org.apache.flink.table.expressions.Expression Maven / Gradle / Ivy
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*
* http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.flink.table.expressions;
import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.table.types.DataType;
import java.util.List;
/**
* General interface for all kinds of expressions.
*
* Expressions represent a logical tree for producing a computation result. Every expression
* consists of zero, one, or more subexpressions. Expressions might be literal values, function
* calls, or field references.
*
*
Expressions are part of the API. They might be transformed multiple times within the API stack
* until they are fully {@link ResolvedExpression}s. Value types and output types are expressed as
* instances of {@link DataType}.
*/
@PublicEvolving
public interface Expression {
/**
* Returns a string that summarizes this expression for printing to a console. An implementation
* might skip very specific properties.
*
* @return summary string of this expression for debugging purposes
*/
String asSummaryString();
List getChildren();
R accept(ExpressionVisitor visitor);
}