Add campsite_type_pet_cost relation to hold price of dogs in campsites
It is a separate relation, instead of having a field in campsite_type,
because not all campsite types allow dogs. I could have added a new
field to campsite_type, but then its values it would be meaningless for
campsites that do not allow dogs, and a nullable field is not a valid
solution because NULL means “unknown”, but we **do** know the price —
none.
A separate relation encodes the same information without ambiguities nor
null values, and, in fact, removed the dogs_allowed field from
campsite_type to prevent erroneous status, such as a campsite type that
allows dogs without having a cost — even if the cost is zero, it has to
be added to the new relation.
2024-02-10 05:18:30 +00:00
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-- Deploy camper:campsite_type_pet_cost to pg
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-- requires: roles
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-- requires: schema_camper
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-- requires: campsite_type
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-- requires: user_profile
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2024-02-13 21:12:30 +00:00
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-- requires: nonnegative_integer
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Add campsite_type_pet_cost relation to hold price of dogs in campsites
It is a separate relation, instead of having a field in campsite_type,
because not all campsite types allow dogs. I could have added a new
field to campsite_type, but then its values it would be meaningless for
campsites that do not allow dogs, and a nullable field is not a valid
solution because NULL means “unknown”, but we **do** know the price —
none.
A separate relation encodes the same information without ambiguities nor
null values, and, in fact, removed the dogs_allowed field from
campsite_type to prevent erroneous status, such as a campsite type that
allows dogs without having a cost — even if the cost is zero, it has to
be added to the new relation.
2024-02-10 05:18:30 +00:00
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begin;
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set search_path to camper, public;
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create table campsite_type_pet_cost (
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campsite_type_id integer primary key references campsite_type,
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2024-02-13 21:12:30 +00:00
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cost_per_night nonnegative_integer not null
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Add campsite_type_pet_cost relation to hold price of dogs in campsites
It is a separate relation, instead of having a field in campsite_type,
because not all campsite types allow dogs. I could have added a new
field to campsite_type, but then its values it would be meaningless for
campsites that do not allow dogs, and a nullable field is not a valid
solution because NULL means “unknown”, but we **do** know the price —
none.
A separate relation encodes the same information without ambiguities nor
null values, and, in fact, removed the dogs_allowed field from
campsite_type to prevent erroneous status, such as a campsite type that
allows dogs without having a cost — even if the cost is zero, it has to
be added to the new relation.
2024-02-10 05:18:30 +00:00
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);
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grant select on table campsite_type_pet_cost to guest;
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grant select on table campsite_type_pet_cost to employee;
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grant select, insert, update, delete on table campsite_type_pet_cost to admin;
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alter table campsite_type_pet_cost enable row level security;
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create policy guest_ok
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on campsite_type_pet_cost
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for select
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using (true)
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;
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create policy insert_to_company
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on campsite_type_pet_cost
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for insert
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with check (
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exists (select 1 from campsite_type join user_profile using (company_id) where campsite_type.campsite_type_id = campsite_type_pet_cost.campsite_type_id)
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)
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;
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create policy update_company
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on campsite_type_pet_cost
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for update
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using (
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exists (select 1 from campsite_type join user_profile using (company_id) where campsite_type.campsite_type_id = campsite_type_pet_cost.campsite_type_id)
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)
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;
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create policy delete_from_company
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on campsite_type_pet_cost
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for delete
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using (
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exists (select 1 from campsite_type join user_profile using (company_id) where campsite_type.campsite_type_id = campsite_type_pet_cost.campsite_type_id)
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)
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;
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commit;
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