We went through hundreds of StackOverflow + Reddit threads on ClickHouse and after seeing the same pain points surface repeatedly, we wrote up the 5 most common ClickHouse mistakes engineers make in production: Expecting ReplacingMergeTree to deduplicate reliably. It does, but eventually and not synchronously Picking the wrong table engine (MergeTree when you need Aggregating/Replacing) Treating PRIMARY KEY like it enforces uniqueness (it doesn't and ORDER BY column order matters far more) Too Many Parts errors from small inserts. Almost always fixable with batching JOINs behave differently than PostgreSQL. Smaller table must go on the right Check the concrete fix for each of them, with SQL examples: https://www.glassflow.dev/blog/clickhouse-mistakes-engineers-make?utm_source=reddit&utm_medium=socialmedia&utm_campaign=reddit_organic Happy to discuss any of these in the comments, especially the dedup one, which seems to trip up almost everyone coming from a relational background. submitted by /u/glassflow-dev [link] [comments]