org.eigenbase.sql
Class SqlSampleSpec

java.lang.Object
  org.eigenbase.sql.SqlSampleSpec

Direct Known Subclasses:

SqlSampleSpec.SqlSubstitutionSampleSpec, SqlSampleSpec.SqlTableSampleSpec

public abstract class SqlSampleSpec
extends Object

Specification of a SQL sample.

For example, the query

SELECT *
 FROM emp TABLESAMPLE SUBSTITUTE('medium')

declares a sample which is created using createNamed(java.lang.String).

A sample is not a SqlNode. To include it in a parse tree, wrap it as a literal, viz: SqlLiteral.createSample(SqlSampleSpec, SqlParserPos).

Nested Class Summary

static class	SqlSampleSpec.SqlSubstitutionSampleSpec
static class	SqlSampleSpec.SqlTableSampleSpec

Constructor Summary

protected

SqlSampleSpec()

Method Summary

static SqlSampleSpec	createNamed(String name) Creates a sample which substitutes one relation for another.
static SqlSampleSpec	createTableSample(boolean isBernoulli, float samplePercentage) Creates a table sample without repeatability.
static SqlSampleSpec	createTableSample(boolean isBernoulli, float samplePercentage, int repeatableSeed) Creates a table sample with repeatability.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SqlSampleSpec

protected SqlSampleSpec()

Method Detail

createNamed

public static SqlSampleSpec createNamed(String name)

Creates a sample which substitutes one relation for another.

createTableSample

public static SqlSampleSpec createTableSample(boolean isBernoulli,
                                              float samplePercentage)

Creates a table sample without repeatability.

Parameters:

isBernoulli - true if Bernoulli style sampling is to be used; false for implementation specific sampling

samplePercentage - likelihood of a row appearing in the sample

createTableSample

public static SqlSampleSpec createTableSample(boolean isBernoulli,
                                              float samplePercentage,
                                              int repeatableSeed)

Creates a table sample with repeatability.

Parameters:

isBernoulli - true if Bernoulli style sampling is to be used; false for implementation specific sampling

samplePercentage - likelihood of a row appearing in the sample

repeatableSeed - seed value used to reproduce the same sample