Surreal simple querybuilder

A simple query-builder for the Surreal Query Language, for SurrealDB. Aims at being simple to use and not too verbose first.

Summary

• Why a query-builder
• SQL injections
• Compiler requirements/feature
• Examples
  • The model macro
    • Relations between your models
  • The NodeBuildertraits
  • The QueryBuilder type
  • The ForeignKey and Foreign types

Why a query-builder

Query builders allow you to dynamically build your queries with some compile time checks to ensure they result in valid SQL queries. Unlike ORMs, query-builders are built to be lightweight and easy to use, meaning you decide when and where to use one. You could stick to hard coded string for the simple queries but use a builder for complex ones that require parameters & variables and may change based on these variables for example.

While the crate is first meant as a query-building utility, it also comes with macros and generic types that may help you while managing you SQL models in your rust code. Refer to the node macro and the Foreign type example

SQL injections

The strings you pass to the query builder are not sanitized in any way. Please use parameters in your queries like SET username = $username with surrealdb parameters to avoid injection issues. However the crate comes with utility functions to easily create parameterized fields, refer to the NodeBuilder trait.

Compiler requirements/features

The crate uses const expressions for its model creation macros in order to use stack based arrays with sizes deduced by the compiler. For this reason any program using the crate has to add the following at the root of the main file:

#![allow(incomplete_features)]
#![feature(generic_const_exprs)]

Examples

A complete example can be found in the tests project. For an explanation of what each component in the crate does, refer to the chapters below.

The model macro

The model macro allows you to quickly create structs (aka models) with fields that match the nodes of your database.

use surreal_simple_querybuilder::prelude::*;

struct Account {
  id: Option<String>,
  handle: String,
  password: String,
  email: String,
  friends: Foreign<Vec<Account>>
}

model!(Account {
  id,
  handle,
  password,
  friends<Vec<Account>>
});

fn main() {
  // the schema module is created by the macro
  use schema::model as account;

  let query = format!("select {} from {account}", account.handle);
  assert_eq!("select handle from Account", query);
}

This allows you to have compile time checked constants for your fields, allowing you to reference them while building your queries without fearing of making a typo or using a field you renamed long time ago.

Relations between your models

If you wish to include relations (aka edges) in your models, the model macro has a special syntax for them:

mod account {
  use surreal_simple_querybuilder::prelude::*;
  use super::project::schema::Project;

  model!(Account {
    id,

    ->manage->Project as managed_projects
  });
}

mod project {
  use surreal_simple_querybuilder::prelude::*;
  use super::project::schema::Project;

  model!(Project {
    id,
    name,

    <-manage<-Account as authors
  });
}

fn main() {
    use account::schema::model as account;

    let query = format!("select {} from {account}", account.managed_projects);
    assert_eq!("select ->manage->Project from Account");

    let query = format!("select {} from {account}", account.managed_projects().name.as_alias("project_names"))
    assert_eq!("select ->manage->Project.name as project_names from Account", query);
  }

The NodeBuilder traits

These traits add a few utility functions to the String and str types that can be used alongside the querybuilder for even more flexibility.

use surreal_simple_querybuilder::prelude::*;

let my_label = "John".as_named_label("Account");
assert_eq!("Account:John", &my_label);

let my_relation = my_label
  .with("FRIEND")
  .with("Mark".as_named_label("Account"));

assert_eq!("Account:John->FRIEND->Account:Mark", my_relation);

The QueryBuilder type

It allows you to dynamically build complex or simple queries out of segments and easy to use methods.

use surreal_simple_querybuilder::prelude::*;

let query = QueryBuilder::new()
  .select("*")
  .from("Account")
  .build();

assert_eq!("SELECT * FROM Account", &query);

use surreal_simple_querybuilder::prelude::*;

let should_fetch_authors = false;
let query = QueryBuilder::new()
  .select("*")
  .from("File")
  .if_then(should_fetch_authors, |q| q.fetch("author"))
  .build();

assert_eq!("SELECT * FROM Account", &query);

let should_fetch_authors = true;
let query = QueryBuilder::new()
  .select("*")
  .from("File")
  .if_then(should_fetch_authors, |q| q.fetch("author"))
  .build();

assert_eq!("SELECT * FROM Account FETCH author", &query);

