kbendick commented on code in PR #4944: URL: https://github.com/apache/iceberg/pull/4944#discussion_r890400771
########## format/puffin-spec.md: ########## @@ -0,0 +1,144 @@ +--- +url: puffin-spec +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. + --> + +# Puffin file format + +This is a specification for Puffin, a file format designed to store +information such as indexes and statistics about data managed in an +Iceberg table that cannot be stored directly within the Iceberg manifest. A +Puffin file contains arbitrary pieces of information (here called "blobs"), +along with metadata necessary to interpret them. The blobs supported by Iceberg +are documented at [Blob types](#blob-types). + +## Format specification + +A file conforming to the Puffin file format specification should have the structure +as described below. + +### Versions + +Currently, there is a single version of the Puffin file format, described below. + +### File structure + +The Puffin file has the following structure + +``` +Magic Blob₁ Blob₂ ... Blobₙ Footer +``` + +where + +- `Magic` is four bytes 0x50, 0x46, 0x41, 0x31 (short for: Puffin _Fratercula + arctica_, version 1), +- `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 + +``` +Magic FooterPayload FooterPayloadSize Flags Magic +``` + +where + +- `Magic`: four bytes, same as at the beginning of the file +- `FooterPayload`: optionally compressed, UTF-8 encoded JSON payload describing the Review Comment: The mentioning of lz4 as the compression option should ideally be placed near the first mention of compression imo. Or perhaps a mention of the compression section would suffice. I had to go looking for an indication of the compression type after reading this line which was somewhat confusing for me. -- 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]
