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32 lines
1.3 KiB
Markdown
32 lines
1.3 KiB
Markdown
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# Snapshots & Time Travel
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Every read in OmniGraph happens against a **snapshot** — a consistent, cross-table
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view of the graph at one manifest version. A query holds one snapshot for its whole
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lifetime, so it never sees a partial write from a concurrent commit (see
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[transactions](transactions.md)).
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## Reading the past
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- **Current head** — by default a read targets the current head of the bound branch.
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- **By snapshot id** — read a branch or a specific snapshot id (`--snapshot` on
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`omnigraph read`).
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- **By version** — reconstruct a historical snapshot from any past manifest version.
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- **Single entity** — look up one entity at a past version without building a full
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snapshot (cheaper when you only need one node or edge).
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Snapshots are cheap to build: a snapshot is just the set of visible sub-table
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versions at a manifest version, so cross-table reads stay snapshot-isolated.
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## CLI
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```bash
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# Read a query against a past snapshot
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omnigraph read --query ./q.gq --name find --snapshot <snapshot-id> s3://bucket/graph.omni
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```
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Time travel composes with branches: every branch has its own version history, and
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you can read any branch at any of its past versions. Commits and the commit DAG
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that these versions correspond to are described in
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[branches & commits](index.md); diffing two versions is on the
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[changes](changes.md) page.
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