Fix rowid 1 vs 0 indexing offset problem (by using a custom Id column with 0 indexing), switch child-class-providing-entry-specific-impls to a if constexpr() based template approach

2 files changed, 311 insertions, 398 deletions

diff --git a/core/src/Model/TransactionsModel.cpp b/core/src/Model/TransactionsModel.cpp
index 3df7990..7d53f89 100644
--- a/core/src/Model/TransactionsModel.cpp
+++ b/core/src/Model/TransactionsModel.cpp
@@ -11,7 +11,7 @@ SalesTable::SalesTable(TransactionModel& db)
 	// language=SQLite
 	: GetRowCount(db.GetSQLite(), "SELECT Count(*) FROM Sales")
 	// language=SQLite
-	, GetRows(db.GetSQLite(), "SELECT * FROM Sales WHERE Id >= ? AND Id < ?")
+	, GetRows(db.GetSQLite(), "SELECT * FROM Sales LIMIT ? OFFSET ?")
 	// language=SQLite
 	, GetItems(db.GetSQLite(), "SELECT * FROM SalesItems WHERE SaleId == ?")
 {
@@ -21,7 +21,7 @@ PurchasesTable::PurchasesTable(TransactionModel& db)
 	// language=SQLite
 	: GetRowCount(db.GetSQLite(), "SELECT Count(*) FROM Purchases")
 	// language=SQLite
-	, GetRows(db.GetSQLite(), "SELECT * FROM Purchases WHERE Id >= ? AND Id < ?")
+	, GetRows(db.GetSQLite(), "SELECT * FROM Purchases LIMIT ? OFFSET ?")
 	// language=SQLite
 	, GetItems(db.GetSQLite(), "SELECT * FROM PurchasesItems WHERE PurchaseId == ?")
 {
diff --git a/core/src/UI/UI_DatabaseView.cpp b/core/src/UI/UI_DatabaseView.cpp
index b9d9d81..bc65080 100644
--- a/core/src/UI/UI_DatabaseView.cpp
+++ b/core/src/UI/UI_DatabaseView.cpp
@@ -19,17 +19,24 @@
 namespace {
 
 // TODO move to Settings
-constexpr int kMaxEntriesPerPage = 20;
+constexpr int kMaxEntriesPerPage = 32;
 constexpr int kSummaryItemCount = 3;
 constexpr int kSummaryMaxLength = 25;
 
+std::pair<int, int> SplitEntryIndex(int entryIdx)
+{
+	int page = entryIdx / kMaxEntriesPerPage;
+	int row = entryIdx % kMaxEntriesPerPage;
+	return { page, row };
+}
+
 enum class DeliveryDirection
 {
 	FactoryToWarehouse,
 	WarehouseToCustomer,
 };
 
-struct ItemEntry
+struct Item
 {
 	int ItemId;
 	int Count;
@@ -37,7 +44,7 @@ struct ItemEntry
 
 struct DeliveryEntry
 {
-	std::vector<ItemEntry> Items;
+	std::vector<Item> Items;
 	std::string ItemsSummary;
 	std::string ShipmentTime;
 	std::string ArriveTime;
@@ -52,55 +59,93 @@ struct DeliveryEntry
 	}
 };
 
+struct SaleEntry
+{
+	static constexpr auto kType = DeliveryDirection::WarehouseToCustomer;
+
+	std::vector<DeliveryEntry> AssociatedDeliveries;
+	std::vector<Item> Items;
+	std::string ItemsSummary;
+	std::string Customer;
+	std::string Deadline;
+	std::string DeliveryTime;
+	int Id;
+	bool DeliveriesCached = false;
+};
+
+struct PurchaseEntry
+{
+	static constexpr auto kType = DeliveryDirection::FactoryToWarehouse;
+
+	std::vector<DeliveryEntry> AssociatedDeliveries;
+	std::vector<Item> Items;
+	std::string ItemsSummary;
+	std::string Factory;
+	std::string OrderTime;
+	std::string DeliveryTime;
+	int Id;
+	bool DeliveriesCached;
+};
+
+template <class T>
 class GenericTableView
 {
+public:
+	// clang-format off
+	static constexpr bool kHasItems = requires(T t)
+	{
+		t.Items;
+		t.ItemsSummary;
+	};
+	static constexpr bool kHasCustomer = requires(T t) { t.Customer; };
+	static constexpr bool kHasDeadline = requires(T t) { t.Deadline; };
+	static constexpr bool kHasFactory = requires(T t) { t.Factory; };
+	static constexpr bool kHasOrderTime = requires(T t) { t.OrderTime; };
+	static constexpr bool kHasCompletionTime = requires(T t) { t.DeliveryTime; };
+	static constexpr int kColumnCount = kHasItems + kHasCustomer + kHasDeadline + kHasFactory + kHasOrderTime + kHasCompletionTime;
+	// clang-format on
+
+	using Page = std::vector<T>;
+
+	struct QueryStatements
+	{
+		SQLite::Statement* GetRowCount;
+		SQLite::Statement* GetRows;
+		SQLite::Statement* GetItems;
+		SQLite::Statement* FilterRows;
+	} Statements;
+
 protected:
 	// Translation entries for implementer to fill out
 	const char* mEditDialogTitle;
 
