Graphersal and TinkerPop
Apache TinkerPop™ defines the property graph model and the Gremlin language that many graph databases implement. Graphersal is an independent implementation in Rust: it does not use TinkerPop's Java code, and it is not a Gremlin Server, so a TinkerPop driver does not connect to it. What it shares with TinkerPop is the language and its meaning.
Same meaning, checked by TinkerPop's own tests
The rule is simple: a step that Graphersal implements behaves as the TinkerPop specification
says, unless a difference is documented. The specification is TinkerPop's own test suite, a set of
Gherkin scenarios (TinkerPop 3.8.2) that runs with every cargo test of Graphersal. A scenario
that passes once is protected from regressing, and the number of supported steps whose results
are wrong is kept at zero. The current numbers are on
TinkerPop Compliance.
Not every step exists yet. An unimplemented step is an error that names it, never a silently different result; the gaps are listed in Current Limitations.
Deliberate differences
A few behaviours differ on purpose, each for a reason that is written down. The most visible ones:
- Every traversal is a transaction. A failing traversal leaves nothing behind (Transactions).
- Ids are strings, so they sort as text (Predicates).
- One integer and one float type (
int64,float64) instead of Java's number tower. - A removed element stays removed: reading it through an old reference finds nothing, and writing to it is an error (Dropping Elements).
- No
match(),io()or graph-computer algorithms; files are read and written by the API and the command line instead.
Every difference, with its page, is in TinkerPop Deviations.
The query text
TinkerPop's reference language is Gremlin embedded in Groovy or Java. Graphersal's text form is Gremlin embedded in Rhai, a small scripting language for Rust. A Groovy line usually pastes as it is; the differences are small:
| Gremlin Groovy | Graphersal |
|---|---|
'single quotes' | "double quotes" |
order().by('age', desc) | order().by("age", Order.desc) (token classes are written out) |
out() inside where(...), repeat(...) | __.out() (anonymous traversals always start with __.) |
[name: 'ann'] (a map) | #{name: "ann"} |
def x = ... | let x = ...; |
The full copy-paste table is in Repeated Labels: select with Pop.
Every step also has a snake_case name (has_label, out_e) next to its camelCase one
(hasLabel, outE), and the Rust API uses the snake_case names.
Additions
Graphersal adds what an embedded engine needs: schemas, saved queries in the graph, path keys into
nested values (jpath), multi-label vertices, change capture, permissions and resource limits, a
durable Store, and profile() with memory figures. These are extensions: they do not change what
a TinkerPop query means.