Reading Data

how-to

How to read documents in Couchbase.

Introduction

Retrieving documents by ID is the fastest and simplest way to read data in Couchbase. The Key-Value (KV) or Data Service allows you to retrieve a full document when you need to fetch all of the data stored. However, in instances where this can be costly and unnecessary, Couchbase also provides access to specific paths within a document.

Read the following for further information about the clients available:

Please note that the examples in this guide will alter the data in your sample buckets. To restore your sample data, remove and reinstall the travel-sample bucket. Refer to Sample Buckets for details.

Reading a Document

To read a single document in Couchbase, perform a get operation.

cbc
.NET
Java
Node.js
Python

Use the cbc cat command to retrieve a document by ID and output its data.

The example below retrieves document hotel-123 from the travel-sample.inventory.hotel keyspace.

cbc cat hotel-123 -u Administrator -P password -U couchbase://localhost/travel-sample \
	--scope='inventory' \
	--collection='hotel'

Result

hotel-123            CAS=0x16ba896b78930000, Flags=0x0, Size=567, Datatype=0x01(JSON)

{
  "id": 123,
  "name": "Medway Youth Hostel",
  "address": "Capstone Road, ME7 3JE",
  "url": "http://www.yha.org.uk",
  "geo": {
    "lat": 51.35785,
    "lon": 0.55818,
    "accuracy": "RANGE_INTERPOLATED"
  },
  "country": "United Kingdom",
  "city": "Medway",
  "state": null,
  "reviews": [
    {
      "content": "This was our 2nd trip here and we enjoyed it more than last year.",
      "author": "Ozella Sipes",
      "date": "2021-11-17T17:35:05.351Z"
    }
  ],
  "vacancy": true,
  "description": "40 bed summer hostel about 3 miles from Gillingham."
}

The output has been prettified for readability.

If the document cannot be found, cbc will return a LCB_ERR_DOCUMENT_NOT_FOUND error.

For further details, refer to cbc(1).

Use the GetAsync() method to retrieve a document by ID.

A GetResult object is returned, which includes the content, cas value, and other valuable metadata.

The example below retrieves document hotel-123 from the travel-sample.inventory.hotel keyspace.

var getResult = await hotelCollection.GetAsync("hotel-123");

// Print some result metadata to the console.
Console.WriteLine($"CAS: {getResult.Cas}");
Console.WriteLine($"Data: {getResult.ContentAs<JObject>()}");

If the document doesn’t exist, the SDK will return a DocumentNotFoundException error.

Click the GitHub button to view this code in context.

For further details, refer to CollectionExtensions.

Use the get() method to retrieve a document by ID.

A GetResult object is returned, which includes the content, cas value, and other valuable metadata.

The example below retrieves document hotel-123 from the travel-sample.inventory.hotel keyspace.

GetResult getResult = hotelCollection.get("hotel-123");

// Print the result's CAS metadata to the console.
System.out.println("CAS:" + getResult.cas());

If the document doesn’t exist, the SDK will return a DocumentNotFoundException error.

Click the GitHub button to view this code in context.

For further details, refer to Collection.

Use the get() function to retrieve a document by ID.

A GetResult promise is returned, which includes the content, cas value, and other valuable metadata.

The example below retrieves document hotel-123 from the travel-sample.inventory.hotel keyspace.

const getResult = await hotelCollection.get('hotel-123')

// Print some result metadata to the console.
console.log('CAS:', getResult.cas)
console.log('Data:', JSON.stringify(getResult.content, null, '  '))

If the document doesn’t exist, the SDK will return a DocumentNotFoundError error.

Click the GitHub button to view this code in context.

For further details, refer to Collection.

Use the get() function to retrieve a document by ID.

A GetResult object is returned, which includes the content, cas value, and other valuable metadata.

The example below retrieves document hotel-123 from the travel-sample.inventory.hotel keyspace.

get_result = hotel_collection.get("hotel-123")

# Print some result metadata to the console.
print("CAS:", get_result.cas)
print("Data: {}".format(get_result.content_as[dict]))

If the document doesn’t exist, the SDK will return a DocumentNotFoundException error.

