test(bench): measure row lineage placement against a checked workload by BubbleCal · Pull Request #9340 · lance-format/lance

BubbleCal · 2026-09-17T07:55:56Z

Last of the §5.3 stack (#8931, #9250). The benchmark for row lineage placement, inline in the manifest versus spilled to data file columns.

Everything it measures is on main: this PR only adds rust/lance/benches/rowid_spill.rs and its [[bench]] entry in rust/lance/Cargo.toml.

Stack

feat(format): define hidden row lineage columns #9253, feat(dataset): read and write spilled row lineage columns #9336, feat(dataset): spill row lineage at compaction #9337, feat(table): load spilled row lineage ahead of a commit #9338, feat(dataset): spill row lineage when updating rows #9339, feat(dataset): write compaction's spilled lineage into the fragment's data file #9347 (merged)
this PR: test(bench): measure row lineage placement against a checked workload

What it measures

LANCE_ENABLE_UNSTABLE_SPILLED_ROW_LINEAGE=1 cargo bench -p lance --profile release-with-debug --bench rowid_spill

It is sized with BENCH_FRAGMENTS, BENCH_ROWS_PER_FRAGMENT, BENCH_DELETE_PERCENT, BENCH_APPENDS, BENCH_SCENARIOS and BENCH_INLINE_MAX_BYTES. Bad values are rejected up front.

There are two workloads:

deleted: a share of rows is deleted, then compacted. The sequences still run-encode.
shuffled: every row is rewritten in random order, with its real created-at and last-updated-at versions, then compacted. No run structure survives.

Within each workload, the inline arm never opts in, and the spilled arm sets lance.row_lineage.spill=true with the given budget.

Per arm it reports:

steady-state manifest bytes, split by sequence;
the compaction manifest and transaction file;
cold open;
the commit of a small append, timed apart from the data write;
one cold sequence load;
the row id index build;
a take by row id with the fragment's sequence preloaded;
compaction time and the bytes compaction wrote.

Timed rows report the median and the minimum of their samples.

The bench checks itself outside the timers:

the spilled arm must actually have spilled, and the inline arm must not;
a full scan asserts every row's _rowid, created-at and last-updated-at against the workload;
every take probe must return the row it asked for.

Smoke run

This is one small run, not a performance claim. It ran on an x86 r8i.8xlarge (local NVMe) with 2 fragments x 200,000 rows, BENCH_INLINE_MAX_BYTES=0 so everything spills, the release-with-debug profile, and each arm once. Lower is better for every row, and the ratio is inline / spilled.

Scenario / metric	Inline	Spilled	Ratio
shuffled: steady-state manifest	7.49 MB	< 0.01 MB	10367x smaller
shuffled: cold dataset open (median)	4.32 ms	0.12 ms	36.5x faster
shuffled: append commit (median)	6.27 ms	0.78 ms	8.1x faster
shuffled: row id index build, cold (median)	36.11 ms	35.53 ms	1.0x
shuffled: one sequence load, cold (median)	0.18 ms	1.97 ms	0.09x (spilled is slower)
shuffled: compaction output (data files)	1.93 MB	2.96 MB	0.65x (spilled is larger)
deleted: steady-state manifest	0.14 MB	< 0.01 MB	237x smaller
deleted: row id index build, cold (median)	2.53 ms	5.48 ms	0.46x (spilled is slower)

The trade-off is the one the design expects. Spilling takes the per-row lineage out of every manifest read and write, so open and commit stop scaling with the table. The cost moves to a column read the first time a sequence is needed, and 2 to 3 bytes per row in the compacted data files. On the deleted workload the sequences are small either way, which is why the default 200 KiB budget keeps them inline.

Validation

cargo fmt --all -- --check, cargo clippy --all --tests --benches -- -D warnings on the head of this branch
The smoke run above completed with every self-check passing.

