[CALCITE-4426] Short-circuit evaluating when comparing two "RelTraitSet"s (Jiatao Tao)

[Aaaaaaron]

No description provided.

[MalteBellmann]

Hi, 
wouldn't it be easier to read and more general to implement this short-circuit in RelTraitSet#satisfies, as it is explained in the JavaDoc that "each trait set satisfies itself"? 
With this change:

public boolean satisfies(RelTraitSet that) {
    if (this == that){
      return true;
    }

    // now the normal check...
}

[Aaaaaaron]

Hi, 
wouldn't it be easier to read and more general to implement this short-circuit in RelTraitSet#satisfies, as it is explained in the JavaDoc that "each trait set satisfies itself"? 
With this change:

public boolean satisfies(RelTraitSet that) {
    if (this == that){
      return true;
    }

    // now the normal check...
}

Yes, it's better, thanks!

[liyafan82]

LGTM. This is clearly a safe improvment.

[vlsi]

@Aaaaaaron , please remove to improve the performance of RelSubset#getRelList from JIRA and from the commit message.
The commit has virtually nothing to do with RelSubset#getRelList

[Aaaaaaron]

@Aaaaaaron , please remove to improve the performance of RelSubset#getRelList from JIRA and from the commit message.
The commit has virtually nothing to do with RelSubset#getRelList

Sure, in the first version, the change is in getRelList and after I update the code, I forgot to change the message, thanks @vlsi !

[hsyuan]

matches can do the same as satisfies.
It is a legit change.

[Aaaaaaron]

Hi @amaliujia, could you help please review this PR? Thanks!

[amaliujia]

LGTM

if there is no objections, I will merge this PR.