-	SQLite::Statement* mGetRowCountStatement;
-	SQLite::Statement* mGetRowsStatement;
-	SQLite::Statement* mFilterRowsStatement;
-
 	Project* mProject;
+	Page* mCurrentPage = nullptr;
 
 	/// Current active filter object, or \c nullptr.
 	std::unique_ptr<TableRowsFilter> mActiveFilter;
 
-	/// Inclusive.
-	/// \see mLastCachedRowId
-	int64_t mFirstCachedRowId;
-	/// Inclusive.
-	/// \see mFirstCachedRowId
-	int64_t mLastCachedRowId;
+	tsl::robin_map<int, Page> mPages;
 
-	/// A vector of row ids of entries (in \c mEntries) that are visible under the current filter. To use these indices, the elements should be mapped to
-	/// index of the list of entries by adding \c mFirstCachedRowId.
-	/// The list of entries is a cached, contiguous (row id of each entry is monotonically increasing, but not necessarily starts at 0) list
-	/// of ready-to-be-presented entries, held by the implementer.
+	/// A vector of entry indices (in \c mEntries) that are visible under the current filter.
 	std::vector<int> mActiveEntries;
 
 	/// Number of rows in the table.
 	int mRowCount;
 	/// Last possible page for the current set table and filter (inclusive).
 	int mLastPage;
+
 	/// The current page the user is on.
-	int mCurrentPage;
+	int mCurrentPageNumber;
 
-	int mSelectedEntryRowId;
+	/// Row index of the select entry
+	int mSelectRow;
 
 public:
-	static int CalcPageForRowId(int64_t rowId)
+	/// Calculate the first visible row's entry index.
+	int GetFirstVisibleRowIdx() const
 	{
-		return rowId / kMaxEntriesPerPage;
-	}
-
-	/// Calculate range [begin, end) of index for the list of entries that are currently visible that the path-th page would show.
-	/// i.e. when there is a filter, look into \c mActiveEntryIndices; when there is no filter, use directly.
-	static std::pair<int64_t, int64_t> CalcRangeForPage(int page)
-	{
-		int begin = page * kMaxEntriesPerPage;
-		return { begin, begin + kMaxEntriesPerPage };
+		return mCurrentPageNumber * kMaxEntriesPerPage;
 	}
 
 	Project* GetProject() const
@@ -108,27 +153,27 @@ public:
 		return mProject;
 	}
 
-	virtual void OnProjectChanged(Project* newProject)
+	void OnProjectChanged(Project* newProject)
 	{
 		mProject = newProject;
 
-		if (mGetRowCountStatement->executeStep()) {
-			mRowCount = mGetRowCountStatement->getColumn(0).getInt();
+		auto& stmt = *Statements.GetRowCount;
+		if (stmt.executeStep()) {
+			mRowCount = stmt.getColumn(0).getInt();
 		} else {
 			std::cerr << "Failed to fetch row count from SQLite.\n";
 			mRowCount = 0;
 		}
 
-		mFirstCachedRowId = 0;
-		mLastCachedRowId = 0;
-
-		ClearEntries();
+		mActiveFilter = nullptr;
 		mActiveEntries.clear();
 
+		mPages.clear();
+		mCurrentPage = nullptr;
 		UpdateLastPage();
 		SetPage(0);
 
-		mSelectedEntryRowId = -1;
+		mSelectRow = -1;
 	}
 
 	TableRowsFilter* GetFilter() const
@@ -136,9 +181,9 @@ public:
 		return mActiveFilter.get();
 	}
 
-	virtual void OnFilterChanged()
+	void OnFilterChanged()
 	{
-		auto& stmt = *mFilterRowsStatement;
+		auto& stmt = *Statements.FilterRows;
 		// clang-format off
 		DEFER { stmt.reset(); };
 		// clang-format on
@@ -153,7 +198,7 @@ public:
 		UpdateLastPage();
 		SetPage(0);
 
-		mSelectedEntryRowId = -1;
+		mSelectRow = -1;
 	}
 
 	void OnFilterChanged(std::unique_ptr<TableRowsFilter> filter)
@@ -162,32 +207,32 @@ public:
 		OnFilterChanged();
 	}
 
-	void Draw()
+	void Display()
 	{
 		bool dummy = true;
 		auto ls = LocaleStrings::Instance.get();
 
-		if (ImGui::Button(ICON_FA_ARROW_LEFT, mCurrentPage == 0)) {
-			mSelectedEntryRowId = -1;
-			SetPage(mCurrentPage - 1);
+		if (ImGui::Button(ICON_FA_ARROW_LEFT, mCurrentPageNumber == 0)) {
+			SetPage(mCurrentPageNumber - 1);
 		}
 
