Make explain of ProjectOperator with alias show both name and alias info

[qianheng-aws]

Description

Add name information as well in the explain of ProjectOperator with alias, so user can identify whether the field in his plan comes from the right source.

POST _plugins/_sql/_explain
{
  "query": "SELECT (FlightTimeMin + 1) as FlightTimeMinPlusOne FROM opensearch_dashboards_sample_data_flights LIMIT 5"
}


#Before this PR
{
  "root": {
    "name": "ProjectOperator",
    "description": {
      "fields": "[FlightTimeMinPlusOne]"
    },
    "children": [
      {
        "name": "OpenSearchIndexScan",
        "description": {
          "request": """OpenSearchQueryRequest(indexName=opensearch_dashboards_sample_data_flights, sourceBuilder={"from":0,"size":5,"timeout":"1m","_source":{"includes":["FlightTimeMin"],"excludes":[]}}, searchDone=false)"""
        },
        "children": []
      }
    ]
  }
}

#With this PR
{
  "root": {
    "name": "ProjectOperator",
    "description": {
      "fields": "[(FlightTimeMin + 1) AS FlightTimeMinPlusOne]"
    },
    "children": [
      {
        "name": "OpenSearchIndexScan",
        "description": {
          "request": """OpenSearchQueryRequest(indexName=opensearch_dashboards_sample_data_flights, sourceBuilder={"from":0,"size":5,"timeout":"1m","_source":{"includes":["FlightTimeMin"],"excludes":[]}}, searchDone=false)"""
        },
        "children": []
      }
    ]
  }
}

Related Issues

Resolves #2901

Check List

• New functionality includes testing.
• New functionality has been documented.
• New functionality has javadoc added.
• New functionality has a user manual doc added.
• API changes companion pull request created.
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• Public documentation issue/PR created.

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[dai-chen]

Thanks for the changes!

[LantaoJin]

Looks like you should add a new method getNameWithAlias() in this class similar to getNameOrAlias().
And I have some concerns when to use getNameOrAlias() and when to use getNameWithAlias()?
Could you deep dive in it?

[qianheng-aws]

getNameOrAlias are used to get the field name to use in other operator. While in its toString, I just want to add more info than the field name, and it won't break the usage since it's just for explanation, no execution affection.

I think we don't need to add such a new function as it will only be used in this toString method if added, we should add it unless it can be reused in other places as well.

[LantaoJin]

we should add it unless it can be reused in other places as well.

I doubt are there any other places to replace to getNameWithAlias either as toString does. Can you help to confirm them?

[qianheng-aws]

Having scanned over all the usage of getNameOrAlias, I don't see any other places need to be replaced. They are all related to execution.

[LantaoJin]

Thanks @qianheng-aws . @dai-chen Can u help to double confirm it since u are the author of this class?

[dai-chen]

Sorry I can't recall the specific details. I think it should be safe to change the toString method only.

[LantaoJin]

Could you overwrite some more complex cases:

1. SELECT <field-list> <alias-list> (compound)
2. SELECT field as alias1, alias1 as alias2, alias2 as alias3 (nested alias)
3. SELECT 1 as existing-field from t (override)

[qianheng-aws]

1. Does SQL support such syntax? Or do you mean filed1 as alias1, filed2 as alias2?
2. Seems SQL don't support nested alias.
3. ditto.

[LantaoJin]

1. Compound case means not only contains pure fields but also contains fields with alias
2. It should be a bug if it's unsupported. Translate to PPL, it should be a multiple-rename pipeline.
3. Same as above.

[qianheng-aws]

1. I see. We have such cases in UT. Maybe make this IT be the compound case as well.
2. yeah. PPL supports while SQL doesn't.

[LantaoJin]

For 2 and 3, could you create two issues for that?

[qianheng-aws]

Sure, but I think they may be the same cause. It's because we only use ProjectOperator instead of EvalOperator for SQL, while project don't support update and evaluate nested fields like eval.

[qianheng-aws]

Create a new issue to bring out this problem here: #2933

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.50%. Comparing base (7e73f12) to head (460189e).
Report is 39 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #2911   +/-   ##
=========================================
  Coverage     94.49%   94.50%           
- Complexity     5230     5236    +6     
=========================================
  Files           514      515    +1     
  Lines         14771    14791   +20     
  Branches        978      978           
=========================================
+ Hits          13958    13978   +20     
  Misses          772      772           
  Partials         41       41           

Flag	Coverage Δ
sql-engine	94.50% <100.00%> (+<0.01%)	⬆️

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