rdblue commented on code in PR #69: URL: https://github.com/apache/iceberg-docs/pull/69#discussion_r841290322
########## landing-page/content/common/statistics-format-spec.md: ########## @@ -0,0 +1,111 @@ +--- +url: statistics-format +toc: false +--- +<!-- + - 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. + --> + +# Plain Format for Iceberg Statistics + +This is a specification for the Plain Format for Iceberg Statistics, a file +format designed to store information such as statistics about data managed in an +Iceberg table that cannot be stored directly within the Iceberg manifest. A +statistics file contains arbitrary pieces of information (here called "blobs"), +along with metadata necessary to interpret them. + +## Format specification + +A file conforming to the format specification should have the structure as +described below. + +### File structure + +The file has the following structure + +``` +Magic Blob₁ Blob₂ ... Blobₙ Footer +``` + +where + +- `Magic` is four bytes 0x80, 0x70, 0x73, 0x83 (short for: Plain Format for + Iceberg Statistics), +- `Blobᵢ` is i-th blob contained in the file, to be interpreted by application + according to the footer, +- `Footer` is defined below. + +### Footer structure Review Comment: What do you think about making this a header instead of a footer? There are a couple good reasons to do this: 1. All of the blobs will be pre-computed and will likely be in memory or in other files already because they were aggregated from an incoming data stream. All of the blobs are finished at the same time, end of the incoming data stream. 2. Header-based formats are simpler because you don't need to do calculations to find where the footer starts 3. Seeks to the end of the file and then backward seeks to get content are expensive -- 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: dev-unsubscr...@iceberg.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