 		ImGui::SameLine();
 		// +1 to convert from 0-based indices to 1-based, for human legibility
-		ImGui::Text("%d/%d", mCurrentPage + 1, mLastPage + 1);
+		ImGui::Text("%d/%d", mCurrentPageNumber + 1, mLastPage + 1);
 
 		ImGui::SameLine();
-		if (ImGui::Button(ICON_FA_ARROW_RIGHT, mCurrentPage == mLastPage)) {
-			mSelectedEntryRowId = -1;
-			SetPage(mCurrentPage + 1);
+		if (ImGui::Button(ICON_FA_ARROW_RIGHT, mCurrentPageNumber == mLastPage)) {
+			SetPage(mCurrentPageNumber + 1);
 		}
 
 		ImGui::SameLine();
-		if (ImGui::Button(ls->Edit.Get(), mSelectedEntryRowId == -1)) {
+		if (ImGui::Button(ls->Edit.Get(), mSelectRow == -1)) {
 			ImGui::OpenPopup(mEditDialogTitle);
 		}
 		if (ImGui::BeginPopupModal(mEditDialogTitle, &dummy, ImGuiWindowFlags_AlwaysAutoResize)) {
-			EditEntry(mSelectedEntryRowId);
+			auto& entry = (*mCurrentPage)[mSelectRow];
+			int entryIdx = GetFirstVisibleRowIdx() + mSelectRow;
+			EditEntry(entry, entryIdx, mSelectRow);
 			ImGui::EndPopup();
 		}
 
@@ -197,42 +242,74 @@ public:
 		}
 
 		ImGui::SameLine();
-		if (ImGui::Button(ls->Delete.Get(), mSelectedEntryRowId == -1)) {
+		if (ImGui::Button(ls->Delete.Get(), mSelectRow == -1)) {
 			// TODO
 		}
 
 		ImGui::Columns(2);
 		{
-			DrawMainTable();
+			DisplayMainTable();
 			ImGui::NextColumn();
 
-			if (mSelectedEntryRowId == -1) {
+			if (mSelectRow == -1) {
 				ImGui::TextWrapped("%s", ls->SelectOrderToShowAssociatedDeliveries.Get());
 			} else {
-				DrawDeliveriesTable();
+				DisplayDeliveriesTable();
 			}
 			ImGui::NextColumn();
 		}
 		ImGui::Columns(1);
 	}
 
-	void DrawMainTable()
+	void SetPage(int page)
 	{
-		if (ImGui::BeginTable("DataTable", GetTableColumnCount(), ImGuiTableFlags_Borders | ImGuiTableFlags_ScrollX)) {
-			SetupTableColumns();
+		mCurrentPageNumber = page;
+		mCurrentPage = &LoadAndGetPage(page);
+		mSelectRow = -1;
+	}
+
+private:
+	static int CalcPageForRowId(int64_t entryIdx)
+	{
+		return entryIdx / kMaxEntriesPerPage;
+	}
+
+	/// Calculate range [begin, end) of index for the list of entries that are currently visible that the path-th page would show.
+	/// i.e. when there is a filter, look into \c mActiveEntryIndices; when there is no filter, use directly.
+	static std::pair<int64_t, int64_t> CalcRangeForPage(int page)
+	{
+		int begin = page * kMaxEntriesPerPage;
+		return { begin, begin + kMaxEntriesPerPage };
+	}
+
+	void DisplayMainTable()
+	{
+		auto ls = LocaleStrings::Instance.get();
+		if (ImGui::BeginTable("DataTable", kColumnCount, ImGuiTableFlags_Borders | ImGuiTableFlags_ScrollX)) {
+
+			if constexpr (kHasCustomer) ImGui::TableSetupColumn(ls->DatabaseCustomerColumn.Get());
+			if constexpr (kHasDeadline) ImGui::TableSetupColumn(ls->DatabaseDeadlineColumn.Get());
+			if constexpr (kHasFactory) ImGui::TableSetupColumn(ls->DatabaseFactoryColumn.Get());
+			if constexpr (kHasOrderTime) ImGui::TableSetupColumn(ls->DatabaseOrderTimeColumn.Get());
+			if constexpr (kHasCompletionTime) ImGui::TableSetupColumn(ls->DatabaseCompletionTimeColumn.Get());
+			if constexpr (kHasItems) ImGui::TableSetupColumn(ls->DatabaseItemsColumn.Get());
 			ImGui::TableHeadersRow();
 
-			auto [begin, end] = CalcRangeForPage(mCurrentPage);
 			if (mActiveFilter) {
+				// TODO
+				auto [begin, end] = CalcRangeForPage(mCurrentPageNumber);
 				end = std::min(end, (int64_t)mActiveEntries.size() - 1);
 				for (int i = begin; i < end; ++i) {
-					int rowId = mActiveEntries[i];
-					DisplayEntry(rowId);
+					int rowIdx = mActiveEntries[i];
+					DisplayEntry(rowIdx);
 				}
 			} else {
-				end = std::min(end, mLastCachedRowId);
-				for (int rowId = begin; rowId < end; ++rowId) {
-					DisplayEntry(rowId);
+				int firstRowIdx = mCurrentPageNumber * kMaxEntriesPerPage;
+				auto& page = *mCurrentPage;
+
+				int end = std::min((int)page.size(), kMaxEntriesPerPage);
+				for (int i = 0; i < end; ++i) {
+					DisplayEntry(page[i], i, firstRowIdx + i);
 				}
 			}
 
