -701,11 +701,11 @@ Y_UNIT_TEST_SUITE(TPart) {
         const auto part = (*wrap).Eggs.Lone();
 
         const NPage::TCompare<NPage::TIndex::TRecord> cmp(part->Scheme->Groups[0].ColsKeyIdx, *(*lay).Keys);
-        UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*part->Index->Begin(), TRowTool(*lay).KeyCells(*TSchemedCookRow(*lay).Col(1u, prefix + "aaa"))), 0);
-        UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*(part->Index->Begin() + 1), TRowTool(*lay).KeyCells(*TSchemedCookRow(*lay).Col(1u, prefix + "b"))), 0);
-        UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*(part->Index->Begin() + 2), TRowTool(*lay).KeyCells(*TSchemedCookRow(*lay).Col(2u, nullptr))), 0);
-        UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*(part->Index->Begin() + 3), TRowTool(*lay).KeyCells(*TSchemedCookRow(*lay).Col(2u, prefix + "ccx"))), 0);
-        UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*part->Index.GetLastKeyRecord(), TRowTool(*lay).KeyCells(*TSchemedCookRow(*lay).Col(2u, prefix + "cxz"))), 0);
+        UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*IndexTools::GetRecord(*part, 0), TRowTool(*lay).KeyCells(*TSchemedCookRow(*lay).Col(1u, prefix + "aaa"))), 0);
+        UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*IndexTools::GetRecord(*part, 1), TRowTool(*lay).KeyCells(*TSchemedCookRow(*lay).Col(1u, prefix + "b"))), 0);
+        UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*IndexTools::GetRecord(*part, 2), TRowTool(*lay).KeyCells(*TSchemedCookRow(*lay).Col(2u, nullptr))), 0);
+        UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*IndexTools::GetRecord(*part, 3), TRowTool(*lay).KeyCells(*TSchemedCookRow(*lay).Col(2u, prefix + "ccx"))), 0);
+        UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*IndexTools::GetLastRecord(*part), TRowTool(*lay).KeyCells(*TSchemedCookRow(*lay).Col(2u, prefix + "cxz"))), 0);
     }
 
     Y_UNIT_TEST(CutKeys_Seek)
@@ -762,11 +762,11 @@ Y_UNIT_TEST_SUITE(TPart) {
         UNIT_ASSERT_GT(fullPart->IndexesRawSize, cutPart->IndexesRawSize);
         
         const NPage::TCompare<NPage::TIndex::TRecord> cmp(cutPart->Scheme->Groups[0].ColsKeyIdx, *(*lay).Keys);
-        UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*cutPart->Index->Begin(), TRowTool(*lay).KeyCells(*TSchemedCookRow(*lay).Col(1u, "aaa"))), 0);
-        UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*(cutPart->Index->Begin() + 1), TRowTool(*lay).KeyCells(*TSchemedCookRow(*lay).Col(1u, "b"))), 0);
-        UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*(cutPart->Index->Begin() + 2), TRowTool(*lay).KeyCells(*TSchemedCookRow(*lay).Col(2u, nullptr))), 0);
-        UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*(cutPart->Index->Begin() + 3), TRowTool(*lay).KeyCells(*TSchemedCookRow(*lay).Col(2u, "ccx"))), 0);
-        UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*cutPart->Index.GetLastKeyRecord(), TRowTool(*lay).KeyCells(*TSchemedCookRow(*lay).Col(2u, "cxz"))), 0);
+        UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*IndexTools::GetRecord(*cutPart, 0), TRowTool(*lay).KeyCells(*TSchemedCookRow(*lay).Col(1u, "aaa"))), 0);
+        UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*IndexTools::GetRecord(*cutPart, 1), TRowTool(*lay).KeyCells(*TSchemedCookRow(*lay).Col(1u, "b"))), 0);
+        UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*IndexTools::GetRecord(*cutPart, 2), TRowTool(*lay).KeyCells(*TSchemedCookRow(*lay).Col(2u, nullptr))), 0);
+        UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*IndexTools::GetRecord(*cutPart, 3), TRowTool(*lay).KeyCells(*TSchemedCookRow(*lay).Col(2u, "ccx"))), 0);
+        UNIT_ASSERT_VALUES_EQUAL(cmp.Compare(*IndexTools::GetLastRecord(*cutPart), TRowTool(*lay).KeyCells(*TSchemedCookRow(*lay).Col(2u, "cxz"))), 0);
 
