Added working notes on DB identifiers

assets/.lua/dbidents.lua.txt

@@ -0,0 +1,159 @@
+local re = require "re"
+
+--[[
+	Instead of describing node and field types as tuples, as in Drupal, I'll describe them in the DB schema itself.
+	If I have a node of type "blogpost" with fields "title" and "body", I'll store it like this:
+	CREATE TABLE "node:blogpost" (id INTEGER PRIMARY KEY, "title" TEXT NOT NULL, "body" TEXT NOT NULL);
+
+	Complex fields will use a similar system. Here is a field type called "mood", and a node type that uses it called "moody blogpost".
+	CREATE TABLE "field:mood" (id INTEGER PRIMARY KEY, "description" TEXT NOT NULL, "intensity" INT NOT NULL);
+	CREATE TABLE "node:moody blogpost" (
+		id INTEGER PRIMARY KEY,
+		"today's mood:mood" INTEGER NOT NULL REFERENCES "field:mood"(id)
+	);
+
+	Complex fields can be arbitrarily nested.
+
+	TODO Primitive date/time types
+	TODO Lists
+	TODO Variants
+]]
+
+-- type path = [string]
+
+local function path_to_tablename(path)
+	-- We join path segments with ':', so escape ':' to [[\:]]' and [[\]] to [[\\]].
+	local pattern = [=[[:\]]=]
+	local escaped_path = {}
+	for _, segment in ipairs(path) do
+		local escaped_segment = segment:gsub(pattern, [[\%0]])
+		table.insert(escaped_path, escaped_segment)
+	end
+	return table.concat(escaped, ':')
+end
+
+local function tablename_to_path(path)
+	-- Reverse of path_to_tablename.
+	-- Then write a test of the property that ∀s:string, s == path_to_tablename(tablename_to_path(s)).
+end
+
+
+
+
+
+--[[
+
+
+Node
+Field
+
+
+The website schema needs to be discoverable. The sqlite_schema table (or the table_list pragma) and the table_info pragma are essential.
+The following facts need to be discoverable:
+- The name of each node type.
+- The fields in each node type.
+- The type of each field in a node.
+- The subfields in each field type.
+- The type of each subfield in a field.
+- Whether a field or subfield is repeated, optional, or single.
+- Whether a field has an application-primitive, but non-sqlite-primitive, type, such as datetime.
+- Discriminated union fields.
+
+Field types need to be acyclic.
+	Do they really?
+
+Field values need to be deleted when the node that contains them is deleted.
+
+If field types are namespaced to a node type, then SQLite schema object naming will get harder.
+	Maybe just let them be shared.
+
+(node blogpost)
+(composite-field car)
+(node "car review")
+(field cars)
+(field car)
+node:blogpost
+field:
+
+
+(: road-review node)
+(: car composite-field)
+-- 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.
+-- I think qualification is best, because then SQLite will prevent duplicates by the requirement that table names be unique.
+(list (: car composite-field))
+
+
+create table "car:composite-field" (
+	id integer primary key,
+	"Make" text not null,
+	"Model" text not null,
+	"Year" text not null,
+	"Test distance" int not null,
+	"Test date:date" text not null,
+);
+
+create table "road review.cars:(list-field (road review:node))" (
+	"Road review:node" int primary key references "road review:node",
+	"Car:composite-field" int primary key references "car:composite-field",
+);
+
+create table "Road review:node" (
+	id integer primary key,
+	"Title" text not null,
+	"Cars:(list car)"
+);
+
+(field car)
+(node review)
+(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.
+-- 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.
+primitive-field-type := int | text | date | 
+record-field-type := (record <field-type-name> ((<field-name> <field-type>) ...))
+variant-field-type := (variant <field-type-name> ((<field-name> <field-type>) ...))
+field-type := (field <field-type-name>)
+node-type := (node <node-type-name>)
+parent-object-type := <field-type> | <node-type> 
+list := (list <element-type> <parent-object-type> <field-name>)
+
+
+
+
+(record car)
+	(id integer)
+	(make text)
+	(model text)
+	(year text)
+	(test-distance integer)
+	(test-date date)
+
+(list car)
+	(node road-review)
+	(car car)
+
+(node road-review)
+	(id integer)
+	(title text)
+	(cars (list car))
+
+
+(node <node-type-name>)
+	id integer primary key
+	(<composite-type-name> <field-name>) <db-type> ...
+(list <composite-type-name>)
+	id
+(list-item <composite-type-name>)
+	list-id references (list <composite-type-name>) primary key
+	sequence-number primary key
+	item-id references (composite-value <composite-type-name>)
+(composite-value <composite-type-name>)
+	id
+	-- This indirection is so that SQLite will prevent duplicate field type names in table names.
+	<record|variant>-value-id references (<record|variant>-value <composite-type-name>)
+(record-value <composite-type-name>)
+	id integer primary key
+	(<composite-type-name> <field-name>) <db-type> ...
+(variant-value <composite-type-name>)
+	id integer primary key
+	(<composite-type-name> <field-name>) <db-type> ...
+
+]]