@@ -240,7 +317,71 @@ public:
 		}
 	}
 
-	void DrawDeliveriesTable()
+	void DisplayEntry(int rowIdx)
+	{
+		// TODO
+		// auto [pageNumber, pageEntry] = SplitRowIndex(rowIdx);
+		// auto& entry = LoadAndGetPage(pageNumber)[pageEntry];
+		// DisplayEntry(entry, rowIdx);
+	}
+
+	void DisplayEntry(T& entry, int rowIdx, int entryIdx)
+	{
+		auto ls = LocaleStrings::Instance.get();
+
+		ImGui::PushID(rowIdx);
+		ImGui::TableNextRow();
+
+		if constexpr (kHasCustomer) {
+			ImGui::TableNextColumn();
+			if (ImGui::Selectable(entry.Customer.c_str(), mSelectRow == rowIdx, ImGuiSelectableFlags_SpanAllColumns)) {
+				mSelectRow = rowIdx;
+			}
+		}
+
+		if constexpr (kHasDeadline) {
+			ImGui::TableNextColumn();
+			ImGui::TextUnformatted(entry.Deadline.c_str());
+		}
+
+		if constexpr (kHasFactory) {
+			ImGui::TableNextColumn();
+			if (ImGui::Selectable(entry.Factory.c_str(), mSelectRow == rowIdx, ImGuiSelectableFlags_SpanAllColumns)) {
+				mSelectRow = rowIdx;
+			}
+		}
+
+		if constexpr (kHasOrderTime) {
+			ImGui::TableNextColumn();
+			ImGui::TextUnformatted(entry.OrderTime.c_str());
+		}
+
+		if constexpr (kHasCompletionTime) {
+			ImGui::TableNextColumn();
+			if (entry.DeliveryTime.empty()) {
+				ImGui::TextUnformatted(ls->NotDelivered.Get());
+			} else {
+				ImGui::TextUnformatted(entry.DeliveryTime.c_str());
+			}
+		}
+
+		if constexpr (kHasItems) {
+			ImGui::TableNextColumn();
+			if (ImGui::TreeNode(entry.ItemsSummary.c_str())) {
+				DrawItems(entry.Items);
+				ImGui::TreePop();
+			}
+		}
+
+		ImGui::PopID();
+	}
+
+	void EditEntry(T& entry, int rowIdx, int entryIdx)
+	{
+		// TODO
+	}
+
+	void DisplayDeliveriesTable()
 	{
 		auto ls = LocaleStrings::Instance.get();
 		if (ImGui::BeginTable("DeliveriesTable", 3, ImGuiTableFlags_Borders | ImGuiTableFlags_ScrollX)) {
@@ -250,7 +391,8 @@ public:
 			ImGui::TableSetupColumn(ls->DatabaseItemsColumn.Get());
 			ImGui::TableHeadersRow();
 
-			auto& deliveries = GetEntryAssociatedDeliveries(mSelectedEntryRowId);
+			auto& entry = (*mCurrentPage)[mSelectRow];
+			auto& deliveries = entry.AssociatedDeliveries;
 			for (auto& delivery : deliveries) {
 				ImGui::TableNextRow();
 
@@ -271,35 +413,19 @@ public:
 		}
 	}
 
-	void SetPage(int page)
-	{
-		mCurrentPage = page;
-		EnsureCacheCoversPage(page);
-	}
-
-	int RowIdToIndex(int64_t rowId) const
-	{
-		return rowId - mFirstCachedRowId;
-	}
-
-	int64_t IndexToRowId(int index) const
-	{
-		return index + mFirstCachedRowId;
-	}
-
-	std::vector<ItemEntry> LoadItems(SQLite::Statement& stmt, int64_t rowId)
+	std::vector<Item> LoadItems(SQLite::Statement& stmt, int64_t id)
 	{
 		// clang-format off
 		DEFER { stmt.reset(); };
 		// clang-format on
 
-		stmt.bind(1, rowId);
+		stmt.bind(1, id);
 
-		std::vector<ItemEntry> entries;
+		std::vector<Item> entries;
 		int itemIdCol = stmt.getColumnIndex("ItemId");
 		int countCol = stmt.getColumnIndex("Count");
 		while (stmt.executeStep()) {
-			entries.push_back(ItemEntry{
+			entries.push_back(Item{
 				.ItemId = stmt.getColumn(itemIdCol).getInt(),
 				.Count = stmt.getColumn(countCol).getInt(),
 			});
@@ -308,7 +434,7 @@ public:
 		return entries;
 	}
 