Refs #8931, #9250

🤖 Generated with Claude Code

github-actions · 2026-09-17T07:56:16Z

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First of a stack for §5.3 of the Stable Row ID GA design (#8931, tracked as #9250): let a fragment's row lineage sequences -- its row ids and its created-at and last-updated-at versions -- leave the manifest and live as hidden `uint64` columns of a Lance data file. This PR defines the format; the stack continues with readers and the spill primitives, then compaction, the commit read-ahead, the update path, and compaction writing the columns into its own output files. Builds on the prototype in #8953 (Will is co-author). ## Stack 1. this PR feat(format): define hidden row lineage columns 2. #9336 feat(dataset): read and write spilled row lineage columns 3. #9337 feat(dataset): spill row lineage at compaction 4. #9338 feat(table): load spilled row lineage ahead of a commit 5. #9339 feat(dataset): spill row lineage when updating rows 6. #9347 feat(dataset): write compaction's spilled lineage into the fragment's data file 7. #9340 test(bench): row lineage spill benchmark ## Problem Each sequence is stored inline in the fragment's manifest entry. An appended fragment's sequences are single runs and cost a few dozen bytes, but once compaction merges fragments whose rows came from many places the row id sequence degrades to 4-8 bytes per row and the version sequences to a run per row. The manifest then grows with the table's row count and every commit rewrites all of it (#8621). ## Format - Every negative field id is reserved for system use and never names a schema field; readers skip any negative id in a data file's `fields`. `-1` and `-2` keep their meaning; `-3`, `-4`, `-5` are the hidden `_rowid`, `_row_created_at_version` and `_row_last_updated_at_version` columns. - `DataFragment` gains an empty `RowLineageColumn` marker arm on each lineage oneof: `column_row_ids = 12`, `column_last_updated_at_versions = 13`, `column_created_at_versions = 14`. The marker carries no file reference: the column lives in one of the fragment's `files`, the single entry whose `fields` carry the reserved id, and its `column_indices` locates it like a user column. Zero or several carriers is corruption. The three sequences may share one file with each other or with the fragment's user data. - The columns have an executable schema: three non-nullable `uint64` fields, each holding exactly `physical_rows` values in physical row order. A null or a length mismatch is corruption and is rejected, never defaulted. - The marker is valid only in a fragment whose data files are Lance v2 files: a legacy v1 `DataFile` has no `column_indices` to locate the column, and a fragment cannot mix v1 and v2 files. A writer on a v1 dataset leaves every sequence inline. - New feature flag `FLAG_UNSTABLE_SPILLED_ROW_LINEAGE = 1 << 11` (value 2048), the next free bit after the two fragment-reuse flags; `FLAG_UNKNOWN` moves to `1 << 12`. Every earlier build has its unknown boundary at or below bit 11 (v11.0.0 at 256, the v12/v13 pre-releases at 512, main before this PR at 2048), so each already refuses such a dataset. Like data overlay files, release builds understand the bit only with `LANCE_ENABLE_UNSTABLE_SPILLED_ROW_LINEAGE=1`; debug builds always do. - The `external_*` arms (field numbers 6, 8, 10) are retired: no writer ever emitted them and the column arms replace that design. Their numbers and names are reserved in the proto, and the `External` variants of `RowIdMeta` and `RowDatasetVersionMeta` go away with them. `ExternalFile` itself stays; the fragment reuse index uses it. Placement rule, which the writers in later PRs follow: a value the commit assigns -- an appended fragment's row ids, an inserted row's created-at, every row's last-updated-at -- can change when a commit conflict is retried, so it stays inline where the retry can rewrite it. A value carried over from existing rows is fixed before the commit and may go to a data file. ## Code - `RowIdMeta::Column` and `RowDatasetVersionMeta::Column` unit variants, with proto and JSON round trips (`{"column": {}}`, mirroring the empty proto message) and manifest interning. `Fragment::row_lineage_file(field_id)` finds the carrier among `files` and reports more than one as corruption. Because the carrier is an ordinary entry of `files`, cleanup, shallow-clone `base_id` rewriting, file listing and validation already cover it; validation skips the negative ids in a file's `fields`. - `apply_feature_flags` sets the flag when any fragment uses a column arm. - Nothing writes the columns yet. Reading one -- in the row id loader, the fragment reader, and the commit-time paths that resolve an update's lineage from existing fragments -- returns `NotSupported` instead of falling back to defaults. - `assign_row_ids` treats a spilled sequence as covering every physical row, as it always does. ## Validation - `cargo test -p lance-table` - `cargo test -p lance --lib -- rowid row_version stable_row optimize::tests dataset_transactions fragment::tests feature_flag update::tests merge_insert::tests dataset_io` - `cargo clippy --all --tests --benches -- -D warnings`, `cargo fmt --all` - `cargo check --manifest-path python/Cargo.toml`, `cargo check --manifest-path java/lance-jni/Cargo.toml` Refs #8931, #9250 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-authored-by: Will Jones <willjones127@gmail.com> Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

