further reduce ufos batch limits, avoid oom?

....

ufos/src/consumer.rs

···
 
 use crate::{CreateRecord, DeleteAccount, DeleteRecord, EventBatch, ModifyRecord, UpdateRecord};
 
-const MAX_BATCHED_RECORDS: usize = 128; // *non-blocking* limit. drops oldest batched record per collection once reached.
-const MAX_BATCHED_MODIFIES: usize = 512; // hard limit, total updates and deletes across all collections.
-const MAX_ACCOUNT_REMOVES: usize = 512; // hard limit, total account deletions. actually the least frequent event, but tiny.
-const MAX_BATCHED_COLLECTIONS: usize = 64; // hard limit, MAX_BATCHED_RECORDS applies per collection
+const MAX_BATCHED_RECORDS: usize = 64; // *non-blocking* limit. drops oldest batched record per collection once reached.
+const MAX_BATCHED_MODIFIES: usize = 32; // hard limit, total updates and deletes across all collections.
+const MAX_ACCOUNT_REMOVES: usize = 128; // hard limit, total account deletions. actually the least frequent event, but tiny.
+const MAX_BATCHED_COLLECTIONS: usize = 32; // hard limit, MAX_BATCHED_RECORDS applies per collection
 const MIN_BATCH_SPAN_SECS: f64 = 2.; // try to get a bit of rest a bit.
 const MAX_BATCH_SPAN_SECS: f64 = 60.; // hard limit of duration from oldest to latest event cursor within a batch, in seconds.
 
 const SEND_TIMEOUT_S: f64 = 60.;
-const BATCH_QUEUE_SIZE: usize = 512; // 4096 got OOM'd. update: 1024 also got OOM'd during L0 compaction blocking
+const BATCH_QUEUE_SIZE: usize = 64; // 4096 got OOM'd. update: 1024 also got OOM'd during L0 compaction blocking
 
 #[derive(Debug)]
 struct Batcher {

ufos/src/store.rs

···
         // 4. reverse and try to walk back MAX_RETAINED steps
         // 5. if we didn't end iteration yet, start deleting records (and their forward links) until we get to the end
 
+        // oh we might be able to walk *forward* instead of reverse from the cursor, which might help avoid iterating over a lot of deletion tombstones
+
         // ... we can probably do even better with cursor ranges too, since we'll have a cursor range from rollup and it's in the by_collection key
 
         Ok(())