KIKIMR-19139 Interface

ydb/core/tablet_flat/flat_part_charge.h

@@ -185,7 +185,7 @@ namespace NTable {
 
             // Note: as we may have cut index key we may both need prev and next pages
 
-            if (auto prev = found; --prev) {
+            if (auto prev = found; prev.Off() && --prev) {
                 TRowId pageBegin = prev->GetRowId();
                 TRowId pageEnd = found ? found->GetRowId() : Index.GetEndRowId();
                 if (pageBegin < endRowId && beginRowId < pageEnd) {

ydb/core/tablet_flat/flat_part_index_iter.h

@@ -0,0 +1,128 @@
+#pragma once
+
+#include "flat_part_iface.h"
+#include "flat_page_index.h"
+#include "flat_table_part.h"
+
+
+namespace NKikimr::NTable {
+
+class TPartIndexIt {
+public:
+    using TCells = NPage::TCells;
+    using TRecord = NPage::TIndex::TRecord;
+    using TIndex = NPage::TIndex;
+    using TIter = NPage::TIndex::TIter;
+    using TGroupId = NPage::TGroupId;
+
+    TPartIndexIt(const TPart* part, TGroupId groupId)
+        : Part(part)
+        , GroupId(groupId)
+        , EndRowId(part->GetGroupIndex(groupId).GetEndRowId())
+    { }
+
+    EReady Seek(TRowId rowId, bool restart = false) {
+        auto index = TryGetIndex();
+        if (!index) {
+            return EReady::Page;
+        }
+
+        Iter = index->LookupRow(rowId, restart ? TIter() : Iter);
+        return DataOrGone();
+    }
+
+    EReady Seek(TCells key, ESeek seek, const TPartScheme::TGroupInfo &scheme, const TKeyCellDefaults *keyDefaults) {
+        auto index = TryGetIndex();
+        if (!index) {
+            return EReady::Page;
+        }
+
+        Iter = index->LookupKey(key, scheme, seek, keyDefaults);
+        return DataOrGone();
+    }
+
+    EReady SeekReverse(TCells key, ESeek seek, const TPartScheme::TGroupInfo &scheme, const TKeyCellDefaults *keyDefaults) {
+        auto index = TryGetIndex();
+        if (!index) {
+            return EReady::Page;
+        }
+
+        Iter = index->LookupKeyReverse(key, scheme, seek, keyDefaults);
+        return DataOrGone();
+    }
+
+    EReady Next() {
+        auto index = TryGetIndex();
+        if (!index) {
+            return EReady::Page;
+        }
+        Iter++;
+        return DataOrGone();
+    }
+
+    EReady Prev() {
+        auto index = TryGetIndex();
+        if (!index) {
+            return EReady::Page;
+        }
+        if (Iter.Off() == 0) {
+            return EReady::Gone;
+        }
+        Iter--;
+        return DataOrGone();
+    }
+
+    bool IsValid() {
+        return bool(Iter);
+    }
+
+public:
+    TRowId GetEndRowId() {
+        return EndRowId;
+    }
+
+    TPageId GetPageId() {
+        Y_VERIFY(Index);
+        return Iter->GetPageId();
+    }
+
+    TRowId GetRowId() {
+        Y_VERIFY(Index);
+        return Iter->GetRowId();
+    }
+
+    TRowId GetNextRowId() {
+        Y_VERIFY(Index);
+        auto next = Iter + 1;
+        return next
+            ? next->GetRowId()
+            : Max<TRowId>();
+    }
+    const TRecord * GetRecord() {
+        Y_VERIFY(Index);
+        return Iter.GetRecord();
+    }
+
+private:
+    EReady DataOrGone() {
+        return Iter ? EReady::Data : EReady::Gone;
+    }
+
+    TIndex* TryGetIndex() {
+        if (Index) {
+            return &*Index;
+        }
+        // TODO: get index from Env
+        Index = Part->GetGroupIndex(GroupId);
+        return &*Index;
+    }
+
+private:
+    const TPart* const Part;
+    const TGroupId GroupId;
+    std::optional<TIndex> Index;
+    TIter Iter;
+    TRowId EndRowId;
+};
+
+}