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LimitOffsetScanToOrderByLimitConverter.java
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LimitOffsetScanToOrderByLimitConverter.java
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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.beam.sdk.extensions.sql.zetasql.translation;
import static java.util.stream.Collectors.toList;
import static org.apache.beam.vendor.calcite.v1_20_0.org.apache.calcite.rel.RelFieldCollation.Direction.ASCENDING;
import static org.apache.beam.vendor.calcite.v1_20_0.org.apache.calcite.rel.RelFieldCollation.Direction.DESCENDING;
import com.google.zetasql.resolvedast.ResolvedNode;
import com.google.zetasql.resolvedast.ResolvedNodes.ResolvedLimitOffsetScan;
import com.google.zetasql.resolvedast.ResolvedNodes.ResolvedOrderByItem;
import com.google.zetasql.resolvedast.ResolvedNodes.ResolvedOrderByScan;
import java.util.Collections;
import java.util.List;
import org.apache.beam.vendor.calcite.v1_20_0.org.apache.calcite.rel.RelCollation;
import org.apache.beam.vendor.calcite.v1_20_0.org.apache.calcite.rel.RelCollationImpl;
import org.apache.beam.vendor.calcite.v1_20_0.org.apache.calcite.rel.RelFieldCollation;
import org.apache.beam.vendor.calcite.v1_20_0.org.apache.calcite.rel.RelFieldCollation.Direction;
import org.apache.beam.vendor.calcite.v1_20_0.org.apache.calcite.rel.RelNode;
import org.apache.beam.vendor.calcite.v1_20_0.org.apache.calcite.rel.logical.LogicalProject;
import org.apache.beam.vendor.calcite.v1_20_0.org.apache.calcite.rel.logical.LogicalSort;
import org.apache.beam.vendor.calcite.v1_20_0.org.apache.calcite.rex.RexLiteral;
import org.apache.beam.vendor.calcite.v1_20_0.org.apache.calcite.rex.RexNode;
/** Converts ORDER BY LIMIT. */
class LimitOffsetScanToOrderByLimitConverter extends RelConverter<ResolvedLimitOffsetScan> {
LimitOffsetScanToOrderByLimitConverter(ConversionContext context) {
super(context);
}
@Override
public boolean canConvert(ResolvedLimitOffsetScan zetaNode) {
return zetaNode.getInputScan() instanceof ResolvedOrderByScan;
}
@Override
public List<ResolvedNode> getInputs(ResolvedLimitOffsetScan zetaNode) {
// The immediate input is the ORDER BY scan which we don't support,
// but we can handle the ORDER BY LIMIT if we know the underlying projection, for example.
return Collections.singletonList(
((ResolvedOrderByScan) zetaNode.getInputScan()).getInputScan());
}
@Override
public RelNode convert(ResolvedLimitOffsetScan zetaNode, List<RelNode> inputs) {
ResolvedOrderByScan inputOrderByScan = (ResolvedOrderByScan) zetaNode.getInputScan();
RelNode input = convertOrderByScanToLogicalScan(inputOrderByScan, inputs.get(0));
RelCollation relCollation = getRelCollation(inputOrderByScan);
RexNode offset =
zetaNode.getOffset() == null
? null
: getExpressionConverter().convertRexNodeFromResolvedExpr(zetaNode.getOffset());
RexNode fetch =
getExpressionConverter()
.convertRexNodeFromResolvedExpr(
zetaNode.getLimit(), zetaNode.getColumnList(), input.getRowType().getFieldList());
if (RexLiteral.isNullLiteral(offset) || RexLiteral.isNullLiteral(fetch)) {
throw new UnsupportedOperationException("Limit requires non-null count and offset");
}
return LogicalSort.create(input, relCollation, offset, fetch);
}
/** Collation is a sort order, as in ORDER BY DESCENDING/ASCENDING. */
private static RelCollation getRelCollation(ResolvedOrderByScan node) {
final long inputOffset = node.getColumnList().get(0).getId();
List<RelFieldCollation> fieldCollations =
node.getOrderByItemList().stream()
.map(item -> orderByItemToFieldCollation(item, inputOffset))
.collect(toList());
return RelCollationImpl.of(fieldCollations);
}
private static RelFieldCollation orderByItemToFieldCollation(
ResolvedOrderByItem item, long inputOffset) {
Direction sortDirection = item.getIsDescending() ? DESCENDING : ASCENDING;
final long fieldIndex = item.getColumnRef().getColumn().getId() - inputOffset;
return new RelFieldCollation((int) fieldIndex, sortDirection);
}
private RelNode convertOrderByScanToLogicalScan(ResolvedOrderByScan node, RelNode input) {
List<RexNode> projects =
getExpressionConverter()
.retrieveRexNodeFromOrderByScan(getCluster(), node, input.getRowType().getFieldList());
List<String> fieldNames = getTrait().retrieveFieldNames(node.getColumnList());
return LogicalProject.create(input, projects, fieldNames);
}
}