Package org.apache.calcite.plan

Class RelOptSamplingParameters

  • public class RelOptSamplingParameters
extends java.lang.Object
    RelOptSamplingParameters represents the parameters necessary to produce a sample of a relation.

    It's parameters are derived from the SQL 2003 TABLESAMPLE clause.

    • Constructor Summary

      Constructors 
      Constructor Description
      RelOptSamplingParameters​(boolean isBernoulli, float samplingPercentage, boolean isRepeatable, int repeatableSeed)  

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      int getRepeatableSeed()
      If isRepeatable() returns true, this method returns a user-specified seed value.
      float getSamplingPercentage()
      Returns the sampling percentage.
      boolean isBernoulli()
      Indicates whether Bernoulli or system sampling should be performed.
      boolean isRepeatable()
      Indicates whether the sample results should be repeatable.

      • Methods inherited from class java.lang.Object

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

    • Field Detail

      • isBernoulli

        private final boolean isBernoulli

      • samplingPercentage

        private final float samplingPercentage

      • isRepeatable

        private final boolean isRepeatable

      • repeatableSeed

        private final int repeatableSeed

    • Constructor Detail

      • RelOptSamplingParameters

        public RelOptSamplingParameters​(boolean isBernoulli,
                                float samplingPercentage,
                                boolean isRepeatable,
                                int repeatableSeed)

    • Method Detail

      • isBernoulli

        public boolean isBernoulli()
        Indicates whether Bernoulli or system sampling should be performed. Bernoulli sampling requires the decision whether to include each row in the the sample to be independent across rows. System sampling allows implementation-dependent behavior.
        Returns:
        true if Bernoulli sampling is configured, false for system sampling

      • getSamplingPercentage

        public float getSamplingPercentage()
        Returns the sampling percentage. For Bernoulli sampling, the sampling percentage is the likelihood that any given row will be included in the sample. For system sampling, the sampling percentage indicates (roughly) what percentage of the rows will appear in the sample.
        Returns:
        the sampling percentage between 0.0 and 1.0, exclusive

      • isRepeatable

        public boolean isRepeatable()
        Indicates whether the sample results should be repeatable. Sample results are only required to repeat if no changes have been made to the relation's content or structure. If the sample is configured to be repeatable, then a user-specified seed value can be obtained via getRepeatableSeed().
        Returns:
        true if the sample results should be repeatable

      • getRepeatableSeed

        public int getRepeatableSeed()
        If isRepeatable() returns true, this method returns a user-specified seed value. Samples of the same, unmodified relation should be identical if the sampling mode, sampling percentage and repeatable seed are the same.
        Returns:
        seed value for repeatable samples