Possible regression in plans. Only one assignment shows up in plans rather than two previously.

These two tests (rbo)

asterixdb/asterix-app/src/test/resources/optimizerts/results/array-index/atomic-and-array-queries/query9.plan
asterixdb/asterix-app/src/test/resources/optimizerts/results/array-index/atomic-and-array-queries/query8.plan

The original plan had two assigns back to back. Now we have only one assign. Need to investigate and make sure this is not a regression.

--------------------------------

Ok, here are the critical differences in the final plans.

Before NEO (assign is done in two steps)
assign [$$69, $$68] <- [to-bigint($$65), to-bigint($$67)]
– ASSIGN |PARTITIONED| <<<< I do not know why this is here???
assign [$$60, $$58, $$67, $$65] <- [to-bigint($$D2.getField("field4")), to-bigint($$D2.getField("field1")), $$D2.getField("field2"), $$D2.getField("field3")]
NEO (happens in one step).
assign [$$69, $$68, $$60, $$58] <- [to-bigint($$D2.getField("field3")), to-bigint($$D2.getField("field2")), to-bigint($$D2.getField("field4")), to-bigint($$D2.getField("field1"))]
Eventually, all the 4 variables have the same mapping. The NEO plan is more compact as well.

These changes are expected. GG says:

this is expected — for INL-JOINs (both columns and array) there is a need to push down all function calls out of the predicate (or else the JOIN doesn’t get recognized) — for array INLJ in particular, the rule that does the push down for column index JOINs doesn’t apply to array index JOINs so we do it ourselves in JoinFromSubplanRewrite

(and doing it ourselves results in two ASSIGNs)

This is done in file

JoinFromSubplanRewrite (the change in expressions happens in the last two lines).

 if (new HashSet<>(varsFromLeftBranch).containsAll(usedVarsFromFunc)) {

                newAssign.getInputs().add(new MutableObject<>(leftBranchRoot));

                context.computeAndSetTypeEnvironmentForOperator(newAssign);

                joinOp.getInputs().get(0).setValue(newAssign);

                context.computeAndSetTypeEnvironmentForOperator(joinOp); <<<

                arg.setValue(newVarRef); <<<

            }