Function reduce_cond_op

src/execution_plan/optimizations/utilize_indices.c:424–509

try to replace given Conditional Traverse operation and a set of Filter operations with a single Index Scan operation

// try to replace given Conditional Traverse operation and a set of Filter operations with
// a single Index Scan operation
void reduce_cond_op(ExecutionPlan *plan, OpCondTraverse *cond) {
	// make sure there's an index for scanned label
	const char *edge = AlgebraicExpression_Edge(cond->ae);
	if(!edge) return;
	
	QGEdge *e = QueryGraph_GetEdgeByAlias(cond->op.plan->query_graph, edge);
	if(QGEdge_RelationCount(e) != 1) return;

	const char *label = QGEdge_Relation(e, 0);
	GraphContext *gc = QueryCtx_GetGraphCtx();
	Index idx = GraphContext_GetIndex(gc, label, NULL, 0, IDX_EXACT_MATCH,
			SCHEMA_EDGE);
	if(idx == NULL) return;

	// get all applicable filter for index
	OpFilter **filters = _applicableFilters((OpBase *)cond, edge, idx);

	// no filters, return
	uint filters_count = array_len(filters);
	if(filters_count == 0) goto cleanup;

	RSIndex *rs_idx = Index_RSIndex(idx);
	FT_FilterNode *root = _Concat_Filters(filters);
	OpBase *indexOp = NewEdgeIndexScanOp(cond->op.plan, cond->graph, e, rs_idx,
			root);

	// The OPType_ALL_NODE_SCAN operation is redundant
	// because OPType_EDGE_BY_INDEX_SCAN will resolve source nodes
	if(cond->op.children[0]->type == OPType_ALL_NODE_SCAN) {
		OpBase *allNodeScan = cond->op.children[0];
		// remove all node scan op
		ExecutionPlan_RemoveOp(plan, allNodeScan);
		OpBase_Free(allNodeScan);
	}

	
	const char *other_alias  =  AlgebraicExpression_Dest(cond->ae);
	QGNode     *other_node   =  QueryGraph_GetNodeByAlias(cond->op.plan->query_graph, other_alias);
	ASSERT(other_node != NULL);
	uint other_label_count   =  QGNode_LabelCount(other_node);
	if(other_label_count > 0) {
		// create func expression
		const char *func_name = "hasLabels";
		AR_ExpNode *op = AR_EXP_NewOpNode(func_name, true, 2);

		// create node expression
		AR_ExpNode *node_exp = AR_EXP_NewVariableOperandNode(other_alias);

		// create labels expression
		SIValue labels = SI_Array(other_label_count);
		for (uint i = 0; i < other_label_count; i++) {
			SIArray_Append(&labels, SI_ConstStringVal((char *)other_node->labels[i]));
		}
		AR_ExpNode *labels_exp = AR_EXP_NewConstOperandNode(labels);

		// set function arguments
		op->op.children[0] = node_exp;
		op->op.children[1] = labels_exp;