Second of the §5.3 stack (#8931, #9250), on top of #9253. The previous PR defined the hidden row lineage columns; this one reads them and adds the primitives that write them. Nothing calls the writer yet; compaction does in the next PR. ## Stack 1. #9253 feat(format): define hidden row lineage columns 2. this PR feat(dataset): read and write spilled row lineage columns 3. #9337 feat(dataset): spill row lineage at compaction 4. #9338 feat(table): load spilled row lineage ahead of a commit 5. #9339 feat(dataset): spill row lineage when updating rows 6. #9347 feat(dataset): write compaction's spilled lineage into the fragment's data file 7. #9340 test(bench): row lineage spill benchmark ## Read - `load_row_id_sequence` gains a `Column` arm that reads the `_rowid` column back through the ordinary file reader, projected by field id, into the same per-fragment cache as inline sequences. - New `load_row_version_sequence(dataset, fragment, RowVersionKind)` loads either version sequence wherever it is stored; a spilled one is cached per fragment and file, an inline one decodes from the manifest bytes as before. - `FileFragment::open` loads the version sequences asynchronously alongside the row ids and hands them to the reader, instead of the reader builder decoding them synchronously and silently falling back to version 1 on any failure. The `NotSupported` guard from the previous PR goes away with it. - `Dataset::validate` checks the length of spilled version sequences too. ## Write primitives `place_row_lineage(dataset, &RowLineage)` encodes a fragment's three sequences and, for each one whose encoding exceeds the table's inline budget, writes it as a column of one new lineage file per fragment. It returns a `PlacedRowLineage`: the three arms to put on the fragment plus the lineage file, which `apply` adds to the fragment's `files` so the marker can be resolved. It is only correct for lineage a commit conflict cannot change, which is what its callers carry over from existing rows. Spilling is opt-in per table: `lance.row_lineage.spill=true`, with `lance.row_lineage.inline_max_bytes` overriding the 200 KiB default. A table that never sets it is unchanged, and a build that does not understand the feature flag never spills either, so it cannot write a dataset it then refuses to open. A legacy v1 dataset never spills regardless of its config, since the format only allows the columns in v2 files. The primitives are public so a writer outside this crate that assembles its own transactions can spill at write time. ## Validation - `cargo test -p lance --lib rowids::` (round trip of all three columns through one shared file, found by field id among the fragment's files; only the sequences over the budget spill; a table that has not opted in never spills; a v1 table never spills) - `cargo test -p lance --lib -- rowid stable_row fragment::tests dataset_transactions` - `cargo clippy --all --tests --benches -- -D warnings`, `cargo fmt --all` - `cargo check --manifest-path python/Cargo.toml`, `cargo check --manifest-path java/lance-jni/Cargo.toml` Refs #8931, #9250 🤖 Generated with [Claude Code](https://claude.com/claude-code) --------- Co-authored-by: Will Jones <willjones127@gmail.com> Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

