Add columnar index mode overview

[lcawl]

Summary

Relates to elastic/roadmap#290

This PR adds an introductory overview of the new columnar index mode (and small links and comments in the related pages in the "Manage data" section of the documentation).

NOTE: Unlike the existing logsdb page (https://www.elastic.co/docs/manage-data/data-store/data-streams/logs-data-stream), this overview does not include details about how to enable the index mode. Those (and other advanced) details are underway in elastic/elasticsearch#151739 If those steps ought to be moved, that can occur as needed.

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Tool(s) and model(s) used: Cursor Grok 4.5

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Elastic Docs Style Checker (Vale)

Summary: 3 suggestions found

💡 Suggestions (3): Optional style improvements. Apply when helpful.

File	Line	Rule	Message
manage-data/data-store/columnar.md	16	Elastic.Semicolons	Use semicolons judiciously.
manage-data/data-store/columnar.md	56	Elastic.WordChoice	Consider using 'can, might' instead of 'may', unless the term is in the UI.
manage-data/data-store/columnar.md	62	Elastic.Semicolons	Use semicolons judiciously.

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[github-actions]

🔍 Preview links for changed docs

• manage-data/data-store.md
• manage-data/data-store/columnar.md
• manage-data/data-store/data-streams/logs-data-stream.md
• manage-data/data-store/index-basics.md

[wajihaparvez]

Suggested change

Columnar index mode turns {{es}} into an analytical and search columnar store for the indices where you enable it. Instead of keeping multiple copies of each field for different query paths, columnar mode stores fields once as [doc values](elasticsearch://reference/elasticsearch/mapping-reference/doc-values.md) by default, which can reduce storage cost for high-volume, analytics-heavy data while keeping the same APIs, dashboards, and integrations.

Columnar index mode turns {{es}} into an analytical and search columnar store for the indices where you enable it. Instead of keeping multiple copies of each field for different query paths, columnar mode stores fields once as [doc values](elasticsearch://reference/elasticsearch/mapping-reference/doc-values.md) by default. This helps reduce storage cost for high-volume, analytics-heavy data while keeping the same APIs, dashboards, and integrations.

[wajihaparvez]

Suggested change

	Prefer a standard index (or another specialized mode) when your workload is document-centric search that needs the original JSON `_source` as submitted, or when you rely on inverted indexes and related structures on most fields by default.
	Prefer a `standard` index (or another specialized mode) when your workload is document-centric search that needs the original JSON `_source` as submitted, or when you rely on inverted indexes and related structures on most fields by default.

[wajihaparvez]

Adding line break and putting "standard" in backticks to match the format used earlier on the page

[wajihaparvez]

I wonder if all this info about use cases would work better in a table. Might be easier to reference which mode to use when

[wajihaparvez]

Suggested change

	For a fully columnar storage profile for logs, you can set `index.mode` to `logsdb_columnar` instead. For when to choose that mode, refer to [Columnar index mode](/manage-data/data-store/columnar.md).
	For a fully columnar logs storage profile, you can set `index.mode` to `logsdb_columnar` instead. To learn when to choose that mode, refer to [](/manage-data/data-store/columnar.md).

Just a suggestion to avoid reusing "for" ;) + removing link text since it's the same as the page title, so docsbuilder should auto-populate it (easier maintenance)