Adjusted query result interfacesHEADmaster

Now, the vector<> is part of the user-defined type, not required by the
framework. This should allow for more flexibility in either using
alternative containers, or for more sensible implementations of queries
with single value results (like range count).

3 files changed, 92 insertions, 115 deletions

diff --git a/include/framework/DynamicExtension.h b/include/framework/DynamicExtension.h
index 5a95679..719232e 100644
--- a/include/framework/DynamicExtension.h
+++ b/include/framework/DynamicExtension.h
@@ -202,7 +202,7 @@ public:
    *  @return A future, from which the query results can be retrieved upon
    *          query completion
    */
-  std::future<std::vector<QueryResult>>
+  std::future<QueryResult>
   query(Parameters &&parms) {
     return schedule_query(std::move(parms));
   }
@@ -628,26 +628,17 @@ private:
     QueryType::distribute_query(parms, local_queries, buffer_query);
 
     /* execute the local/buffer queries and combine the results into output */
-    std::vector<QueryResult> output;
+    QueryResult output;
     do {
-      std::vector<std::vector<LocalResult>>
-          query_results(shards.size() + 1);
+      std::vector<LocalResult> query_results(shards.size() + 1);
       for (size_t i = 0; i < query_results.size(); i++) {
-        std::vector<LocalResult> local_results;
-        ShardID shid;
-
         if (i == 0) { /* execute buffer query */
-          local_results = QueryType::local_query_buffer(buffer_query);
-          shid = INVALID_SHID;
+          query_results[i] = QueryType::local_query_buffer(buffer_query);
         } else { /*execute local queries */
-          local_results = QueryType::local_query(shards[i - 1].second,
+          query_results[i] = QueryType::local_query(shards[i - 1].second,
                                                  local_queries[i - 1]);
-          shid = shards[i - 1].first;
         }
 
-        /* framework-level, automatic delete filtering */
-        query_results[i] = std::move(local_results);
-
         /* end query early if EARLY_ABORT is set and a result exists */
         if constexpr (QueryType::EARLY_ABORT) {
           if (query_results[i].size() > 0)
@@ -695,7 +686,7 @@ private:
     m_sched.schedule_job(reconstruction, 0, args, RECONSTRUCTION);
   }
 
-  std::future<std::vector<QueryResult>>
+  std::future<QueryResult>
   schedule_query(Parameters &&query_parms) {
     auto args =
         new QueryArgs<ShardType, QueryType, DynamicExtension>();
diff --git a/include/framework/interface/Query.h b/include/framework/interface/Query.h
index 1b64646..97a973d 100644
--- a/include/framework/interface/Query.h
+++ b/include/framework/interface/Query.h
@@ -12,18 +12,6 @@
 
 namespace de {
 
-/*
- * FIXME: It would probably be best to absorb the std::vector into
- *        this type too; this would allow user-defined collections for
- *        intermediate results, which could allow for more merging
- *        optimizations. However, this would require an alternative
- *        approach to doing delete checks, so we'll leave it for now.
- */
-template <typename R>
-concept LocalResultInterface = requires(R res) {
-  { res.is_deleted() } -> std::convertible_to<bool>;
-  { res.is_tombstone() } -> std::convertible_to<bool>;
-};
 
 /*
  *
@@ -35,102 +23,100 @@ template <typename QUERY, typename SHARD,
           typename PARAMETERS = typename QUERY::Parameters,
           typename LOCAL = typename QUERY::LocalQuery,
           typename LOCAL_BUFFER = typename QUERY::LocalQueryBuffer>
-concept QueryInterface = LocalResultInterface<LOCAL_RESULT> &&
+concept QueryInterface =
     requires(PARAMETERS *parameters, LOCAL *local, LOCAL_BUFFER *buffer_query,
              SHARD *shard, std::vector<LOCAL *> &local_queries,
-             std::vector<std::vector<LOCAL_RESULT>> &local_results,
-             std::vector<RESULT> &result,
+             std::vector<LOCAL_RESULT> &local_results, RESULT &result,
              BufferView<typename SHARD::RECORD> *bv) {
+      /*
+       * Given a set of query parameters and a shard, return a local query
+       * object for that shard.
+       */
+      {
+        QUERY::local_preproc(shard, parameters)
+      } -> std::convertible_to<LOCAL *>;
 