Third of the §5.3 stack (#8931, #9250), on top of #9336. Compaction becomes the first writer of the hidden row lineage columns. ## Stack 1. #9253 feat(format): define hidden row lineage columns 2. #9336 feat(dataset): read and write spilled row lineage columns 3. this PR feat(dataset): spill row lineage at compaction 4. #9338 feat(table): load spilled row lineage ahead of a commit 5. #9339 feat(dataset): spill row lineage when updating rows 6. #9347 feat(dataset): write compaction's spilled lineage into the fragment's data file 7. #9340 test(bench): row lineage spill benchmark ## Change Compaction used to rechunk the row ids and the two version sequences in two separate passes and write each back inline. It now computes all three together, then places each one through `place_row_lineage`: inline when its encoding fits the table's budget, otherwise as a column of one lineage file per output fragment, listed among the fragment's files after its data file. The sixth PR of the stack moves those columns into the data file itself. Compaction's output is retry-stable -- every value is carried over from the input fragments -- so spilling it needs nothing from the commit. Only tables that set `lance.row_lineage.spill=true` are affected; a table that never opts in compacts exactly as before. ## Not in this PR Updating rows of a table whose compaction has spilled still returns `NotSupported` from the commit, which cannot read a data file; the next PR lifts that. With this PR alone, a user who opts in must not update the table until then, which is why the flag stays unstable and the config defaults off. ## Benchmarks `LANCE_ENABLE_UNSTABLE_SPILLED_ROW_LINEAGE=1 cargo bench --bench rowid_spill` (the benchmark lands as the last PR of the stack), 8 fragments x 1,000,000 rows, local NVMe (macOS), one run per arm, measured on the pre-split branch whose compaction and read code is what this stack carries. The two arms differ only in the table config: the inline arm never opts in (today's behavior), the spilled arm sets `lance.row_lineage.spill=true` with the default 200 KiB budget. Byte counts are deterministic; latencies are single samples (cold open averaged over 10, sequence loads over 3), so treat differences under about 2x as noise. Lower is better for every row. **deleted**: 30% of rows deleted, then compacted. The row id sequences still run-encode as range plus bitmap, so this is the workload where spilling is a bad trade on bytes. | Scenario / metric | Baseline (inline) | This PR (spilled) | Benefit | | --- | ---: | ---: | ---: | | manifest size | 5.73 MiB | < 0.01 MiB | >500x smaller | | compaction transaction file | 2.86 MiB | < 0.01 MiB | >500x smaller | | cold dataset open | 1.45 ms | 0.55 ms | 2.6x speedup | | append commit (mean of 5) | 3.65 ms | 1.46 ms | 2.5x speedup | | load one fragment's sequence (cold) | 0.15 ms | 4.88 ms | 33x slowdown | | row id index build (cold) | 0.11 ms | 16.34 ms | 150x slowdown | | take by row id, index built | 0.54 ms | 4.55 ms | 8x slowdown (first touch, see below) | | compaction | 221 ms | 258 ms | 1.2x slowdown | | data files on disk | 74.4 MiB | 89.2 MiB | 1.2x larger | **shuffled**: every row rewritten in random order, then compacted. No run structure survives, which is the workload the design is for. | Scenario / metric | Baseline (inline) | This PR (spilled) | Benefit | | --- | ---: | ---: | ---: | | manifest size | 30.52 MiB | < 0.01 MiB | >3000x smaller | | compaction transaction file | 61.04 MiB | 30.52 MiB | 2x smaller | | cold dataset open | 5.54 ms | 0.20 ms | 28x speedup | | append commit (mean of 5) | 15.73 ms | 1.34 ms | 12x speedup | | load one fragment's sequence (cold) | 2.35 ms | 2.30 ms | 1.0x | | row id index build (cold) | 142 ms | 165 ms | 1.2x slowdown | | take by row id, index built | 2.65 ms | 2.75 ms | 1.0x | | compaction | 305 ms | 296 ms | 1.0x | | data files on disk | 136.0 MiB | 158.1 MiB | 1.2x larger | The `deleted` take row: `FileFragment::open` loads the fragment's row id sequence whenever the table uses stable row ids, whether or not `_rowid` is projected, and the index build reads sequences uncached, so the first take after it pays one spilled-file read per fragment. That eager load predates this stack; making it conditional on the projection is a follow-up. ## Validation - `cargo test -p lance --lib rowids::` (compaction spills all three sequences into one lineage file among the fragment's files and reads them back through the scan and the loaders; cleanup keeps the live lineage file; a cold reopen serves the columns) - `cargo test -p lance --lib -- rowid stable_row optimize::tests cleanup::tests dataset_transactions` - `cargo clippy --all --tests --benches -- -D warnings`, `cargo fmt --all` Refs #8931, #9250 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-authored-by: Will Jones <willjones127@gmail.com> Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

