Function _Index_PopulateEdgeIndex

src/index/index_construct.c:112–218

index edges in an asynchronous manner edges are being indexed in batchs while the graph's read lock is held to avoid interfering with the DB ongoing operation after each batch of edges is indexed the graph read lock is released alowing for write queries to be processed it is safe to run a write query which effects the index by either: adding/removing/updating an entity while the index is being po

// adding/removing/updating an entity while the index is being populated
// in the "worst" case we will index that entity twice which is perfectly OK
static void _Index_PopulateEdgeIndex
(
	Index idx,
	Graph *g
) {
	ASSERT(g   != NULL);
	ASSERT(idx != NULL);

	GrB_Info  info;
	EntityID  src_id       = 0;     // current processed row idx
	EntityID  dest_id      = 0;     // current processed column idx
	EntityID  edge_id      = 0;     // current processed edge id
	EntityID  prev_src_id  = 0;     // last processed row idx
	EntityID  prev_dest_id = 0;     // last processed column idx
	int       indexed      = 0;     // number of entities indexed in current batch
	int       batch_size   = 1000;  // max number of entities to index in one go
	RG_MatrixTupleIter it  = {0};

	while(true) {
		// lock graph for reading
		Graph_AcquireReadLock(g);

		// index state changed, abort indexing
		// this can happen if for example the following sequance is issued:
		// 1. CREATE INDEX FOR (:Person)-[e:WORKS]-(:Company) ON (e.since)
		// 2. CREATE INDEX FOR (:Person)-[e:WORKS]-(:Company) ON (e.title)
		if(Index_PendingChanges(idx) > 1) {
			break;
		}

		// reset number of indexed edges in batch
		indexed      = 0;
		prev_src_id  = src_id;
		prev_dest_id = dest_id;

		// fetch relation matrix
		const RG_Matrix m = Graph_GetRelationMatrix(g, Index_GetLabelID(idx),
				false);
		ASSERT(m != NULL);

		//----------------------------------------------------------------------
		// resume scanning from previous row/col indices
		//----------------------------------------------------------------------

		info = RG_MatrixTupleIter_attach(&it, m);
		ASSERT(info == GrB_SUCCESS);
		info = RG_MatrixTupleIter_iterate_range(&it, src_id, UINT64_MAX);
		ASSERT(info == GrB_SUCCESS);

		// skip previously indexed edges
		while((info = RG_MatrixTupleIter_next_UINT64(&it, &src_id, &dest_id,
						&edge_id)) == GrB_SUCCESS &&
				src_id == prev_src_id &&
				dest_id < prev_dest_id);

		// process only if iterator is on an active entry
		if(info != GrB_SUCCESS) {
			break;