[Bug] Allow "IF NOT EXISTS" check on branches

[emalit]

Search before asking

• I searched in the issues and found nothing similar.

Paimon version

Paimon 1.2.0

Compute Engine

Flink 1.20.1

Minimal reproduce step

1. Create a paimon table for a sink
2. Create an empty branch for that table
3. Create a Flink job that takes data from any source and sinks it into that branch
4. Re-run the job

What doesn't meet your expectations?

Upon re-running the job, it crashes with this error:

Caused by: java.lang.IllegalArgumentException: Branch name 'my_branch_name' already exists.

Since flink jobs can be restarted and redeployed, we should have a way to check whether the branch name already exists and skip creating it. For example, CREATE TABLE can be modified by IF NOT EXISTS. This should also be available for branches so redeploying the job doesn't crash.

Anything else?

No response

Are you willing to submit a PR?

• I'm willing to submit a PR!