Fourth of the §5.3 stack (#8931, #9250), on top of #9337. Updates on a table with spilled lineage keep every row's lineage, the way they do on an inline table. ## Stack 1. #9253 feat(format): define hidden row lineage columns 2. #9336 feat(dataset): read and write spilled row lineage columns 3. #9337 feat(dataset): spill row lineage at compaction 4. this PR feat(table): load spilled row lineage ahead of a commit 5. #9339 feat(dataset): spill row lineage when updating rows 6. #9347 feat(dataset): write compaction's spilled lineage into the fragment's data file 7. #9340 test(bench): row lineage spill benchmark ## Problem Building a manifest is synchronous and has no object store. Two commit-time paths need existing lineage: resolving which rows an update rewrote, to carry each row's created-at version over (`resolve_update_version_metadata`), and overlaying a partial column rewrite's patched offsets onto the fragment's last-updated-at sequence (`refresh_row_latest_update_meta_for_partial_frag_rewrite_cols`). Once a fragment's sequences are spilled, neither can read them, and the previous PRs made them refuse with `NotSupported`. ## Change The commit path in `lance` reads every spilled sequence of the current manifest ahead of each build attempt (`load_spilled_row_lineage`, served from the same caches the readers use) and hands them over in `ManifestBuildConfig::spilled_row_lineage`. The two paths consult that map for a spilled fragment and still refuse if a sequence they need is missing, so a caller of `build_manifest` that skips the read-ahead gets an error rather than defaulted lineage. Loaded per attempt, so a rebase onto a newer manifest sees that manifest's fragments; only `Update` and `DataOverlay` operations pay for it. `UpdateBuilder`, `merge_insert` in both write modes, and externally assembled `Operation::Update`s therefore work on a spilled table unchanged. The lineage they produce for the rewritten rows is inline; a refreshed last-updated-at sequence goes back inline as well. An update-heavy table thus regrows its manifest between compactions and the next compaction spills it again. ## Validation - `cargo test -p lance-table row_version` (spilled source lineage resolves from the config; missing lineage still refuses) - `cargo test -p lance --lib rowids::` (update keeps the rewritten row's id and created-at; merge_insert keeps matched rows' lineage and stamps inserted ones; a partial column rewrite on a spilled fragment stamps only the patched rows) - `cargo test -p lance --lib -- rowid row_version stable_row update::tests merge_insert::tests dataset_transactions` - `cargo clippy --all --tests --benches -- -D warnings`, `cargo fmt --all` Refs #8931, #9250 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

