Migration to fix wrong values of label_ids in epics index

What does this MR do and why?

When we removed the labels from epics, there was a bug not updating the label_ids in the epics index. This MR is to reindex all the epics which don't have new SCHEMA_VERSION = 23_10. The schema_version with 2310 is set after the underlying bug gets fixed.

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Before	After

How to set up and validate locally

• Ensure elasticsearch is enabled
• For a fresh test, create a new group. Create an epic in this group.
• Update the schema_version and label_ids for this epic in the elastic by running the following command. Replace the group_id with the one you have just created.

curl -XPOST "http://localhost:9200/gitlab-development-epics/_update_by_query" -H "kbn-xsrf: reporting" -H "Content-Type: application/json" -d'
{
  "query": {
    "bool": {
      "filter": [
        {
          "term": {
            "group_id": group_id
          }
        }
      ]
    }
  },
  "script": {
    "source": "ctx._source.schema_version = 2309;ctx._source.label_ids=[0]"
  }
}' | json_pp

• Ensure on Elastic that the epic has been updated successfully by running the following command. Verify that the schema_version is 2309 and label_ids is [0]. Replace the group_id with the one you just created.

curl -XGET "http://localhost:9200/gitlab-development-epics/_search" -H "kbn-xsrf: reporting" -H "Content-Type: application/json" -d'
{
  "query": {
    "bool": {
      "filter": [
        {
          "term": {
            "group_id": group_id
          }
        }
      ]
    }
  }
}' | json_pp

• Open the rails console

bundle exec rails c

• Run the following command

Elastic::DataMigrationService[20231016162120].send(:migration).migrate

• And then again run the above XGET curl command and ensure the schema_version is 2310 and the label_ids is an empty array. It might take a few seconds to reflect the changes. If it takes longer than 1 minute then restart the rails-background-jobs and check again.

gdk restart rails-background-jobs

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Run time

34 minutes

[8] pry(main)> documents_count = 308639
=> 308639
[9] pry(main)> throttle_delay = 1.minute
=> 1 minute
[10] pry(main)> batch_size = 9_000
=> 9000
[11] pry(main)> ((documents_count / batch_size) * throttle_delay)
=> 34 minutes

Related to #424198 (closed)

#427593 (closed)