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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.flink.table.operations.utils;
import org.apache.flink.annotation.Internal;
import org.apache.flink.table.api.ValidationException;
import org.apache.flink.table.expressions.ApiExpressionUtils;
import org.apache.flink.table.expressions.Expression;
import org.apache.flink.table.expressions.UnresolvedCallExpression;
import org.apache.flink.table.expressions.UnresolvedReferenceExpression;
import org.apache.flink.table.expressions.utils.ApiExpressionDefaultVisitor;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Set;
import java.util.stream.Collectors;
import static java.lang.String.format;
import static org.apache.flink.table.expressions.ApiExpressionUtils.unresolvedRef;
import static org.apache.flink.table.functions.BuiltInFunctionDefinitions.AS;
import static org.apache.flink.table.operations.utils.OperationExpressionsUtils.extractName;
/** Utility class for creating projection expressions from column operation. */
@Internal
final class ColumnOperationUtils {
private static final DropColumnsExtractor dropColumnsExtractor = new DropColumnsExtractor();
private static final RenameColumnExtractor renameColumnExtractor = new RenameColumnExtractor();
/**
* Creates a projection list that renames existing columns to new names.
*
* NOTE: Resulting expression are still unresolved.
*
* @param inputFields names of current columns
* @param newAliases new aliases for current columns
* @return projection expressions
*/
static List renameColumns(List inputFields, List newAliases) {
LinkedHashMap finalFields = new LinkedHashMap<>();
inputFields.forEach(field -> finalFields.put(field, unresolvedRef(field)));
newAliases.forEach(
expr -> {
String name = expr.accept(renameColumnExtractor);
finalFields.put(name, expr);
});
return new ArrayList<>(finalFields.values());
}
/**
* Creates a projection list that adds new or replaces existing (if a column with corresponding
* name already exists) columns.
*
* NOTE: Resulting expression are still unresolved.
*
* @param inputFields names of current columns
* @param newExpressions new columns to add
* @return projection expressions
*/
static List addOrReplaceColumns(
List inputFields, List newExpressions) {
LinkedHashMap finalFields = new LinkedHashMap<>();
inputFields.forEach(field -> finalFields.put(field, unresolvedRef(field)));
newExpressions.forEach(
expr -> {
String name = extractName(expr).orElse(expr.toString());
finalFields.put(name, expr);
});
return new ArrayList<>(finalFields.values());
}
/**
* Creates a projection list that removes given columns.
*
* NOTE: Resulting expression are still unresolved.
*
* @param inputFields names of current columns
* @param dropExpressions columns to remove
* @return projection expressions
*/
static List dropFields(List inputFields, List dropExpressions) {
Set columnsToDrop =
dropExpressions.stream()
.map(expr -> expr.accept(dropColumnsExtractor))
.collect(Collectors.toSet());
columnsToDrop.forEach(
c -> {
if (!inputFields.contains(c)) {
throw new ValidationException(
format("Field %s does not exist in source table", c));
}
});
return inputFields.stream()
.filter(oldName -> !columnsToDrop.contains(oldName))
.map(ApiExpressionUtils::unresolvedRef)
.collect(Collectors.toList());
}
private static class DropColumnsExtractor extends ApiExpressionDefaultVisitor {
@Override
public String visit(UnresolvedReferenceExpression unresolvedReference) {
return unresolvedReference.getName();
}
@Override
protected String defaultMethod(Expression expression) {
throw new ValidationException("Unexpected drop column expression: " + expression);
}
}
private static class RenameColumnExtractor extends ApiExpressionDefaultVisitor {
@Override
public String visit(UnresolvedCallExpression unresolvedCall) {
if (unresolvedCall.getFunctionDefinition() == AS
&& unresolvedCall.getChildren().get(0)
instanceof UnresolvedReferenceExpression) {
UnresolvedReferenceExpression resolvedFieldReference =
(UnresolvedReferenceExpression) unresolvedCall.getChildren().get(0);
return resolvedFieldReference.getName();
} else {
return defaultMethod(unresolvedCall);
}
}
@Override
protected String defaultMethod(Expression expression) {
throw new ValidationException(
format(
"Invalid alias for a renaming column operation. Renaming must add an alias to an"
+ "existing field. E.g.: 'a as a1'. But was: %s",
expression));
}
}
private ColumnOperationUtils() {}
}