pvary commented on code in PR #16961: URL: https://github.com/apache/iceberg/pull/16961#discussion_r3542314298
########## format/index.md: ########## @@ -0,0 +1,322 @@ +--- +title: "Index Spec" +--- +<!-- + - 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. + --> + +# Iceberg Index Specification + +## Background and Motivation + +Indexes enable query engines to locate relevant rows without scanning entire datasets. +They can accelerate point lookups, range predicates, and other retrieval patterns +while preserving Iceberg's table format, snapshot isolation, and interoperability. + +This specification defines: + +- A portable metadata format for indexes +- A catalog-managed index object independent from table metadata +- A common storage architecture for index data +- A framework for defining new index types and transform functions + +Indexes are optional. Engines may choose to create, maintain, consume, or ignore them. + +## Goals + +- Define a common metadata format for indexes +- Allow indexes to evolve independently from table metadata +- Enable index sharing across engines +- Provide a foundation for future index types + +## Definitions + +### Index Type + +The index type defines the logical category of an index and the class of queries it is designed to accelerate. + +The following index type is defined in this specification: + +| Type | +|--------| +| SCALAR | Review Comment: In most cases the query engine is only interested in the index type which could be served by multiple transform functions. In specific cases the transform function is important. Possible combinations: - Flink needs SCALAR index with HASH transform function to effectively read the index on job restarts. With HASH it doesn't need an extra shuffle to distribute the index in the job state. - Spark delete range query on PK needs a SCALAR index with IDENTITY or HILBERT transform function. HASH transform would result in a full index scan. - Spark point lookup query with PK can ignore the transform function itself. It could rely on the requirement that only a single leaf file should be returned for a single key. -- 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]
