Fabrice Lecomte
a7e66ab8b5
Remove paginated Remove Entity classes Add Annotation for serialize object rename selectOne/selectMultiple to execute
94 lines
2.5 KiB
Markdown
94 lines
2.5 KiB
Markdown
Multi Level Queries
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===================
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## Define schema, query and kotlin object
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1. Schema
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```postgresql
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create table parent (
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id uuid primary key,
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name text not null
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);
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create table child (
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id uuid primary key,
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name text not null,
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parent_id uuid not null references parent
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)
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```
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2. Insert some data for tests
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```postgresql
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insert into parent (id, name) VALUES ('379e0687-9e4a-4781-b0e9-d94a62e4261f', 'Bernard');
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insert into child (id, name, parent_id) VALUES (uuid_generate_v4(), 'Noé', '379e0687-9e4a-4781-b0e9-d94a62e4261f');
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insert into child (id, name, parent_id) VALUES (uuid_generate_v4(), 'John', '379e0687-9e4a-4781-b0e9-d94a62e4261f');
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```
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3. Define Model
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```kotlin
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import java.util.UUID
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class Parent(val id: UUID, val name: String, val children: List<Child>)
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class Child(val id: UUID, val name: String)
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```
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4. Define request function
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```postgresql
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-- resource/sql/functions/find_parent_by_id.sql
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create or replace function find_parent_by_id(in _id uuid, out resource json) language plpgsql as
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$$
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begin
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select to_json(t) into resource
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from (
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select
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p.*,
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json_agg(to_jsonb(c) - 'parent_id') as children
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from parent p
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join child c on c.parent_id = p.id
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where p.id = _id
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group by p.id
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) t;
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end;
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$$;
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```
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## Execute the function
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You just to use `Requester` and set the sql function name, then pass arguments.
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If you need to return more than one entry, use `.select()` instead of `.selecteOne()`
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See the [Paginated example](./paginated.md)
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```kotlin
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import fr.postgresjson.connexion.Requester
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val requester: Requester = TODO()
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val result: Parent = requester
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.getFunction("find_parent_by_id")
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.execute("id" to "379e0687-9e4a-4781-b0e9-d94a62e4261f")
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```
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The requester create dynamically this request
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```postgresql
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select * from find_parent_by_id(_id => '379e0687-9e4a-4781-b0e9-d94a62e4261f');
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```
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*Watch the underscore as prefix is added if necessary.
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The requester known the parameters because it parses all SQL functions and reads the names of the parameters from them.*
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And the SQL return is a JSON like follow:
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```json
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{
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"id": "379e0687-9e4a-4781-b0e9-d94a62e4261f",
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"name": "Bernard",
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"child": [
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{
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"id": "c2d0ec81-7cac-4689-8086-2644a3b309b5",
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"name": "Noé"
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},
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{
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"id": "255d911a-0cbc-4156-bf8c-0204e89494d9",
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"name": "John"
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}
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]
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}
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```
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But the requester deserialize the result automatically into a Kotlin object with their children objects. **And do that in only one request**.
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