Add ToString and Print method for JoinRelationSetManager and Fix JoinNode Print

[Light-City]

1.When we want to debug JoinRelationSetManager., we need to add the ToString and Print method.

for example: explain SELECT COUNT(*) FROM t1, t2, t3, t4 WHERE t1.c1 = t2.c1 AND t2.c2 = t3.c2 AND t3.c3 = t4.c3 ;

set_manager.Print();

will output:

child: 0
  relation: [0]
  child: 1
      relation: [0, 1]
child: 1
  relation: [1]
  child: 2
      relation: [1, 2]
child: 3
  relation: [3]
child: 2
  relation: [2]
  child: 3
      relation: [2, 3]

2.Change PrintJoinNode to Print and implement it.

[Tmonster]

Thank you for the PR! This should indeed come in handy when debugging. Just have some notes.

The RelationSetManager keeps track of already created relations. The way these references are stored isn't very intuitive, and muddies the logic as to what the RelationSetManager is actually doing, but it's an efficient implementation if joins have a very large number of relations. Currently it is a type of tree structure where every node has a reference to the relation set.

That being said, can we instead just iterate over all the JoinRelationSets/Values in the tree, add each JoinRelationSet to a "to_print" variable and print all the join relations created so far? This way we don't have to do this indenting stuff with "child" nodes. Relations technically don't even have children.

For your example, I think a better output would look like this.

RelationSets created:
[0]
[0,1]
[1]
[1,2]
[3]
[2]
[2,3]

[Light-City]

Thank you for the PR! This should indeed come in handy when debugging. Just have some notes.

The RelationSetManager keeps track of already created relations. The way these references are stored isn't very intuitive, and muddies the logic as to what the RelationSetManager is actually doing, but it's an efficient implementation if joins have a very large number of relations. Currently it is a type of tree structure where every node has a reference to the relation set.

That being said, can we instead just iterate over all the JoinRelationSets/Values in the tree, add each JoinRelationSet to a "to_print" variable and print all the join relations created so far? This way we don't have to do this indenting stuff with "child" nodes. Relations technically don't even have children.

For your example, I think a better output would look like this.

RelationSets created:
[0]
[0,1]
[1]
[1,2]
[3]
[2]
[2,3]

Indeed, I very much agree with your point of view. I have made modifications to the code.

[Light-City]

In addition, I found that PrintJoinNode of JoinNode is not defined. Here I modify it to Print and implement it.

[Light-City]

In addition, I found that PrintJoinNode of JoinNode is not defined. Here I modify it to Print and implement it.

related issue is #9067

[Tmonster]

Thanks! Pr looks good to me

[Light-City]

@Tmonster @Mytherin

Can this PR be merged? Are there any modifications needed?

[Mytherin]

Thanks