Thanks @yoff, this leaves us with the following evaluation, which looks
very close to the one in the other fix (but with cleaner implementation)
-- both at 688k max tuples (although numbers are not exactly the same).
```
[2021-11-24 13:48:40] (14s) Tuple counts for PoorMansFunctionResolution::getSimpleMethodReferenceWithinClass#ff/2@e5f05asv after 74ms:
47493 ~3% {3} r1 = JOIN Class::Class::getAMethod_dispred#ff WITH py_Classes ON FIRST 1 OUTPUT Lhs.1, 0, Lhs.0
47335 ~0% {2} r2 = JOIN r1 WITH AstGenerated::Function_::getArg_dispred#fff ON FIRST 2 OUTPUT Rhs.2, Lhs.2
46683 ~0% {2} r3 = JOIN r2 WITH DataFlowPublic::ParameterNode::getParameter_dispred#fb_10#join_rhs ON FIRST 1 OUTPUT Rhs.1, Lhs.1
259968 ~4% {2} r4 = JOIN r3 WITH LocalSources::Cached::hasLocalSource#ff_10#join_rhs ON FIRST 1 OUTPUT Rhs.1, Lhs.1
161985 ~0% {3} r5 = JOIN r4 WITH Attributes::AttrRef::accesses_dispred#bff_102#join_rhs ON FIRST 1 OUTPUT Rhs.1 'result', Lhs.1, Rhs.2
161985 ~2% {3} r6 = JOIN r5 WITH Attributes::AttrRead#class#f ON FIRST 1 OUTPUT Lhs.2, Lhs.1, Lhs.0 'result'
688766 ~0% {3} r7 = JOIN r6 WITH Function::Function::getName_dispred#ff_10#join_rhs ON FIRST 1 OUTPUT Lhs.1, Rhs.1 'func', Lhs.2 'result'
20928 ~0% {2} r8 = JOIN r7 WITH Class::Class::getAMethod_dispred#ff ON FIRST 2 OUTPUT Lhs.1 'func', Lhs.2 'result'
return r8
```
This predicate was materialised as a _big_, _cached_ relation:
```
(169s) Tuple counts for PointsTo::InterProceduralPointsTo::named_argument_transfer#ffff#join_rhs/4@38ce07 after 53.4s:
25212 ~4% {3} r1 = SCAN Function::Function::getArgByName_dispred#fff OUTPUT In.1, In.0 'arg1', In.2 'arg2'
159751200 ~0% {4} r2 = JOIN r1 WITH Flow::CallNode::getArgByName_dispred#fff_102#join_rhs ON FIRST 1 OUTPUT Rhs.1 'arg0', Lhs.1 'arg1', Lhs.2 'arg2', Rhs.2 'arg3'
return r2
```
... However it's only used in a single place (where it is immediately
joined with the points-to relation to relate the caller and argument),
none of these joins were ever larger than 2000 tuples. This made it
pretty clear that we could gain something by pushing in that points-to
join as a bit of manual magic.
However, doing so didn't actually fix anything, since the join-orderer
then decided to join `func.getArgByName(name)` with
`call.getArgByName(name)` on `name` as the first thing (which caused a
join of the same size as above).
Unbinding didn't work, since `name` would then be an unbound `string`,
so instead I factored out relating the function, parameter, and name
thereof into its own predicate. (I could also have done this with the
call, but I would expect there to be more calls than function
definitions in general.)
Overall, this resulted in going from
```
(709s)
Definitions.ql-7:PointsTo::InterProceduralPointsTo::named_argument_transfer#ffff#join_rhs ......... 53.5s
Definitions.ql-7:Instances::InstanceObject::initializer_dispred#fbf ............................... 35.3s (456 evaluations with max 136ms in Instances::InstanceObject::initializer_dispred#fbf/3@i110#0508e8)
Definitions.ql-10:DefinitionTracking::jump_to_defn_attribute#fbf .................................. 27s (100 evaluations with max 12.8s in DefinitionTracking::jump_to_defn_attribute#fbf/3@i1#fc1f7x)
Definitions.ql-7:PointsTo::PointsToInternal::pointsTo#ffff ........................................ 16.1s (681 evaluations with max 2.5s in PointsTo::PointsToInternal::pointsTo#ffff/4@i4#0508eg)
Definitions.ql-7:Constants::ConstantObjectInternal::attribute#ffff ................................ 13.4s (505 evaluations with max 50ms in Constants::ConstantObjectInternal::attribute#ffff/4@i153#0508e5)
Definitions.ql-10:DefinitionTracking::assignment_jump_to_defn_attribute#fbf ....................... 12.4s (99 evaluations with max 11.8s in DefinitionTracking::assignment_jump_to_defn_attribute#fbf/3@i2#fc1f
7z)
...
