fixed issue #5977: Unexpected execution plan when subquery contains COLLECT (#5983)

CHANGELOG

@@ -1,6 +1,8 @@
 v3.3.13 (XXXX-XX-XX)
 --------------------
 
+* fixed issue #5977: Unexpected execution plan when subquery contains COLLECT
+
 * Bugfix: The AQL syntax variants `UPDATE/REPLACE k WITH d` now correctly take
   _rev from k instead of d (when ignoreRevs is false) and ignore d._rev.
 

arangod/Aql/CollectBlock.cpp

@@ -973,6 +973,9 @@ int DistinctCollectBlock::getOrSkipSome(size_t atLeast, size_t atMost,
       if (!skipping) {
         size_t i = 0;
         for (auto& it : _groupRegisters) {
+          if (skipped > 0) {
+            res->copyValuesFromFirstRow(skipped, static_cast<RegisterId>(cur->getNrRegs()));
+          }
           res->setValue(skipped, it.first, groupValues[i].clone());
           ++i;
         }

js/server/tests/aql/aql-distinct.js

@@ -207,6 +207,17 @@ function ahuacatlDistinct () {
       assertEqual(100, integers.length);
       assertEqual(100, strings.length);
     },
+            
+    testDistinctInOptimizedAwaySubquery : function () {
+      let query = "LET values = (FOR i IN " + c.name() + " RETURN DISTINCT i.value1) FOR doc IN values RETURN 42";
+      containsDistinct(query);
+      let result = AQL_EXECUTE(query).json;
+
+      assertEqual(100, result.length);
+  
+      let plan = AQL_EXPLAIN(query).plan;
+      assertNotEqual(-1, plan.rules.indexOf("inline-subqueries"));
+    },
 
 ////////////////////////////////////////////////////////////////////////////////
 /// @brief distinct usage