Graph:
C -- A -- B
Solution with seed 5:
HASH_JOIN
---leftEmbeddingField: b
---rightEmbeddingField: (none)
---joinPredicates:
------b = a
---Outer:
------COLLSCAN
---------ns = test.b
---------filter = $and
---------nodeId = 1
---------fetched = 1
---------sortedByDiskLoc = 0
---------providedSorts = {baseSortPattern: {}, ignoredFields: []}
---Inner:
------NESTED_LOOP_JOIN
---------leftEmbeddingField: c
---------rightEmbeddingField: (none)
---------joinPredicates:
------------c = a
---------Outer:
------------COLLSCAN
---------------ns = test.c
---------------filter = $and
---------------nodeId = 2
---------------fetched = 1
---------------sortedByDiskLoc = 0
---------------providedSorts = {baseSortPattern: {}, ignoredFields: []}
---------Inner:
------------COLLSCAN
---------------ns = test.a
---------------filter = $and
---------------nodeId = 3
---------------fetched = 1
---------------sortedByDiskLoc = 0
---------------providedSorts = {baseSortPattern: {}, ignoredFields: []}

Solution with seed 7:
INDEXED_NESTED_LOOP_JOIN
---leftEmbeddingField: (none)
---rightEmbeddingField: b
---joinPredicates:
------a = b
---Outer:
------NESTED_LOOP_JOIN
---------leftEmbeddingField: (none)
---------rightEmbeddingField: c
---------joinPredicates:
------------a = c
---------Outer:
------------COLLSCAN
---------------ns = test.a
---------------filter = $and
---------------nodeId = 1
---------------fetched = 1
---------------sortedByDiskLoc = 0
---------------providedSorts = {baseSortPattern: {}, ignoredFields: []}
---------Inner:
------------COLLSCAN
---------------ns = test.c
---------------filter = $and
---------------nodeId = 2
---------------fetched = 1
---------------sortedByDiskLoc = 0
---------------providedSorts = {baseSortPattern: {}, ignoredFields: []}
---Inner:
------FETCH
---------ns = test.b
---------nodeId = 5
---------fetched = 1
---------sortedByDiskLoc = 0
---------providedSorts = {baseSortPattern: {}, ignoredFields: []}
---------Child:
------------INDEX_PROBE
---------------Namespace: test.b Index: { b: 1 }

With retries force INLJ, Graph:
 C -- A -- B
Solution with seed 0:
INDEXED_NESTED_LOOP_JOIN
---leftEmbeddingField: (none)
---rightEmbeddingField: c
---joinPredicates:
------a = c
---Outer:
------INDEXED_NESTED_LOOP_JOIN
---------leftEmbeddingField: (none)
---------rightEmbeddingField: b
---------joinPredicates:
------------a = b
---------Outer:
------------COLLSCAN
---------------ns = test.a
---------------filter = $and
---------------nodeId = 1
---------------fetched = 1
---------------sortedByDiskLoc = 0
---------------providedSorts = {baseSortPattern: {}, ignoredFields: []}
---------Inner:
------------FETCH
---------------ns = test.b
---------------nodeId = 3
---------------fetched = 1
---------------sortedByDiskLoc = 0
---------------providedSorts = {baseSortPattern: {}, ignoredFields: []}
---------------Child:
------------------INDEX_PROBE
---------------------Namespace: test.b Index: { b: 1 }
---Inner:
------FETCH
---------ns = test.c
---------nodeId = 6
---------fetched = 1
---------sortedByDiskLoc = 0
---------providedSorts = {baseSortPattern: {}, ignoredFields: []}
---------Child:
------------INDEX_PROBE
---------------Namespace: test.c Index: { c: 1 }

