Working with data
Reading data
Instant uses a declarative syntax for querying. It's like GraphQL without the configuration. Here's how you can query data with InstaQL.
Fetch namespace
One of the simplest queries you can write is to simply get all entities of a namespace.
const query = { goals: {} };
const { isLoading, error, data } = db.useQuery(query);
Inspecting data, we'll see:
console.log(data)
{
"goals": [
{
"id": healthId,
"title": "Get fit!"
},
{
"id": workId,
"title": "Get promoted!"
}
]
}
For comparison, the SQL equivalent of this would be something like:
const data = { goals: doSQL('SELECT * FROM goals') };
Fetch multiple namespaces
You can fetch multiple namespaces at once:
const query = { goals: {}, todos: {} };
const { isLoading, error, data } = db.useQuery(query);
We will now see data for both namespaces.
console.log(data)
{
"goals": [...],
"todos": [
{
"id": focusId,
"title": "Code a bunch"
},
{
"id": proteinId,
"title": "Drink protein"
},
...
]
}
The equivalent of this in SQL would be to write two separate queries.
const data = {
goals: doSQL('SELECT * from goals'),
todos: doSQL('SELECT * from todos'),
};
Fetch a specific entity
If you want to filter entities, you can use the where keyword. Here we fetch a specific goal
const query = {
goals: {
$: {
where: {
id: healthId,
},
},
},
};
const { isLoading, error, data } = db.useQuery(query);
console.log(data)
{
"goals": [
{
"id": healthId,
"title": "Get fit!"
}
]
}
The SQL equivalent would be:
const data = { goals: doSQL("SELECT * FROM goals WHERE id = 'healthId'") };
Fetch associations
We can fetch goals and their related todos.
const query = {
goals: {
todos: {},
},
};
const { isLoading, error, data } = db.useQuery(query);
goals would now include nested todos
console.log(data)
{
"goals": [
{
"id": healthId,
"title": "Get fit!",
"todos": [...],
},
{
"id": workId,
"title": "Get promoted!",
"todos": [...],
}
]
}
Comparing with SQL
The SQL equivalent for this would be something along the lines of:
const query = "
SELECT g.*, gt.todos
FROM goals g
JOIN (
SELECT g.id, json_agg(t.*) as todos
FROM goals g
LEFT JOIN todos t on g.id = t.goal_id
GROUP BY 1
) gt on g.id = gt.id
"
const data = {goals: doSQL(query)}
Notice the complexity of this SQL query. Although fetching associations in SQL is straightforward via JOIN, marshalling the results in a nested structure via SQL is tricky. An alternative approach would be to write two straight-forward queries and then marshall the data on the client.
const _goals = doSQL("SELECT * from goals")
const _todos = doSQL("SELECT * from todos")
const data = {goals: _goals.map(g => (
return {...g, todos: _todos.filter(t => t.goal_id === g.id)}
))
Now compare these two approaches with InstaQL
const query = {
goals: {
todos: {},
},
};
const { isLoading, error, data } = db.useQuery(query);
Modern applications often need to render nested relations, InstaQL really starts to shine for these use cases.
Fetch specific associations
A) Fetch associations for filtered namespace
We can fetch a specific entity in a namespace as well as it's related associations.
const query = {
goals: {
$: {
where: {
id: healthId,
},
},
todos: {},
},
};
const { isLoading, error, data } = db.useQuery(query);
Which returns
console.log(data)
{
"goals": [
{
"id": healthId,
"title": "Get fit!",
"todos": [
{
"id": proteinId,
"title": "Drink protein"
},
{
"id": sleepId,
"title": "Go to bed early"
},
{
"id": workoutId,
"title": "Go on a run"
}
]
}
]
}
B) Filter namespace by associated values
We can filter namespaces by their associations
const query = {
goals: {
$: {
where: {
'todos.title': 'Code a bunch',
},
},
todos: {},
},
};
const { isLoading, error, data } = db.useQuery(query);
Returns
console.log(data)
{
"goals": [
{
"id": workId,
"title": "Get promoted!",
"todos": [
{
"id": focusId,
"title": "Code a bunch"
},
{
"id": reviewPRsId,
"title": "Review PRs"
},
{
"id": standupId,
"title": "Do standup"
}
]
}
]
}
C) Filter associations
We can also filter associated data.
