com.hazelcast.org.apache.calcite.sql.SqlSampleSpec 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 com.hazelcast.com.liance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.com.hazelcast.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.sql;
import com.hazelcast.org.apache.calcite.sql.dialect.CalciteSqlDialect;
/**
* Specification of a SQL sample.
*
* For example, the query
*
*
* SELECT *
* FROM emp TABLESAMPLE SUBSTITUTE('medium')
*
*
* declares a sample which is created using {@link #createNamed}.
*
* A sample is not a {@link SqlNode}. To include it in a parse tree, wrap it
* as a literal, viz:
* {@link SqlLiteral#createSample(SqlSampleSpec, com.hazelcast.org.apache.calcite.sql.parser.SqlParserPos)}.
*/
public abstract class SqlSampleSpec {
//~ Constructors -----------------------------------------------------------
protected SqlSampleSpec() {
}
//~ Methods ----------------------------------------------------------------
/**
* Creates a sample which substitutes one relation for another.
*/
public static SqlSampleSpec createNamed(String name) {
return new SqlSubstitutionSampleSpec(name);
}
/**
* Creates a table sample without repeatability.
*
* @param isBernoulli true if Bernoulli style sampling is to be used;
* false for implementation specific sampling
* @param samplePercentage likelihood of a row appearing in the sample
*/
public static SqlSampleSpec createTableSample(
boolean isBernoulli,
float samplePercentage) {
return new SqlTableSampleSpec(isBernoulli, samplePercentage);
}
/**
* Creates a table sample with repeatability.
*
* @param isBernoulli true if Bernoulli style sampling is to be used;
* false for implementation specific sampling
* @param samplePercentage likelihood of a row appearing in the sample
* @param repeatableSeed seed value used to reproduce the same sample
*/
public static SqlSampleSpec createTableSample(
boolean isBernoulli,
float samplePercentage,
int repeatableSeed) {
return new SqlTableSampleSpec(
isBernoulli,
samplePercentage,
repeatableSeed);
}
//~ Inner Classes ----------------------------------------------------------
/** Sample specification that orders substitution. */
public static class SqlSubstitutionSampleSpec extends SqlSampleSpec {
private final String name;
private SqlSubstitutionSampleSpec(String name) {
this.name = name;
}
public String getName() {
return name;
}
public String toString() {
return "SUBSTITUTE("
+ CalciteSqlDialect.DEFAULT.quoteStringLiteral(name)
+ ")";
}
}
/** Sample specification. */
public static class SqlTableSampleSpec extends SqlSampleSpec {
private final boolean isBernoulli;
private final float samplePercentage;
private final boolean isRepeatable;
private final int repeatableSeed;
private SqlTableSampleSpec(boolean isBernoulli, float samplePercentage) {
this.isBernoulli = isBernoulli;
this.samplePercentage = samplePercentage;
this.isRepeatable = false;
this.repeatableSeed = 0;
}
private SqlTableSampleSpec(
boolean isBernoulli,
float samplePercentage,
int repeatableSeed) {
this.isBernoulli = isBernoulli;
this.samplePercentage = samplePercentage;
this.isRepeatable = true;
this.repeatableSeed = repeatableSeed;
}
/**
* Indicates Bernoulli vs. System sampling.
*/
public boolean isBernoulli() {
return isBernoulli;
}
/**
* Returns sampling percentage. Range is 0.0 to 1.0, exclusive
*/
public float getSamplePercentage() {
return samplePercentage;
}
/**
* Indicates whether repeatable seed should be used.
*/
public boolean isRepeatable() {
return isRepeatable;
}
/**
* Seed to produce repeatable samples.
*/
public int getRepeatableSeed() {
return repeatableSeed;
}
public String toString() {
StringBuilder b = new StringBuilder();
b.append(isBernoulli ? "BERNOULLI" : "SYSTEM");
b.append('(');
b.append(samplePercentage * 100.0);
b.append(')');
if (isRepeatable) {
b.append(" REPEATABLE(");
b.append(repeatableSeed);
b.append(')');
}
return b.toString();
}
}
}