Add coalesce PPL command

[salyh]

Description

Add coalesce PPL command

Issues Resolved

#519

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.

[salyh]

Will need to add tests and readme

[YANG-DB]

@salyh plz update branch to resolve latest merge conflict
thanks

[salyh]

Done. Now you can use it as a function like eval c=coalesce('a','b')

[salyh]

If that looks good to you I will add tests and docs

[LantaoJin]

If that looks good to you I will add tests and docs

Yes, I think so.

[YANG-DB]

can you please add tests for this functionality ?
and also please update the README with an example query

[YANG-DB]

@salyh plz fix the Developer Certificate of Origin Check ...

[salyh]

@salyh plz fix the Developer Certificate of Origin Check ...

fixed

[YANG-DB]

sorry - @lukasz-soszynski-eliatra can u plz rebase and merge the conflicts ?
its probably due to the latest merge ...
Thanks

[lukasz-soszynski-eliatra]

Done

[opensearch-trigger-bot]

The backport to 0.5 failed:

The process '/usr/bin/git' failed with exit code 128

To backport manually, run these commands in your terminal:

# Navigate to the root of your repository
cd $(git rev-parse --show-toplevel)
# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add ../.worktrees/opensearch-spark/backport-0.5 0.5
# Navigate to the new working tree
pushd ../.worktrees/opensearch-spark/backport-0.5
# Create a new branch
git switch --create backport/backport-609-to-0.5
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 c6b388a99b25a635e0cd80081fa9ed9292533395
# Push it to GitHub
git push --set-upstream origin backport/backport-609-to-0.5
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/opensearch-spark/backport-0.5

Then, create a pull request where the base branch is 0.5 and the compare/head branch is backport/backport-609-to-0.5.

[opensearch-trigger-bot]

The backport to 0.5-nexus failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Navigate to the root of your repository
cd $(git rev-parse --show-toplevel)
# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add ../.worktrees/opensearch-spark/backport-0.5-nexus 0.5-nexus
# Navigate to the new working tree
pushd ../.worktrees/opensearch-spark/backport-0.5-nexus
# Create a new branch
git switch --create backport/backport-609-to-0.5-nexus
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 c6b388a99b25a635e0cd80081fa9ed9292533395
# Push it to GitHub
git push --set-upstream origin backport/backport-609-to-0.5-nexus
# Go back to the original working tree
popd
# Delete the working tree
git worktree remove ../.worktrees/opensearch-spark/backport-0.5-nexus

Then, create a pull request where the base branch is 0.5-nexus and the compare/head branch is backport/backport-609-to-0.5-nexus.