Fix invariants optimization involving views (#7388)

[dyemanov]

The idea is that we should not compare view field's stream with streams from other RSEs until the field has been expanded to the proper expression. Once it's done, sub->pass1() will recursively take care of the invariant checking. The test case from #7388 now shows good performance in both cases, but I'd like to have a second opinion.

[livius2]

Is it possible to see difference of such execution in explain plan?
As now both plans are equal. Do you consider some extension to it?

[dyemanov]

I agree it could be useful. Will take look at possible implementation.

[dyemanov]

This is the suggested plan output:

Sub-query (invariant)
    -> Singularity Check
        -> Aggregate
            -> Nested Loop Join (outer)
                -> Filter
                    -> Hash Join (inner)
                        -> Table "RDB$RELATION_FIELDS" as "SUB RF" Full Scan
                        -> Record Buffer (record length: 529)
                            -> Table "RDB$RELATIONS" as "SUB R" Full Scan
                -> Filter
                    -> Table "RDB$SECURITY_CLASSES" as "SUB SC" Access By ID
                        -> Bitmap
                            -> Index "RDB$INDEX_7" Unique Scan
Select Expression
    -> Filter
        -> Nested Loop Join (outer)
            -> Nested Loop Join (inner)
                -> Filter
                    -> Table "RDB$RELATIONS" as "SUB R" Access By ID
                        -> Bitmap
                            -> Index "RDB$INDEX_1" Range Scan (full match)
                -> Filter
                    -> Table "RDB$RELATION_FIELDS" as "SUB RF" Access By ID
                        -> Bitmap
                            -> Index "RDB$INDEX_4" Range Scan (full match)
            -> Filter
                -> Table "RDB$SECURITY_CLASSES" as "SUB SC" Access By ID
                    -> Bitmap
                        -> Index "RDB$INDEX_7" Unique Scan

[livius2]

Will be good to see both plans in new version.
It will be now like this?

Sub-query (invariant)
    -> Singularity Check

and second version

Select Expression
    -> Singularity Check

or it will look differently?

Sub-query (invariant)
    -> Singularity Check

and second version

Sub-query (variant)
    -> Singularity Check

[dyemanov]

"Select Expression" is the main query, it does not change. For sub-query now we see also "Select Expression", after the patch it will look as either "Sub-query" or "Sub-query (invariant)".

[dyemanov]

Most sub-queries are correlated in practice, so reporting them as "variant" IMO is about to cause more questions than keeping is simple.

[livius2]

Yes, my concern was only if for variant there will be Select Expression or also Sub-query :)

[dyemanov]

Plan explain improvements will be applied separately.