Push down limit through eval

[qianheng-aws]

Description

Add a rule EvalPushDown.PUSH_DOWN_LIMIT, this rule will push down limit under eval. Thus, limit has chance to be pushed down into TableScanBuilder later.

e.g.

POST _plugins/_ppl/_explain
{
  "query": """
    source=opensearch_dashboards_sample_data_flights |  eval FlightMin = FlightTimeMin | head 5 | fields  FlightMin
  """
}

# Before optimization
{
  "root": {
    "name": "ProjectOperator",
    "description": {
      "fields": "[FlightMin]"
    },
    "children": [
      {
        "name": "LimitOperator",
        "description": {
          "limit": 5,
          "offset": 0
        },
        "children": [
          {
            "name": "EvalOperator",
            "description": {
              "expressions": {
                "FlightMin": "FlightTimeMin"
              }
            },
            "children": [
              {
                "name": "OpenSearchIndexScan",
                "description": {
                  "request": """OpenSearchQueryRequest(indexName=opensearch_dashboards_sample_data_flights, 

sourceBuilder={"from":0,"size":200,"timeout":"1m"}, searchDone=false)"""
                },
                "children": []
              }
            ]
          }
        ]
      }
    ]
  }
}

# After optimization
{
  "root": {
    "name": "ProjectOperator",
    "description": {
      "fields": "[FlightMin]"
    },
    "children": [
      {
        "name": "EvalOperator",
        "description": {
          "expressions": {
            "FlightMin": "FlightTimeMin"
          }
        },
        "children": [
          {
            "name": "OpenSearchIndexScan",
            "description": {
              "request": """OpenSearchQueryRequest(indexName=opensearch_dashboards_sample_data_flights, 

sourceBuilder={"from":0,"size":5,"timeout":"1m"}, searchDone=false)"""
            },
            "children": []
          }
        ]
      }
    ]
  }
}

Note: Also added TODOs in this PR to implement rules PUSH_DOWN_SORT and PUSH_DOWN_PROJECT as follow-ups, which are more complex due to expression replacement.

Related Issues

Resolves #2903

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.
• Commits are signed per the DCO using --signoff.
• Public documentation issue/PR created.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
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[codecov]

Codecov Report

Attention: Patch coverage is 95.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 94.62%. Comparing base (593ffab) to head (b7c4129).
Report is 6 commits behind head on main.

Files	Patch %	Lines
...search/sql/planner/optimizer/pattern/Patterns.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #2876   +/-   ##
=========================================
  Coverage     94.62%   94.62%           
- Complexity     5166     5170    +4     
=========================================
  Files           508      509    +1     
  Lines         14539    14559   +20     
  Branches        959      959           
=========================================
+ Hits          13758    13777   +19     
- Misses          740      741    +1     
  Partials         41       41           

Flag	Coverage Δ
sql-engine	94.62% <95.00%> (+<0.01%)	⬆️

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[dai-chen]

Minor comment. Thanks for the changes!

[LantaoJin]

@qianheng-aws could you update the PR title more precise? PR title will be recorded in release notes.

[LantaoJin]

LGTM