```
to
```
(668s)
Definitions.ql-7:Instances::InstanceObject::initializer_dispred#fbf ................... 35.4s (456 evaluations with max 140ms in Instances::InstanceObject::initializer_dispred#fbf/3@i110#bf4328)
Definitions.ql-10:DefinitionTracking::jump_to_defn_attribute#fbf ...................... 27.4s (100 evaluations with max 13.3s in DefinitionTracking::jump_to_defn_attribute#fbf/3@i1#679d7x)
Definitions.ql-7:PointsTo::PointsToInternal::pointsTo#ffff ............................ 16.1s (681 evaluations with max 2.5s in PointsTo::PointsToInternal::pointsTo#ffff/4@i4#bf432g)
Definitions.ql-7:Constants::ConstantObjectInternal::attribute#ffff .................... 14.4s (505 evaluations with max 51ms in Constants::ConstantObjectInternal::attribute#ffff/4@i140#bf4325)
Definitions.ql-10:DefinitionTracking::assignment_jump_to_defn_attribute#fbf ........... 12.3s (99 evaluations with max 11.7s in DefinitionTracking::assignment_jump_to_defn_attribute#fbf/3@i2#679d
7z)
...
```
It seems the optimiser has started getting the wrong end of the stick
whenever we write `foo.getScope() = bar.getScope()` for some expressions
`foo` and `bar`.
This lead to things like
```
(196s) Tuple counts for Definitions::ModuleVariable::global_variable_callnode#ff/2@5ab278 after 2m33s:
2952757013 ~0% {2} r1 = JOIN Definitions::ModuleVariable::global_variable_callnode#ff#shared WITH Variables::Variable::getScope_dispred#ff_10#join_rhs ON FIRST 1 OUTPUT Rhs.1 'this', Lhs.1 'result'
495693 ~0% {2} r2 = JOIN r1 WITH Variables::GlobalVariable#class#f ON FIRST 1 OUTPUT Lhs.0 'this', Lhs.1 'result'
453589 ~0% {2} r3 = JOIN r2 WITH Definitions::ModuleVariable#f ON FIRST 1 OUTPUT Lhs.0 'this', Lhs.1 'result'
return r3
```
and
```
(315s) Tuple counts for Definitions::SsaSourceVariable::getAUse_dispred#ff/2@a39328 after 1m57s:
...
1785275 ~3% {2} r24 = Definitions::ModuleVariable::global_variable_callnode#ff#shared UNION Definitions::SsaSourceVariable::getAUse_dispred#ff#shared
3008614987 ~0% {2} r25 = JOIN r24 WITH Variables::Variable::getScope_dispred#ff_10#join_rhs ON FIRST 1 OUTPUT Rhs.1 'this', Lhs.1 'result'
127 ~1% {2} r26 = JOIN r25 WITH Definitions::NonLocalVariable#class#f ON FIRST 1 OUTPUT Lhs.0 'this', Lhs.1 'result'
127 ~1% {2} r27 = JOIN r26 WITH Variables::LocalVariable#f ON FIRST 1 OUTPUT Lhs.0 'this', Lhs.1 'result'
...
```
(Note the timings: 2m33s and 1m57s.)
Now we have the much more reasonable
```
(38s) Tuple counts for Definitions::ModuleVariable::global_variable_callnode#ff/2@c53031 after 42ms:
453589 ~0% {2} r1 = JOIN Definitions::ModuleVariable::global_variable_callnode#ff#shared WITH Definitions::ModuleVariable::scope_as_global_variable#ff_10#join_rhs ON FIRST 1 OUTPUT Rhs.1 'this', Lhs.1 'result'
return r1
```
and
```
(46s) Tuple counts for Definitions::SsaSourceVariable::getAUse_dispred#ff/2@4b19de after 375ms:
...
```
