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docs/design/2022-04-28-architecture-of-storage-engine-pagestorage.md

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 The following figure describes the "Delta ValueSpace" and "Stable ValueSpace" of DT. The data in "Delta ValueSpace" is continuously updated. After `delta merge` occurs, the delta data in PageStorage will be read and compacted into the "Stable ValueSpace".
 
 ![tiflash-dt-architecture](./images/tiflash-dt-architecture.png)
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 As one of the important components of DT, PageStorage mainly provides a KV storage service that also supports MVCC. Unlike other KV services, the KV interface provided by PageStorage is limited. Specifically, Key is limited to uint64_t, and Value is limited to a buffer or an array of buffers (also called fields) or null.
 ## Capability