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787d41ec5f
Replace the fixed frontier<=1024 && hops<=6 dispatch threshold with a pure,
IO-free cost model. choose_expand_mode compares the indexed path's
frontier-relative work (hops * frontier * fanout, or hops * |E| when BTREE
coverage is degraded) against the cost of building the whole-graph CSR
(BUILD_FACTOR * |E|), from cheap manifest row counts. Under good coverage this
reduces to a selectivity ratio independent of |E|, preserving the flat-in-|E|
indexed win for selective traversals while routing dense / deep / high-fanout
or degraded-and-expensive traversals to CSR.
execute_expand decides cardinality-first and only opens the edge dataset to
confirm coverage when it leans indexed (no open on a clearly-CSR traversal).
The two env knobs become hard ceilings layered on the model; the
OMNIGRAPH_TRAVERSAL_MODE override still forces a path; the chosen mode is
traced. Results are unchanged across modes — only the path differs.
Adds inline crossover unit tests and extends the traversal_indexed both_modes
harness with an auto pass asserting the chooser is result-preserving across
every traversal shape. Documents the new flag semantics in
docs/user/{constants,query-language}.md.
38 lines
2.7 KiB
Markdown
38 lines
2.7 KiB
Markdown
# Constants & Tunables (cheat sheet)
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| Name | Value | Where |
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|---|---|---|
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| `MANIFEST_DIR` | `__manifest` | `db/manifest/layout.rs` |
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| Commit graph dir | `_graph_commits.lance` | `db/commit_graph.rs` |
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| Run registry dir (legacy, removed MR-771) | `_graph_runs.lance` | inert post-v0.4.0; bytes remain until a `delete_prefix` primitive lands |
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| Run branch prefix (legacy, removed MR-771/MR-770) | `__run__` | swept off `__manifest` by the v2→v3 migration; no longer a reserved name |
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| Schema apply lock | `__schema_apply_lock__` | `db/mod.rs` |
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| Manifest publisher retry budget | `PUBLISHER_RETRY_BUDGET = 5` | `db/manifest/publisher.rs` |
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| Internal manifest schema version | `INTERNAL_MANIFEST_SCHEMA_VERSION = 3` | `db/manifest/migrations.rs` |
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| Merge stage batch | `MERGE_STAGE_BATCH_ROWS = 8192` | `exec/merge.rs` |
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| Maintenance concurrency | `OMNIGRAPH_MAINTENANCE_CONCURRENCY=8` | `db/omnigraph/optimize.rs` |
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| Lance blob compaction support | `LANCE_SUPPORTS_BLOB_COMPACTION = false` | `db/omnigraph/optimize.rs` |
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| Graph index cache size | `8` (LRU) | `runtime_cache.rs` |
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| Expand indexed-path frontier ceiling | `OMNIGRAPH_EXPAND_INDEXED_MAX_FRONTIER=1024` | `exec/query.rs` |
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| Expand indexed-path hop ceiling | `OMNIGRAPH_EXPAND_INDEXED_MAX_HOPS=6` | `exec/query.rs` |
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| Expand CSR-build cost factor | `CSR_BUILD_FACTOR = 1.5` | `exec/query.rs` |
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| Expand mode override | `OMNIGRAPH_TRAVERSAL_MODE` (`indexed`\|`csr`; unset = cost-based auto) | `exec/query.rs` |
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| Default body limit | `1 MB` | `omnigraph-server/lib.rs` |
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| Ingest body limit | `32 MB` | `omnigraph-server/lib.rs` |
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| Engine embed model | `gemini-embedding-2-preview` | `omnigraph/embedding.rs` |
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| Compiler embed model | `text-embedding-3-small` | `omnigraph-compiler/embedding.rs` |
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| Embed timeout | `30 000 ms` | both clients |
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| Embed retries | `4` | both clients |
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| Embed retry backoff | `200 ms` | both clients |
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| LANCE memory pool default | `1 GB` (raised in v0.3.0) | runtime |
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**Expand traversal dispatch.** With `OMNIGRAPH_TRAVERSAL_MODE` unset, the engine
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chooses the indexed (per-hop BTREE) vs CSR (whole-graph in-memory) path with a
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cost model over cheap manifest counts (frontier size, |E|, source-vertex count,
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hops) plus the index-coverage signal: the indexed path is preferred when its
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frontier-relative work beats building the CSR (≈ when `hops × frontier` is a
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small fraction of the source-vertex set), and CSR is preferred for dense/deep
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traversals or when the BTREE coverage is degraded and a full scan would be paid
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per hop. The two ceilings above are hard caps — beyond them CSR is always used —
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and the override flag forces a path (the `auto` result is identical either way;
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only the path differs).
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