In most cases GraphJin will discover and learn the relationship graph within your database automatically. It does this using
Foreign Key relationships that you have defined in your database schema.
The below configs are only needed in special cases such as when you don't use foreign keys or when you want to create a relationship between two tables where a foreign key is not defined or cannot be defined.
For example in the sample below a relationship is defined between the
tags column on the
posts table with the
slug column on the
tags table. This cannot be defined as using foreign keys since the
tags column is of type array
text and Postgres for one does not allow foreign keys with array columns.
Normally two tables are connected together by creating a foreign key on one of the tables. But what if you wanted one table to connect to a union of tables? This is an association that frameworks like Ruby-on-Rails made popular https://guides.rubyonrails.org/association_basics.html#polymorphic-associations. Your database cannot help you here as foreign keys are only between two fixed tables.
One use case for this can be in a
notifications table where you want to link each row to the table the notification is about. For example a notification about a comment to a comment table or a notification about a like to the table for the blog post, etc.
To make the type of a relationaship queryable you'll have to add a virtual table to the table config like below. This will automatically add a polymorphic relationship on any table in your database that has the columns
subject_id where the former holds the name of the related table and the latter its
Example notifications table
Example table config entry
Query that uses this relationship
The ablity to have
Array columns is often considered in the top most useful features of Postgres. There are many cases where using an array or a json column saves space and reduces complexity in your app. The only issue with these columns is that your SQL queries can get harder to write and maintain.
GraphJin steps in here to help you by supporting these columns right out of the box. It allows you to work with these columns just like you would with tables. Joining data against or modifying array columns using the
disconnect keywords in mutations is fully supported. Another very useful feature is the ability to treat
binary json (jsonb) columns as separate tables, even using them in nested queries joining against related tables. To replicate these features on your own will take a lot of complex SQL. Using GraphJin means you don't have to deal with any of this - it just works.
Configure a relationship between an array column
tag_ids which contains integer ids for tags and the column
id in the table
Configure a JSON column called
tag_count in the table
products into a separate table. This JSON column contains a json array of objects each with a tag id and a count of the number of times the tag was used. As a seperate table you can nest it into your GraphQL query and treat it like table using any of the standard features like
where clauses, etc.
The configuration below tells GraphJin to create a virtual table called
tag_count using the column
tag_count from the
products table. And that this new table has two columns
count of the listed types and with the defined relationships.
It often happens that after fetching some data from the DB we need to call another API to fetch some more data and all this combined into a single JSON response. For example along with a list of users you need their last 5 payments from Stripe. This requires you to query your DB for the users and Stripe for the payments. GraphJin handles all this for you also only the fields you requested from the Stripe API are returned.
Is this fast?
GraphJin is able fetch remote data and merge it with the DB response in an efficient manner. Several optimizations such as parallel HTTP requests and a zero-allocation JSON merge algorithm makes this very fast. All of this without you having to write a line of code.
For example you need to list the last 3 payments made by a user. You will first need to look up the user in the database and then call the Stripe API to fetch his last 3 payments. For this to work your user table in the db has a
customer_id column that contains his Stripe customer ID.
Similiarly you could also fetch the users last tweet, lead info from Salesforce or whatever else you need. It's fine to mix up several different
remote joins into a single GraphQL query.
The configuration is self explanatory. A
payments field has been added under the
customers table. This field is added to the
remotes subsection that defines fields associated with
customers that are remote and not real database columns.
id parameter maps a column from the
customers table to the
$id variable. In this case it maps
$id to the
payments like you would any other GraphQL selector under the
customers selector. GraphJin will call the configured API for you and stitch (merge) the JSON the API sends back with the JSON generated from the database query. GraphQL features like aliases and fields all work.
And voila here is the result. You get all of this advanced and honestly complex querying capability without writing a single line of code.
Even tracing data is availble in the GraphJin web UI if tracing is enabled in the config. By default it is enabled in development. Additionally there you can set
debug: true to enable http request / response dumping to help with debugging.
Every app these days needs search. Enought his often means reaching for something heavy like Solr. While this will work why add complexity to your infrastructure when Postgres has really great and fast full text search built-in. And since it's part of Postgres it's also available in GraphJin.
This query will use the
tsvector column in your database table to search for products that contain the query phrase or some version of it. To get the internal relevance ranking for the search results using the
search_rank field. And to get the highlighted context within any of the table columns you can use the
search_headline_ field prefix. For example
search_headline_name will return the contents of the products name column which contains the matching query marked with the
<b></b> html tags.