Can ClickHouse DELETE Data? A 2026 PR-by-PR Analysis

TL;DR ClickHouse has supported DELETE operations since 2018. As of 2026, it ships four production-grade deletion paths: heavyweight ALTER TABLE DELETE, lightweight DELETE FROM (default since v23.3), patch-part DELETEs (v25.7), and ALTER TABLE DROP PARTITION for bulk operations. The "ClickHouse is immutable / append-only" narrative is outdated by eight years and 80+ merged PRs spanning five architectural eras, and the evidence is in the commit history. We analyzed 80+ GitHub pull requests, official ClickHouse changelogs, and release blogs to trace the full evolution of DELETE support from 2018 through early 2026. In 2018, ClickHouse shipped ALTER TABLE … DELETE as a heavyweight asynchronous mutation that rewrote affected data parts. The criticism that "deletes require heavy mutations" was fair — for that era. It was also the only delete path for four years. By early 2026, ClickHouse ships standard SQL DELETE FROM (lightweight by default since v23.3), ALTER TABLE DELET