-	std::string CreateItemsSummary(const std::vector<ItemEntry>& items)
+	std::string CreateItemsSummary(const std::vector<Item>& items)
 	{
 		if (items.empty()) {
 			return "<empty>";
@@ -334,7 +460,7 @@ public:
 		return result;
 	}
 
-	std::vector<DeliveryEntry> LoadDeliveriesEntries(int64_t orderRowId, DeliveryDirection type)
+	std::vector<DeliveryEntry> LoadDeliveriesEntries(int64_t orderId, DeliveryDirection type)
 	{
 		bool outgoingFlag;
 		switch (type) {
@@ -347,7 +473,7 @@ public:
 		DEFER { stmt.reset(); };
 		// clang-format on
 
-		stmt.bind(1, orderRowId);
+		stmt.bind(1, orderId);
 		stmt.bind(2, outgoingFlag);
 
 		std::vector<DeliveryEntry> entries;
@@ -372,94 +498,96 @@ public:
 		return entries;
 	}
 
-protected:
-	virtual int GetTableColumnCount() const = 0;
-	virtual void SetupTableColumns() = 0;
+	Page& LoadAndGetPage(int page)
+	{
+		auto iter = mPages.find(page);
+		if (iter != mPages.end()) {
+			return iter.value();
+		}
 
-	virtual const std::vector<DeliveryEntry>& GetEntryAssociatedDeliveries(int rowId) = 0;
-	virtual void DisplayEntry(int rowId) = 0;
-	virtual void EditEntry(int rowId) = 0;
+		auto& stmt = *Statements.GetRows;
+		// clang-format off
+		DEFER { stmt.reset(); };
+		// clang-format on
 
-	virtual void ClearEntries() = 0;
+		stmt.bind(1, kMaxEntriesPerPage);
+		stmt.bind(2, page * kMaxEntriesPerPage);
 
-	void DrawItems(const std::vector<ItemEntry>& items)
-	{
-		for (auto& item : items) {
-			auto& name = mProject->Products.Find(item.ItemId)->GetName();
-			ImGui::Text("%s × %d", name.c_str(), item.Count);
-		}
-	}
+		// If a field flag is false, the column index won't be used (controlled by other if constexpr's downstream)
+		// so there is no UB here
 
-	void EnsureCacheCoversPage(int page)
-	{
-		auto [begin, end] = CalcRangeForPage(page);
-		EnsureCacheCovers(begin, end - 1);
-	}
+		// This column is always necessary (and present) because the deliveries table require it
+		int idCol = stmt.getColumnIndex("Id");
 
-	void EnsureCacheCovers(int64_t firstRow, int64_t lastRow)
-	{
-		if (firstRow > lastRow) {
-			std::swap(firstRow, lastRow);
-		}
+		int customerCol;
+		if constexpr (kHasCustomer) customerCol = stmt.getColumnIndex("Customer");
 
-		int newFirst = mFirstCachedRowId;
-		int newLast = mLastCachedRowId;
+		int deadlineCol;
+		if constexpr (kHasDeadline) deadlineCol = stmt.getColumnIndex("Deadline");
 
-		bool doRebuild = false;
-		if (firstRow < mFirstCachedRowId) {
-			newFirst = (CalcPageForRowId(firstRow) + 1) * kMaxEntriesPerPage;
-			doRebuild = true;
-		}
-		if (lastRow > mLastCachedRowId) {
-			newLast = (CalcPageForRowId(lastRow) + 1) * kMaxEntriesPerPage;
-			doRebuild = true;
-		}
-		if (!doRebuild) return;
+		int factoryCol;
+		if constexpr (kHasFactory) factoryCol = stmt.getColumnIndex("Factory");
 
-		EnsureCacheCoversImpl(newFirst, newLast);
-	}
+		int orderTimeCol;
+		if constexpr (kHasOrderTime) orderTimeCol = stmt.getColumnIndex("OrderTime");
 
-	/// To be implemented by child classes, presumable calling LoadRange() to get the front and back new contents.
-	/// \param newFirst The first rowid the new cache should cover
-	/// \param newLast The last rowid the new cache should cover
-	virtual void EnsureCacheCoversImpl(int newFirst, int newLast) = 0;
+		int deliveryTimeCol;
+		if constexpr (kHasCompletionTime) deliveryTimeCol = stmt.getColumnIndex("DeliveryTime");
 
-	template <class TEntry, class TCollector>
-	void LoadExtraEntries(std::vector<TEntry>& entries, int newFirst, int newLast, TCollector&& collector)
-	{
-		auto front = LoadRange<TEntry>(newFirst, mFirstCachedRowId, collector);
-		auto back = LoadRange<TEntry>(mLastCachedRowId + 1, newLast + 1, collector);
+		Page entries;
+		while (stmt.executeStep()) {
+			auto& entry = entries.emplace_back();
 
