Apache Data Lakehouse Weekly: July 21 to July 29, 2026

This was a week where the open lakehouse stack spent most of its energy on contracts. Not legal contracts, but the promises that formats, catalogs, and clients make to each other. Iceberg debated whether equality deletes belong in V4 and whether incremental scan semantics belong in the spec at all. Parquet voted a new floating point encoding into the format and argued about who owns the Thrift file that defines everything. Polaris tried to ship 1.7.0, found a licensing gap in 44 staged jars, and pulled the release candidate. Arrow wrestled with what the nullable flag actually means. Across all of it, a pattern showed up again and again: the community is done with informal conventions and wants written guarantees. Here is what happened, project by project. Apache Iceberg The week opened with a personnel note that matters more than personnel notes usually do. Steven Wu announced that Maximilian Michels joined the project as a committer , and the thread ran to 30 messages of congratulations from across the contributor base. Iceberg has grown into a project where the streaming and Flink side of the ecosystem carries real weight, and adding committers who live in that part of the codebase keeps the review load from concentrating on a handful of people. The size of the congratulations thread is its own signal about how many active humans are now paying attention to this list. The most consequential technical debate of the week was about deletes. Huaxin Gao pushed forward on the proposal to deprecate equality deletes in Iceberg V4 , and the thread drew 15 messages including strong support from Ryan Blue. Equality deletes are the mechanism that lets a streaming writer say "delete every row where id equals 42" without knowing which file that row lives in. They make writes cheap and reads expensive. Every scan has to carry the delete predicates forward and apply them against candidate files, and scan planning cannot prune as aggressively because the planner does not know whic