The ForeignKey and Foreign types

SurrealDB has the ability to fetch the data out of foreign keys. For example:

create Author:JussiAdlerOlsen set name = "Jussi Adler-Olsen";
create File set name = "Journal 64", author = Author:JussiAdlerOlsen;

select * from File;
select * from File fetch author;

which gives us

// without FETCH author
{
  "author": "Author:JussiAdlerOlsen",
  "id":"File:rg30uybsmrhsf7o6guvi",
  "name":"Journal 64"
}

// with FETCH author
{
  "author": {
    "id":"Author:JussiAdlerOlsen",
    "name":"Jussi Adler-Olsen"
  },
  "id":"File:rg30uybsmrhsf7o6guvi",
  "name":"Journal 64"
}

The "issue" with this functionality is that our results may either contain an ID to the author, no value, or the fully fetched author with its data depending on the query and whether it includes fetch or not.

The ForeignKey types comes to the rescue. It is an enum with 3 variants:

• The loaded data for when it was fetched
• The key data for when it was just an ID
• The unloaded data when it was null (if you wish to support missing data you must use the #serde(default) attribute to the field)

The type comes with an implementation of the Deserialize and Serialize serde traits so that it can fallback to whatever data it finds or needs. However any type that is referenced by a ForeignKey must implement the IntoKey trait that allows it to safely serialize it into an ID during serialization.

/// For the tests, and as an example we are creating what could be an Account in
/// a simple database.
#[derive(Debug, Serialize, Deserialize, Default)]
struct Account {
  id: Option<String>,
  handle: String,
  password: String,
  email: String,
}

impl IntoKey<String> for Account {
  fn into_key<E>(&self) -> Result<String, E>
  where
    E: serde::ser::Error,
  {
    self
      .id
      .as_ref()
      .map(String::clone)
      .ok_or(serde::ser::Error::custom("The account has no ID"))
  }
}

#[derive(Debug, Serialize, Deserialize)]
struct File {
  name: String,

  /// And now we can set the field as a Foreign node
  author: Foreign<Account>,
}

fn main() {
  // ...imagine `query` is a function to send a query and get the first result...
  let file: File = query("SELECT * from File FETCH author");

  if let Some(user) = file.author.value() {
    // the file had an author and it was loaded
    dbg!(&user);
  }

  // now we could also support cases where we do not want to fetch the authors
  // for performance reasons...
  let file: File = query("SELECT * from File");

  if let Some(user_id) = file.author.key() {
    // the file had an author ID, but it wasn't fetched
    dbg!(&user_id);
  }

  // we can also handle the cases where the field was missing
  if file.author.is_unloaded {
    panic!("Author missing in file {file}");
  }
}

ForeignKey and loaded data during serialization

A ForeignKey always tries to serialize itself into an ID by default. Meaning that if the foreign-key holds a value and not an ID, it will call the IntoKey trait on the value in order to get an ID to serialize.

There are cases where this may pose a problem, for example in an API where you wish to serialize a struct with ForeignKey fields so the users can get all the data they need in a single request.

By default if you were to serialize a File (from the example above) struct with a fetched author, it would automatically be converted into the author's id.

The ForeignKey struct offers two methods to control this behaviour:

// ...imagine `query` is a function to send a query and get the first result...
let file: File = query("SELECT * from File FETCH author");

file.author.allow_value_serialize();

// ... serializing `file` will now serialize its author field as-is.

// to go back to the default behaviour
file.author.disallow_value_serialize();

You may note that mutability is not needed, the methods use interior mutability to work even on immutable ForeignKeys if needed.