Fetched https://lance.org/format/table/mem_wal/ in full via npx mdrip.
The "Overview / Details / Implementation" sidebar items turned out to
be anchor sections on the same URL, not separate pages.
Key findings (relevant to MR-847's recovery reconciler design):
* MemWAL is opt-in. Requires (1) unenforced primary key in schema,
(2) explicit shard config, (3) writers using the LSM-tree write
path. omnigraph does NOT enable it; we use direct write_fragments +
commit(Operation::Append).
* MemWAL is intra-table — addresses streaming-write throughput for
one Lance base table via MemTables → flushed MemTables → async
merge. It does not coordinate across multiple tables.
* MemWAL's recovery is intra-table: WAL replay reconstructs MemTable
state for one table. It does NOT help with omnigraph's cross-table
manifest-pinned-vs-Lance-HEAD drift class.
Conclusion: MR-847's recovery reconciler design is unaffected. The
two operate at different abstraction layers.
Borrowable: MemWAL's epoch-based fencing pattern is structurally
similar to a future multi-coordinator sidecar protocol; noted on
MR-847 for if MR-668 (multi-process) ever lands.
Curates the Lance documentation site (lance.org) into a problem-domain
index so agents fetch the right page when working on Lance-touching
code instead of guessing or grepping our codebase. Organized by topic:
storage format & file layout, branching/tags/time travel, indexes
(scalar + system + vector), reads/writes, schema evolution, object
store, data types, performance, compaction, DataFusion integration,
SDK reference, plus quick-starts and the upstream AGENTS.md.
Skips ~200 irrelevant URLs from the upstream sitemap (Namespace REST
API model surface, Spark/Trino/Databricks/etc. integrations,
Python/Ray/HuggingFace docs, community pages) since omnigraph is
Rust-only and doesn't run a Lance Namespace catalog.
AGENTS.md surfaces it in the topic index and adds a directive: "when
you hit a Lance-shaped problem, consult docs/lance.md and fetch the
upstream URL before guessing."
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
