db-src-tsv

The groupant beside tools/db/src/tsv.rs in the Mova repository: what the code computes, what it never does, how to go back from its outputs, its invariants, cost and checks.

Facts

Implementation material. A Mova code model describes this code at one source revision: partial models, finite checks and their stated scope. It is not a reviewed general exposition, and its labels are shown as written, never raised.

Components

component	label	where
approximant	partial	approximant
ast	partial	`syntax.json`
composition	partial	composition
cost	partial	invariant-and-cost
descriptant	present	descriptant
invariant	partial	invariant-and-cost
tests	bounded checks partial scope	tests

Obernants

The typed relations around the forward model: the behaviour complement (what the code never does), the reverse reconstruction (every input compatible with an output) and specialised views.

id	type	label	where
`behavior_complement`	behavior_complement	partial source derived model	behavior_complement
`reverse_reconstruction`	reverse_reconstruction	partial source derived model	reverse_reconstruction
`null_empty_separation`	null_empty_separation	partial source derived model	null_empty_separation
`partial_write_frontier`	partial_write_frontier	partial source derived model	partial_write_frontier
`numeric_range`	numeric_range	partial source derived model	numeric_range
`header_as_data`	header_as_data	partial source derived model	header_as_data

Parts

db-src-tsv-row-write

Model text

descriptant

Raw TSV representation and partial writes

create truncates/creates file and writes joined header. row checks arity then writes columns left-to-right with tabs; Null emits backslash-N, strings reject tab/LF/CR/sentinel, integers decimal and booleans lowercase. Successful newline increments rows. finish flushes and returns count. read splits every file line without removing header, mapping exact sentinel to None; s/int check presence then parse.

Prospective epoch — 2026-10-31

Full source was reviewed before edits; external prospective.md records API states, failure order and predicted checks. Production prefix remains byte-identical; test additions are isolated cfg(test)/test items.

Observed epoch — 2026-10-31

2026-10-31 wave31: 16 selected target/name cases passed twice debug and twice release with identical sorted outcomes; six compiled source-behavior mutants failed assertions, exact bytes restored and positive checks passed. Evidence scope is only the named helpers/fixtures. External receipt directory: $MOVA_DATA/runs/octopus-wave31-store-2026-10-31. No DuckDB integration, production loader/corpus, training or GPU run.

Retained limitations

No SQL evaluation was substituted with a mock process. Missing DuckDB is a dependency gap, not passing database evidence. Partial syntax has no macro expansion/name resolution/types; Rust helpers and fixtures do not prove all models.

approximant

Raw TSV representation and partial writes forward relation

Domain

Finite valid-UTF8 inputs, representable counters/IDs, available memory; filesystem fixtures confined to owned temporary root. SQL semantics are conditional and unexecuted. Subject is the source and SHA256 bound in manifest; fragment applies only to declared byte range.

Approximation limits

Categorical parsing, exact identity, transactional effects and resource errors have no useful percentage approximation metric here. No executable surrogate is claimed. Future profiles, if justified, may use only 1%, 2%, 5%, 10% with a defined metric/reference/domain.

composition

Local scope composition

Parent relation: create truncates/creates file and writes joined header. row checks arity then writes columns left-to-right with tabs; Null emits backslash-N, strings reject tab/LF/CR/sentinel, integers decimal and booleans lowercase. Successful newline increments rows. finish flushes and returns count. read splits every file line without removing header, mapping exact sentinel to None; s/int check presence then parse.

Child fragments isolate selected mechanisms and do not cover the entire file. Invocation order and shared state remain the parent's relation. Costs of a child are included in parent cost, not added a second time; independent branch scopes are tagged. A child reverse relation must preserve intermediate state compatibility, not imply unique whole-file reconstruction.

Children: [{"id":"db-src-tsv-row-write","path":"row-write.groupant"}]

models

Raw TSV representation and partial writes typed model catalog

Observation is one call/trace in the declared scope. Operators below are partial source-derived relations; complement is a proposed inner exclusion relation, reverse an outer compatible-antecedent relation retaining ambiguity. No universal proof follows from finite checks. Each oracle is the relevant named helper check below when it reaches the behavior; remaining SQL/effect cases are source review or proposed real-CLI checks.

behavior_complement

Wrong arity cannot write any row prefix; invalid later cell cannot produce a successful row count increment. A literal backslash-N string cannot be represented as a successful non-NULL cell.

Domain/assumptions: Finite valid-UTF8 inputs, representable counters/IDs, available memory; filesystem fixtures confined to owned temporary root. SQL semantics are conditional and unexecuted. Subject is the source and SHA256 bound in manifest; fragment applies only to declared byte range.