const query = {
goals: {
todos: {
$: {
where: {
'todos.title': 'Go on a run',
},
},
},
},
};
const { isLoading, error, data } = db.useQuery(query);
This will return goals and filtered todos
console.log(data)
{
"goals": [
{
"id": healthId,
"title": "Get fit!",
"todos": [
{
"id": workoutId,
"title": "Go on a run"
}
]
},
{
"id": workId,
"title": "Get promoted!",
"todos": []
}
]
}
Notice the difference between these three cases.
- A) Fetched all todos for goal with id
health - B) Filtered goals with a least one todo titled
Code a bunch - C) Fetched all goals and filtered associated todos by title
Go on a run
Inverse Associations
Associations are also available in the reverse order.
const query = {
todos: {
goals: {},
},
};
const { isLoading, error, data } = db.useQuery(query);
console.log(data)
{
"todos": [
{
"id": focusId,
"title": "Code a bunch",
"goals": [
{
"id": workId,
"title": "Get promoted!"
}
]
},
...,
]
}
Pagination
You can limit the number of items from a top level namespace by adding a limit to the option map:
const query = {
todos: {
// limit is only supported for top-level namespaces right now
// and not for nested namespaces.
$: { limit: 10 },
},
};
const { isLoading, error, data, pageInfo } = db.useQuery(query);
Instant supports both offset-based and cursor-based pagination for top-level namespaces.
Offset
To get the next page, you can use an offset:
const query = {
todos: {
$: {
limit: 10,
// similar to `limit`, `offset` is only supported for top-level namespaces
offset: 10,
},
},
};
const { isLoading, error, data, pageInfo } = db.useQuery(query);
In a React application, your offset-based pagination code might look something like this:
const [pageNumber, setPageNumber] = React.useState(1);
const pageSize = 10;
const query = {
todos: {
$: {
limit: pageSize,
offset: pageSize * (pageNumber - 1),
},
},
};
const { isLoading, error, data } = db.useQuery(query);
// Load the next page by increasing the page number, which will
// increase the offset by the page size.
const loadNextPage = () => {
setPageNumber(pageNumber + 1);
};
// Load the previous page by decreasing the page number, which will
// decrease the offset by the page size.
const loadPreviousPage = () => {
setPageNumber(pageNumber - 1);
};
Cursors
You can also get the next page with the endCursor returned in the pageInfo map from the previous result:
const query = {
todos: {
$: {
// These also are only supported for top-level namespaces
first: 10,
after: pageInfo?.todos?.endCursor,
},
},
};
To get the previous page, use the startCursor in the before field of the option map and ask for the last items:
const query = {
todos: {
$: {
last: 10,
before: pageInfo?.todos?.startCursor,
},
},
};
In a React application, your cursor-based pagination code might look something like this:
const pageSize = 10;
const [cursors, setCursors] = React.useState({ first: pageSize });
const query = {
todos: {
$: {
...cursors,
},
},
};
const { isLoading, error, data, pageInfo } = db.useQuery(query);
const loadNextPage = () => {
const endCursor = pageInfo?.todos?.endCursor;
if (endCursor) {
setCursors({ after: endCursor, first: pageSize });
}
};
const loadPreviousPage = () => {
const startCursor = pageInfo?.todos?.startCursor;
if (startCursor) {
setCursors({
before: startCursor,
// Ask for the `last` 10 items so that we get the items just
// before our startCursor
last: pageSize,
});
}
};
Ordering
The default ordering is by the time the objects were created, in ascending order. You can change the order with the order key in the option map for top-level namespaces:
const query = {
todos: {
$: {
limit: 10,
// Similar to limit, order is limited to top-level namespaces right now
order: {
serverCreatedAt: 'desc',
},
},
},
};
The serverCreatedAt field is a reserved key that orders by the time that the object was first persisted on the Instant backend. It can take the value 'asc' (the default) or 'desc'.
