Query instances

A panproto instance is a graph of records. Queries filter and project that graph using the expression language.

Prerequisites

A schema and an instance loaded against it. The expression-language reference for predicates.

The task

Filter and project

executeQuery is exported from @panproto/core. Its signature is executeQuery(query, instance, wasm) (query first, instance second, WASM module third). The query keys are anchor, predicate (an Expr object, not a string), projection (string array), groupBy, limit, and path.

import { executeQuery, parseExpr, ExprBuilder } from '@panproto/core';

const recent = executeQuery(
  {
    anchor: 'post',
    predicate: parseExpr('post.created_at > "2024-01-01"'),
    projection: ['id', 'title'],
  },
  instance,
  panproto._wasm,
);

The predicate is evaluated against each matched node; projection selects the fields included in each QueryMatch.

Following edges

Use the path field to traverse from the anchor before predicate matching:

const userPosts = executeQuery(
  { anchor: 'user', path: ['authored'], projection: ['title'] },
  instance,
  panproto._wasm,
);

To filter on edge presence, build a predicate with the instance-aware builtins (Edge, Children, HasEdge, EdgeCount) using ExprBuilder or parseExpr.

Verification

Predicates are type-checked against the schema before evaluation; an ill-typed predicate raises before any data is touched.

Common mistakes

• Using Edge, Children, etc. in the standard evaluator. They return Null outside an instance environment. The query API sets the environment correctly; reaching for the bare evaluator does not.
• Hitting the step budget on large records. Heavy string operations on long fields will exceed the budget; either narrow the predicate or raise the budget at the call site.

See also

• Reference: expression language.
• Convert data between formats.