         for (auto r : fullRows) {
             cutWrap.Has(*TSchemedCookRow(*lay).Col(r.first, r.second));
@@ -951,11 +951,11 @@ Y_UNIT_TEST_SUITE(TPart) {
             slice.FirstInclusive = true;
             slice.FirstRowId = rowId;
             if (rowId > 0)
-                slice.FirstKey = getKey(cutPartTmp->Index.At(slice.FirstRowId));
+                slice.FirstKey = getKey(IndexTools::GetRecord(*cutPartTmp, slice.FirstRowId));
             slice.LastInclusive = false;
             slice.LastRowId = rowId + RandomNumber<ui32>(2) + 1;
             if (slice.LastRowId < fullRows.size())
-                slice.LastKey = getKey(cutPartTmp->Index.At(slice.LastRowId));
+                slice.LastKey = getKey(IndexTools::GetRecord(*cutPartTmp, slice.LastRowId));
             slices->push_back(slice);
             rowId = slice.LastRowId;
         }
@@ -1043,7 +1043,7 @@ Y_UNIT_TEST_SUITE(TPart) {
 
             Cerr << DumpPart(*part, 2) << Endl;
 
-            TString actual((part->Index->Begin() + 1).GetRecord()->Cell(part->Scheme->Groups[0].ColsKeyIdx[0]).AsBuf());
+            TString actual(IndexTools::GetRecord(*part, 1)->Cell(part->Scheme->Groups[0].ColsKeyIdx[0]).AsBuf());
             UNIT_ASSERT_VALUES_EQUAL_C(actual, expected, testId << ": '" << a << "', '" << b << "'");
         };
 
@@ -1150,7 +1150,7 @@ Y_UNIT_TEST_SUITE(TPart) {
 
             Cerr << DumpPart(*part, 2) << Endl;
 
-            TString actual((part->Index->Begin() + 1).GetRecord()->Cell(part->Scheme->Groups[0].ColsKeyIdx[0]).AsBuf());
+            TString actual(IndexTools::GetRecord(*part, 1)->Cell(part->Scheme->Groups[0].ColsKeyIdx[0]).AsBuf());
             UNIT_ASSERT_VALUES_EQUAL_C(actual, expected, testId << ": '" << a << "', '" << b << "'");
         };
 
diff --git a/ydb/core/tablet_flat/ut/ut_slice_loader.cpp b/ydb/core/tablet_flat/ut/ut_slice_loader.cpp
index 0ba12913ed9..9122a0b0337 100644
--- a/ydb/core/tablet_flat/ut/ut_slice_loader.cpp
+++ b/ydb/core/tablet_flat/ut/ut_slice_loader.cpp
@@ -16,6 +16,7 @@
 namespace NKikimr {
 namespace NTable {
 
+using namespace NTest;
 using TPageCollectionProtoHelper = NTabletFlatExecutor::TPageCollectionProtoHelper;
 using TCache = NTabletFlatExecutor::TPrivatePageCache::TInfo;
 
@@ -194,12 +195,12 @@ Y_UNIT_TEST_SUITE(TPartSliceLoader) {
         for (int startOff = 0; startOff < 5; startOff++) {
             for (int endOff = -5; endOff < 5; endOff++) {
                 TVector<TScreen::THole> holes;
-                holes.emplace_back(Part0()->Index->Begin()->GetRowId() + startOff, Part0()->Index.GetEndRowId() + endOff);
+                holes.emplace_back(IndexTools::GetRecord(*Part0(), 0)->GetRowId() + startOff, IndexTools::GetEndRowId(*Part0()) + endOff);
                 TIntrusiveConstPtr<TScreen> screen = new TScreen(std::move(holes));
                 auto result = RunLoaderTest(Part0(), screen);
 