-  /*
-   * Given a set of query parameters and a shard, return a local query
-   * object for that shard.
-   */
-  { QUERY::local_preproc(shard, parameters) } -> std::convertible_to<LOCAL *>;
-
-  /*
-   * Given a set of query parameters and a buffer view, return a local
-   * query object for the buffer.
-   * NOTE: for interface reasons, the pointer to the buffer view MUST be
-   *       stored inside of the local query object. The future buffer
-   *       query routine will access the buffer by way of this pointer.
-   */
-  {
-    QUERY::local_preproc_buffer(bv, parameters)
-    } -> std::convertible_to<LOCAL_BUFFER *>;
+      /*
+       * Given a set of query parameters and a buffer view, return a local
+       * query object for the buffer.
+       * NOTE: for interface reasons, the pointer to the buffer view MUST be
+       *       stored inside of the local query object. The future buffer
+       *       query routine will access the buffer by way of this pointer.
+       */
+      {
+        QUERY::local_preproc_buffer(bv, parameters)
+      } -> std::convertible_to<LOCAL_BUFFER *>;
 
-  /*
-   * Given a full set of local queries, and the buffer query, make any
-   * necessary adjustments to the local queries in-place, to account for
-   * global information. If no additional processing is required, this
-   * function can be left empty.
-   */
-  {QUERY::distribute_query(parameters, local_queries, buffer_query)};
+      /*
+       * Given a full set of local queries, and the buffer query, make any
+       * necessary adjustments to the local queries in-place, to account for
+       * global information. If no additional processing is required, this
+       * function can be left empty.
+       */
+      { QUERY::distribute_query(parameters, local_queries, buffer_query) };
 
-  /*
-   * Answer the local query, defined by `local` against `shard` and return
-   * a vector of LOCAL_RESULT objects defining the query result.
-   */
-  {
-    QUERY::local_query(shard, local)
-    } -> std::convertible_to<std::vector<LOCAL_RESULT>>;
+      /*
+       * Answer the local query, defined by `local` against `shard` and return
+       * a vector of LOCAL_RESULT objects defining the query result.
+       */
+      { QUERY::local_query(shard, local) } -> std::convertible_to<LOCAL_RESULT>;
 
-  /*
-   * Answer the local query defined by `local` against the buffer (which
-   * should be accessed by a pointer inside of `local`) and return a vector
-   * of LOCAL_RESULT objects defining the query result.
-   */
-  {
-    QUERY::local_query_buffer(buffer_query)
-    } -> std::convertible_to<std::vector<LOCAL_RESULT>>;
+      /*
+       * Answer the local query defined by `local` against the buffer (which
+       * should be accessed by a pointer inside of `local`) and return a vector
+       * of LOCAL_RESULT objects defining the query result.
+       */
+      {
+        QUERY::local_query_buffer(buffer_query)
+      } -> std::convertible_to<LOCAL_RESULT>;
 
-  /*
-   * Process the local results from the buffer and all of the shards,
-   * stored in `local_results`, and insert the associated ResultType
-   * objects into the `result` vector, which represents the final result
-   * of the query. Updates to this vector are done in-place.
-   */
-  {QUERY::combine(local_results, parameters, result)};
+      /*
+       * Process the local results from the buffer and all of the shards,
+       * stored in `local_results`, and insert the associated ResultType
+       * objects into the `result` vector, which represents the final result
+       * of the query. Updates to this vector are done in-place.
+       */
+      { QUERY::combine(local_results, parameters, result) };
 
