Refactor prefetch functionality. (#722)

* Refactor prefetch functionality.
Split functionality to two categories. With default min/max levels prefetch only requested tiles.
With valid levels, which differs prefetch all tiles in subtree from min to max levels.
Create slicing of subtree using depth equal 4.
Update tests. Add integration test for sibling tiles.

Resolves:OLPSUP-9847

Signed-off-by: Liubov Didkivska <[email protected]>

Author: Liubov Didkivska

olp-cpp-sdk-dataservice-read/include/olp/dataservice/read/PrefetchTilesRequest.h

@@ -45,7 +45,7 @@ namespace read {
 class DATASERVICE_READ_API PrefetchTilesRequest final {
  public:
   /**
-   * @brief Gets a vector with the tile keys.
+   * @brief Get the vector of the root tile keys.
    *
    * @return The vector with the tile keys.
    */
@@ -54,9 +54,9 @@ class DATASERVICE_READ_API PrefetchTilesRequest final {
   }
 
   /**
-   * @brief Sets the tile keys for the request.
+   * @brief Sets the vector of the root tile keys for the request.
    *
-   * @param tile_keys The vector with the tile keys.
+   * @param tile_keys The vector with the root tile keys of the prefetch.
    *
    * @return A reference to the updated `PrefetchTilesRequest` instance.
    */
@@ -67,9 +67,10 @@ class DATASERVICE_READ_API PrefetchTilesRequest final {
   }
 
   /**
-   * @brief Sets the tile keys for the request.
+   * @brief Sets the vector of the root tile keys for the request.
    *
-   * @param tile_keys The rvalue reference to the vector with the tile keys.
+   * @param tile_keys The rvalue reference to the vector with the root tile keys
+   * of the prefetch.
    *
    * @return A reference to the updated `PrefetchTilesRequest` instance.
    */
@@ -80,25 +81,26 @@ class DATASERVICE_READ_API PrefetchTilesRequest final {
   }
 
   /**
-   * @brief Gets the minimum tile level.
+   * @brief Gets the minimum tiles level to prefetch.
    *
    * @return The minimum tile level.
    */
   inline unsigned int GetMinLevel() const { return min_level_; }
 
   /**
-   * @brief Sets the minimum tile level for the request.
+   * @brief Sets the minimum tiles level for the request.
    *
-   * @param min_level The minimum tile level.
+   * @param min_level The minimum tiles level to prefetch.
    *
    * @return A reference to the updated `PrefetchTilesRequest` instance.
    */
   inline PrefetchTilesRequest& WithMinLevel(unsigned int min_level) {
     min_level_ = min_level;
     return *this;
   }
+
   /**
-   * @brief Gets the maximum tile level.
+   * @brief Gets the maximum tiles level to prefetch.
    *
    * @return The maximum tile level.
    */
@@ -107,7 +109,7 @@ class DATASERVICE_READ_API PrefetchTilesRequest final {
   /**
    * @brief Sets the maximum tile level for the request.
    *
-   * @param max_level The maximum tile level.
+   * @param max_level The maximum tile level to prefetch.
    *
    * @return A reference to the updated `PrefetchTilesRequest` instance.
    */

olp-cpp-sdk-dataservice-read/include/olp/dataservice/read/VersionedLayerClient.h

@@ -278,10 +278,12 @@ class DATASERVICE_READ_API VersionedLayerClient final {
   /**
    * @brief Prefetches a set of tiles asynchronously.
    *
-   * This method recursively downloads all tile keys from the `minLevel`
-   * parameter to the `maxLevel` parameter of the \c PrefetchTilesRequest
-   * object. It helps to reduce the network load by using the prefetched tiles
-   * data from the cache.
+   * This method recursively downloads all tile keys from the `min_level`
+   * parameter to the `max_level` parameter of the \c PrefetchTilesRequest
+   * object for the given root tiles. If min_level/max_level are the same or
+   * default, only tiles listed in \c PrefetchTilesRequest will be downloaded.
+   * Only tiles will be downloaded which are not already present in the cache,
+   * this helps reduce the network load.
    *
    * @note This method does not guarantee that all tiles are available offline
    * as the cache might overflow, and data might be evicted at any point.
@@ -300,10 +302,12 @@ class DATASERVICE_READ_API VersionedLayerClient final {
   /**
    * @brief Prefetches a set of tiles asynchronously.
    *
-   * This method recursively downloads all tile keys from the `minLevel`
-   * parameter to the `maxLevel` parameter of the \c PrefetchTilesRequest
-   * object. It helps to reduce the network load by using the prefetched tiles
-   * data from the cache.
+   * This method recursively downloads all tile keys from the `min_level`
+   * parameter to the `max_level` parameter of the \c PrefetchTilesRequest
+   * object for the given root tiles. If min_level/max_level are the same or
+   * default, only tiles listed in \c PrefetchTilesRequest will be downloaded.
+   * Only tiles will be downloaded which are not already present in the cache,
+   * this helps reduce the network load.
    *
    * @note This method does not guarantee that all tiles are available offline
    * as the cache might overflow, and data might be evicted at any point.

