GraphML export Go API

In v1.4.4, apocexport.GraphML(nodes, relationships) returns (string, error). Go consumers must handle the error; there is no string-only compatibility entry point. Bundled registration and ToString(..., "graphml") use this same owner.

output, err := apocexport.GraphML(nodes, relationships)
if err != nil {
    return err
}
// output contains a complete XML document.

Property names, property string representations and relationship types preserve XML-special characters and Unicode after XML decoding. XML whitespace is escaped so attribute normalization and line-ending normalization do not change values.

Malformed UTF-8, unpaired UTF-16 units and characters outside XML 1.0's Char production are rejected. They cannot be represented losslessly in that format. The in-memory API returns an empty result with its error. File export validates the document before opening its destination: rejected input neither creates a new file nor changes an existing one. Write errors are returned to the caller; this is not a guarantee of atomic replacement for an operating-system write failure.

File export Go API

The canonical file-writing entry points are context-first: ToFile, JsonAll, Csv, CypherAll and GraphMLAll take the caller's context as their first Go argument. pkg/apocio is the one owner of that admission and destination: AdmitExport resolves the named path through the caller's APOC export capability. WriteExport writes text or bytes to that admitted destination beneath the configured export root. A context without an export capability performs no write and reports the owner's error, and a caller that already stopped writes nothing.

if err := apocexport.GraphMLAll(ctx, nodes, relationships, "/path/to/graph.graphml"); err != nil {
    return err
}

The in-memory producers Json, Cypher, GraphML and ToString are unchanged and stay context-free, so apoc.Call still invokes them without a context. A query executor binds the statement context to a context-first file handler; a standalone Go caller binds one explicitly with apocio.WithCapability. Root apoc.Call cannot invoke a context-first file export, because the caller's lifetime is not part of that surface.

Go callers of the retired forwarding GraphMLData function use GraphMLAll. The public APOC names apoc.export.graphMLAll and apoc.export.graphMLData both register that canonical implementation directly and remain supported. An empty destination retains the established no-file behavior: no capability is needed and nothing is written. Text-to-byte conversion is deferred until an actual file write; the empty-destination path allocates nothing even for a 1 MiB input. The whole-graph file exports create the destination's parent directories, and destination errors are returned to the caller.

This change preserves the exporter's existing graph selection and document shape. It does not introduce GraphML schema/key declarations or claim XSD validation. No database keys, payloads, WAL formats or storage versions change.

Measured export cost

Five isolated 200ms samples per workload on Apple M2 Max, Darwin/arm64, Go 1.27.3 compare the release implementation with this correction. Each graph has one string property per node and relationship, one relationship per node, and either ordinary text or XML markup/Unicode/whitespace. Medians:

Graph	Text	Before ns/op	After ns/op	Before → after B/op	Before → after allocs/op
1 node + 1 relationship	ordinary	2,164	2,896	1,048 → 920	16 → 15
1 node + 1 relationship	markup	2,627	3,561	1,097 → 1,681	16 → 16
100 nodes + 100 relationships	ordinary	256,306	161,859	116,261 → 100,269	1,215 → 1,016
100 nodes + 100 relationships	markup	227,947	175,468	149,762 → 175,582	1,216 → 1,018

The old markup result is malformed XML, so this comparison measures correction cost rather than equivalent valid encoders. Escaping expands the output and increases bytes in markup-heavy cases; the table does not attribute every extra byte exclusively to the final output. Single-element validation/encoding adds sub-microsecond latency. The CPU profile includes standard escaping and the explicit XML-character validation; no custom competing XML escaper was retained. These helper workloads do not establish whole-database throughput or every property-type cost.

Reproduce with go test -tags='noui nolocalllm' ./apoc/export -run='^$' -bench='^BenchmarkGraphMLExport$' -benchmem -benchtime=200ms -count=5.

Canonical file helpers and aliases

Retired Go forwarding entry points migrate to canonical context-first calls:

Retired Go helper	Canonical helper
JsonData(nodes, rels, path)	JsonAll(ctx, nodes, rels, path)
CypherData(nodes, rels, path)	CypherAll(ctx, nodes, rels, path)
CsvData(nodes, path)	Csv(ctx, nodes, path)
CsvAll(nodes, ignoredRelationships, path)	Csv(ctx, nodes, path)
GraphMLData(nodes, rels, path)	GraphMLAll(ctx, nodes, rels, path)

Their bundled APOC names bind directly to the canonical functions. The bundled apoc.export.csvAll handler now takes nodes and path; its ignored relationship argument is removed. Native Cypher CALL apoc.export.csv.all(...) and the other native procedure signatures are unchanged. There are no compatibility wrappers.