Struct Predicate 

pub struct Predicate { /* private fields */ }

One condition on a contract’s payload or on its row.

Implementations

impl Predicate

pub fn eq(path: impl IntoPath, value: impl Into<Value>) -> Self

A field of the payload equals value.

The comparison is JSON equality, so it is exact for every type: a Numeric that LF-JSON carries as "10.0" matches "10.0" and not 10.0, which is the distinction the encoding makes on purpose.

pub fn not_eq(path: impl IntoPath, value: impl Into<Value>) -> Self

A field of the payload does not equal value — including when the field is absent.

Rendered as IS DISTINCT FROM rather than <>, and the difference is not pedantic here. <> against a missing path yields SQL NULL, so the row is excluded — and missing paths are the normal case for this crate, because qname deliberately matches on the package name so a query survives a Smart Contract Upgrade. A result set therefore mixes payloads of different versions with different field sets. Under <>, adding a field in v2 would silently drop every v1 contract from a not_eq on it, with no error and no warning.

pub fn compare(path: impl IntoPath, op: Op, value: impl Into<Value>) -> Self

An ordered comparison on a field.

A contract whose payload lacks the field is not returned: there is no answer to “is the missing value greater than 10”. That is the right verdict, unlike for not_eq, but it is worth knowing when a query spans two versions of a template — use contains or a not_eq if the absent case should count.

A JSON number compares numerically and a JSON string compares as text. That distinction is not cosmetic: LF-JSON carries Int64 and Numeric as strings, so comparing an amount lexically would order "9" after "10". Pass a number to compare numerically — the cast is applied for you — and a string only where the field really is text.

pub fn contains(value: impl Into<Value>) -> Self

The payload contains this JSON object (@>).

The predicate a GIN index on payload can serve.

pub fn signatory(party: impl Into<String>) -> Self

The party is among the contract’s signatories.

pub fn observer(party: impl Into<String>) -> Self

The party is among the contract’s observers.

pub fn witness(party: impl Into<String>) -> Self

The party is among the parties that witnessed it.

pub fn contract_id(id: impl Into<String>) -> Self

The contract id is exactly this.

Trait Implementations

impl Clone for Predicate

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Predicate

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.