Interface Converter
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- All Superinterfaces:
java.lang.Cloneable
,RelNode
,RelOptNode
- All Known Implementing Classes:
AbstractConverter
,CassandraToEnumerableConverter
,ConverterImpl
,ElasticsearchToEnumerableConverter
,EnumerableBindable
,EnumerableInterpretable
,EnumerableToSparkConverter
,GeodeToEnumerableConverter
,InterpretableConverter
,JdbcToEnumerableConverter
,JdbcToSparkConverter
,MongoToEnumerableConverter
,NoneConverter
,PigToEnumerableConverter
,SparkToEnumerableConverter
public interface Converter extends RelNode
A relational expression implements the interfaceConverter
to indicate that it converts a physical attribute, ortrait
, of a relational expression from one value to another.Sometimes this conversion is expensive; for example, to convert a non-distinct to a distinct object stream, we have to clone every object in the input.
A converter does not change the logical expression being evaluated; after conversion, the number of rows and the values of those rows will still be the same. By declaring itself to be a converter, a relational expression is telling the planner about this equivalence, and the planner groups expressions which are logically equivalent but have different physical traits into groups called
RelSet
s.In principle one could devise converters which change multiple traits simultaneously (say change the sort-order and the physical location of a relational expression). In which case, the method
getInputTraits()
would return aRelTraitSet
. But for simplicity, this class only allows one trait to be converted at a time; all other traits are assumed to be preserved.
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Nested Class Summary
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Nested classes/interfaces inherited from interface org.apache.calcite.rel.RelNode
RelNode.Context
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Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method Description RelNode
getInput()
Returns the sole input relational expressionRelTraitSet
getInputTraits()
Returns the trait of the input relational expression.RelTraitDef
getTraitDef()
Returns the definition of trait which this converter works on.-
Methods inherited from interface org.apache.calcite.rel.RelNode
accept, accept, childrenAccept, collectVariablesSet, collectVariablesUsed, computeSelfCost, computeSelfCost, copy, estimateRowCount, explain, getChildExps, getCollationList, getConvention, getCorrelVariable, getExpectedInputRowType, getInput, getInputs, getQuery, getRelTypeName, getRows, getRowType, getTable, getVariablesSet, getVariablesStopped, isDistinct, isKey, isValid, isValid, metadata, onRegister, recomputeDigest, register, replaceInput
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Methods inherited from interface org.apache.calcite.plan.RelOptNode
getCluster, getDescription, getDigest, getId, getTraitSet
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Method Detail
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getInputTraits
RelTraitSet getInputTraits()
Returns the trait of the input relational expression.- Returns:
- input trait
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getTraitDef
RelTraitDef getTraitDef()
Returns the definition of trait which this converter works on.The input relational expression (matched by the rule) must possess this trait and have the value given by
getInputTraits()
, and the traits of the output of this converter given byRelOptNode.getTraitSet()
will have one trait altered and the other orthogonal traits will be the same.- Returns:
- trait which this converter modifies
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getInput
RelNode getInput()
Returns the sole input relational expression- Returns:
- child relational expression
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