row_iterator_sync have been implemented. [API-1762] (#1161)

* row_iterator_sync is added.
---------

Co-authored-by: Ali Keles <[email protected]>

Author: OzanCansel

Reference_Manual.md

@@ -149,6 +149,7 @@
          * [7.11.8 Iterators](#7118-iterators)
             * [7.11.8.1 page_iterator](#71181-page_iterator)
             * [7.11.8.2 page_iterator_sync](#71182-page_iterator)
+            * [7.11.8.3 row_iterator_sync](#71182-row_iterator)
    * [8. Development and Testing](#8-development-and-testing)
       * [8.1. Testing](#81-testing)
    * [9. Getting Help](#9-getting-help)
@@ -3690,6 +3691,8 @@ Exceptions which can be thrown by SQL API are stated at below:
 - `sql_page::sql_row::get_object(std::string)` can throw `illegal_argument` exception if the column doesn't exist.
 - `sql_result::page_iterator_sync::operator++()` can throw `no_such_element` exception if the fetch operation is timed out.
 - `sql_result::page_iterator_sync::operator*()` can throw `no_such_element` exception if the iterator points to past-end element;
+- `sql_result::row_iterator_sync::operator++()` can throw `no_such_element` exception if the fetch operation is timed out.
+- `sql_result::row_iterator_sync::operator*()` can throw `no_such_element` exception if the iterator points to past-end element;
 
 In addition, any method which returns `boost::future<T>` can throw an exception.
 Unless otherwise is stated, `sql::hazelcast_sql_exception` is thrown.
@@ -3699,6 +3702,7 @@ There are several iterators in SQL Api to satisfy different use cases. They are
 
 - `page_iterator` (Async page iterator)
 - `page_iterator_sync` (Sync page iterator)
+- `row_iterator_sync` (Sync row iterator)
 
 Reminder 1, only one type of iterator can be used. So it is suggested to choose appropriate one to fetch `SELECT` query results.
 
