Support function coalesce with Calcite

.github/CODEOWNERS

@@ -1,2 +1,2 @@
 # This should match the owning team set up in https://github.com/orgs/opensearch-project/teams
-*   @pjfitzgibbons @ps48 @kavithacm @derek-ho @joshuali925 @dai-chen @YANG-DB @rupal-bq @mengweieric @vamsi-amazon @swiddis @penghuo @seankao-az @MaxKsyunz @Yury-Fridlyand @anirudha @forestmvey @acarbonetto @GumpacG
+*   @pjfitzgibbons @ps48 @kavithacm @derek-ho @joshuali925 @dai-chen @YANG-DB @rupal-bq @mengweieric @vamsi-amazon @swiddis @penghuo @seankao-az @MaxKsyunz @Yury-Fridlyand @anirudha @forestmvey @acarbonetto @GumpacG @ykmr1224 @LantaoJin @noCharger @qianheng-aws

.github/ISSUE_TEMPLATE/request_of_comments.md

@@ -0,0 +1,32 @@
+---
+name: 📄 Request of comments 
+about: Create a request of comments to initiate an discussion on feature implementation / design. 
+title: '[RFC]'
+labels: 'rfc, untriaged'
+assignees: ''
+---
+
+**Problem Statement**
+Describes the issue or challenge that needs to be addressed.
+
+**Current State**
+Explains the existing setup or context and its shortcomings.
+
+**Long-Term Goals**
+* Describe the ideal outcome or future state you aim to achieve.
+* What are the primary objectives of this solution should fulfill in the long run?
+* How will this solution ensure sustainability or scalability over time?
+* Consider whether the solution addresses the root problem and aligns with the overall goals.
+* How confident are we that this solution solves the problem?
+
+**Proposal**
+Summarizes the suggested solution or improvement.
+
+**Approach**
+Details the steps or strategy to implement the proposal.
+
+**Alternative**
+Alternative that can serve as workarounds to partially or temporarily solve the problem.
+
+**Implementation Discussion**
+Outlines point the discussion regarding the proposed implementation.

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,16 +1,18 @@
 ### Description
 [Describe what this change achieves]
-
-### Issues Resolved
-[List any issues this PR will resolve]
-
+
+### Related Issues
+Resolves #[Issue number to be closed when this PR is merged]
+<!-- List any other related issues here -->
+
 ### Check List
 - [ ] New functionality includes testing.
-  - [ ] All tests pass, including unit test, integration test and doctest
 - [ ] New functionality has been documented.
-  - [ ] New functionality has javadoc added
-  - [ ] New functionality has user manual doc added
-- [ ] Commits are signed per the DCO using --signoff 
+ - [ ] New functionality has javadoc added.
+ - [ ] New functionality has a user manual doc added.
+- [ ] API changes companion pull request [created](https://github.com/opensearch-project/opensearch-api-specification/blob/main/DEVELOPER_GUIDE.md).
+- [ ] Commits are signed per the DCO using `--signoff`.
+- [ ] Public documentation issue/PR [created](https://github.com/opensearch-project/documentation-website/issues/new/choose).
 
 By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
-For more information on following Developer Certificate of Origin and signing off your commits, please check [here](https://github.com/opensearch-project/OpenSearch/blob/main/CONTRIBUTING.md#developer-certificate-of-origin).
+For more information on following Developer Certificate of Origin and signing off your commits, please check [here](https://github.com/opensearch-project/sql/blob/main/CONTRIBUTING.md#developer-certificate-of-origin).

.github/workflows/codeql-analysis.yml

@@ -7,6 +7,7 @@ on:
       - '[1-9]+.[0-9x]+'
   push:
     branches-ignore:
+      - 'backport/**'
       - 'dependabot/**'
     paths:
       - '**/*.java'
@@ -27,7 +28,11 @@ jobs:
     steps:
     - name: Checkout repository
       uses: actions/checkout@v3
-
+    - name: Set up JDK 21
+      uses: actions/setup-java@v3
+      with:
+          distribution: temurin
+          java-version: 21
     - name: Initialize CodeQL
       uses: github/codeql-action/init@v2
       with:

.github/workflows/integ-tests-with-security.yml

@@ -4,6 +4,7 @@ on:
   pull_request:
   push:
     branches-ignore:
+      - 'backport/**'
       - 'dependabot/**'
     paths:
       - 'integ-test/**'
@@ -20,21 +21,22 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        java: [ 11, 17 ]
-
+        java: [21, 23]
     runs-on: ubuntu-latest
     container:
       # using the same image which is used by opensearch-build team to build the OpenSearch Distribution
       # this image tag is subject to change as more dependencies and updates will arrive over time
       image: ${{ needs.Get-CI-Image-Tag.outputs.ci-image-version-linux }}
-      # need to switch to root so that github actions can install runner binary on container without permission issues.
-      options: --user root
+      options: ${{ needs.Get-CI-Image-Tag.outputs.ci-image-start-options }}
 
     steps:
-    - uses: actions/checkout@v3
+    - name: Run start commands
+      run: ${{ needs.Get-CI-Image-Tag.outputs.ci-image-start-command }}
+
+    - uses: actions/checkout@v4
 
