Function processJoin

packages/db/src/query/compiler/joins.ts:106–345

* Processes a single join clause with lazy loading optimization. * For LEFT/RIGHT/INNER joins, marks one side as "lazy" (loads on-demand based on join keys).

(
  pipeline: NamespacedAndKeyedStream,
  joinClause: JoinClause,
  sources: Record<string, KeyedStream>,
  mainCollectionId: string,
  mainSource: string,
  allInputs: Record<string, KeyedStream>,
  cache: QueryCache,
  queryMapping: QueryMapping,
  collections: Record<string, Collection>,
  subscriptions: Record<string, CollectionSubscription>,
  callbacks: Record<string, LazyCollectionCallbacks>,
  lazySources: Set<string>,
  optimizableOrderByCollections: Record<string, OrderByOptimizationInfo>,
  setWindowFn: (windowFn: (options: WindowOptions) => void) => void,
  rawQuery: QueryIR,
  onCompileSubquery: CompileQueryFn,
  aliasToCollectionId: Record<string, string>,
  aliasRemapping: Record<string, string>,
  sourceWhereClauses: Map<string, BasicExpression<boolean>>,
)

 * For LEFT/RIGHT/INNER joins, marks one side as "lazy" (loads on-demand based on join keys).
 */
function processJoin(
  pipeline: NamespacedAndKeyedStream,
  joinClause: JoinClause,
  sources: Record<string, KeyedStream>,
  mainCollectionId: string,
  mainSource: string,
  allInputs: Record<string, KeyedStream>,
  cache: QueryCache,
  queryMapping: QueryMapping,
  collections: Record<string, Collection>,
  subscriptions: Record<string, CollectionSubscription>,
  callbacks: Record<string, LazyCollectionCallbacks>,
  lazySources: Set<string>,
  optimizableOrderByCollections: Record<string, OrderByOptimizationInfo>,
  setWindowFn: (windowFn: (options: WindowOptions) => void) => void,
  rawQuery: QueryIR,
  onCompileSubquery: CompileQueryFn,
  aliasToCollectionId: Record<string, string>,
  aliasRemapping: Record<string, string>,
  sourceWhereClauses: Map<string, BasicExpression<boolean>>,
): NamespacedAndKeyedStream {
  const isCollectionRef = joinClause.from.type === `collectionRef`

  // Get the joined source alias and input stream
  const {
    alias: joinedSource,
    input: joinedInput,
    collectionId: joinedCollectionId,
  } = processJoinSource(
    joinClause.from,
    allInputs,
    collections,
    subscriptions,
    callbacks,
    lazySources,
    optimizableOrderByCollections,
    setWindowFn,
    cache,
    queryMapping,
    onCompileSubquery,
    aliasToCollectionId,
    aliasRemapping,
    sourceWhereClauses,
  )

  // Add the joined source to the sources map
  sources[joinedSource] = joinedInput
  if (isCollectionRef) {
    // Only direct collection references form new alias bindings. Subquery
    // aliases reuse the mapping returned from the recursive compilation above.
    aliasToCollectionId[joinedSource] = joinedCollectionId
  }

  const mainCollection = collections[mainCollectionId]
  const joinedCollection = collections[joinedCollectionId]

  if (!mainCollection) {
    throw new JoinCollectionNotFoundError(mainCollectionId)