Support semi join

[Dandandan]

Which issue does this PR close?

Closes #461

Rationale for this change

Adds semi join support. This will enable us to rewrite WHERE id IN (..) and WHERE EXISTS to a (semi) join.

What changes are included in this PR?

Add semi join to hash join implementation.
What's not in this PR

• Semi join sql (should be added to sqlparser if we want to) / dataframe syntax
• Using the semi join in the planner for in/exists

Are there any user-facing changes?

No

[codecov-commenter]

Codecov Report

Merging #470 (9cb007a) into master (c8ab5a4) will increase coverage by 0.50%.
The diff coverage is 77.55%.

@@            Coverage Diff             @@
##           master     #470      +/-   ##
==========================================
+ Coverage   75.30%   75.80%   +0.50%     
==========================================
  Files         152      153       +1     
  Lines       25275    25924     +649     
==========================================
+ Hits        19033    19652     +619     
- Misses       6242     6272      +30     

Impacted Files	Coverage Δ
...sta/rust/core/src/serde/logical_plan/from_proto.rs	36.17% <0.00%> (-0.05%)	⬇️
...lista/rust/core/src/serde/logical_plan/to_proto.rs	62.32% <0.00%> (-0.08%)	⬇️
...ta/rust/core/src/serde/physical_plan/from_proto.rs	39.63% <0.00%> (-0.15%)	⬇️
...ista/rust/core/src/serde/physical_plan/to_proto.rs	50.46% <0.00%> (-0.16%)	⬇️
datafusion/src/logical_plan/builder.rs	90.08% <0.00%> (-0.39%)	⬇️
datafusion/src/logical_plan/plan.rs	80.62% <ø> (+0.52%)	⬆️
datafusion/src/physical_plan/planner.rs	80.32% <0.00%> (-0.14%)	⬇️
datafusion/src/optimizer/hash_build_probe_order.rs	58.53% <20.00%> (-1.97%)	⬇️
datafusion/src/physical_plan/hash_join.rs	86.45% <97.29%> (+0.39%)	⬆️
datafusion/src/physical_plan/hash_utils.rs	98.50% <100.00%> (+0.02%)	⬆️
... and 18 more

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[alamb]

I plan to review this tomorrow

[Dandandan]

Related PR for anti join here: #482

[houqp]

should the readme be updated to include semi join as well?

[Dandandan]

should the readme be updated to include semi join as well?

I think for now we don't - I would say that at least need to have in or exists to be mapped to a semi join, as currently there is not really a way for anyone to create it (other than creating a LogicalPlan explicitly).

[alamb]

Looks good to me @Dandandan ! Nice work

[alamb]

should you also possibly conditionalize this on being a SemiJoin? like

Suggested change

	| LogicalPlan::Join { .. }
	| LogicalPlan::Join if *join_type == JoinType::Semi { .. }

So if we add a new join type in the future it doesn't accidentally get allowed / disallowed in some confusing way

[Dandandan]

Tried that in earlier commit... But than the exhaustiveness checking gets in the way unfortunately.

[Dandandan]

I think the only way the compiler can do it now is by explicitly matching on all the join types, but as this feature is not added https://github.com/rust-lang/rfcs/blob/master/text/2535-or-patterns.md that would be quite verbose currently

[Dandandan]

I rewrote it a bit to use a function in the body of the join match

[alamb]

👍