fix(core): merge WAL generations across schema changes - #175
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…erate drained generations (#200) Three fixes the rollout store received but `DatagenStore` never did. Each is latent today and becomes reachable as soon as datagen sees concurrent or long-lived use. ## 1. Merge used the compile-time schema, not the live one `merge_own_shard` built its append batch from `datagen_log_schema()`. A base table written by an older binary can lack columns the current schema has, and merging a batch built from the compile-time schema into it **fails outright**. Now aligned via `align_batch_to_schema` — the rollout store hit exactly this and was fixed in #175. ## 2. `Drop` swallowed the writer's close error ```rust let _ = writer.close().await; // before ``` A failed close leaks the writer's background tasks and, if the memtable was still buffered, **strands rows that are durable in the WAL but never sealed** — with no signal anywhere. Now logged, and the no-runtime path says so too. (Rollout equivalent: #190.) ## 3. A concurrently-drained generation failed the whole lookup `get_blob` propagated not-found when a merge drained and deleted a generation between snapshot and open. Those rows are already in the base table, so it now skips and falls through — as the rollout store does. ## Sharing `align_batch_to_schema` and `is_not_found_error` become `pub(crate)` so both stores share one implementation instead of drifting again. This drift is the actual pattern here: all three bugs are cases where rollout was fixed and datagen was not. ## Scope note — worth reading I expected datagen to have the write-lock stall fixed in #199. **It does not**, and I verified rather than assumed: - `DatagenStore::append` is already `&mut self` (its writer is a bare `Option<ShardWriter>`, not behind a mutex), so appends need the exclusive lock **regardless of merge** — the read/write lock split from #199 would buy nothing. - `write_with_resident_writer` already retries on fence, so `claim_epoch` fencing its own writer is handled. Restoring `claim_epoch` leaves the new test **green**, confirming this empirically. - Datagen is not yet wired into any server route or sweeper. So the epoch change from #199 is deliberately **not** ported. These three divergences are the real defects. ## Testing New test asserts a merge does not fence the store's own resident writer, so an append immediately after a merge still succeeds and both rows stay readable, and a second merge still converges. 9 datagen tests pass; `clippy --all-targets -D warnings` and `cargo fmt` clean. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-authored-by: Claude <noreply@anthropic.com>
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Summary
rollout_schema()before WAL merge, adding missing nullable columns as all-null arraysscan_one_by_idandlsm_scanner_for_sourceread pathNoneTesting
cargo fmt --all -- --checkcargo clippy --workspace --all-targets -- -D warningscargo test -p lance-context-core -p lance-context-master --libcargo test -p lance-context-core --lib claim_check -- --nocapture