                 UNIT_ASSERT_VALUES_EQUAL_C(result.Pages, 3, // index + first + last
-                    "Restoring slice [" << startOff << ", " << Part0()->Index.GetEndRowId() + endOff << "] bounds needed "
+                    "Restoring slice [" << startOff << ", " << IndexTools::GetEndRowId(*Part0()) + endOff << "] bounds needed "
                         << result.Pages << " extra pages");
             }
         }
@@ -210,22 +211,23 @@ Y_UNIT_TEST_SUITE(TPartSliceLoader) {
         {
             // Construct screen from every index page
             TVector<TScreen::THole> holes;
-            auto index = Part0()->Index->Begin();
-            while (index) {
-                if (auto next = index + 1) {
-                    holes.emplace_back(index->GetRowId(), next->GetRowId());
-                    index = next;
-                } else {
-                    holes.emplace_back(index->GetRowId(), Max<TRowId>());
-                    break;
+            TTestEnv env;
+            TPartIndexIt index(&*Part0(), &env, { });
+            Y_VERIFY(index.Seek(0) == EReady::Data);
+            while (index.IsValid()) {
+                auto from = index.GetRowId();
+                auto to = Max<TRowId>();
+                if (index.Next() == EReady::Data) {
+                    to = index.GetRowId();
                 }
+                holes.emplace_back(from, to);
             }
-            UNIT_ASSERT_C(holes.size() == Part0()->Index->Count,
+            UNIT_ASSERT_C(holes.size() == IndexTools::CountMainPages(*Part0()),
                 "Generated screen has " << holes.size() << " intervals");
             screen = new TScreen(std::move(holes));
         }
         auto result = RunLoaderTest(Part0(), screen);
-        UNIT_ASSERT_VALUES_EQUAL_C(result.Pages, 1 + Part0()->Index->End().End(), // index + all data pages
+        UNIT_ASSERT_VALUES_EQUAL_C(result.Pages, 1 + IndexTools::CountMainPages(*Part0()), // index + all data pages
             "Restoring slice bounds needed " << result.Pages << " extra pages");
     }
 
@@ -234,23 +236,25 @@ Y_UNIT_TEST_SUITE(TPartSliceLoader) {
         {
             // Construct screen from every even index page
             TVector<TScreen::THole> holes;
-            auto index = Part0()->Index->Begin();
-            while (index) {
-                if (auto next = index + 1) {
-                    holes.emplace_back(index->GetRowId(), next->GetRowId());
-                    index = next + 1;
-                } else {
-                    holes.emplace_back(index->GetRowId(), Max<TRowId>());
-                    break;
+            TTestEnv env;
+            TPartIndexIt index(&*Part0(), &env, { });
+            Y_VERIFY(index.Seek(0) == EReady::Data);
+            while (index.IsValid()) {
+                auto from = index.GetRowId();
+                auto to = Max<TRowId>();
+                if (index.Next() == EReady::Data) {
+                    to = index.GetRowId();
+                    index.Next();
                 }
+                holes.emplace_back(from, to);
             }
-            UNIT_ASSERT_C(holes.size() > 2, "Generated screen has only " << holes.size() << " intervals");
+            UNIT_ASSERT_C(holes.size() == (IndexTools::CountMainPages(*Part0()) + 1) / 2, "Generated screen has only " << holes.size() << " intervals");
             // Make sure the last page is always included
             holes.back().End = Max<TRowId>();
             screen = new TScreen(std::move(holes));
         }
         auto result = RunLoaderTest(Part0(), screen);
-        UNIT_ASSERT_VALUES_EQUAL_C(result.Pages, 1 + Part0()->Index->End().End(), // index + all data pages
+        UNIT_ASSERT_VALUES_EQUAL_C(result.Pages, 1 + IndexTools::CountMainPages(*Part0()), // index + all data pages
             "Restoring slice bounds needed " << result.Pages << " extra pages");
     }
 
@@ -259,16 +263,17 @@ Y_UNIT_TEST_SUITE(TPartSliceLoader) {
         {
             // Use every even index page, without first and last key
             TVector<TScreen::THole> holes;
-            auto index = Part0()->Index->Begin();
-            while (index) {
-                TRowId begin = index->GetRowId() + 1;
+            TTestEnv env;
+            TPartIndexIt index(&*Part0(), &env, { });
+            Y_VERIFY(index.Seek(0) == EReady::Data);
+            while (index.IsValid()) {
+                TRowId begin = index.GetRowId() + 1;
                 TRowId end;
-                if (auto next = index + 1) {
-                    end = next->GetRowId() - 1;
-                    index = next + 1;
+                if (index.Next() == EReady::Data) {
+                    end = index.GetRowId() - 1;
+                    index.Next();
                 } else {
-                    end = Part0()->Index.GetLastKeyRecord()->GetRowId();
-                    ++index;
+                    end = IndexTools::GetEndRowId(*Part0()) - 1;
                 }
                 if (begin < end) {
                     holes.emplace_back(begin, end);