gianm commented on code in PR #12745: URL: https://github.com/apache/druid/pull/12745#discussion_r915184392
########## processing/src/main/java/org/apache/druid/frame/Frame.java: ########## @@ -0,0 +1,448 @@ +/* + * 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.druid.frame; + +import com.google.common.primitives.Ints; +import net.jpountz.lz4.LZ4Compressor; +import net.jpountz.lz4.LZ4Factory; +import net.jpountz.lz4.LZ4SafeDecompressor; +import org.apache.datasketches.memory.Memory; +import org.apache.datasketches.memory.WritableMemory; +import org.apache.druid.io.Channels; +import org.apache.druid.java.util.common.IAE; +import org.apache.druid.java.util.common.ISE; + +import javax.annotation.Nullable; +import java.io.IOException; +import java.nio.ByteBuffer; +import java.nio.ByteOrder; +import java.nio.channels.WritableByteChannel; + +/** + * A data frame. + * + * Frames are split into contiguous "regions". With columnar frames ({@link FrameType#COLUMNAR}) each region + * is a column. With row-based frames ({@link FrameType#ROW_BASED}) there are always two regions: row offsets + * and row data. + * + * This object is lightweight. It has constant overhead regardless of the number of rows or regions. + * + * Frames are written with {@link org.apache.druid.frame.write.FrameWriter} and read with + * {@link org.apache.druid.frame.read.FrameReader}. + * + * Frame format: Review Comment: I did not consider it at the time but I'm considering it now. I definitely see the benefit of using a format that allows easier evolution. My immediate thought is we don't use protobuf or thrift for anything in core right now and I hesitate to add them just for this. We do use JSON/Smile for headers in the segment format. Maybe that would be OK here. Frames are going to be relatively large (I expect 1–8MB will be typical) so the overhead of reading one few-bytes-long Smile header should be minimal, if not negligible. What do you think? -- 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: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
