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Jack YeandClaude Sonnet 5
d0b0efcd47
## Summary Follow-up to the Mermaid brand-theming PR, addressing review feedback: - Diagram text was hard to read at the previous 15px font size; bumped to 18px, light and dark alike. - The dark-mode orange accent border was brighter and more saturated than its fill or the default border, reading as too loud against the dark background. It now reuses the same muted orange already used for the light-mode accent border, which was fine as is. ## Companion change lancedb/sophon#9719 makes the same two changes across its own diagrams. Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>
95 lines
3.7 KiB
Plaintext
95 lines
3.7 KiB
Plaintext
---
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title: "Data Page Cache"
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sidebarTitle: "Data Page Cache"
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description: "How LanceDB Enterprise caches table data pages to avoid re-reading object storage."
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icon: "database"
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availability:
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embedded: unavailable
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enterprise: available
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---
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The data page cache holds fixed-size pages of raw table data read from
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object storage, keyed by their location, so a later read of the same range
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is served from memory or local disk instead of round-tripping to the
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backing store. Plan executors and query nodes each keep their own cache for
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the pages they serve. A background prewarm job can populate a cache ahead
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of a request that needs it, rather than filling it lazily on first read.
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See [Architecture](/index#architecture).
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<div className="hidden dark:block">
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```mermaid
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%%{init: {"theme": "base", "themeVariables": {
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"background": "#171513", "primaryColor": "#1e1b19", "primaryTextColor": "#f4ebe8",
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"primaryBorderColor": "#4c443f", "lineColor": "#847770", "textColor": "#f4ebe8",
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"edgeLabelBackground": "#171513", "fontFamily": "Inter, sans-serif", "fontSize": "18px"
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}}}%%
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flowchart LR
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R["Read request<br/>for a data page"] --> M{"In memory?"}
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M -->|hit| Return["Served from memory"]
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M -->|miss| D{"In local disk cache?"}
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D -->|hit| Promote["Loaded into memory,<br/>served"]
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D -->|miss| O[("Object storage")]
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O --> Fill["Fills memory and disk,<br/>served"]
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classDef default fill:#1e1b19,stroke:#4c443f,stroke-width:1px,color:#f4ebe8
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```
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</div>
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<div className="block dark:hidden">
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```mermaid
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%%{init: {"theme": "base", "themeVariables": {
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"background": "#ffffff", "primaryColor": "#ffffff", "primaryTextColor": "#221d19",
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"primaryBorderColor": "#ad9e95", "lineColor": "#6b625c", "textColor": "#221d19",
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"edgeLabelBackground": "#ffffff", "fontFamily": "Inter, sans-serif", "fontSize": "18px"
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}}}%%
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flowchart LR
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R["Read request<br/>for a data page"] --> M{"In memory?"}
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M -->|hit| Return["Served from memory"]
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M -->|miss| D{"In local disk cache?"}
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D -->|hit| Promote["Loaded into memory,<br/>served"]
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D -->|miss| O[("Object storage")]
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O --> Fill["Fills memory and disk,<br/>served"]
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classDef default fill:#ffffff,stroke:#ad9e95,stroke-width:1px,color:#221d19
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```
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</div>
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A table's local disk cache shares one budget with the
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[tiered index cache](/enterprise/tiered-index-cache#disk-budget)'s disk
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tier where both are enabled on the same executor -- raising one's share of
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that budget lowers the other's.
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## Prewarming on demand {#prewarm}
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[Cache Prewarm](/enterprise/cache-prewarm)'s `startup_prewarm_idx` only
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warms the [tiered index cache](/enterprise/tiered-index-cache), not this
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one. The data page cache has its own, separate on-demand prewarm, run by a
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deployment operator rather than called from application code, optionally
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scoped to specific columns:
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<CodeGroup>
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```bash CLI icon="terminal"
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lancedb admin cache prewarm data --table embedding_table --column embedding
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```
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</CodeGroup>
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The command returns once the request is accepted, not once prewarming
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finishes; it is idempotent and safe to run concurrently from multiple
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clients. Prewarming has a large upfront cost, so it pays off for workloads
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that repeatedly query the same columns -- large columns such as embeddings
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or binary data may not be practical to prewarm this way.
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<Warning>
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The OSS SDK's `table.prewarm_data()` targets LanceDB Cloud, a different
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product; calling it against an Enterprise deployment 404s. Use the admin
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command above instead.
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</Warning>
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## Cache interfaces {#interfaces}
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- [Tiered Index Cache](/enterprise/tiered-index-cache) for the related
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cache that holds deserialized index structures instead of raw data pages.
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- [Query plans](/basics/sql#query-plans) for inspecting what a query actually read.
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