Part of the §5.3 stack (#8931, #9250). #9253, #9336, #9337 and #9338 are merged; this PR is now based on `main`. Updates on a table that opts into spilling move the lineage of the rows they rewrite out of the manifest, so an update-heavy table no longer regrows its manifest between compactions. It also fixes schema-only commits dropping the file a spilled sequence lives in, which has been reachable since #9337. ## Stack 1. #9253 feat(format): define hidden row lineage columns (merged) 2. #9336 feat(dataset): read and write spilled row lineage columns (merged) 3. #9337 feat(dataset): spill row lineage at compaction (merged) 4. #9338 feat(table): load spilled row lineage ahead of a commit (merged) 5. this PR: feat(dataset): spill row lineage when updating rows 6. #9347 feat(dataset): write compaction's spilled lineage into the fragment's data file 7. #9340 test(bench): row lineage spill benchmark ## Change **Update places the lineage it carries over, only when it spills.** - `UpdateBuilder` resolves the table's inline budget before any IO. A malformed `lance.row_lineage.inline_max_bytes` now fails the update before anything is written. - Only on a table that can spill (opted in, v2 files, a build that understands the flag) does the scan project `_row_created_at_version` next to `_rowid`. `make_rowid_capture_stream` captures it run-length encoded, so a rewrite of N rows written at a few versions costs a few runs rather than 8 bytes per row. - After the write, each new fragment's row ids and created-at versions are split to its size. They leave the manifest only when one of them is over the budget, into a lineage-only file added to the fragment's `files`. Last-updated-at is never placed by the writer; it is the commit's. - A table that never opted in, or an update whose sequences fit inline, leaves created-at to the commit exactly as `main` does. **Commit contract** (`resolve_update_version_metadata`, `has_writer_placed_lineage`): - A new fragment whose row ids or created-at versions are `Column` is writer-placed. It keeps its created-at and gets last-updated-at stamped with the commit version. - Placed inline created-at must have one value per physical row, or the commit is refused. - Every other fragment is resolved from the existing fragments as before. A caller-supplied inline created-at is still recomputed, which keeps the documented contract for fragments committed from Python. - The commit skips the created-at lookup for writer-placed fragments, and the read-ahead from #9338 is skipped for an update whose new fragments are all writer-placed. **Spilled lineage survives schema-only commits.** `Operation::Project` (drop, rename, nullability), `DataReplacement` and the cast in `alter_columns` kept only files with a live schema field, so they dropped the only carrier of a spilled sequence and left a `Column` arm pointing at nothing. After cleanup, those row ids and versions were gone. All three now keep a file that carries one of the fragment's spilled ids. `build_manifest` also refuses to commit a fragment whose `Column` arm has no carrier, or a carrier in a v1 file, so a future path cannot commit that state silently. `merge_insert` is unchanged: its rewritten rows still get inline lineage resolved at commit time. ## Validation Run on an x86 build host (r8i.8xlarge): - `cargo fmt --all -- --check`, `cargo clippy --all --tests --benches -- -D warnings` - `cargo test -p lance-table`: 573 passed, including `project_keeps_file_carrying_spilled_row_lineage`, `data_replacement_keeps_lineage_carrier`, `build_manifest_rejects_spilled_arm_without_carrier` and the new `row_version` contract tests. - `cargo test -p lance --lib -- rowids:: row_version stable_row rowid optimize::tests dataset_transactions fragment::tests cleanup::tests feature_flag update::tests merge_insert::tests io::commit dataset_io schema_evolution versions:: write::tests utils::tests`: 1545 passed, including `schema_change_keeps_spilled_lineage` (update or compaction followed by rename, drop or cast), `update_leaves_inline_created_at_to_the_commit`, `update_rejects_malformed_inline_max_bytes_before_writing` and `place_rewritten_lineage_splits_lineage_by_output_fragment`. - `cargo check --manifest-path python/Cargo.toml`, `cargo check --manifest-path java/lance-jni/Cargo.toml` Refs #8931, #9250 🤖 Generated with [Claude Code](https://claude.com/claude-code) --------- Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

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lance-gatekeeper

❌ Gate recommendation: request changes.

The benchmark is a useful end-to-end comparison, but #9347 is still draft and its production lineage changes are also in this PR's current diff. Land that prerequisite first, then rebase this PR so it contains only the benchmark and its target.

lance-gatekeeper · 2026-09-29T07:50:19Z

+use lance::dataset::optimize::{CompactionOptions, compact_files};
+use lance::dataset::rowids::{
+    DEFAULT_INLINE_ROW_LINEAGE_MAX_BYTES, INLINE_ROW_LINEAGE_MAX_BYTES_CONFIG_KEY,
+    SPILL_ROW_LINEAGE_CONFIG_KEY, get_row_id_index, load_row_id_sequence,


This benchmark depends on the spill behavior introduced by #9347. That PR remains draft, while this PR's diff also includes its storage and compaction changes; merging the benchmark now would ship that production path before its prerequisite is ready. Please merge #9347 first and rebase this PR onto that result.

Agreed on the order. #9347 is now rebased onto main (on top of the merged #9339) and marked ready for review, so it can land first. GitHub won't let a stacked PR change its base, so I can't retarget this one at #9347's branch by hand, but it rebases stacked PRs automatically when the one below merges, as it did here when #9339 landed. Once #9347 merges, this PR's diff will be just rust/lance/benches/rowid_spill.rs and its [[bench]] entry in rust/lance/Cargo.toml, and it shouldn't be merged before then.

Thanks. I verified that #9347 is now ready for review but remains unmerged, and #9340 still includes its production changes. The sequence you outlined is the safe one: land #9347 first, then leave this PR benchmark-only. I’ll keep this finding active until that dependency lands.

Fixed in 8ebfde6: #9347 has merged, and this PR’s current diff contains only the benchmark and its Cargo target. The merge-order concern is resolved.

lance-gatekeeper

❌ Gate recommendation: request changes.

