omnigraph/docs/user/errors.md

Errors and Result Serialization

Error taxonomy (omnigraph::error::OmniError)

• Compiler(...) — schema/query parse/typecheck errors
• Lance(String) — storage layer
• DataFusion(String) — execution layer
• Io(io::Error)
• Manifest(ManifestError { kind: BadRequest|NotFound|Conflict|Internal, details: Option<ManifestConflictDetails>, … })
  • ManifestConflictDetails::ExpectedVersionMismatch { table_key, expected, actual } — caller's expected_table_versions did not match the manifest's current latest non-tombstoned version (set by OmniError::manifest_expected_version_mismatch).
  • ManifestConflictDetails::RowLevelCasContention — Lance row-level CAS rejected the publish because a concurrent writer landed the same object_id. Retried internally by the publisher; only surfaces if the retry budget exhausts.
  • D₂ parse-time rejection (MR-794): a single mutation query that mixes inserts/updates with deletes errors out before any I/O with kind BadRequest. Message: mutation '<name>' on the same query mixes inserts/updates and deletes; split into separate mutations: (1) inserts and updates, then (2) deletes. See docs/user/query-language.md for the rule and docs/dev/runs.md for the underlying staged-write rationale.
• MergeConflicts(Vec<MergeConflict>)

Compiler-side NanoError covers parse / catalog / type / storage / plan / execution / arrow / lance / IO / manifest / unique-constraint, each with structured spans (SourceSpan { start, end }) for ariadne-style diagnostics.

Result serialization (omnigraph_compiler::result::QueryResult)

• to_arrow_ipc() — efficient binary
• to_sdk_json() — JS-safe JSON (large i64 wrapped in metadata)
• to_rust_json() — Rust-friendly JSON
• batches() — direct Arrow RecordBatch access

Mutation results: { affectedNodes: usize, affectedEdges: usize } (also exposed as a tiny Arrow batch).