7x/field resolver performance

[Mpdreamz]

This brings some performance enhancements to the way we resolve Field, Fields and PropertyName when these are instantiated using an Expression. E.g if you do q.Term<Project>(p=>p.Name, "value")

We were visiting the expression multiple times

1. To create a comparison value we used a specialized visitor
2. This visitor calls tostring which in turns calls the BCL tostring visitor
3. Then we did some regex replace to create a sane key
4. Visit expression and check if there are compilable parts and if so make sure we do not cache the expression
5. Finally resolve the expression using the connection settings using another visitor

This PR

Combines the comparison vistor/tostring visitor/caching visitor into one. We no longer rely on Expression.ToString() and since we only need to deal with a certain type of expression our tostring performance better then the BCL one.

Then if its we pass it off the FieldExpressionVisitor if not in local cache already. While writing this I wonder if FieldExpressionVisitor could reuse the stack from our new ToStringVisitor. Will follow up in a comment.

The benchmark compares:

1. Expression<Func<T, object>>.ToString() as Boxed Expression
2. Expression<Func<T, TValue>>.ToString() as Unboxed Expression
3. FieldInferrer.Resolve(Expression<Func<T, object>>) as Field Resolver
4. FieldInferrer.Resolve(Expression<Func<T, TValue>>) as Field Resolver Unboxed , only available on last benchmark

before

Method	Jit	Runtime	Mean	Error	StdDev	Gen 0/1k Op	Gen 1/1k Op	Gen 2/1k Op	Allocated Memory/Op
'Boxed Expression'	LegacyJit	Clr	5.622 ns	2.8143 ns	0.1543 ns	0.0004	-	-	-
'Unboxed Expression'	LegacyJit	Clr	2.970 ns	1.6041 ns	0.0879 ns	0.0003	-	-	-
'Field Resolver'	LegacyJit	Clr	9.877 ns	3.5268 ns	0.1933 ns	0.0004	-	-	-
'Boxed Expression'	RyuJit	Clr	5.638 ns	1.6133 ns	0.0884 ns	0.0004	-	-	-
'Unboxed Expression'	RyuJit	Clr	2.994 ns	1.3333 ns	0.0731 ns	0.0003	-	-	-
'Field Resolver'	RyuJit	Clr	9.668 ns	2.2694 ns	0.1244 ns	0.0004	-	-	-
'Boxed Expression'	RyuJit	Core	5.097 ns	1.2232 ns	0.0670 ns	0.0003	-	-	2 B
'Unboxed Expression'	RyuJit	Core	3.496 ns	2.1039 ns	0.1153 ns	0.0003	-	-	2 B
'Field Resolver'	RyuJit	Core	10.640 ns	0.3072 ns	0.0168 ns	0.0004	-	-	2 B

after

Method	Jit	Runtime	Mean	Error	StdDev	Gen 0/1k Op	Gen 1/1k Op	Gen 2/1k Op	Allocated Memory/Op
'Boxed Expression'	LegacyJit	Clr	6.140 ns	0.2625 ns	0.0144 ns	0.0004	-	-	-
'Unboxed Expression'	LegacyJit	Clr	3.275 ns	0.9076 ns	0.0497 ns	0.0003	-	-	-
'Field Resolver'	LegacyJit	Clr	4.938 ns	6.8149 ns	0.3735 ns	0.0003	-	-	-
'Field Resolver Unboxed'	LegacyJit	Clr	3.777 ns	1.1002 ns	0.0603 ns	0.0003	-	-	-
'Boxed Expression'	RyuJit	Clr	6.201 ns	2.6049 ns	0.1428 ns	0.0004	-	-	-
'Unboxed Expression'	RyuJit	Clr	3.491 ns	6.1798 ns	0.3387 ns	0.0003	-	-	-
'Field Resolver'	RyuJit	Clr	5.049 ns	2.4973 ns	0.1369 ns	0.0003	-	-	-
'Field Resolver Unboxed'	RyuJit	Clr	3.810 ns	5.3521 ns	0.2934 ns	0.0003	-	-	-
'Boxed Expression'	RyuJit	Core	5.981 ns	7.2205 ns	0.3958 ns	0.0003	-	-	2 B
'Unboxed Expression'	RyuJit	Core	7.120 ns	58.5053 ns	3.2069 ns	0.0003	-	-	2 B
'Field Resolver'	RyuJit	Core	6.504 ns	9.8342 ns	0.5390 ns	0.0003	-	-	2 B
'Field Resolver Unboxed'	RyuJit	Core	5.464 ns	9.9388 ns	0.5448 ns	0.0003	-	-	2 B

[Mpdreamz]

Tried locally to reuse the visit of the ToStringVisitor and it creating a second stack for the fieldname to resolve so it doesn't need to visit the expression as well.

Don't see any real benefit and it adds quite some complexity so resetting locally.

Benchmark for reference

Method	Jit	Runtime	Mean	Error	StdDev	Gen 0/1k Op	Gen 1/1k Op	Gen 2/1k Op	Allocated Memory/Op
'Boxed Expression'	LegacyJit	Clr	5.914 ns	7.5240 ns	0.4124 ns	0.0004	-	-	-
'Unboxed Expression'	LegacyJit	Clr	3.445 ns	3.2429 ns	0.1778 ns	0.0003	-	-	-
'Field Resolver'	LegacyJit	Clr	5.022 ns	1.4263 ns	0.0782 ns	0.0004	-	-	-
'Field Resolver Unboxed'	LegacyJit	Clr	3.657 ns	4.1828 ns	0.2293 ns	0.0003	-	-	-
'Boxed Expression'	RyuJit	Clr	6.113 ns	0.0929 ns	0.0051 ns	0.0004	-	-	-
'Unboxed Expression'	RyuJit	Clr	3.317 ns	0.1476 ns	0.0081 ns	0.0003	-	-	-
'Field Resolver'	RyuJit	Clr	6.347 ns	31.5901 ns	1.7316 ns	0.0004	-	-	-
'Field Resolver Unboxed'	RyuJit	Clr	3.754 ns	0.0714 ns	0.0039 ns	0.0003	-	-	-
'Boxed Expression'	RyuJit	Core	5.315 ns	0.9369 ns	0.0514 ns	0.0003	-	-	2 B
'Unboxed Expression'	RyuJit	Core	3.855 ns	7.7585 ns	0.4253 ns	0.0003	-	-	2 B
'Field Resolver'	RyuJit	Core	6.263 ns	0.8671 ns	0.0475 ns	0.0004	-	-	2 B
'Field Resolver Unboxed'	RyuJit	Core	4.779 ns	0.2023 ns	0.0111 ns	0.0003	-	-	2 B

[Mpdreamz]

Reviewed this morning during our sync meeting so merging myself

[Mpdreamz]

cherry-picked to master