Finn Völkel

I am working on a Datalog database engine à la Datomic on top of object storage.

Thoughts on N-way joins in DBSP and WCOJ in DBSP after some discussion on the Feldera Discord server I used the following recursive formula for multi-joins in Efficient multi-joins in DBSP \[\begin{align*} \Delta_{1..i} &= \Delta_{1..i-1} \bowtie \Delta R…

Edit(2026-04-30): After having thought some more about this post there a multiple issues.

Edit(2026-04-30): There are some issues with the complexity claims below.

Edit(07-06-2026): I have realized that the OrPrefixExtender below is not quite right, as variable instantiations from other or branches can “leak” into extensions in lower variable levels.

Explanation of a worst-case-optimal variable oriented join algorithm - GenericJoin 1 We discussed what Worst-case optimal join (WCOJ) is in a previous post.

An introduction and motivation for Worst Case Optimal Joins Consider the TPC-H query 5 (Local Supplier Volume) and just focus on the join part of the query.

Continuation Passing Style (CPS henceforth) is usually something from esoteric functional programming languages.

Alex Miller recently wrote a good blog post in which he details how to decompose transactional systems according to the following steps: Every transactional system does four things: It executes transactions.

TLDR: Some practical information of how to implement window functions based on the paper: Efficient Processing of Window Functions in Analytical SQL Queries, Leis et al.