-		mFirstCachedRowId -= front.size();
-		mLastCachedRowId += back.size();
+			auto id = stmt.getColumn(idCol).getInt64();
+			entry.AssociatedDeliveries = LoadDeliveriesEntries(id, T::kType);
 
-		entries.insert(entries.begin(), std::make_move_iterator(front.begin()), std::make_move_iterator(front.end()));
-		entries.insert(entries.end(), std::make_move_iterator(back.begin()), std::make_move_iterator(back.end()));
-	}
+			if constexpr (kHasItems) {
+				auto items = LoadItems(
+					*Statements.GetItems,
+					id);
+				auto itemsSummary = CreateItemsSummary(items);
+				entry.Items = std::move(items);
+				entry.ItemsSummary = std::move(itemsSummary);
+			}
 
-	template <class TEntry, class TCollector>
-	std::vector<TEntry> LoadRange(int64_t begin, int64_t end, TCollector&& collector)
-	{
-		std::vector<TEntry> result;
+			if constexpr (kHasCustomer) {
+				auto customerId = stmt.getColumn(customerCol).getInt();
+				entry.Customer = mProject->Customers.Find(customerId)->GetName();
+			}
 
-		size_t size = end - begin;
-		if (size == 0) {
-			return result;
-		}
+			if constexpr (kHasDeadline) {
+				auto timeStamp = stmt.getColumn(deadlineCol).getInt64();
+				entry.Deadline = StringifyTimeStamp(timeStamp);
+			}
 
-		result.reserve(size);
+			if constexpr (kHasFactory) {
+				auto factoryId = stmt.getColumn(factoryCol).getInt();
+				entry.Factory = mProject->Factories.Find(factoryId)->GetName();
+			}
 
-		// clang-format off
-		DEFER { mGetRowsStatement->reset(); };
-		// clang-format on
-		mGetRowsStatement->bind(1, begin);
-		mGetRowsStatement->bind(2, end);
+			if constexpr (kHasOrderTime) {
+				auto timeStamp = stmt.getColumn(orderTimeCol).getInt64();
+				entry.OrderTime = StringifyTimeStamp(timeStamp);
+			}
 
-		collector(result);
-		return result;
+			if constexpr (kHasCompletionTime) {
+				auto timeStamp = stmt.getColumn(deliveryTimeCol).getInt64();
+				entry.DeliveryTime = StringifyTimeStamp(timeStamp);
+			}
+		}
+
+		auto [res, _] = mPages.try_emplace(page, std::move(entries));
+		return res.value();
+	}
+
+	void DrawItems(const std::vector<Item>& items)
+	{
+		for (auto& item : items) {
+			auto& name = mProject->Products.Find(item.ItemId)->GetName();
+			ImGui::Text("%s × %d", name.c_str(), item.Count);
+		}
 	}
 
-private:
 	void UpdateLastPage()
 	{
 		mLastPage = mActiveEntries.empty()
@@ -468,23 +596,8 @@ private:
 	}
 };
 
-struct SaleEntry
+class SalesTableView : public GenericTableView<SaleEntry>
 {
-	std::vector<DeliveryEntry> AssociatedDeliveries;
-	std::vector<ItemEntry> Items;
-	std::string ItemsSummary;
-	std::string Customer;
-	std::string Deadline;
-	std::string DeliveryTime;
-	bool DeliveriesCached = false;
-};
-
-class SalesTableView : public GenericTableView
-{
-private:
-	/// A cached, contiguous (row id of each entry is monotonically increasing, but not necessarily starts at 0) list ready-to-be-presented entries. May be incomplete.
-	std::vector<SaleEntry> mEntries;
-
 public:
 	SalesTableView()
 	{
@@ -492,129 +605,24 @@ public:
 		mEditDialogTitle = ls->EditSaleEntryDialogTitle.Get();
 	}
 
