chore: added wal/snapshot doc #25856
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hiltontj
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Jan 20, 2025
| │ ┌────────────┐ | ||
| └───────────────►│clear buffer│ (whatever snapshotted is removed) | ||
| └────────────┘ | ||
| ``` |
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A useful addition to this diagram would be to show the entry point for writes from user, i.e., where do writes go from the user (wal buffer?), via an arrow. Otherwise, it is not clear on the order of operations. If you could connect the numbers from the steps described below to locations / arrows on the diagram, that would be helpful.
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Good point - I'll try to link the steps to the diagram and add the incoming writes as well.
| If going ahead with force snapshotting, pick all the wal periods in the tracker and find the max time from most recent wal period. This will be | ||
| used as the `end_time_marker` to evict data from query buffer. Because forcing a snapshot can be triggered when wal buffer is empty (even though | ||
| queryable buffer is full), we need to add `Noop` (a no-op WalOp) to the wal file to hold the snapshot details in wal file. | ||
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Add a header on this diagram, e.g.,
##### Forced snapshot
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Moving some of my work notes into a doc (might be handy to understand the wal/snapshotting process)