gortiz commented on code in PR #8979: URL: https://github.com/apache/pinot/pull/8979#discussion_r959208614
########## pinot-core/src/main/java/org/apache/pinot/core/operator/query/SelectionPartiallyOrderedByDescOperation.java: ########## @@ -0,0 +1,132 @@ +/** + * 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.pinot.core.operator.query; + +import com.google.common.base.Preconditions; +import com.google.common.base.Supplier; +import java.util.ArrayList; +import java.util.List; +import org.apache.pinot.common.request.context.ExpressionContext; +import org.apache.pinot.core.common.BlockValSet; +import org.apache.pinot.core.common.RowBasedBlockValueFetcher; +import org.apache.pinot.core.operator.blocks.TransformBlock; +import org.apache.pinot.core.operator.transform.TransformOperator; +import org.apache.pinot.core.query.request.context.QueryContext; +import org.apache.pinot.segment.spi.IndexSegment; + + +/** + * An operator for order-by queries DESC that are partially sorted over the sorting keys. + * + * @see LinearSelectionOrderByOperator + */ +public class SelectionPartiallyOrderedByDescOperation extends LinearSelectionOrderByOperator { + + private static final String EXPLAIN_NAME = "SELECT_PARTIAL_ORDER_BY_DESC"; + + private int _numDocsScanned = 0; + private long _numEntriesScannedPostFilter = 0; + + public SelectionPartiallyOrderedByDescOperation(IndexSegment indexSegment, QueryContext queryContext, + List<ExpressionContext> expressions, TransformOperator transformOperator, int sortedExpr) { + super(indexSegment, queryContext, expressions, transformOperator, sortedExpr); + assert queryContext.getOrderByExpressions() != null; + Preconditions.checkArgument(queryContext.getOrderByExpressions().stream() + .filter(expr -> expr.getExpression().getType() == ExpressionContext.Type.IDENTIFIER) + .findFirst() + .orElseThrow(() -> new IllegalArgumentException("The query is not order by identifiers")) + .isDesc(), + "%s can only be used when the first column in order by is DESC", EXPLAIN_NAME); + } + + @Override + protected List<Object[]> fetch(Supplier<ListBuilder> listBuilderSupplier) { + + // Ideally we would use a descending cursor, but we don't actually have them + // Alternatively, we could store all blocks in a list and iterate them in reverse order, but ProjectionBlocks share + // the same DataBlockCache, so they may be ephemeral and being overridden by the next block. + // The only alternative we have right now is to retrieve the last LIMIT elements from each block + + TransformBlock block; + int numColumnsProjected = _transformOperator.getNumColumnsProjected(); + int numExpressions = _expressions.size(); + BlockValSet[] blockValSets = new BlockValSet[numExpressions]; + + List<List<Object[]>> rowsPerBlock = new ArrayList<>(); Review Comment: Also, reading the code now, it seems to me that the solution is incorrect. If elements at the end of one block have the same sorted columns than the elements at the beginning of the next they are in the same partition, but they are never sorted by their unsorted columns -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: commits-unsubscr...@pinot.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: commits-unsubscr...@pinot.apache.org For additional commands, e-mail: commits-h...@pinot.apache.org
