persist: expose API for writing/reading "free-standing" batches #32513
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aljoscha
commented
May 16, 2025
| @@ -121,6 +133,9 @@ pub const BUILD_INFO: BuildInfo = build_info!(); | |||
| // Re-export for convenience. | |||
| pub use mz_persist_types::{PersistLocation, ShardId}; | |||
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| pub use crate::internal::encoding::Schemas; | |||
| pub use crate::internal::state::HollowBatch; | |||
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You might object to these being exposed. We only need HollowBatch because we use it to sniff out the size/num_rows from stashed batches without turning them into a Batch and/or reading them.
aljoscha
commented
May 16, 2025
| /// enough that we can reasonably chunk them up: O(KB) is definitely fine, | ||
| /// O(MB) come talk to us. | ||
| #[instrument(level = "debug", fields(shard = %shard_id))] | ||
| pub async fn batch_builder<K, V, T, D>( |
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These are basically duplicated code. I could add a WriteHandle::batch_builder_inner that doesn't take a self but all the arguments it needs. And then both WriteHandle and the code here could call that one.
Same for read_batches_consolidated below.
I didn't do this for now because I felt that the method signature was almost the largest part of these methods. But happy to change that!
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Add API for writing and reading batches without creating a
WriteHandle/ReadHandle. Writing batches still requires aShardId, which is used for namespacing in blob storage.Work towards
https://github.com/MaterializeInc/database-issues/issues/9180, where we want to use persist batches/blob to stash peek results when sending them back to
environmentd.