> On Sep 12, 2017, at 11:09 AM, Warren Young <war...@etr-usa.com> wrote:
> From my reading of the docs, I don’t see that that is the purpose of 
>    https://www.sqlite.org/deterministic.html 
> <https://www.sqlite.org/deterministic.html>

Actually it is. "A deterministic function always gives the same answer when it 
has the same inputs." That is the definition of a mathematical (also called 
"pure") function. Such a function call can of course be factored out as a 
common subexpression.

> The purpose is simply so that the SQLite internals know whether it is safe to 
> use the user-defined function in certain query types.

The reason SQLITE_DETERMINISTIC was added is to allow such functions to be used 
in indexes and then matched with the same function in a query. That allows 
indexing things like JSON properties (via the deterministic json_value 

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