Restore old size calculation behaviour

src/engine/ExportQueryExecutionTrees.cpp

@@ -784,16 +784,17 @@ ExportQueryExecutionTrees::computeResultAsQLeverJSON(
                 qet, query.constructClause().triples_, query._limitOffset,
                 std::move(result), std::move(cancellationHandle));
 
-  size_t resultSize = 0;
+  size_t numBindingsYielded = 0;
   for (const std::string& b : bindings) {
-    if (resultSize > 0) [[likely]] {
+    if (numBindingsYielded > 0) [[likely]] {
       co_yield ",";
     }
     co_yield b;
-    ++resultSize;
+    ++numBindingsYielded;
   }
 
   RuntimeInformation runtimeInformation = qet.getRootOperation()->runtimeInfo();
+  size_t resultSizeBeforeImplicitLimit = runtimeInformation.numRows_;
   runtimeInformation.addLimitOffsetRow(query._limitOffset, false);
 
   auto timeResultComputation =
@@ -805,7 +806,16 @@ ExportQueryExecutionTrees::computeResultAsQLeverJSON(
       qet.getRootOperation()->getRuntimeInfoWholeQuery());
   jsonSuffix["runtimeInformation"]["query_execution_tree"] =
       nlohmann::ordered_json(runtimeInformation);
-  jsonSuffix["resultsize"] = resultSize;
+  // TODO: This is a simple hack to get the result size for typical SELECT
+  // queries. When the final operation is lazy, it will be the size of the
+  // blocks produced by that operation (which is a lower bound on the size of
+  // the full result). For CONSTRUCT queries, it will be at most the implicit
+  // limit. The proper solution is to reinstate the `send` parameter
+  // (independently from the LIMIT), and if it is set, send only that many
+  // results but compute the full result size.
+  jsonSuffix["resultsize"] = query.hasSelectClause()
+                                 ? resultSizeBeforeImplicitLimit
+                                 : numBindingsYielded;
   jsonSuffix["time"]["total"] =
       absl::StrCat(requestTimer.msecs().count(), "ms");
   jsonSuffix["time"]["computeResult"] =

test/ExportQueryExecutionTreesTest.cpp

@@ -1067,7 +1067,7 @@ TEST(ExportQueryExecutionTrees, LimitOffset) {
     <binding name="s"><uri>g</uri></binding>
   </result>)" + xmlTrailer;
   TestCaseSelectQuery testCaseLimitOffset{
-      kg, objectQuery, 2,
+      kg, objectQuery, 4,
       // TSV
       "?s\n"
       "<d>\n"
@@ -1421,7 +1421,8 @@ TEST(ExportQueryExecutionTrees, verifyQleverJsonContainsValidMetadata) {
   auto& runtimeInformation = runtimeInformationWrapper["query_execution_tree"];
   EXPECT_EQ(runtimeInformation["result_cols"], 3);
   EXPECT_EQ(runtimeInformation["result_rows"], 4);
-  EXPECT_EQ(json["resultsize"], 4);
+  // This number is an implementation detail for lazy results and may change.
+  EXPECT_EQ(json["resultsize"], 6);
   auto& timingInformation = json["time"];
   EXPECT_GE(toChrono(timingInformation["total"].get<std::string_view>()), 1ms);
   // Ensure result is not returned in microseconds and subsequently interpreted