Advanced filtering
And
The where clause supports multiple keys which will filter entities that match all of the conditions.
You can also provide a list of queries under the and key.
Multiple keys in a single where:
const query = {
todos: {
$: {
where: {
completed: true,
'goals.title': 'Get promoted!',
},
},
},
};
const { isLoading, error, data } = db.useQuery(query);
console.log(data)
{
"todos": [
{
"id": focusId,
"title": "Code a bunch",
"completed": true
}
]
}
and key:
The and key is useful when you want an entity to match multiple conditions. In this case we want to find goals that have both Drink protein and Go on a run todos.:
const query = {
goals: {
$: {
where: {
and: [
{ 'todos.title': 'Drink protein' },
{ 'todos.title': 'Go on a run' },
],
},
},
},
};
const { isLoading, error, data } = db.useQuery(query);
console.log(data)
{
"goals": [
{
"id": healthId,
"title": "Get fit!"
}
]
}
OR
The where clause supports or queries that will filter entities that match any of the clauses in the provided list:
const query = {
todos: {
$: {
where: {
or: [{ title: 'Code a bunch' }, { title: 'Review PRs' }],
},
},
},
};
const { isLoading, error, data } = db.useQuery(query);
console.log(data);
{
"todos": [
{
"id": focusId,
"title": "Code a bunch"
},
{
"id": reviewPRsId,
"title": "Review PRs"
},
]
}
$in
The where clause supports $in queries that will filter entities that match any of the items in the provided list. You can think of this as a shorthand for or on a single key.
const query = {
todos: {
$: {
where: {
title: { $in: ['Code a bunch', 'Review PRs'] },
},
},
},
};
const { isLoading, error, data } = db.useQuery(query);
console.log(data)
{
"todos": [
{
"id": focusId,
"title": "Code a bunch"
},
{
"id": reviewPRsId,
"title": "Review PRs"
},
]
}
$not
The where clause supports $not queries that will return entities that don't match the provided value for the field, including entities where the field is null or undefined.
const query = {
todos: {
$: {
where: {
location: { $not: 'work' },
},
},
},
};
const { isLoading, error, data } = db.useQuery(query);
console.log(data)
{
"todos": [
{
"id": cookId,
"title": "Cook dinner",
"location": "home"
},
{
"id": readId,
"title": "Read",
"location": null
},
{
"id": napId,
"title": "Take a nap"
}
]
}
$isNull
The where clause supports $isNull queries that will filters entities by whether the field value is either null or undefined.
Set $isNull to true to return entities where where the field is null or undefined.
Set $isNull to false to return entities where the field is not null and not undefined.
const query = {
todos: {
$: {
where: {
location: { $isNull: false },
},
},
},
};
const { isLoading, error, data } = db.useQuery(query);
console.log(data)
{
"todos": [
{
"id": cookId,
"title": "Cook dinner",
"location": "home"
}
]
}
const query = {
todos: {
$: {
where: {
location: { $isNull: true },
},
},
},
};
const { isLoading, error, data } = db.useQuery(query);
console.log(data)
{
"todos": [
{
"id": readId,
"title": "Read",
"location": null
},
{
"id": napId,
"title": "Take a nap"
}
]
}
Query once
Sometimes, you don't want a subscription, and just want to fetch data once. For example, you might want to fetch data before rendering a page or check whether a user name is available.
In these cases, you can use queryOnce instead of useQuery. queryOnce returns a promise that resolves with the data once the query is complete.
Unlike useQuery, queryOnce will throw an error if the user is offline. This is because queryOnce is intended for use cases where you need the most up-to-date data.
const query = { todos: {} };
const { data } = await db.queryOnce(query);
// returns the same data as useQuery, but without the isLoading and error fields
You can also do pagination with queryOnce:
const query = {
todos: {
$: {
limit: 10,
offset: 10,
},
},
};
const { data, pageInfo } = await db.queryOnce(query);
// pageInfo behaves the same as with useQuery