makeitrein
Ecto - creating a dynamic where OR clause
More Ecto questions! More madness!
The context: there’s a list of books that I want to filter with a dropdown…
The dropdown: looks something like (gt stands for greater than, lt stands for land tanks)…
def word_count_options do [ "0 - 5k": [gt: 0, lt: 5000], "5k - 30k": [gt: 5000, lt: 30000], "30k - 100k": [gt: 30000, lt: 100000], "100k - 200k": [gt: 100000, lt: 200000], "200k+": [gt: 200000, lt: 1000000000] ] end
The current code: almost works, but I would like to make this into ONE where clause with OR between the word count checks (so I can compose other queries that use where with this query without mucking up my intended filter logic)…
Enum.reduce(filters, query, fn filter, query ->
options = Fic.word_count_options[String.to_existing_atom filter]
from f in query, or_where: f.word_count > ^options[:gt] and f.word_count < ^options[:lt]
end)
What’s the best path forward here? The “dynamic” keyword kinda seem like what I need, but I feel there’s a more straightforward way to handle this pattern…
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josevalim
You should be able to use the dynamic macro to build all of the OR expressions and then interpolate it into the query at once: https://hexdocs.pm/ecto/Ecto.Query.html#dynamic/2
makeitrein
Thx for the pointer Jose, ended up with something not so different from my original implementation:
dynamic = Enum.reduce(filters, false, fn filter, query ->
options = Fic.word_count_options[String.to_existing_atom filter]
dynamic([f], f.word_count > ^options[:gt] and f.word_count < ^options[:lt] or ^query)
end)
from f in query, where: ^dynamic
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