Function convertMultiPattern

packages/graph/src/astToSteps.ts:1530–1637

* Convert a MultiPattern (comma-separated patterns like MATCH (a), (b)) into steps. * Creates a Cartesian product of all matching combinations. * * Note: Currently only supports simple node patterns. Patterns with edges * (e.g., MATCH (a)-[:KNOWS]-(b), (c)) are not supported in comma-separated f

(
  multiPattern: MultiPattern,
  whereClause?: WhereClause,
  preservePriorBindings: boolean = false,
)

 * (e.g., MATCH (a)-[:KNOWS]-(b), (c)) are not supported in comma-separated form.
 */
function convertMultiPattern(
  multiPattern: MultiPattern,
  whereClause?: WhereClause,
  preservePriorBindings: boolean = false,
): Step<any>[] {
  const steps: Step<any>[] = [];
  const { patterns } = multiPattern;

  if (patterns.length === 0) {
    throw new Error("MultiPattern must have at least one pattern");
  }

  // Validate that all patterns are simple node patterns (no edges)
  for (let i = 0; i < patterns.length; i++) {
    const pattern = patterns[i]!;
    if (pattern.elements.length > 1) {
      throw new Error(
        `Comma-separated MATCH patterns only support simple node patterns. ` +
          `Pattern ${i + 1} contains edges which is not supported. ` +
          `Use separate MATCH clauses for patterns with relationships.`,
      );
    }
    if (pattern.elements[0]?.type !== "NodePattern") {
      throw new Error(
        `Comma-separated MATCH patterns must start with a NodePattern. ` +
          `Pattern ${i + 1} starts with ${pattern.elements[0]?.type ?? "nothing"}.`,
      );
    }
  }

  // Process first pattern normally
  const firstPattern = patterns[0]!;
  const firstNode = firstPattern.elements[0] as NodePattern;
  const firstStepLabels = firstNode.variable ? [firstNode.variable] : undefined;

  // Use CartesianFetchStep if we need to preserve bindings from a prior WITH clause
  if (preservePriorBindings) {
    steps.push(
      new CartesianFetchStep({
        vertexLabels: firstNode.labels.length > 0 ? firstNode.labels : undefined,
        stepLabels: firstStepLabels,
      }),
    );
  } else {
    steps.push(
      new FetchVerticesStep({
        vertexLabels: firstNode.labels.length > 0 ? firstNode.labels : undefined,
        stepLabels: firstStepLabels,
      }),
    );
  }

  // If there's a label expression on the first node, add a filter
  if (firstNode.labelExpression) {
    steps.push(
      new FilterElementsStep({
        condition: convertLabelExpression(firstNode.labelExpression),
      }),