-- Which node a machine gets a provision from, when more than one could answer.
--
-- One database in a mesh needs no such record: there is one answer and the mesh takes it. Several
-- is entirely ordinary, and then picking one is a choice with consequences -- somebody's data
-- lands on the machine that was chosen -- so the mesh refuses to guess and this is where the
-- answer is kept once a person gives it.
--
-- Per node rather than per mesh, because that is the granularity the choice actually has: two
-- machines may reasonably use two different databases, and a mesh-wide answer could not say so.

create table provision_pin (
    node     uuid        not null references node(id) on delete cascade,
    -- The provision as required -- `database`, not `postgres`. What is being chosen is which node
    -- answers a requirement, and the module answering it may change without the choice changing.
    name     text        not null,
    -- The node it comes from. Not a module: the same module on two machines is two answers, and
    -- which machine is the whole question.
    provider uuid        not null references node(id) on delete cascade,
    pinned_at timestamptz not null default now(),

    primary key (node, name)
);

-- A pin naming a node that leaves the mesh goes with it. The alternative is a machine pointed at
-- something that no longer exists, reported as configured.
create index provision_pin_provider on provision_pin (provider);