MINOR: Make ColumnPath immutable

[findepi]

Make sure you have checked all steps below.

Jira

• My PR addresses the following Parquet Jira issues and references
  them in the PR title. For example, "PARQUET-1234: My Parquet PR"
  • https://issues.apache.org/jira/browse/PARQUET-XXX
  • In case you are adding a dependency, check if the license complies with
    the ASF 3rd Party License Policy.

Tests

• My PR adds the following unit tests OR does not need testing for this extremely good reason: I don't know of an estabilished way of testing for class immutability

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  • To apply the necessary changes, run mvn spotless:apply -Pvector-plugins

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[findepi]

cc @raunaqmorarka

• My PR addresses the following Parquet Jira issues and references
  them in the PR title.

not yet. I will create one if needed

[raunaqmorarka]

I think it would also help to have a boolean equals(String[] path) method so that we can make path equality checks without incurring an unnecessary array copy.

[findepi]

I know it could be useful for Parquet users such as Trino, but was hesitant to add this as not directly related to immutability. Since toArray became copying, i added toList which avoids copy. Maybe this new method also satisfies those needs and we don't need yet another one?

[raunaqmorarka]

ya, i think that new method will help

[raunaqmorarka]

ya, i think that new method will help

[wgtmac]

It seems that you need to run mvn spotless:apply to make the CIs happy.

[findepi]

@wgtmac thanks! can you please allow the workflow again? It passed on my fork this time.

[wgtmac]

BTW, could you please create an issue to explain why do we need this change?

https://github.com/apache/parquet-java/issues/new/choose

[findepi]

I don't think i can describe my reasoning in terms of a end-user perceivable bug. I do believe immutable objects are easier to reason about and ColumnPath looks like it was intended not to be mutated.

[wgtmac]

+1

Thanks @findepi and @raunaqmorarka!