-  /*
-   * Process the post-combine `result` vector of ResultType objects,
-   * in the context of the global and local query parameters, to determine
-   * if the query should be repeated. If so, make any necessary adjustments
-   * to the local query objects and return True. Otherwise, return False.
-   *
-   * If no repetition is needed for a given problem type, simply return
-   * False immediately and the query will end.
-   */
-  {
-    QUERY::repeat(parameters, result, local_queries, buffer_query)
-    } -> std::same_as<bool>;
+      /*
+       * Process the post-combine `result` vector of ResultType objects,
+       * in the context of the global and local query parameters, to determine
+       * if the query should be repeated. If so, make any necessary adjustments
+       * to the local query objects and return True. Otherwise, return False.
+       *
+       * If no repetition is needed for a given problem type, simply return
+       * False immediately and the query will end.
+       */
+      {
+        QUERY::repeat(parameters, result, local_queries, buffer_query)
+      } -> std::same_as<bool>;
 
-  /*
-   * If this flag is True, then the query will immediately stop and return
-   * a result as soon as the first non-deleted LocalRecordType is found.
-   * Otherwise, every Shard and the buffer will be queried and the results
-   * merged, like normal.
-   *
-   * This is largely an optimization flag for use with point-lookup, or
-   * other single-record result queries
-   */
-  { QUERY::EARLY_ABORT } -> std::convertible_to<bool>;
+      /*
+       * If this flag is True, then the query will immediately stop and return
+       * a result as soon as the first non-deleted LocalRecordType is found.
+       * Otherwise, every Shard and the buffer will be queried and the results
+       * merged, like normal.
+       *
+       * This is largely an optimization flag for use with point-lookup, or
+       * other single-record result queries
+       */
+      { QUERY::EARLY_ABORT } -> std::convertible_to<bool>;
 
-  /*
-   * If false, the built-in delete filtering that the framework can
-   * apply to the local results, prior to calling combine, will be skipped.
-   * This general filtering can be inefficient, particularly for tombstone
-   * -based deletes, and so if a more efficient manual filtering can be
-   * performed, it is worth setting this to True and doing that filtering
-   * in the combine step.
-   *
-   * If deletes are not a consideration for your problem, it's also best
-   * to turn this off, as it'll avoid the framework making an extra pass
-   * over the local results prior to combining them.
-   *
-   * TODO: Temporarily disabling this, as we've dropped framework-level
-   *       delete filtering for the time being.
-   */
-   /* { QUERY::SKIP_DELETE_FILTER } -> std::convertible_to<bool>; */
-};
+      /*
+       * If false, the built-in delete filtering that the framework can
+       * apply to the local results, prior to calling combine, will be skipped.
+       * This general filtering can be inefficient, particularly for tombstone
+       * -based deletes, and so if a more efficient manual filtering can be
+       * performed, it is worth setting this to True and doing that filtering
+       * in the combine step.
+       *
+       * If deletes are not a consideration for your problem, it's also best
+       * to turn this off, as it'll avoid the framework making an extra pass
+       * over the local results prior to combining them.
+       *
+       * TODO: Temporarily disabling this, as we've dropped framework-level
+       *       delete filtering for the time being.
+       */
+      /* { QUERY::SKIP_DELETE_FILTER } -> std::convertible_to<bool>; */
+    };
 } // namespace de
diff --git a/include/framework/scheduling/Task.h b/include/framework/scheduling/Task.h
index 6b6f040..34f053a 100644
--- a/include/framework/scheduling/Task.h
+++ b/include/framework/scheduling/Task.h
@@ -35,7 +35,7 @@ struct ReconstructionArgs {
 };
 
 template <ShardInterface S, QueryInterface<S> Q, typename DE> struct QueryArgs {
-  std::promise<std::vector<typename Q::ResultType>> result_set;
+  std::promise<typename Q::ResultType> result_set;
   typename Q::Parameters query_parms;
   DE *extension;
 };