If you want an index on a column (and you probably do if you're going to query over 500 million rows) you have to create it at some point. Creating it after wi

If you want an index on a column (and you probably do if you're going to query over 500 million rows) you have to create it at some point. Creating it after will be more efficient in your case. So what do you mean "too slow?" How long did it take? I don't have any experience with Clickhouse, and not much with columnar databases in general, but if we're talking about a simple table with one index over one text column, I'm not sure whether it makes any difference if you store the tuples row-wise or column-wise on disk. It's an index that covers 100% of the data either way. I don't know anything about your server but it sounds like PostgreSQL just wasn't able to get much IO throughput from your storage system. Things like storage hardware, filesystem type, and kernel parameters are the big factors here.