-	virtual void OnProjectChanged(Project* newProject) override
-	{
-		auto& sales = newProject->GetTransactionsModel().GetSales();
-		mGetRowCountStatement = &sales.GetRowCount;
-		mGetRowsStatement = &sales.GetRows;
-		//		mFilterRowsStatement = &sales.FilterRows;
-
-		GenericTableView::OnProjectChanged(newProject);
-	}
-
-protected:
-	virtual int GetTableColumnCount() const override
-	{
-		return 4;
-	}
-
-	virtual void SetupTableColumns() override
-	{
-		auto ls = LocaleStrings::Instance.get();
-		ImGui::TableSetupColumn(ls->DatabaseCustomerColumn.Get());
-		ImGui::TableSetupColumn(ls->DatabaseDeadlineColumn.Get());
-		ImGui::TableSetupColumn(ls->DatabaseCompletionTimeColumn.Get());
-		ImGui::TableSetupColumn(ls->DatabaseItemsColumn.Get());
-	}
-
-	virtual const std::vector<DeliveryEntry>& GetEntryAssociatedDeliveries(int rowId) override
-	{
-		auto& entry = mEntries[RowIdToIndex(rowId)];
-		if (!entry.DeliveriesCached) {
-			entry.AssociatedDeliveries = LoadDeliveriesEntries(rowId, DeliveryDirection::FactoryToWarehouse);
-			entry.DeliveriesCached = true;
-		}
-		return entry.AssociatedDeliveries;
-	}
-
-	virtual void DisplayEntry(int rowId) override
-	{
-		auto& entry = mEntries[RowIdToIndex(rowId)];
-		auto ls = LocaleStrings::Instance.get();
-
-		ImGui::PushID(rowId);
-		ImGui::TableNextRow();
-
-		ImGui::TableNextColumn();
-		if (ImGui::Selectable(entry.Customer.c_str(), mSelectedEntryRowId == rowId, ImGuiSelectableFlags_SpanAllColumns)) {
-			mSelectedEntryRowId = rowId;
-		}
-
-		ImGui::TableNextColumn();
-		ImGui::TextUnformatted(entry.Deadline.c_str());
-
-		ImGui::TableNextColumn();
-		if (entry.DeliveryTime.empty()) {
-			ImGui::TextUnformatted(ls->NotDelivered.Get());
-		} else {
-			ImGui::TextUnformatted(entry.DeliveryTime.c_str());
-		}
-
-		ImGui::TableNextColumn();
-		if (ImGui::TreeNode(entry.ItemsSummary.c_str())) {
-			DrawItems(entry.Items);
-			ImGui::TreePop();
-		}
-
-		ImGui::PopID();
-	}
-
-	virtual void EditEntry(int rowId) override
+#pragma clang diagnostic push
+#pragma ide diagnostic ignored "HidingNonVirtualFunction"
+	void OnProjectChanged(Project* newProject)
 	{
+		auto& table = newProject->GetTransactionsModel().GetSales();
+		Statements.GetRowCount = &table.GetRowCount;
+		Statements.GetRows = &table.GetRows;
+		Statements.GetItems = &table.GetItems;
 		// TODO
-	}
+		// stmts.FilterRowsStatement = ;
 
-	virtual void ClearEntries() override
-	{
-		mEntries.clear();
+		GenericTableView<SaleEntry>::OnProjectChanged(newProject);
 	}
-
-	virtual void EnsureCacheCoversImpl(int newFirst, int newLast) override
-	{
-		auto CollectRows = [&](std::vector<SaleEntry>& result) {
-			auto& stmt = *mGetRowsStatement;
-			int rowIdCol = stmt.getColumnIndex("Id");
-			int customerCol = stmt.getColumnIndex("Customer");
-			int deadlineCol = stmt.getColumnIndex("Deadline");
-			int deliveryTimeCol = stmt.getColumnIndex("DeliveryTime");
-
-			while (stmt.executeStep()) {
-				auto customerId = stmt.getColumn(customerCol).getInt();
-				auto items = LoadItems(
-					mProject->GetTransactionsModel().GetSales().GetItems,
-					stmt.getColumn(rowIdCol).getInt64());
-				auto itemsSummary = CreateItemsSummary(items);
-
-				result.push_back(SaleEntry{
-					.Items = std::move(items),
-					.ItemsSummary = std::move(itemsSummary),
-					.Customer = mProject->Customers.Find(customerId)->GetName(),
-					.Deadline = StringifyTimeStamp(stmt.getColumn(deadlineCol).getInt64()),
-					.DeliveryTime = StringifyTimeStamp(stmt.getColumn(deliveryTimeCol).getInt64()),
-				});
-			}
-		};
-
-		LoadExtraEntries<SaleEntry>(mEntries, newFirst, newLast, CollectRows);
-	}
-};
-
-struct PurchaseEntry
-{
-	std::vector<DeliveryEntry> AssociatedDeliveries;
-	std::vector<ItemEntry> Items;
-	std::string ItemsSummary;
-	std::string Factory;
-	std::string OrderTime;
-	std::string DeliveryTime;
-	bool DeliveriesCached;
+#pragma clang diagnostic pop
 };
 
-class PurchasesTableView : public GenericTableView
+class PurchasesTableView : public GenericTableView<PurchaseEntry>
 {
-private:
-	std::vector<PurchaseEntry> mEntries;
-
 public:
 	PurchasesTableView()
 	{
@@ -622,115 +630,20 @@ public:
 		mEditDialogTitle = ls->EditPurchaseEntryDialogTitle.Get();
 	}
 