As the author clarified, #9347 is now ready for review. It remains unmerged, and this PR’s current diff still includes its production lineage changes. The safe sequence is unchanged: land #9347 first, then rebase this PR to the benchmark-only diff.

… data file (#9347) Part of the §5.3 stack (#8931, #9250); based on `main` now that #9339 has merged. Compaction writes the lineage sequences it spills into each output fragment's own data file, as hidden columns next to the user columns, instead of a separate lineage file. It also fixes three bugs in reading, placing and reclaiming spilled lineage that the review of this stack found. ## Stack 1. #9253, #9336, #9337, #9338, #9339 (merged) 2. this PR: feat(dataset): write compaction's spilled lineage into the fragment's data file 3. #9340 test(bench): row lineage spill benchmark (lands after this PR) ## Change **Lineage in the data file.** - On a table that can spill, compaction computes its output fragments' lineage before writing. The row ids and versions carry over from the inputs. - A sequence type that is over the inline budget in every output fragment rides along as an extra non-nullable `uint64` column of the batches being written. The fragment's metadata then marks it as spilled into that same data file. - A type that is over budget in some outputs and not others (`RowLineagePlan::PerFragment`) writes no hidden columns. After the write, each fragment is placed on its own, so a cheap `Range` sequence never turns into a column read. - Tables that never opted in compact exactly as before: lineage is rechunked after the write from the written sizes. - `versions::write_fragments` sets the hidden fields aside by their reserved ids before the schema check and puts them back on the written schema. `Schema::validate` admits the reserved ids only on top-level fields with those names. - Binary-copy compaction cannot add columns and still writes a separate lineage file. **Fixes.** - **Written sizes, not planned sizes.** A byte limit (`max_bytes_per_file`) can close a file early and re-split the rows, so the plan's file sizes are not the written ones. Placement used to zip the plan with the written fragments. That made a stable-row-id compaction fail outright, or shift row ids by one when the fragment count happened to match. It now rechunks the planned lineage to each fragment's `physical_rows` and checks every inline sequence's length. - **Reading a spilled column.** `read_spilled_column` took the projected field from the file schema by column index. Once lineage columns follow nested or list user columns, the column index is no longer the top-level position, so the read errored or took the wrong field. The field is now built from the reserved id. Only the needed column's metadata is opened. - **Carriers whose user columns are gone.** Now that #9339 keeps carriers through drop, cast and replace, a data file can hold lineage and only dead user columns. `FileFragment::validate` no longer tries to open it as user data. The compaction planner picks such a fragment up, so the lineage moves into a fresh file and the dead bytes are reclaimed. Lineage-only files never match, so this cannot loop. **Memory.** Spilled sequences are moved into their column values rather than copied. Each batch gets its own buffer, so the encoder no longer cuts a page per batch from a shared slice. Pre-write planning only happens on tables that can spill. ## Validation Run on an x86 build host (r8i.8xlarge): - `cargo fmt --all -- --check`, `cargo clippy --all --tests --benches -- -D warnings` - `cargo test -p lance-table`: 573 passed. - `cargo test -p lance --lib -- rowids:: row_version stable_row rowid optimize::tests dataset_transactions fragment::tests cleanup::tests feature_flag update::tests merge_insert::tests io::commit dataset_io schema_evolution versions:: write::tests utils::tests`: 1576 passed. - New tests: - `compaction_spills_and_reads_back_row_lineage` cases: `flat`, `nested_v2_2`, `list_v2_0`, `multi_output`, `with_deletions`. - `compact_twice_reads_back_in_file_lineage`. - `place_row_lineage_in_files_follows_written_sizes`: extra file, shifted split, mismatched totals. - `plan_row_lineage_spill_decides_per_kind` and `per_fragment_plan_spills_only_the_fragments_over_budget`. - `append_row_lineage_columns_gives_each_batch_its_own_buffer`. - `dropping_every_column_of_a_lineage_carrier_keeps_lineage_until_compaction`: drop, cast, replace. - `compaction_reclaims_lineage_carriers_of_dead_user_columns`. - `cleanup_keeps_a_live_spilled_file`: in-file and lineage-file layouts. - `split_row_lineage_fields_keys_on_reserved_ids`. - `cargo check --manifest-path python/Cargo.toml`, `cargo check --manifest-path java/lance-jni/Cargo.toml` Refs #8931, #9250 🤖 Generated with [Claude Code](https://claude.com/claude-code) --------- Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

