Initial database schema

Diesel is used for schema migrations (written in raw SQL; targetting
PostgreSQL at the moment) and conversions between SQL and Rust
datatypes. Structs are defined, but not used yet.

Cargo.toml

@@ -16,5 +16,7 @@ categories = [
 publish = false
 
 [dependencies]
+chrono = "0.4.13"
+diesel = { version = "1.4.5", features = ["postgres"] }
 rocket = "0.4.5"
 rocket_contrib = {version = "0.4.5", features = ["json"]}

diesel.toml

@@ -0,0 +1,8 @@
+# For documentation on how to configure this file,
+# see diesel.rs/guides/configuring-diesel-cli
+
+[print_schema]
+file = "src/storage/sql/schema.rs"
+
+[migrations_directory]
+dir = "src/storage/sql/migrations"

src/main.rs

@@ -5,13 +5,16 @@
 
 #![feature(proc_macro_hygiene, decl_macro)]
 
+#[macro_use]
+extern crate diesel;
 #[macro_use]
 extern crate rocket;
 #[macro_use]
 extern crate rocket_contrib;
 
 mod application;
 mod routes;
+mod storage;
 
 fn main() {
     let app = application::create_app();

src/storage/mod.rs

@@ -0,0 +1,3 @@
+// Do not fail compilation until we've started using that code
+#[allow(dead_code)]
+pub mod sql;

src/storage/sql/migrations/00000000000000_diesel_initial_setup/down.sql

@@ -0,0 +1,6 @@
+-- This file was automatically created by Diesel to setup helper functions
+-- and other internal bookkeeping. This file is safe to edit, any future
+-- changes will be added to existing projects as new migrations.
+
+DROP FUNCTION IF EXISTS diesel_manage_updated_at(_tbl regclass);
+DROP FUNCTION IF EXISTS diesel_set_updated_at();

src/storage/sql/migrations/00000000000000_diesel_initial_setup/up.sql

@@ -0,0 +1,36 @@
+-- This file was automatically created by Diesel to setup helper functions
+-- and other internal bookkeeping. This file is safe to edit, any future
+-- changes will be added to existing projects as new migrations.
+
+
+
+
+-- Sets up a trigger for the given table to automatically set a column called
+-- `updated_at` whenever the row is modified (unless `updated_at` was included
+-- in the modified columns)
+--
+-- # Example
+--
+-- ```sql
+-- CREATE TABLE users (id SERIAL PRIMARY KEY, updated_at TIMESTAMP NOT NULL DEFAULT NOW());
+--
+-- SELECT diesel_manage_updated_at('users');
+-- ```
+CREATE OR REPLACE FUNCTION diesel_manage_updated_at(_tbl regclass) RETURNS VOID AS $$
+BEGIN
+    EXECUTE format('CREATE TRIGGER set_updated_at BEFORE UPDATE ON %s
+                    FOR EACH ROW EXECUTE PROCEDURE diesel_set_updated_at()', _tbl);
+END;
+$$ LANGUAGE plpgsql;
+
+CREATE OR REPLACE FUNCTION diesel_set_updated_at() RETURNS trigger AS $$
+BEGIN
+    IF (
+        NEW IS DISTINCT FROM OLD AND
+        NEW.updated_at IS NOT DISTINCT FROM OLD.updated_at
+    ) THEN
+        NEW.updated_at := current_timestamp;
+    END IF;
+    RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;

src/storage/sql/migrations/2020-07-25-065258_create_snippets/down.sql

@@ -0,0 +1,3 @@
+DROP TABLE tags;
+DROP TABLE changesets;
+DROP TABLE snippets;

src/storage/sql/migrations/2020-07-25-065258_create_snippets/up.sql

@@ -0,0 +1,58 @@
+CREATE TABLE snippets (
+    -- an internal autoincrementing identifier used in foreign keys.
+    -- Normally not visible publicly, except for the case when it is
+    -- used for looking legacy snippets up by id
+    id SERIAL PRIMARY KEY,
+    -- a short unique snippet identifier visible to users
+    slug TEXT NOT NULL,
+
+    title TEXT,
+    syntax TEXT,
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW() NOT NULL,
+    updated_at TIMESTAMP WITH TIME ZONE,
+
+    -- slugs must be unique (this will also automatically create a unique index)
+    CONSTRAINT uq_slug UNIQUE (slug)
+);
+
+
+-- will be used for pagination; slug guarantees uniqueness of the sorting key
+CREATE INDEX snippets_created_at_slug ON snippets (created_at, slug);
+
+
+CREATE TABLE changesets (
+    id SERIAL PRIMARY KEY,
+    snippet_id INTEGER NOT NULL,
+
+    -- numeric index used to determine the ordering of changesets for a given snippet
+    version INTEGER DEFAULT 0 NOT NULL,
+    content TEXT NOT NULL,
+    created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW() NOT NULL,
+    updated_at TIMESTAMP WITH TIME ZONE,
+
+    -- there can be multiple changesets per snippet
+    CONSTRAINT fk_snippet FOREIGN KEY (snippet_id) REFERENCES snippets(id),
+    -- but each one is supposed to have a unique version number
+    CONSTRAINT uq_version UNIQUE (snippet_id, version),
+    -- sanity check: do not allow empty changesets
+    CONSTRAINT check_not_empty CHECK (LENGTH(content) > 0),
+    -- sanity check: version numbers are non-negative integers
+    CONSTRAINT check_non_negative_version CHECK (version >= 0)
+);
+
+
+-- tags could have been associated with snippets as M:M via an auxiliary table,
+-- but Diesel only supports child-parent associations, so let's do that instead
+CREATE TABLE tags (
+    id SERIAL PRIMARY KEY,
+    snippet_id INTEGER NOT NULL,
+
+    value TEXT NOT NULL,
+
+    -- there can be multiple tags per snippet
+    CONSTRAINT fk_snippet FOREIGN KEY (snippet_id) REFERENCES snippets(id),
+    -- do not allow to abuse the tags for storing too much data
+    CONSTRAINT check_length CHECK (LENGTH(value) < 128),
+    -- do not allow repeated tags per snippet
+    CONSTRAINT uq_snippet_tag UNIQUE (snippet_id, value)
+);

src/storage/sql/mod.rs

@@ -0,0 +1,4 @@
+mod models;
+mod schema;
+
+pub use models::{Changeset, Snippet, Tag};