Click the GitHub button to view this code in context.

For further details, refer to Collection.

Reading with Options

To specify further parameters, such as expiry, add options to the get operation.

cbc
.NET
Java
Node.js
Python

Use the cbc cat command to retrieve a document by ID and pass options as required.

The example below uses an --expiry option for the cat command which adds an expiry of 60 seconds to the hotel-123 document.

cbc cat hotel-123 -u Administrator -P password -U couchbase://localhost/travel-sample \
	--scope='inventory' \
	--collection='hotel' \
	--expiry=60

Result

hotel-123            CAS=0x16bcec98e00c0000, Flags=0x0, Size=567, Datatype=0x01(JSON)

{
  "id": 123,
  "name": "Medway Youth Hostel",
  "address": "Capstone Road, ME7 3JE",
  "url": "http://www.yha.org.uk",
  "geo": {
    "lat": 51.35785,
    "lon": 0.55818,
    "accuracy": "RANGE_INTERPOLATED"
  },
  "country": "United Kingdom",
  "city": "Medway",
  "state": null,
  "reviews": [
    {
      "content": "This was our 2nd trip here and we enjoyed it more than last year.",
      "author": "Ozella Sipes",
      "date": "2021-11-17T17:35:05.351Z"
    }
  ],
  "vacancy": true,
  "description": "40 bed summer hostel about 3 miles from Gillingham."
}

The output has been prettified for readability.

For further details, refer to cbc(1).

Pass any required options to the GetAsync() method when retrieving a document.

A GetResult object is returned, which may include extra metadata, depending on the options passed.

The example below retrieves a document hotel-123 with additional expiry metadata.

var getResult = await hotelCollection.GetAsync("hotel-456", options =>
{
	options.Expiry();
});

// Print some result metadata to the console.
Console.WriteLine($"CAS: {getResult.Cas}");
Console.WriteLine($"Data: {getResult.ContentAs<JObject>()}");
Console.WriteLine($"Expiry: {getResult.ExpiryTime}");

Click the GitHub button to view this code in context.

For further details, refer to CollectionExtensions.

Pass any required options to the get() method when retrieving a document.

A GetResult object is returned, which may include extra metadata, depending on the options passed.

The example below retrieves a document hotel-123 with additional expiry metadata.

GetResult getResult = hotelCollection.get("hotel-123", 
    GetOptions.getOptions().withExpiry(true)
);

// Print the result's CAS metadata to the console.
System.out.println("CAS:" + getResult.cas());
System.out.println("Data:" + getResult.contentAsObject());
System.out.println("Expiry:" + getResult.expiryTime());

Click the GitHub button to view this code in context.

For further details, refer to Collection.

Pass any required options to the get() method when retrieving a document.

A GetResult object is returned, which may include extra metadata, depending on the options passed.

The example below retrieves a document hotel-123 with additional expiry metadata.

const getResult = await hotelCollection.get('hotel-456', {
  withExpiry: true,
})

// Print some result metadata to the console.
console.log('CAS:', getResult.cas)
console.log('Data:', JSON.stringify(getResult.content, null, '  '))
console.log('Expiry time:', getResult.expiryTime)

Click the GitHub button to view this code in context.

For further details, refer to Collection.

Pass any required options to the get() method when retrieving a document.

A GetResult object is returned, which may include extra metadata, depending on the options passed.

The example below retrieves a document hotel-123 with additional expiry metadata.

get_result = hotel_collection.get(
    "hotel-456", GetOptions(with_expiry=True)
)

# Print some result metadata to the console.
print("CAS:", get_result.cas)
print("Data: {}".format(get_result.content_as[dict]))
print("Expiry time: {}".format(get_result.expiryTime))

Click the GitHub button to view this code in context.

For further details, refer to Collection.

Reading a Sub-Document

JSON documents can contain a lot of nested data — which might not necessarily need to be accessed all at once. Reading full documents to access a field or two is not ideal and could cause performance issues in your application. Instead, a better practice would be to access specific paths, or sub-documents, to perform more efficient read operations.

