hashCode functions using multiply method

[Albert]

Hi ,
    I've noticed a lot of the places, calcite codes is using something like
this:

result = 31 * result + (body != null ? body.hashCode() : 0);

using multiply in hash code calculation probably isn't best practice.
something like shift operator should be more efficient.  since the project
is already depending on guava, why not using their hash code utils ?


thanks.



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