rdblue commented on code in PR #69: URL: https://github.com/apache/iceberg-docs/pull/69#discussion_r841288257
########## 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 + +Footer has the following structure + +``` +FooterPayload FooterPayloadSize Reserved FileFormatVersion Magic +``` + +where + +- `FooterPayload` LZ4-compressed, UTF-8 encoded JSON payload describing the + blobs in the file, with the structure described below, +- `FooterPayloadSize` is a length in bytes of the `FooterPayload`, stored as 4 + byte integer, little-endian, Review Comment: This should specify that the size is for the compressed payload. I don't think that we need an uncompressed size. It should be fine. -- 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