-	virtual void OnProjectChanged(Project* newProject) override
-	{
-		auto& purchases = newProject->GetTransactionsModel().GetPurchases();
-		mGetRowCountStatement = &purchases.GetRowCount;
-		mGetRowsStatement = &purchases.GetRows;
-		//		mFilterRowsStatement = &purchases.FilterRowsStatement;
-
-		GenericTableView::OnProjectChanged(newProject);
-	}
-
-protected:
-	virtual int GetTableColumnCount() const override
-	{
-		return 4;
-	}
-
-	virtual void SetupTableColumns() override
-	{
-		auto ls = LocaleStrings::Instance.get();
-		ImGui::TableSetupColumn(ls->DatabaseFactoryColumn.Get());
-		ImGui::TableSetupColumn(ls->DatabaseOrderTimeColumn.Get());
-		ImGui::TableSetupColumn(ls->DatabaseCompletionTimeColumn.Get());
-		ImGui::TableSetupColumn(ls->DatabaseItemsColumn.Get());
-	}
-
-	virtual const std::vector<DeliveryEntry>& GetEntryAssociatedDeliveries(int rowId) override
-	{
-		auto& entry = mEntries[RowIdToIndex(rowId)];
-		if (!entry.DeliveriesCached) {
-			entry.AssociatedDeliveries = LoadDeliveriesEntries(rowId, DeliveryDirection::FactoryToWarehouse);
-			entry.DeliveriesCached = true;
-		}
-		return entry.AssociatedDeliveries;
-	}
-
-	virtual void DisplayEntry(int rowId) override
-	{
-		auto& entry = mEntries[RowIdToIndex(rowId)];
-		auto ls = LocaleStrings::Instance.get();
-
-		ImGui::PushID(rowId);
-		ImGui::TableNextRow();
-
-		ImGui::TableNextColumn();
-		if (ImGui::Selectable(entry.Factory.c_str(), mSelectedEntryRowId == rowId, ImGuiSelectableFlags_SpanAllColumns)) {
-			mSelectedEntryRowId = rowId;
-		}
-
-		ImGui::TableNextColumn();
-		if (entry.OrderTime.empty()) {
-			ImGui::TextUnformatted(ls->NotDelivered.Get());
-		} else {
-			ImGui::TextUnformatted(entry.OrderTime.c_str());
-		}
-
-		ImGui::TableNextColumn();
-		if (entry.DeliveryTime.empty()) {
-			ImGui::TextUnformatted(ls->NotDelivered.Get());
-		} else {
-			ImGui::TextUnformatted(entry.DeliveryTime.c_str());
-		}
-
-		ImGui::TableNextColumn();
-		if (ImGui::TreeNode(entry.ItemsSummary.c_str())) {
-			DrawItems(entry.Items);
-			ImGui::TreePop();
-		}
-
-		ImGui::PopID();
-	}
-
-	virtual void EditEntry(int rowId) override
+#pragma clang diagnostic push
+#pragma ide diagnostic ignored "HidingNonVirtualFunction"
+	void OnProjectChanged(Project* newProject)
 	{
+		auto& table = newProject->GetTransactionsModel().GetPurchases();
+		Statements.GetRowCount = &table.GetRowCount;
+		Statements.GetRows = &table.GetRows;
+		Statements.GetItems = &table.GetItems;
 		// TODO
-	}
-
-	virtual void ClearEntries() override
-	{
-		mEntries.clear();
-	}
-
-	virtual void EnsureCacheCoversImpl(int newFirst, int newLast) override
-	{
-		auto CollectRows = [&](std::vector<PurchaseEntry>& result) {
-			auto& stmt = *mGetRowsStatement;
-			int rowIdCol = stmt.getColumnIndex("Id");
-			int factoryCol = stmt.getColumnIndex("Factory");
-			int orderTimeCol = stmt.getColumnIndex("OrderTime");
-			int deliveryTimeCol = stmt.getColumnIndex("DeliveryTime");
-
-			while (stmt.executeStep()) {
-				auto factoryId = stmt.getColumn(factoryCol).getInt();
-				auto items = LoadItems(
-					mProject->GetTransactionsModel().GetPurchases().GetItems,
-					stmt.getColumn(rowIdCol).getInt64());
-				auto itemsSummary = CreateItemsSummary(items);
-
-				result.push_back(PurchaseEntry{
-					.Items = std::move(items),
-					.ItemsSummary = std::move(itemsSummary),
-					.Factory = mProject->Factories.Find(factoryId)->GetName(),
-					.OrderTime = StringifyTimeStamp(stmt.getColumn(orderTimeCol).getInt64()),
-					.DeliveryTime = StringifyTimeStamp(stmt.getColumn(deliveryTimeCol).getInt64()),
-				});
-			}
-		};
+		// stmts.FilterRowsStatement = ;
 
-		LoadExtraEntries<PurchaseEntry>(mEntries, newFirst, newLast, CollectRows);
+		GenericTableView<PurchaseEntry>::OnProjectChanged(newProject);
 	}
+#pragma clang diagnostic pop
 };
 } // namespace
 
@@ -751,11 +664,11 @@ void UI::DatabaseViewTab()
 
 	if (ImGui::BeginTabBar("##DatabaseViewTabs")) {
 		if (ImGui::BeginTabItem(ls->SalesViewTab.Get())) {
-			sales.Draw();
+			sales.Display();
 			ImGui::EndTabItem();
 		}
 		if (ImGui::BeginTabItem(ls->PurchasesViewTab.Get())) {
-			purchases.Draw();
+			purchases.Display();
 			ImGui::EndTabItem();
 		}
 		ImGui::EndTabBar();