Index and query documents

Learn how to use the Redis Query Engine with JSON and hash documents.

This example shows how to create a search index for JSON documents and run queries against the index. It then goes on to show the slight differences in the equivalent code for hash documents.

Initialize

Make sure that you have Redis Open Source or another Redis server available. Also install the node-redis client library if you haven't already done so.

Add the following dependencies:

import {
    createClient,
    SchemaFieldTypes,
    AggregateGroupByReducers,
    AggregateSteps,
} from 'redis';

Create data

Create some test data to add to your database. The example data shown below is compatible with both JSON and hash objects.

const user1 = {
    name: 'Paul John',
    email: '[email protected]',
    age: 42,
    city: 'London'
};

const user2 = {
    name: 'Eden Zamir',
    email: '[email protected]',
    age: 29,
    city: 'Tel Aviv'
};

const user3 = {
    name: 'Paul Zamir',
    email: '[email protected]',
    age: 35,
    city: 'Tel Aviv'
};

Add the index

Connect to your Redis database. The code below shows the most basic connection but see Connect to the server to learn more about the available connection options.

const client = await createClient();
await client.connect();

Create an index. In this example, only JSON documents with the key prefix user: are indexed. For more information, see Query syntax.

await client.ft.create('idx:users', {
    '$.name': {
        type: SchemaFieldTypes.TEXT,
        AS: 'name'
    },
    '$.city': {
        type: SchemaFieldTypes.TEXT,
        AS: 'city'
    },
    '$.age': {
        type: SchemaFieldTypes.NUMERIC,
        AS: 'age'
    }
}, {
    ON: 'JSON',
    PREFIX: 'user:'
});

Add the data

Add the three sets of user data to the database as JSON objects. If you use keys with the user: prefix then Redis will index the objects automatically as you add them. Note that placing the commands in a Promise.all() call is an easy way to create a pipeline, which is more efficient than sending the commands individually.

const [user1Reply, user2Reply, user3Reply] = await Promise.all([
    client.json.set('user:1', '$', user1),
    client.json.set('user:2', '$', user2),
    client.json.set('user:3', '$', user3)
]);

Query the data

You can now use the index to search the JSON objects. The query below searches for objects that have the text "Paul" in any field and have an age value in the range 30 to 40:

let findPaulResult = await client.ft.search('idx:users', 'Paul @age:[30 40]');

console.log(findPaulResult.total); // >>> 1

findPaulResult.documents.forEach(doc => {
    console.log(`ID: ${doc.id}, name: ${doc.value.name}, age: ${doc.value.age}`);
});

Specify query options to return only the city field:

let citiesResult = await client.ft.search('idx:users', '*',{
    RETURN: 'city'
});

console.log(citiesResult.total); // >>> 3

citiesResult.documents.forEach(cityDoc => {
    console.log(cityDoc.value);
});

Use an aggregation query to count all users in each city.

let aggResult = await client.ft.aggregate('idx:users', '*', {
    STEPS: [{
        type: AggregateSteps.GROUPBY,
        properties: '@city',
        REDUCE: [{
            type: AggregateGroupByReducers.COUNT,
            AS: 'count'
        }]
    }]
});

console.log(aggResult.total); // >>> 2

aggResult.results.forEach(result => {
    console.log(`${result.city} - ${result.count}`);
});

Finally, close the connection to Redis.

await client.quit();

Differences with hash documents

Indexing for hash documents is very similar to JSON indexing but you need to specify some slightly different options.

When you create the schema for a hash index, you don't need to add aliases for the fields, since you use the basic names to access the fields anyway. Also, you must use HASH for the ON option when you create the index. The code below shows these changes with a new index called hash-idx:users, which is otherwise the same as the idx:users index used for JSON documents in the previous examples.

await client.ft.create('hash-idx:users', {
    'name': {
        type: SchemaFieldTypes.TEXT
    },
    'city': {
        type: SchemaFieldTypes.TEXT
    },
    'age': {
        type: SchemaFieldTypes.NUMERIC
    }
}, {
    ON: 'HASH',
    PREFIX: 'huser:'
});

You use hSet() to add the hash documents instead of json.set(), but the same flat userX objects work equally well with either hash or JSON:

const [huser1Reply, huser2Reply, huser3Reply] = await Promise.all([
    client.hSet('huser:1', user1),
    client.hSet('huser:2', user2),
    client.hSet('huser:3', user3)
]);

The query commands work the same here for hash as they do for JSON (but the name of the hash index is different). The format of the result is also the same:

let findPaulHashResult = await client.ft.search(
    'hash-idx:users', 'Paul @age:[30 40]'
);

console.log(findPaulHashResult.total); // >>> 1

findPaulHashResult.documents.forEach(doc => {
    console.log(`ID: ${doc.id}, name: ${doc.value.name}, age: ${doc.value.age}`);
});
// >>> ID: huser:3, name: Paul Zamir, age: 35

More information

See the Redis Query Engine docs for a full description of all query features with examples.

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