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docs(clickhouse): entry into the accursed (ibis-project#10174)
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Random number generation is cursed in ClickHouse.
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cpcloud authored Sep 19, 2024
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Expand Up @@ -14,3 +14,13 @@ execution engines.
* Impala's `LTRIM` and `RTRIM` functions accept a _set_ of whitespace (or other)
characters to remove from the left-, and right-hand-side sides of the input
string, but the `TRIM` function only removes _spaces_.

## ClickHouse

* [ClickHouse's random number generating
functions](https://clickhouse.com/docs/en/sql-reference/functions/random-functions)
are considered in [common subexpression
elimination](https://en.wikipedia.org/wiki/Common_subexpression_elimination),
so to get two unique random numbers, users must defeat that optimization.
This is done by passing **any** argument to those functions. It's left as an
exercise for the reader to figure out how to generate two unique inputs.

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