olp-cpp-sdk-dataservice-read/src/VersionedLayerClientImpl.cpp

@@ -229,23 +229,31 @@ client::CancellationToken VersionedLayerClientImpl::PrefetchTiles(
 
         // Calculate the minimal set of Tile keys and depth to
         // cover tree.
-        auto sub_quads = repository::PrefetchTilesRepository::EffectiveTileKeys(
-            request.GetTileKeys(), request.GetMinLevel(),
-            request.GetMaxLevel());
-
-        if (sub_quads.empty()) {
+        bool request_only_input_tiles =
+            !(request.GetMinLevel() > 0 &&
+              request.GetMinLevel() < request.GetMaxLevel() &&
+              request.GetMaxLevel() < geo::TileKey().Level() &&
+              request.GetMinLevel() < geo::TileKey().Level());
+        unsigned int min_level =
+            (request_only_input_tiles ? 0 : request.GetMinLevel());
+        unsigned int max_level =
+            (request_only_input_tiles ? 0 : request.GetMaxLevel());
+
+        auto sliced_tiles = repository::PrefetchTilesRepository::GetSlicedTiles(
+            request.GetTileKeys(), min_level, max_level);
+
+        if (sliced_tiles.empty()) {
           OLP_SDK_LOG_WARNING_F(kLogTag,
                                 "PrefetchTiles: tile/level mismatch, key=%s",
                                 key.c_str());
           return {{ErrorCode::InvalidArgument, "TileKeys/levels mismatch"}};
         }
 
         OLP_SDK_LOG_DEBUG_F(kLogTag, "PrefetchTiles, subquads=%zu, key=%s",
-                            sub_quads.size(), key.c_str());
+                            sliced_tiles.size(), key.c_str());
 
-        // Now get metadata for subtiles using QueryApi::QuadTreeIndex
         auto sub_tiles = repository::PrefetchTilesRepository::GetSubTiles(
-            catalog, layer_id, request, sub_quads, context, settings);
+            catalog, layer_id, request, sliced_tiles, context, settings);
 
         if (!sub_tiles.IsSuccessful()) {
           return sub_tiles.GetError();
@@ -269,19 +277,38 @@ client::CancellationToken VersionedLayerClientImpl::PrefetchTiles(
         std::vector<CancellationContext> contexts;
         contexts.reserve(tiles_result.size() + 1u);
         auto it = tiles_result.begin();
+        auto skip_tile = [&](const geo::TileKey& tile_key) {
+          if (request_only_input_tiles) {
+            if (std::find(request.GetTileKeys().begin(),
+                          request.GetTileKeys().end(),
+                          tile_key) == request.GetTileKeys().end()) {
+              return true;
+            }
+          } else if (tile_key.Level() < request.GetMinLevel() ||
+                     tile_key.Level() > request.GetMaxLevel()) {
+            // tile outside min/max segment, skip this tile
+            return true;
+          }
+          return false;
+        };
 
         while (!context.IsCancelled() && it != tiles_result.end()) {
+          auto tile = it->first;
+          auto handle = it->second;
+          if (skip_tile(tile)) {
+            it++;
+            continue;
+          }
+
           auto promise = std::make_shared<PrefetchResultPromise>();
           auto flag = std::make_shared<std::atomic_bool>(false);
           futures->emplace_back(promise->get_future());
-
-          auto tile = it->first;
-          auto handle = it->second;
           auto context_it = contexts.emplace(contexts.end());
 
           AddTask(settings.task_scheduler, pending_requests,
                   [=](CancellationContext inner_context) {
-                    // Get blob data
+                    // TODO: Get blob data need to be changed to check if data
+                    // in cache, if not, only than load it
                     auto data = repository::DataRepository::GetVersionedData(
                         catalog, layer_id,
                         DataRequest().WithDataHandle(handle).WithBillingTag(