com.hazelcast.org.apache.calcite.rel.core.Sample Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to you under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.hazelcast.org.apache.calcite.rel.core;
import com.hazelcast.org.apache.calcite.plan.Convention;
import com.hazelcast.org.apache.calcite.plan.RelOptCluster;
import com.hazelcast.org.apache.calcite.plan.RelOptSamplingParameters;
import com.hazelcast.org.apache.calcite.plan.RelTraitSet;
import com.hazelcast.org.apache.calcite.rel.RelInput;
import com.hazelcast.org.apache.calcite.rel.RelNode;
import com.hazelcast.org.apache.calcite.rel.RelWriter;
import com.hazelcast.org.apache.calcite.rel.SingleRel;
import java.util.List;
/**
* Relational expression that returns a sample of the rows from its input.
*
* In SQL, a sample is expressed using the {@code TABLESAMPLE BERNOULLI} or
* {@code SYSTEM} keyword applied to a table, view or sub-query.
*/
public class Sample extends SingleRel {
//~ Instance fields --------------------------------------------------------
private final RelOptSamplingParameters params;
//~ Constructors -----------------------------------------------------------
public Sample(RelOptCluster cluster, RelNode child,
RelOptSamplingParameters params) {
super(cluster, cluster.traitSetOf(Convention.NONE), child);
this.params = params;
}
/**
* Creates a Sample by parsing serialized output.
*/
public Sample(RelInput input) {
this(input.getCluster(), input.getInput(), getSamplingParameters(input));
}
//~ Methods ----------------------------------------------------------------
private static RelOptSamplingParameters getSamplingParameters(
RelInput input) {
String mode = input.getString("mode");
float percentage = input.getFloat("rate");
Object repeatableSeed = input.get("repeatableSeed");
boolean repeatable = repeatableSeed instanceof Number;
return new RelOptSamplingParameters(
mode.equals("bernoulli"), percentage, repeatable,
repeatable ? ((Number) repeatableSeed).intValue() : 0);
}
public RelNode copy(RelTraitSet traitSet, List inputs) {
assert traitSet.containsIfApplicable(Convention.NONE);
return new Sample(getCluster(), sole(inputs), params);
}
/**
* Retrieve the sampling parameters for this Sample.
*/
public RelOptSamplingParameters getSamplingParameters() {
return params;
}
@Override public RelWriter explainTerms(RelWriter pw) {
return super.explainTerms(pw)
.item("mode", params.isBernoulli() ? "bernoulli" : "system")
.item("rate", params.getSamplingPercentage())
.item("repeatableSeed",
params.isRepeatable() ? params.getRepeatableSeed() : "-");
}
}