postgres: current_schema: converting NULL to string is unsupported (empty search_path is NULL)

[disq]

Describe the Bug
If the search_path is empty, CURRENT_SCHEMA() returns NULL but the reader tries to read a string so it fails with:

*database.Error: sql: Scan error on column index 0, name "current_schema": converting NULL to string is unsupported in line 0: SELECT CURRENT_SCHEMA()

Steps to Reproduce
Steps to reproduce the behavior:

1. Give it a DSN with empty search path
2. Run migrate
3. It will fail badly

Expected Behavior
Fail better returning ErrNoSchema, in

migrate/database/postgres/postgres.go

Line 99 in 14f6d3a

return nil, ErrNoSchema

Migrate Version
v4.15.0

Loaded Database Drivers
postgres

Go Version
go version go1.17.2 darwin/arm64

Additional context
Should just scan into *string allowing nulls to work.

cq=# set search_path='';
SET
cq=# SELECT CURRENT_SCHEMA();
 current_schema
----------------

(1 row)

cq=# SELECT CURRENT_SCHEMA() is null;
 ?column?
----------
 t
(1 row)

[disq]

Same as #692 which was closed

[itissourav]

Hi @disq I am stucked in this issue..What may be the causes for this issue? Cant find any solution..

[soyayaos]

fixed in #914

[dhui]

Thanks @soyayaos for the fix! Closing this issue for now. Please reopen this if it's still not fixed