Add index.mapping.nested_parents.limit and raise nested fields limit to 100

[jimczi]

This change introduces a new index setting, index.mapping.nested_parents.limit, which limits the number of nested fields that act as parents of other nested fields. Each nested parent requires its own parent bitset in memory, so this new limit (defaulting to 50) prevents excessive bitset creation in deeply nested mappings. Additionally, the existing index.mapping.nested_fields.limit is increased from 50 to 100 to better accommodate common use cases while still protecting against overly complex mappings.

[elasticsearchmachine]

Pinging @elastic/es-search-foundations (Team:Search Foundations)

[elasticsearchmachine]

Hi @jimczi, I've created a changelog YAML for you.

[github-actions]

🔍 Preview links for changed docs

• docs/reference/elasticsearch/index-settings/mapping-limit.md
• docs/reference/elasticsearch/mapping-reference/nested.md

[github-actions]

ℹ️ Important: Docs version tagging

👋 Thanks for updating the docs! Just a friendly reminder that our docs are now cumulative. This means all 9.x versions are documented on the same page and published off of the main branch, instead of creating separate pages for each minor version.

We use applies_to tags to mark version-specific features and changes.

Expand for a quick overview

When to use applies_to tags:

✅ At the page level to indicate which products/deployments the content applies to (mandatory)
✅ When features change state (e.g. preview, ga) in a specific version
✅ When availability differs across deployments and environments

What NOT to do:

❌ Don't remove or replace information that applies to an older version
❌ Don't add new information that applies to a specific version without an applies_to tag
❌ Don't forget that applies_to tags can be used at the page, section, and inline level

🤔 Need help?

• Check out the cumulative docs guidelines
• Reach out in the #docs Slack channel

[andreidan]

Thanks Jim, LGTM