Document GCS bucket retention policy impact on ClickHouse storage

Open Beginner friendly

#147 opened on Jan 2, 2026 0 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty: 1/5
Estimated time: Under an hour
Newbie friendliness: 72/100

Issue type: Documentation
Clarity: Clearly specified
Activity status: Stale
Tech stack: clickhouse, google-cloud
Domain: databases, documentation

Research direction

Read content/en/altinity-kb-integrations/altinity-kb-google-s3-gcs.md and review its existing GCS setup guidance. Add a warning explaining how retention policies block ClickHouse deletion during merges, mutations, and TTL expiration, and recommend using a bucket without a retention policy. Done means the storage-growth and operational-cost risk is clearly documented.

Written by the indexing model from the issue text.

Description

Problem

The current GCS documentation (content/en/altinity-kb-integrations/altinity-kb-google-s3-gcs.md) only covers basic setup (HMAC keys, endpoint configuration) but doesn't mention an important operational caveat.

Missing Information

When a GCS bucket has a retention policy enabled, objects cannot be deleted until the retention period expires. This causes issues with ClickHouse because it regularly deletes data during:

Part merges - old parts are removed after merge
Mutations - replaced data is deleted
TTL expiration - expired data is purged

If the bucket retention policy prevents deletion, old data accumulates and storage grows exponentially, leading to unexpected costs and potential operational issues.

Suggested Addition

Add a warning/note to the GCS documentation explaining:

Bucket retention policies prevent ClickHouse from deleting obsolete data
This causes continuous storage growth
Recommendation to disable retention policy or use a bucket without one for ClickHouse storage

If this seems like a good enhancement, I'd be happy to take this up and submit a PR.

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Stars: 62
Forks: 49
Avg merge: 6m
Merged PRs (30d): 3

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