     - name: Set up JDK ${{ matrix.java }}
-      uses: actions/setup-java@v3
+      uses: actions/setup-java@v4
       with:
         distribution: 'temurin'
         java-version: ${{ matrix.java }}
@@ -46,7 +48,7 @@ jobs:
 
     - name: Upload test reports
       if: ${{ always() }}
-      uses: actions/upload-artifact@v2
+      uses: actions/upload-artifact@v4
       continue-on-error: true
       with:
         name: test-reports-${{ matrix.os }}-${{ matrix.java }}
@@ -59,16 +61,16 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ windows-latest, macos-latest ]
-        java: [ 11, 17 ]
+        os: [ windows-latest, macos-13 ]
+        java: [21, 23]
 
     runs-on: ${{ matrix.os }}
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
 
     - name: Set up JDK ${{ matrix.java }}
-      uses: actions/setup-java@v3
+      uses: actions/setup-java@v4
       with:
         distribution: 'temurin'
         java-version: ${{ matrix.java }}
@@ -78,7 +80,7 @@ jobs:
 
     - name: Upload test reports
       if: ${{ always() }}
-      uses: actions/upload-artifact@v2
+      uses: actions/upload-artifact@v4
       continue-on-error: true
       with:
         name: test-reports-${{ matrix.os }}-${{ matrix.java }}

.github/workflows/maven-publish.yml

@@ -23,7 +23,7 @@ jobs:
       - uses: actions/setup-java@v3
         with:
           distribution: temurin # Temurin is a distribution of adoptium
-          java-version: 11
+          java-version: 21
       - uses: actions/checkout@v3
       - uses: aws-actions/configure-aws-credentials@v1.7.0
         with:

.github/workflows/sql-pitest.yml

@@ -21,21 +21,24 @@ jobs:
     strategy:
       matrix:
         java:
-          - 11
-          - 17
+          - 21
+          - 23
     runs-on: ubuntu-latest
     container:
       # using the same image which is used by opensearch-build team to build the OpenSearch Distribution
       # this image tag is subject to change as more dependencies and updates will arrive over time
       image: ${{ needs.Get-CI-Image-Tag.outputs.ci-image-version-linux }}
-      # need to switch to root so that github actions can install runner binary on container without permission issues.
-      options: --user root
+      options: ${{ needs.Get-CI-Image-Tag.outputs.ci-image-start-options }}
+
 
     steps:
-    - uses: actions/checkout@v3
+    - name: Run start commands
+      run: ${{ needs.Get-CI-Image-Tag.outputs.ci-image-start-command }}
+
+    - uses: actions/checkout@v4
 
     - name: Set up JDK ${{ matrix.java }}
-      uses: actions/setup-java@v3
+      uses: actions/setup-java@v4
       with:
         distribution: 'temurin'
         java-version: ${{ matrix.java }}
@@ -47,7 +50,7 @@ jobs:
 
     - name: Upload test reports
       if: always()
-      uses: actions/upload-artifact@v2
+      uses: actions/upload-artifact@v4
       with:
         name: test-reports-${{ matrix.entry.java }}
         path: |

.github/workflows/sql-test-and-build-workflow.yml

@@ -4,6 +4,7 @@ on:
   pull_request:
   push:
     branches-ignore:
+      - 'backport/**'
       - 'dependabot/**'
     paths:
       - '**/*.java'
@@ -28,22 +29,22 @@ jobs:
       # Run all jobs
       fail-fast: false
       matrix:
-        java:
-          - 11
-          - 17
+        java: [21, 23]
     runs-on: ubuntu-latest
     container:
       # using the same image which is used by opensearch-build team to build the OpenSearch Distribution
       # this image tag is subject to change as more dependencies and updates will arrive over time
       image: ${{ needs.Get-CI-Image-Tag.outputs.ci-image-version-linux }}
-      # need to switch to root so that github actions can install runner binary on container without permission issues.
-      options: --user root
+      options: ${{ needs.Get-CI-Image-Tag.outputs.ci-image-start-options }}
 
     steps:
-    - uses: actions/checkout@v3
+    - name: Run start commands
+      run: ${{ needs.Get-CI-Image-Tag.outputs.ci-image-start-command }}
+
+    - uses: actions/checkout@v4
 
     - name: Set up JDK ${{ matrix.java }}
-      uses: actions/setup-java@v3
+      uses: actions/setup-java@v4
       with:
         distribution: 'temurin'
         java-version: ${{ matrix.java }}
@@ -53,11 +54,6 @@ jobs:
         chown -R 1000:1000 `pwd`
         su `id -un 1000` -c "./gradlew --continue build"
 
