Function _reduceScans

src/execution_plan/optimizations/reduce_scans.c:29–57

}

static void _reduceScans(ExecutionPlan *plan, OpBase *scan) {
	// Return early if the scan has no child operations.
	if(scan->childCount == 0) return;

	// The scan operation should be operating on a single alias.
	ASSERT(array_len(scan->modifies) == 1);
	const char *scanned_alias = scan->modifies[0];

	// Collect variables bound before this operation.
	rax *bound_vars = raxNew();
	for(int i = 0; i < scan->childCount; i ++) {
		ExecutionPlan_BoundVariables(scan->children[i], bound_vars,
			scan->children[i]->plan);
	}

	if(raxFind(bound_vars, (unsigned char *)scanned_alias, strlen(scanned_alias)) != raxNotFound) {
		// If the alias the scan operates on is already bound, the scan operation is redundant.
		if(scan->type == OPType_NODE_BY_LABEL_SCAN) {
			// If we are performing a label scan, introduce a conditional traversal to filter by label.
			OpBase *traverse = _LabelScanToConditionalTraverse((NodeByLabelScan *)scan);
			ExecutionPlan_ReplaceOp(plan, scan, traverse);
		} else {
			// Remove the redundant scan op.
			ExecutionPlan_RemoveOp(plan, scan);
		}
		OpBase_Free(scan);
	}
	raxFree(bound_vars);
}

void reduceScans(ExecutionPlan *plan) {
	// Collect all SCAN operations within the execution plan.