Ecto select fields with map function as alias or different name

Questions / Help
1 
iex(18)> fields = [:id]                                                                  
[:id]

iex(19)> fields_map = %{id: :job_id}                                                     
%{id: :job_id}

iex(20)> query = from p in Qber.V1.JobModel, where: p.id == 1, select: map(p, ^fields)
#Ecto.Query<from j in Qber.V1.JobModel, where: j.id == 1, select: map(j, [:id])>

I want to select my fields dynamically with AS names on the basis of params I got(which may have some joins as this app is going to have heavy admin dashboard queries). So I need dynamic solution. is there a way I can pass a map instead of list dynamically to map function and ecto will send me the selected result with custom names I passed in map.

Instead of

[%{id: 1}]

I want the result to be

[%{job_id: 1}]

dynamically.

Some more context
My question is related to this question actually
select-fields-dynamically and I have also posted a question here. As I am joining many tables with same keys and I either want these keys to be alias so that these can be unique or map them inside their table name for uniqueness. Thanks

2

You can’t select and rename dynamically. If the issue is conflict because of joins, one option is to nest those using select merge:

query = from p in Qber.V1.JobModel, where: p.id == 1, select_merge: %{job: map(p, ^fields)}

This way you don’t need renaming and you still get the dynamic selection.

3

I can’t even dynamically nest using select merge I think. if I write query like this

table_name = "dynamic"

query = from p in Qber.V1.JobModel, where: p.id == 1, select_merge: %{^table_name => map(p, ^fields)}

Ecto will automatically try to select $1 I dont know why(if Ecto doesn’t add $1 that would also solve the problem). I have many tables actually which require this so something dynamic would really solve this.

4

Any workaround will be really appreciated

5

Where what? o.O

6

if I run the above query

#Ecto.Query<from j in Qber.V1.JobModel, where: j.id == 1,
select: merge(j, %{^"dynamic" => j})>

, I will get

Repo.all query
[debug] QUERY ERROR source="jobs" db=8.2ms
SELECT j0."id", j0."service_id", j0."location_dest_zone_id", j0."cost", j0."initial_cost", j0."cost_at_heading", j0."cost_at_working", j0."cost_at_complete", j0."expected_work_duration", j0."work_duration_at_heading", j0."work_duration_at_working", j0."arrive_at", j0."confirmed_at", j0."started_heading_at", j0."started_working_at", j0."completed_at", j0."customer_rating", j0."provider_rating", j0."status_id", j0."basic_fee", j0."item_fee", j0."location_src", j0."location_dest", j0."location_src_zone_id", j0."service_params", j0."customer_comments", j0."cancel_reason", j0."provider_rating_friendly", j0."provider_rating_professional", j0."provider_rating_communication", j0."provider_comments", j0."location_src_name", j0."rejected_at", j0."cancelled_by", j0."cancelled_at", j0."wait_started_at", j0."updated_by", j0."approved_at", j0."called_at", j0."approved_by", j0."providers_request_id", j0."inserted_by", j0."title", j0."description", j0."deleted_by", j0."deleted_at", j0."inserted_at", j0."updated_at", $1 FROM "jobs" AS j0 WHERE (j0."id" = 1) AND (j0."deleted_at" IS NULL) ["dynamic"]
** (Postgrex.Error) ERROR 42P18 (indeterminate_datatype): could not determine data type of parameter $1
    (ecto) lib/ecto/adapters/sql.ex:431: Ecto.Adapters.SQL.execute_and_cache/7
    (ecto) lib/ecto/repo/queryable.ex:133: Ecto.Repo.Queryable.execute/5
    (ecto) lib/ecto/repo/queryable.ex:37: Ecto.Repo.Queryable.all/4