Gen4: improvement of joinTree creation

[frouioui]

Description

This pull request contains a bug fix for #8813. The bug happens when we join two queryTrees to create a joinTree.

When pushing a join predicate on a joinTree (pushJoinPredicate), we're looking in the predicate for a ColName that LHS solves, once we find the ColName, we add it to LHS's columns, and we add it into our joinTree's JoinVars.

Then, we create an argument for this new column, along with a new predicate containing the argument and the second column of our join predicate, which is solved by RHS. This new predicate is pushed to RHS using the same function pushJoinPredicate.

However, if RHS is also a joinTree we try to push the predicate as an output column, meaning that we will create new output columns in RHS, and this is done in a recursive fashion (i.e if RHS's RHS is also a joinTree). Instead, we can add the predicate to the first route we find in RHS that solves it, avoiding the creation of unrequired output columns.

Related Issue(s)

• Gen4 Tracking #7280
• Fixes Incorrect Join Vars in Gen4 plan #8813

Checklist

• Tests were added or are not required
• Documentation was added or is not required

[GuptaManan100]

@frouioui the sizegen test is failing. I tried running make codegen locally and nothing changed for me! I don't know why it is failing. We should take a look

[GuptaManan100]

LGTM! 😺