presto-main/src/main/java/io/prestosql/sql/planner/plan/SampleNode.java/SampleNode/SampleNode
class SampleNode:    @JsonCreator
    public SampleNode(
            @JsonProperty("id") PlanNodeId id,
            @JsonProperty("source") PlanNode source,
            @JsonProperty("sampleRatio") double sampleRatio,
            @JsonProperty("sampleType") Type sampleType)
    {
        super(id);

        checkArgument(sampleRatio >= 0.0, "sample ratio must be greater than or equal to 0");
        checkArgument((sampleRatio <= 1.0), "sample ratio must be less than or equal to 1");

        this.sampleType = requireNonNull(sampleType, "sample type is null");
        this.source = requireNonNull(source, "source is null");
        this.sampleRatio = sampleRatio;
    }