pitrou commented on code in PR #45360: URL: https://github.com/apache/arrow/pull/45360#discussion_r2086135451
########## cpp/src/parquet/chunker_internal.h: ########## @@ -0,0 +1,144 @@ +// 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. + +#pragma once + +#include <cstdint> +#include <vector> + +#include "arrow/array.h" +#include "parquet/level_conversion.h" + +namespace parquet::internal { + +// Represents a chunk of data with level offsets and value offsets due to the +// record shredding for nested data. +struct Chunk { + // The start offset of this chunk inside the given levels + int64_t level_offset; + // The start offset of this chunk inside the given values array + int64_t value_offset; + // The length of the chunk in levels + int64_t levels_to_write; +}; + +/// CDC (Content-Defined Chunking) is a technique that divides data into variable-sized +/// chunks based on the content of the data itself, rather than using fixed-size +/// boundaries. +/// +/// For example, given this sequence of values in a column: +/// +/// File1: [1,2,3, 4,5,6, 7,8,9] +/// chunk1 chunk2 chunk3 +/// +/// Assume there is an inserted value between 3 and 4: +/// +/// File2: [1,2,3,0, 4,5,6, 7,8,9] +/// new-chunk chunk2 chunk3 +/// +/// The chunking process will adjust to maintain stable boundaries across data +/// modifications. Each chunk defines a new parquet data page which is contiguously +/// written out to the file. Since each page compressed independently, the files' contents +/// would look like the following with unique page identifiers: +/// +/// File1: [Page1][Page2][Page3]... +/// File2: [Page4][Page2][Page3]... Review Comment: I think that is a made-up example, not actual data that you can reproduce with specific CDC settings :) -- 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: github-unsubscr...@arrow.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
