Show HN: Kaskada – modern, open-source event processing We recently open-sourced Kaskada – an event-processing engine built on Rust and Apache Arrow. It features a high-level, declarative query language designed specifically for reasoning about events in bulk and in real time. Unlike SQL, an aggregation over events produces a timeline indicating the value at each point in time over the events that have occurred up to that point in time. The query language provides composable, expression oriented syntax, including the ability to nest aggregations. Due to the focus on events and temporal queries, it provides capabilities to shift events forward (not backward, to avoid "leaking" information about the future into past values), ticks that create new times (allowing you to observe the current value of an aggregation every day, for instance) and joins that operate "at the current time". Example query: # Purchases up to a point in time let purchases_now = count(purchase) # Shift that *forward* one day (so the value now is from 1 day ago) let purchases_yesterday = purchases_now | shift_by(days(1)) # Compute the difference (purchases since yesterday) in purchases_now - purchases_yesterday More on the history of Kaskada is available in this blog post https://ift.tt/7yrGScd . More information on the project (and documentation) is available at https://kaskada.io . https://ift.tt/dFOA8hW March 31, 2023 at 12:27AM
Show HN: StreetComplete, an OpenStreetMap Editor for Humans StreetComplete is an OpenStreetMap[0] editor directed at people who want to contribute and want to do this using their smartphone, without learning how to edit things[1]. It is available as an Android application. It is intended to be used as one walks, with quests appearing as markers on the map. Selecting a marker allows one to answer a simple question. The answer will be added to the OpenStreetMap database, with app handling selecting objects for editing, transforming answer into OSM tags and making edits. OpenStreetMap account is needed to apply edits, but it is possible to start without it, make some edits and login/register later. Note: I am not the main author, but I am one of the active contributors. Github page is at https://ift.tt/2g8lasH and https://ift.tt/3nR9PzS shows what was recently released. [0]OpenStreetMap is a Wikipedia of maps, available on the open licence. This dataset is already used for many interestin...
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