-    - name: Run backward compatibility tests
-      run: |
-        chown -R 1000:1000 `pwd`
-        su `id -un 1000` -c "./scripts/bwctest.sh"
-
     - name: Create Artifact Path
       run: |
         mkdir -p opensearch-sql-builds
@@ -66,22 +62,22 @@ jobs:
     # This step uses the codecov-action Github action: https://github.com/codecov/codecov-action
     - name: Upload SQL Coverage Report
       if: ${{ always() }}
-      uses: codecov/codecov-action@v3
+      uses: codecov/codecov-action@v4
       continue-on-error: true
       with:
         flags: sql-engine
         token: ${{ secrets.CODECOV_TOKEN }}
 
     - name: Upload Artifacts
-      uses: actions/upload-artifact@v2
+      uses: actions/upload-artifact@v4
       continue-on-error: true
       with:
         name: opensearch-sql-ubuntu-latest-${{ matrix.java }}
         path: opensearch-sql-builds
 
     - name: Upload test reports
       if: ${{ always() }}
-      uses: actions/upload-artifact@v2
+      uses: actions/upload-artifact@v4
       continue-on-error: true
       with:
         name: test-reports-ubuntu-latest-${{ matrix.java }}
@@ -104,17 +100,17 @@ jobs:
       fail-fast: false
       matrix:
         entry:
-          - { os: windows-latest, java: 11, os_build_args: -x doctest  -PbuildPlatform=windows }
-          - { os: macos-latest, java: 11}
-          - { os: windows-latest, java: 17, os_build_args: -x doctest -PbuildPlatform=windows }
-          - { os: macos-latest, java: 17 }
+          - { os: windows-latest, java: 21, os_build_args: -x doctest -PbuildPlatform=windows }
+          - { os: windows-latest, java: 23, os_build_args: -x doctest -PbuildPlatform=windows }
+          - { os: macos-13, java: 21 }
+          - { os: macos-13, java: 23 }
     runs-on: ${{ matrix.entry.os }}
 
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
 
     - name: Set up JDK ${{ matrix.java }}
-      uses: actions/setup-java@v3
+      uses: actions/setup-java@v4
       with:
         distribution: 'temurin'
         java-version: ${{ matrix.entry.java }}
@@ -130,22 +126,22 @@ jobs:
     # This step uses the codecov-action Github action: https://github.com/codecov/codecov-action
     - name: Upload SQL Coverage Report
       if: ${{ always() && matrix.entry.os == 'ubuntu-latest' }}
-      uses: codecov/codecov-action@v3
+      uses: codecov/codecov-action@v4
       continue-on-error: true
       with:
         flags: sql-engine
         token: ${{ secrets.CODECOV_TOKEN }}
 
     - name: Upload Artifacts
-      uses: actions/upload-artifact@v2
+      uses: actions/upload-artifact@v4
       continue-on-error: true
       with:
         name: opensearch-sql-${{ matrix.entry.os }}-${{ matrix.entry.java }}
         path: opensearch-sql-builds
 
     - name: Upload test reports
       if: ${{ always() && matrix.entry.os == 'ubuntu-latest' }}
-      uses: actions/upload-artifact@v2
+      uses: actions/upload-artifact@v4
       continue-on-error: true
       with:
         name: test-reports-${{ matrix.entry.os }}-${{ matrix.entry.java }}
@@ -161,3 +157,49 @@ jobs:
           plugin/build/reports/**
           doctest/build/testclusters/docTestCluster-0/logs/*
           integ-test/build/testclusters/*/logs/*
+
+  bwc-tests:
+    needs: Get-CI-Image-Tag
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        java: [21, 23]
+    container:
+      image: ${{ needs.Get-CI-Image-Tag.outputs.ci-image-version-linux }}
+      options: ${{ needs.Get-CI-Image-Tag.outputs.ci-image-start-options }}
+
+    steps:
+    - name: Run start commands
+      run: ${{ needs.Get-CI-Image-Tag.outputs.ci-image-start-command }}
+
+    - uses: actions/checkout@v4
+
+    - name: Set up JDK ${{ matrix.java }}
+      uses: actions/setup-java@v4
+      with:
+        distribution: 'temurin'
+        java-version: ${{ matrix.java }}
+
+    - name: Run backward compatibility tests
+      run: |
+        chown -R 1000:1000 `pwd`
+        su `id -un 1000` -c "./scripts/bwctest.sh"
+
+    - name: Upload test reports
+      if: ${{ always() }}
+      uses: actions/upload-artifact@v4
+      continue-on-error: true
+      with:
+        name: test-reports-ubuntu-latest-${{ matrix.java }}-bwc
+        path: |
+          sql/build/reports/**
+          ppl/build/reports/**
+          core/build/reports/**
+          common/build/reports/**
+          opensearch/build/reports/**
+          integ-test/build/reports/**
+          protocol/build/reports/**
+          legacy/build/reports/**
+          plugin/build/reports/**
+          doctest/build/testclusters/docTestCluster-0/logs/*
+          integ-test/build/testclusters/*/logs/*