@@ -3741,6 +3745,36 @@ std::vector<std::shared_ptr<sql_page>> pages;
 copy(result->pbegin(), result->pend(), back_inserter(pages));
 ```
 
+#### 7.11.8.3 row_iterator_sync
+`row_iterator_sync` is the third iterator which wraps `page_iterator_sync` and allows user to iterate over rows rather than pages.
+It is similar to native C++ iterators. So it can be used with `algorithm` header.
+It supports `operator*()`, `operator->()`, `operator++()` operators. Post increment operator is marked as `delete`.
+`timeout` can be set, it is used when fetching new page. It throws `exception::no_such_element` exception if the fetch operation is timed out.
+`row_iterator_sync` is copyable but it is there only for convenience. Copy is shallow copy so copied instances should not be used simultaneously.
+This iterator is acquired by `sql_result::begin()` and `sql_result::end()`. Hence, this iterator can be used in `range-for` loop. `timeout` is defaulted to `std::chrono::milliseconds{ -1 }` which means wait forever.
+
+`range-for` loop example:
+``` C++
+auto result = client.get_sql().execute("SELECT * FROM integers").get();
+
+for (const sql_page::sql_row& row : *result) {
+    std::cout << row.get_object<int>(0);
+}
+```
+
+`algorithm` header example:
+``` C++
+auto result = client.get_sql().execute("SELECT * FROM integers").get();
+
+std::vector<int> numbers;
+
+transform(
+    begin(*result),
+    end(*result),
+    back_inserter(numbers),
+    [](const sql_page::sql_row& row) { return *row.get_object<int>(0); });
+```
+
 # 8. Development and Testing
 
 Hazelcast C++ client is developed using C++. If you want to help with bug fixes, develop new features or

examples/sql/CMakeLists.txt

@@ -19,4 +19,5 @@ add_executable(sql_cancellation_example sql_cancellation_example.cpp)
 add_executable(sql_json_example sql_json_example.cpp)
 add_executable(sql_order_by_limit_offset sql_order_by_limit_offset.cpp)
 add_executable(sql_page_iterator_sync sql_page_iterator_sync.cpp)
+add_executable(sql_row_iterator_sync sql_row_iterator_sync.cpp)
 add_executable(sql_advanced_query_options sql_advanced_query_options.cpp)

examples/sql/sql_row_iterator_sync.cpp

@@ -0,0 +1,214 @@
+
+/*
+ * Copyright (c) 2008-2023, Hazelcast, Inc. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include <algorithm>
+#include <iterator>
+
+#include <boost/algorithm/string.hpp>
+
+#include <hazelcast/client/hazelcast_client.h>
+
+using hazelcast::client::hazelcast_client;
+
+void
+populate_map(hazelcast_client&);
+void
+create_mapping(hazelcast_client&);
+void
+for_loop(hazelcast_client&);
+void
+algorithm_copy(hazelcast_client&);
+void
+algorithm_filter(hazelcast_client&);
+void
+timeout(hazelcast_client&);
+
+/**
+ * Normally, cpp-client provides an async api for every features.
+ * But for sake of convenience and similar usages with native C++ iterators
+ * cpp-client provides sync row iterator. So `row_iterator_sync` is a blocking
+ * iterator. It wraps the `page_iterator_sync`.
+ * This example demonstrates how to use `row_iterator_sync` and what
+ * the use cases are.
+ */
+int
+main()
+{
+    auto hz = hazelcast::new_client().get();
+
+    // Preparation
+    populate_map(hz);
+    create_mapping(hz);
+
+    // Use cases, examples
+    for_loop(hz);
+    algorithm_copy(hz);
+    algorithm_filter(hz);
+    timeout(hz);
+
+    return 0;
+}
+
+void
+populate_map(hazelcast_client& client)
+{
+    // Populate a map before using it in sql.
+    auto map = client.get_map("integers").get();
+
+    for (int i = 0; i < 100; ++i) {
+        map->put(i, i).get();
+    }
+}
+
+void
+create_mapping(hazelcast_client& client)
+{
+    // Create mapping for the integers.
+    // This needs to be done only once per map.
+    // It is required to use a map in SQL query.
+    auto result = client.get_sql()
+                    .execute(R"(
+                CREATE OR REPLACE MAPPING integers
+                  TYPE IMap
+                    OPTIONS (
+                      'keyFormat' = 'int',
+                      'valueFormat' = 'int'
+                      )
+                    )")
+                    .get();
+}
+
+std::shared_ptr<hazelcast::client::sql::sql_result>
+select_numbers(hazelcast::client::hazelcast_client& client)
+{
+    using namespace hazelcast::client::sql;
+
+    sql_statement statement(client, "SELECT * FROM integers");
+
+    // Set cursor buffer size to 5
+    // So there will be 20 pages(100 / 5 = 20)
+    statement.cursor_buffer_size(5);
+
+    return client.get_sql().execute(statement).get();
+}
+
+void
+seperator(const std::string& text = std::string{})
+{
+    std::string output(60, '=');
+    boost::replace_first(output, std::string(text.size(), '='), text);
+
+    output = std::string(20, '=') + output;
+
+    std::cout << output << std::endl;
+}
+
+void
+for_loop(hazelcast_client& client)
+{
+    seperator("for_loop() - BEGIN");
+
+    auto result = select_numbers(client);
+
+    for (const auto& row : *result) {
+        std::cout << row.get_object<int>(0);
+    }
+
+    seperator("for_loop() - END");
+    seperator();
+}
+
