dbms: VIEWs: added support for SAMPLE, FINAL, PREWHERE [#METR-13098].

dbms/include/DB/Storages/StorageMaterializedView.h

@@ -18,6 +18,10 @@ public:
 	NameAndTypePair getColumn(const String & column_name) const override;
 	bool hasColumn(const String & column_name) const override;
 
+	bool supportsSampling() const override { return data->supportsSampling(); }
+	bool supportsFinal() 	const override { return data->supportsFinal(); }
+	bool supportsPrewhere() const override { return data->supportsPrewhere(); }
+
 	BlockOutputStreamPtr write(ASTPtr query) override;
 	void drop() override;
 	bool optimize() override;

dbms/include/DB/Storages/StorageView.h

@@ -13,12 +13,16 @@ public:
 	static StoragePtr create(const String & table_name_, const String & database_name_,
 		Context & context_,	ASTPtr & query_, NamesAndTypesListPtr columns_);
 
-	virtual std::string getName() const override { return "View"; }
-	virtual std::string getTableName() const override { return table_name; }
+	std::string getName() const override { return "View"; }
+	std::string getTableName() const override { return table_name; }
 	const NamesAndTypesList & getColumnsList() const override { return *columns; }
 	DB::ASTPtr getInnerQuery() const { return inner_query.clone(); };
 
-	virtual BlockInputStreams read(
+	/// Пробрасывается внутрь запроса и решается на его уровне.
+	bool supportsSampling() const override { return true; }
+	bool supportsFinal() 	const override { return true; }
+
+	BlockInputStreams read(
 		const Names & column_names,
 		ASTPtr query,
 		const Settings & settings,
@@ -26,7 +30,7 @@ public:
 		size_t max_block_size = DEFAULT_BLOCK_SIZE,
 		unsigned threads = 1) override;
 
-	virtual void drop() override;
+	void drop() override;
 
 protected:
 	String select_database_name;

dbms/src/Storages/StorageView.cpp

@@ -61,8 +61,20 @@ BlockInputStreams StorageView::read(
 	size_t max_block_size,
 	unsigned threads)
 {
+	ASTPtr inner_query_clone = getInnerQuery();
+	ASTSelectQuery & inner_select = static_cast<ASTSelectQuery &>(*inner_query_clone);
+	const ASTSelectQuery & outer_select = typeid_cast<const ASTSelectQuery &>(*query);
+
+	/// Пробрасываем внутрь SAMPLE и FINAL, если они есть во внешнем запросе и их нет во внутреннем.
+
+	if (outer_select.sample_size && !inner_select.sample_size)
+		inner_select.sample_size = outer_select.sample_size;
+
+	if (outer_select.final && !inner_select.final)
+		inner_select.final = outer_select.final;
+
 	return BlockInputStreams(1,
-		InterpreterSelectQuery(getInnerQuery(), context, column_names).execute());
+		InterpreterSelectQuery(inner_query_clone, context, column_names).execute());
 }