refactor: do not prevent the reduce-extraction-to-projection optimization in ArangoDB through dangling-edge filter

We currently do not trust edges - if the document they point to does not exist, we ignore the edge.

In the past, this access was done via $node != null. This has the problem that ArangoDB considers it a full document access and no longer applies the reduce-extraction-to-projection optimization rule. This rule is very important to limit query memory limit usage.

Removing the dangling edges filter completely would be breaking, but we can optimize them so the reduce-extraction-to-projection optimization still works.

Author: Yogu

spec/regression/collect/tests/collect-edge-count-access-group/aql/count.aql

@@ -20,7 +20,7 @@ RETURN {
           FOR v_item3
           IN OUTBOUND v_shipment1 @@shipments_deliveries
           FILTER (v_item3.`accessGroup` IN @var5)
-          FILTER v_item3 != null
+          FILTER v_item3._key != null
           RETURN v_item3
         )
         COLLECT WITH COUNT INTO v_count1

spec/regression/collect/tests/collect-edge-count/aql/countAfter.aql

@@ -14,7 +14,7 @@ RETURN {
         IN (
           FOR v_node1
           IN OUTBOUND v_shipment1 @@shipments_deliveries
-          FILTER v_node1 != null
+          FILTER v_node1._key != null
           RETURN v_node1
         )
         COLLECT WITH COUNT INTO v_count1

spec/regression/collect/tests/collect-edge-count/aql/countBefore.aql

@@ -14,7 +14,7 @@ RETURN {
         IN (
           FOR v_node1
           IN OUTBOUND v_shipment1 @@shipments_deliveries
-          FILTER v_node1 != null
+          FILTER v_node1._key != null
           RETURN v_node1
         )
         COLLECT WITH COUNT INTO v_count1

spec/regression/logistics/tests/create-many/aql/create.aql

@@ -236,7 +236,7 @@ RETURN (
     "handlingUnits": (
       FOR v_handlingUnit1
       IN OUTBOUND v_Delivery1 @@deliveries_handlingUnits
-      FILTER v_handlingUnit1 != null
+      FILTER v_handlingUnit1._key != null
       SORT (v_handlingUnit1.`huNumber`)
       RETURN {
         "huNumber": v_handlingUnit1.`huNumber`

spec/regression/logistics/tests/create-many/aql/query.aql

@@ -63,7 +63,7 @@ RETURN {
       "handlingUnits": (
         FOR v_handlingUnit1
         IN OUTBOUND v_delivery1 @@deliveries_handlingUnits
-        FILTER v_handlingUnit1 != null
+        FILTER v_handlingUnit1._key != null
         SORT (v_handlingUnit1.`huNumber`)
         RETURN {
           "huNumber": v_handlingUnit1.`huNumber`

spec/regression/logistics/tests/create-with-to-many-relation/aql/check.aql

@@ -9,11 +9,11 @@ RETURN {
       "handlingUnits": (
         FOR v_handlingUnit1
         IN OUTBOUND v_delivery1 @@deliveries_handlingUnits
-        FILTER v_handlingUnit1 != null
+        FILTER v_handlingUnit1._key != null
         LET v_delivery2 = FIRST((
           FOR v_node1
           IN INBOUND v_handlingUnit1 @@deliveries_handlingUnits
-          FILTER v_node1 != null
+          FILTER v_node1._key != null
           RETURN v_node1
         ))
         RETURN {

spec/regression/logistics/tests/create-with-to-one-relation/aql/check.aql

@@ -7,7 +7,7 @@ RETURN {
     LET v_delivery1 = FIRST((
       FOR v_node1
       IN INBOUND v_handlingUnit1 @@deliveries_handlingUnits
-      FILTER v_node1 != null
+      FILTER v_node1._key != null
       RETURN v_node1
     ))
     RETURN {

spec/regression/logistics/tests/delete-all-related/aql/deleteByDelivery.aql

@@ -5,7 +5,7 @@ RETURN (
   FILTER (FIRST((
     FOR v_node1
     IN INBOUND v_handlingUnit1 @@deliveries_handlingUnits
-    FILTER v_node1 != null
+    FILTER v_node1._key != null
     RETURN v_node1
   ))._key == @var1)
   SORT (v_handlingUnit1.`huNumber`)

spec/regression/logistics/tests/delete-all-related/aql/deliveries.aql

@@ -7,7 +7,7 @@ RETURN {
     LET v_delivery1 = FIRST((
       FOR v_node1
       IN INBOUND v_handlingUnit1 @@deliveries_handlingUnits
-      FILTER v_node1 != null
+      FILTER v_node1._key != null
       RETURN v_node1
     ))
     RETURN {

spec/regression/logistics/tests/field-permission-denied/aql/select.aql

@@ -16,7 +16,7 @@ LET v_handlingUnit1 = FIRST((
 LET v_delivery3 = FIRST((
   FOR v_node1
   IN INBOUND v_handlingUnit1 @@deliveries_handlingUnits
-  FILTER v_node1 != null
+  FILTER v_node1._key != null
   RETURN v_node1
 ))
 LET v_country1 = FIRST((