112 lines
3.5 KiB
Markdown
112 lines
3.5 KiB
Markdown
The website schema needs to be discoverable. The `sqlite_schema` table (or the `table_list` pragma) and the `table_info` pragma are essential.
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The following facts need to be discoverable:
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- The name of each node type.
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- The fields in each node type.
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- The type of each field in a node.
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- The subfields in each field type.
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- The type of each subfield in a field.
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- Whether a field or subfield is repeated, optional, or single.
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- Whether a field has an application-primitive, but non-sqlite-primitive, type, such as datetime.
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- Discriminated union fields.
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Field types need to be acyclic. *Do they really?*
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Field values need to be deleted when the node that contains them is deleted.
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If field types are namespaced to a node type, then SQLite schema object naming will get harder.
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Maybe just let them be shared.
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```
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(node blogpost)
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(composite-field car)
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(node "car review")
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(field cars)
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(field car)
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node:blogpost
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field:
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(: road-review node)
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(: car composite-field)
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-- Entity names must be qualified by their type/kind, or there can't be e.g. a node type and field type that share a name.
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-- I think qualification is best, because then SQLite will prevent duplicates by the requirement that table names be unique.
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(list (: car composite-field))
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create table "car:composite-field" (
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id integer primary key,
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"Make" text not null,
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"Model" text not null,
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"Year" text not null,
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"Test distance" int not null,
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"Test date:date" text not null,
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);
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create table "road review.cars:(list-field (road review:node))" (
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"Road review:node" int primary key references "road review:node",
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"Car:composite-field" int primary key references "car:composite-field",
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);
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create table "Road review:node" (
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id integer primary key,
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"Title" text not null,
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"Cars:(list car)"
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);
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(field car)
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(node review)
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(list (field car) (node review)) -- If we parameterize each list relation by both the listed field and the containing node or field, then we've basically monomorphized it.
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-- However, that won't cut it if a node or field contains multiple lists of the same type. We also need to parameterize list relations by the field name in the containing node or field.
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```
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```
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primitive-field-type := int | text | date |
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record-field-type := (record <field-type-name> ((<field-name> <field-type>) ...))
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variant-field-type := (variant <field-type-name> ((<field-name> <field-type>) ...))
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field-type := (field <field-type-name>)
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node-type := (node <node-type-name>)
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parent-object-type := <field-type> | <node-type>
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list := (list <element-type> <parent-object-type> <field-name>)
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```
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```
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(record car)
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(id integer)
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(make text)
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(model text)
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(year text)
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(test-distance integer)
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(test-date date)
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(list car)
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(node road-review)
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(car car)
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(node road-review)
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(id integer)
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(title text)
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(cars (list car))
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```
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```
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(node <node-type-name>)
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id integer primary key
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(<composite-type-name> <field-name>) <db-type> ...
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(list <composite-type-name>)
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id
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(list-item <composite-type-name>)
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list-id references (list <composite-type-name>) primary key
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sequence-number primary key
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item-id references (composite-value <composite-type-name>)
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(composite-value <composite-type-name>)
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id
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-- This indirection is so that SQLite will prevent duplicate field type names in table names.
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<record|variant>-value-id references (<record|variant>-value <composite-type-name>)
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(record-value <composite-type-name>)
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id integer primary key
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(<composite-type-name> <field-name>) <db-type> ...
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(variant-value <composite-type-name>)
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id integer primary key
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(<composite-type-name> <field-name>) <db-type> ...
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``` |