Two workloads bracket what the run encoding can do with a sequence: 30% of rows deleted then compacted, where the row ids still encode as a range plus a bitmap, and every row rewritten in random order then compacted, where no run structure survives. Within each, the two arms differ only in the table's lance.row_lineage.spill setting, and the benchmark reports manifest and transaction-file bytes, cold open, small-append commit latency, sequence load, row id index build, a take by row id, compaction wall time and bytes on disk. Co-authored-by: Will Jones <willjones127@gmail.com> Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

The shuffled workload rewrote every row without its created-at and last-updated-at versions, so compaction fell back to a single version run: the benchmark never inlined or spilled a real version sequence, and the table it measured claimed every row was created at version 1. The rewrite now derives each row's lineage from its id (write_table hands out row ids in id order and creates fragment k at version k + 1), so it no longer scans the table, and it shuffles with a seeded rand SmallRng instead of a hand-written PRNG. At the defaults the shuffled inline arm now carries about 200 MB of version runs in its manifest, which the module doc notes. Nothing checked that the spilled arm spilled or that the lineage it read back was right. The spilled arm must now spill something and the inline arm nothing, with spilled fragments counted per lineage family, and a full scan after compaction compares every row's row id, created-at and last-updated-at version with what the workload handed out. BENCH_INLINE_MAX_BYTES sets the spilled arm's inline budget so that small runs still spill. BENCH_* values that do not parse or are out of range stop the benchmark before any data is written, and a spilled arm that spills nothing stops it after that arm's compaction. Several rows did not measure what their labels said: - manifest size now comes from the first append after compaction, since the compaction's own manifest file can hold an inline transaction copy that readers never download; that file keeps its own row - append commit times only CommitBuilder::execute, with the data file written and the dataset opened outside the timer - the take row warms the target fragment's sequence and data file first, so it is a control rather than a hidden sequence load, and it takes 16 probes, each checked against its value - data bytes are the compaction's output, not the whole data directory - timings keep every sample and report median and minimum, with 10 read samples instead of 3 - each arm's temp directory is removed before the next arm runs Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

lance-gatekeeper

✅ Gate recommendation: approve.

With #9347 merged, the earlier sequencing concern is resolved and this diff is benchmark-only. Both arms use the same generated workload; the benchmark checks lineage placement and row-id reads outside its timed sections, and reports the costs on both sides of the trade-off. The reported smoke run is appropriately framed as one sample.

This was referenced Sep 17, 2026

feat(format): define hidden row lineage columns #9253

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feat(dataset): read and write spilled row lineage columns #9336

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This was referenced Sep 17, 2026

feat(dataset): spill row lineage at compaction #9337

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feat(table): load spilled row lineage ahead of a commit #9338

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feat(dataset): spill row lineage when updating rows #9339

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BubbleCal force-pushed the yang/oss-2269-6-row-lineage-bench branch from f65221b to 3bb5b86 Compare September 17, 2026 08:39

BubbleCal changed the title ~~bench(rowids): measure row lineage placement inline versus spilled~~ test(bench): measure row lineage placement inline versus spilled Sep 17, 2026

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BubbleCal force-pushed the yang/oss-2269-6-row-lineage-bench branch from 3bb5b86 to 3fe94b4 Compare September 17, 2026 08:47

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BubbleCal force-pushed the yang/oss-2269-6-row-lineage-bench branch from 3fe94b4 to b700ea9 Compare September 17, 2026 10:52

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feat(dataset): write compaction's spilled lineage into the fragment's data file #9347

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BubbleCal changed the title ~~test(bench): measure row lineage placement inline versus spilled~~ test(bench): measure row lineage placement against a checked workload Sep 29, 2026

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test(bench): measure row lineage placement against a checked workload - #9340

test(bench): measure row lineage placement against a checked workload#9340
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BubbleCal commented Sep 17, 2026 •

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