+void
+algorithm_copy(hazelcast_client& client)
+{
+    using hazelcast::client::sql::sql_page;
+
+    seperator("algorithm_copy() - BEGIN");
+
+    auto result = select_numbers(client);
+
+    std::vector<int> numbers;
+
+    transform(
+      begin(*result),
+      end(*result),
+      back_inserter(numbers),
+      [](const sql_page::sql_row& row) { return *row.get_object<int>(0); });
+
+    sort(begin(numbers), end(numbers));
+    copy(begin(numbers),
+         end(numbers),
+         std::ostream_iterator<int>(std::cout, "\n"));
+
+    seperator("algorithm_copy - END");
+}
+
+void
+algorithm_filter(hazelcast_client& client)
+{
+    using hazelcast::client::sql::sql_page;
+
+    seperator("algorithm_filter - BEGIN");
+
+    auto result = select_numbers(client);
+
+    std::vector<std::shared_ptr<sql_page>> pages;
+
+    copy_if(result->pbegin(),
+            result->pend(),
+            back_inserter(pages),
+            [](const std::shared_ptr<sql_page>& p) {
+                // Filter out the pages which contains a number which is
+                // divisable by 20
+                return any_of(begin(p->rows()),
+                              end(p->rows()),
+                              [](const sql_page::sql_row& row) {
+                                  return *row.get_object<int>(0) % 20 == 0;
+                              });
+            });
+
+    for (const auto& page : pages) {
+        for (const sql_page::sql_row& row : page->rows()) {
+            std::cout << row.get_object<int>(0) << " ";
+        }
+
+        std::cout << std::endl;
+    }
+
+    seperator("algorithm_filter - END");
+}
+
+void
+timeout(hazelcast_client& client)
+{
+    seperator("timeout - BEGIN");
+
+    // `generate_stream(1)` generates a row per seconds, so it will guaranteed
+    // that it will timeout
+    auto result =
+      client.get_sql().execute("SELECT * FROM TABLE(generate_stream(1))").get();
+
+    auto it = result->begin(std::chrono::milliseconds{ 1 });
+
+    try {
+        ++it;
+        ++it;
+    } catch (hazelcast::client::exception::no_such_element& e) {
+        std::cout << "Timedout" << std::endl;
+    }
+
+    seperator("timeout - END");
+}

hazelcast/include/hazelcast/client/sql/sql_result.h

@@ -180,6 +180,70 @@ class HAZELCAST_API sql_result : public std::enable_shared_from_this<sql_result>
         std::chrono::milliseconds timeout_;
     };
 
+    /**
+     * Copy is allowed for convenience but it does shallow copy so it should be avoided.
+    */
+    class HAZELCAST_API row_iterator_sync
+    {
+    public:
+        using difference_type = void;
+        using value_type = sql_page::sql_row;
+        using pointer = sql_page::sql_row*;
+        using reference = const sql_page::sql_row&;
+        using iterator_category = std::input_iterator_tag;
+
+        /**
+         * Sets timeout for page fetch operation.
+        */
+        void set_timeout(std::chrono::milliseconds);
+
+        /**
+         * Retrieves the timeout
+        */
+        std::chrono::milliseconds timeout() const;
+
+        friend HAZELCAST_API bool operator==(const row_iterator_sync&,
+                                             const row_iterator_sync&);
+        friend HAZELCAST_API bool operator!=(const row_iterator_sync&,
+                                             const row_iterator_sync&);
+
+        /**
+         * Returns current row. It might block in case of the current page is empty.
+         *
+         * @throws exception::no_such_element if the iterator points to the past-end
+        */
+        const sql_page::sql_row& operator*() const;
+
+
+        /**
+         * Returns current row. It might block in case of the current page is empty.
+         *
+         * @throws exception::no_such_element if the iterator points to the past-end
+        */
+        const sql_page::sql_row* operator->() const;
+
+        /**
+         * Post increment operator is deleted because copy is discouraged.
+        */
+        row_iterator_sync operator++(int) = delete;
+
+        /**
+         * Fetches next row in blocking manner. If page is already fetched, it doesn't block, otherwise it blocks.
+         *
+         * @throws exception::no_such_element if the iterator points to the past-end or operation is timedout.
+        */
+        row_iterator_sync& operator++();
+
+    private:
+
+        friend class sql_result;
+        row_iterator_sync(page_iterator_sync&&);
+        row_iterator_sync() = default;
+
+        mutable page_iterator_sync iterator_;
+        std::size_t row_idx_;
+    };
+
     /**
      * The destructor closes the result if it were open.
      */
@@ -236,6 +300,9 @@ class HAZELCAST_API sql_result : public std::enable_shared_from_this<sql_result>
     page_iterator_sync pbegin(
       std::chrono::milliseconds timeout = std::chrono::milliseconds{ -1 });
     page_iterator_sync pend();
+    row_iterator_sync begin(
+      std::chrono::milliseconds timeout = std::chrono::milliseconds{ -1 });
+    row_iterator_sync end();
 
 private:
     friend class sql_service;