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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.schema.expressiontransforms;
import com.yahoo.schema.RankProfile;
import com.yahoo.searchlib.rankingexpression.RankingExpression;
import com.yahoo.searchlib.rankingexpression.rule.CompositeNode;
import com.yahoo.searchlib.rankingexpression.rule.ExpressionNode;
import com.yahoo.searchlib.rankingexpression.rule.FunctionNode;
import com.yahoo.searchlib.rankingexpression.rule.ReferenceNode;
import com.yahoo.searchlib.rankingexpression.transform.ExpressionTransformer;
/**
* Transforms function nodes to reference nodes if a rank profile function shadows a built-in function.
* This has the effect of allowing rank profile functions to redefine built-in functions.
* Another effect is that we can add built-in functions over time
* without fear of breaking existing users' functions with the same name.
*
* However, there is a (largish) caveat. If a user has a function with a certain number
* of arguments, and we add in a built-in function with a different arity,
* this will cause parse errors as the Java parser gives precedence to
* built-in functions.
*
* @author lesters
*/
public class FunctionShadower extends ExpressionTransformer<RankProfileTransformContext> {
@Override
public RankingExpression transform(RankingExpression expression, RankProfileTransformContext context) {
ExpressionNode node = expression.getRoot();
ExpressionNode result = transform(node, context);
return (result == node)
? expression
: new RankingExpression(expression.getName(), result);
}
@Override
public ExpressionNode transform(ExpressionNode node, RankProfileTransformContext context) {
if (node instanceof FunctionNode)
return transformFunctionNode((FunctionNode) node, context);
if (node instanceof CompositeNode)
return transformChildren((CompositeNode)node, context);
return node;
}
private ExpressionNode transformFunctionNode(FunctionNode function, RankProfileTransformContext context) {
String name = function.getFunction().toString();
RankProfile.RankingExpressionFunction rankingExpressionFunction = context.rankProfile().findFunction(name);
if (rankingExpressionFunction == null)
return transformChildren(function, context);
int functionArity = function.getFunction().arity();
if (functionArity != rankingExpressionFunction.function().arguments().size())
return transformChildren(function, context);
ReferenceNode node = new ReferenceNode(name, function.children(), null);
return transformChildren(node, context);
}
}
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