Bulk insert with only one record fails when no primary keys specified in select=

[gavrilyak]

postgrest fails with cryptic message when only one record is posted in bulk insert (or simple insert) and select parameter does not ask for primary key.
When more then one record posted then everything works fine.
As I understood the problem is with headers field, database returns null in this case and with

              let (isSingle, nRows) = case pjType of
                                        PJArray len -> (len == 1, len)

In this case postgres unexpectedly wants to return location header and fails.

Simple test scenario snippet follows

$ psql -c 'CREATE TABLE test_bulk(id serial primary key, code text)'

$ curl -X POST -d '{"code":42}'  -H 'Prefer:return=representation' -H "Content-type: application/json" -H http://localhost:3000/test_bulk?select=code
{"details":"Row number 0","message":"Row error: unexpected null"}

$ curl -X POST -d '[{"code":42}]'  -H 'Prefer:return=representation' -H "Content-type: application/json" -H http://localhost:3000/test_bulk?select=code
{"details":"Row number 0","message":"Row error: unexpected null"}

$ curl -X POST -d '[{"code":42}]'  -H 'Prefer:return=representation' -H "Content-type: application/json" -H  http://localhost:3000/test_bulk?select=id,code
[{"id":18,"code":"42"}]

$ curl -X POST -d '[{"code":42},{"code":43}]'  -H 'Prefer:return=representation' -H "Content-type: application/json"  http://localhost:3000/test_bulk?select=code
[{"code":"42"},{"code":"43"}]

Version: current stable 4.4.0 from docker hub

[steve-chavez]

The test case doesn't fail on master:

curl -v -d '{"code":42}' \
-H 'Prefer:return=representation' \
-H "Content-type: application/json" \
http://localhost:3000/test_bulk?select=code
# Server: postgrest/0.4.4.0 (32c7e32)
# Content-Type: application/json; charset=utf-8
# Content-Range: */*
# Gives: [{"code":"42"}]
# No Location header present

This is because of this coalesce that was introduced in #1048.

A problem that comes with that change is that the Location header will be missing for successful POSTs and it shouldn't, I think the best solution for this issue would be making the Location header independent of the select.

[steve-chavez]

There's no error on the latest version, but the Location header is missing, I've opened a new issue #1162 for this, now is more of a minor bug.