Reduce planning time of high depth Traversals (#3942)

* Improved the cost estimation of traversals to be independent from max search depth. This fixes #3917

* fix failing test on MSVC

CHANGELOG

@@ -1,6 +1,9 @@
 devel
 -----
 
+* fixed issue #3917: traversals with high maximal depth take extremely long
+  in planning phase.
+  
 * UI: fixed issue #3822: disabled name input field for system collections
 
 * fixed issue #3741: fix terminal color output in Windows 

arangod/Aql/ExecutionPlan.cpp

@@ -61,6 +61,14 @@ static uint64_t checkTraversalDepthValue(AstNode const* node) {
                                    "invalid traversal depth");
   }
   double v = node->getDoubleValue();
+  if (v > static_cast<double>(INT64_MAX)) {
+    // we cannot safely represent this value in an int64_t.
+    // which is already far bigger than we will ever traverse, so
+    // we can safely abort here and not care about uint64_t.
+    THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_QUERY_PARSE,
+                                   "invalid traversal depth");
+  }
+
   double intpart;
   if (modf(v, &intpart) != 0.0 || v < 0.0) {
     THROW_ARANGO_EXCEPTION_MESSAGE(TRI_ERROR_QUERY_PARSE,

arangod/Graph/TraverserOptions.cpp

@@ -532,7 +532,7 @@ double TraverserOptions::estimateCost(size_t& nrItems) const {
   size_t baseCreateItems = 0;
   double baseCost = costForLookupInfoList(_baseLookupInfos, baseCreateItems);
 
-  for (uint64_t depth = 0; depth < maxDepth; ++depth) {
+  for (uint64_t depth = 0; depth < maxDepth && depth < 10; ++depth) {
     auto liList = _depthLookupInfo.find(depth);
     if (liList == _depthLookupInfo.end()) {
       // No LookupInfo for this depth use base
@@ -545,6 +545,12 @@ double TraverserOptions::estimateCost(size_t& nrItems) const {
       count *= createItems;
     }
   }
+
+  if (maxDepth > 10) {
+    // We have a too high depth this cost will be pruned anyway
+    cost *= (maxDepth - 10) * 10;
+    count *= (maxDepth - 10) * 10;
+  }
   nrItems = count;
   return cost;
 }

js/server/tests/aql/aql-graph-traverser.js

@@ -1644,7 +1644,82 @@ function complexInternaSuite () {
       let res = db._query(query);
       assertEqual(res.count(), 1);
       assertEqual(res.toArray(), [vertex.B]);
-    }
+    },
+
+    testLargeMaxDepth: function () {
+      let query = `
+      WITH ${vn}
+      FOR v, e, p IN 1..4294967295 OUTBOUND "${vn}/A" ${en}
+      FILTER p.edges[1]._id != "${edge.BC}"
+      FILTER p.vertices[2]._id != "${vertex.C}"
+      RETURN v._id`;
+
+      let res = db._query(query);
+      assertEqual(res.count(), 1);
+      assertEqual(res.toArray(), [vertex.B]);
+    },
+
+    testInt64MaxMaxDepth: function () {
+      let query = `
+      WITH ${vn}
+      FOR v, e, p IN 1..9223372036854775807 OUTBOUND "${vn}/A" ${en}
+      FILTER p.edges[1]._id != "${edge.BC}"
+      FILTER p.vertices[2]._id != "${vertex.C}"
+      RETURN v._id`;
+
+      let res = db._query(query);
+      assertEqual(res.count(), 1);
+      assertEqual(res.toArray(), [vertex.B]);
+    },
+
+
+    testEvenLargerMaxDepth: function () {
+      let query = `
+      WITH ${vn}
+      FOR v, e, p IN 1..18446744073709551615 OUTBOUND "${vn}/A" ${en}
+      FILTER p.edges[1]._id != "${edge.BC}"
+      FILTER p.vertices[2]._id != "${vertex.C}"
+      RETURN v._id`;
+
+      try {
+        db._query(query);
+        fail();
+      } catch (e) {
+        assertEqual(e.errorNum, errors.ERROR_QUERY_PARSE.code);
+      }
+    },
+
+    testNegativeMinDepth: function () {
+      let query = `
+      WITH ${vn}
+      FOR v, e, p IN -1..3 OUTBOUND "${vn}/A" ${en}
+      FILTER p.edges[1]._id != "${edge.BC}"
+      FILTER p.vertices[2]._id != "${vertex.C}"
+      RETURN v._id`;
+      try {
+        db._query(query);
+        fail();
+      } catch (e) {
+        assertEqual(e.errorNum, errors.ERROR_QUERY_PARSE.code);
+      }
+    },
+
+    testNegativeMaxDepth: function () {
+      let query = `
+      WITH ${vn}
+      FOR v, e, p IN 1..-3 OUTBOUND "${vn}/A" ${en}
+      FILTER p.edges[1]._id != "${edge.BC}"
+      FILTER p.vertices[2]._id != "${vertex.C}"
+      RETURN v._id`;
+
+      try {
+        db._query(query);
+        fail();
+      } catch (e) {
+        assertEqual(e.errorNum, errors.ERROR_QUERY_PARSE.code);
+      }
+    },
+
   };
 }