To fetch a specific field inside a document, you can perform a sub-document get operation.

cbc-subdoc
.NET
Java
Node.js
Python

Connect to the cbc-subdoc interactive shell.
Use the get command to access specific fields in a JSON document with the --path argument.

The example below fetches the geo data from the airport_1254 document.

airport_1254

{
  "id": 1254,
//  ...
  "geo": {
    "lat": 50.962097,
    "lon": 1.954764,
    "alt": 12
  }
}

cbc-subdoc -u Administrator -P password -U couchbase://localhost/travel-sample
subdoc> get airport_1254 --path geo

Result

airport_1254         CAS=0x16b815068df80000
0. Size=43, RC=LCB_SUCCESS (0)
{"lat":50.962097,"lon":1.954764,"alt":12.0}

If the path cannot be found, cbc-subdoc will return a LCB_ERR_SUBDOC_PATH_NOT_FOUND error.

For further details, refer to cbc-subdoc(1).

Call the LookupInAsync() method, which takes a document ID and an IEnumerable containing LookUpInSpec objects.
Use the LookUpInSpec object to specify the sub-operation to be performed within the lookup.

A LookupInResult object is returned, containing the result and metadata relevant to the sub-document get operation.

The example below fetches the geo data from the hotel-123 document.

var lookupInResult = await hotelCollection.LookupInAsync("hotel-123",
		specs => specs.Get("geo")
);

Console.WriteLine($"CAS: {lookupInResult.Cas}");
Console.WriteLine($"Geo: {lookupInResult.ContentAs<JObject>(0)}");

Click the GitHub button to view this code in context.

For further details, refer to CollectionExtensions.

Call the lookupIn() method, which takes a document ID and an array of LookUpInSpec objects.
Use the LookUpInSpec object to specify the sub-operation to be performed within the lookup.

A LookupInResult object is returned, containing the result and metadata relevant to the sub-document get operation.

The example below fetches the geo data from the hotel-123 document.

List<LookupInSpec> specs = Arrays.asList(LookupInSpec.get("geo"));

LookupInResult lookupInResult = hotelCollection.lookupIn("hotel-123", specs);
System.out.println("CAS:" + lookupInResult.cas());
System.out.println("Geo:" + lookupInResult.contentAsObject(0));

If the document path can’t be found, the SDK will return a PathNotFoundException error.

Click the GitHub button to view this code in context.

For further details, refer to Collection.

Call the lookupIn() function, which takes a document ID and an array of LookUpInSpec objects.
Use the LookUpInSpec object to specify the sub-operation to be performed within the lookup.

A LookupInResult promise is returned containing the result and metadata relevant to the sub-document get operation.

The example below fetches the geo data from the hotel-123 document.

const lookupInResult = await hotelCollection.lookupIn('hotel-123', [
  couchbase.LookupInSpec.get('geo'),
])
console.log('CAS:', lookupInResult.cas)
console.log('Geo:', lookupInResult.content[0].value)

Click the GitHub button to view this code in context.

For further details, refer to Collection.

Call the lookup_in() function, which takes a document ID and a list of LookUpInSpec objects.
Use the LookUpInSpec object to represent the sub-operation to be performed within the lookup.

A LookupInResult object is returned containing the result and metadata relevant to the sub-document get operation.

The example below fetches the geo data from the hotel-123 document.

lookup_in_result = hotel_collection.lookup_in(
    "hotel-123", [subdocument.get("geo")]
)
print("CAS:", lookup_in_result.cas)
print("Data:", lookup_in_result.content_as[dict](0))

If the document path can’t be found, the SDK will return a PathNotFoundException error.

Click the GitHub button to view this code in context.

For further details, refer to Collection.

Key-Value Operations with SDKs:

C | .NET | Go | Java | Node.js | PHP | Python | Ruby | Scala

Sub-Document operations with SDKs:

C | .NET | Go | Java | Node.js | PHP | Python | Ruby | Scala

Reading Data

Introduction

Reading a Document

Reading with Options

Reading a Sub-Document

Related Links