UPDATE

UPDATE replaces a document that already exists with updated values.

Prerequisites

RBAC Privileges

User executing the UPDATE statement must have the Query Update privilege on the target keyspace. If the statement has any clauses that needs data read, such as SELECT clause, or RETURNING clause, then Query Select privilege is also required on the keyspaces referred in the respective clauses. For more details about user roles, see Authorization.

Please note that the examples below 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.

For example,

To execute the following statement, you must have the Query Update privilege on `travel-sample`.inventory.airport.
```
UPDATE `travel-sample`.inventory.airport SET foo = 5;
```
To execute the following statement, you must have the Query Update privilege on `travel-sample`.inventory.airport and Query Select privilege on `beer-sample`.
```
UPDATE `travel-sample`.inventory.airport
SET foo = 9
WHERE city IN (SELECT RAW city FROM `beer-sample` WHERE type = "brewery");
```
To execute the following statement, you must have the Query Update and Query Select privileges on `travel-sample`.inventory.airport.
```
UPDATE `travel-sample`.inventory.airport
SET city = "San Francisco"
WHERE lower(city) = "san francisco"
RETURNING *;
```

A user with the Data Writer privilege may set documents to expire. When the document expires, the data service deletes the document, even though the user may not have the Query Delete privilege.

Syntax

UPDATE update-target [update-hint] [set-clause] [unset-clause] [where-clause] [limit-clause] [returning-clause]

Update Target

update-target ::= keyspace-ref [ [ AS ] alias ]

( namespace ':' )? keyspace ( 'AS'? alias )?

The update target is the keyspace which you want to update.

Keyspace Reference

keyspace-ref ::= keyspace-path | keyspace-partial

keyspace-path ::= [ namespace ':' ] bucket [ '.' scope '.' collection ]

( namespace ':' )? bucket ( '.' scope '.' collection )?

keyspace-partial ::= collection

Keyspace reference for the update target. For more details, refer to Keyspace Reference.

AS Alias

Assigns another name to the keyspace reference. For details, refer to AS Clause.

alias: String to assign an alias.

Assigning an alias to the keyspace reference is optional. If you assign an alias to the keyspace reference, the AS keyword may be omitted.

Update Hint

You can use a USE KEYS hint on the update target to specify the keys of the data items to be updated. For details, refer to USE KEYS Clause.

SET Clause

set-clause ::= SET ( meta '=' expiration | path '=' expr [ update-for ] )
             [ ',' ( meta '=' expiration | path '=' expr [ update-for ] ) ]*

'SET' ( meta '=' expiration | path '=' expr update-for? ) ( ',' ( meta '=' expiration | path '=' expr update-for? ) )*

Specifies the value for an attribute to be changed.

path: A path specifying the attribute to be changed.
expr: The value may be a generic expression term, a subquery, or an expression that resolves to nested array elements.

The SET clause also supports alternative arguments which enable you to set the expiration of the document.

meta: A META().expiration expression specifying the expiration property of the document being updated.
expiration: An integer, or an expression resolving to an integer, representing the document expiration in seconds.

If the document expiration is not specified, the document expiration is set according to the request-level preserve_expiration parameter. If this is true, the existing document expiration is preserved; if false, the document expiration defaults to 0, meaning the document expiration is the same as the bucket expiration.

UNSET Clause

unset-clause ::= UNSET path [ update-for ] [ ',' path [ update-for ] ]*

'UNSET' path update-for? (',' path update-for?)*

Removes the specified attribute from the document.

path: A path specifying the attribute to be removed.

You cannot use the UNSET clause to unset the document expiration. To unset the document expiration, set the document expiration to 0. Alternatively, if the request-level preserve_expiration parameter is set to false, simply update the document without specifying the document expiration.

FOR Clause

update-for ::= ( FOR [ name-var ':' ] var ( IN | WITHIN ) path
               [ ',' [ name-var ':' ] var ( IN | WITHIN ) path ]* )+
               [ WHEN cond ] END

('FOR' (name-var ':')? var ('IN' | 'WITHIN') path (',' (name-var ':')? var ('IN' | 'WITHIN') path)*)+ ('WHEN' cond)? 'END'

path ::= identifier [ '[' expr ']' ]* [ '.' path ]

'identifier ('[' expr ']')* ( '.' path )?

Uses the FOR statement to iterate over a nested array to SET or UNSET the given attribute for every matching element in the array. The FOR clause can evaluate functions and expressions, and the UPDATE statement supports multiple nested FOR expressions to access and update fields in nested arrays. Additional array levels are supported by chaining the FOR clauses.

WHERE Clause

where-clause ::= WHERE cond

Specifies the condition that needs to be met for data to be updated. Optional.

LIMIT Clause

limit-clause ::= LIMIT expr

Specifies the greatest number of objects that can be updated. This clause must have a non-negative integer as its upper bound. Optional.

RETURNING Clause

returning-clause ::= RETURNING ( result-expr [ ',' result-expr ]* | ( RAW | ELEMENT | VALUE ) expr )

'RETURNING' (result-expr (',' result-expr)* | ('RAW' | 'ELEMENT' | 'VALUE') expr)

Specifies the information to be returned by the operation as a query result. For more details, refer to RETURNING Clause.

Examples

For some of these examples, the Query Workbench may warn you that the query has no WHERE clause and will update all documents. In this case, you can ignore the warning: the USE KEYS hint in these examples ensures that the query updates only one document.

Example 1. Set an attribute

The following statement sets the nickname of the landmark "Tradeston Pedestrian Bridge" to "Squiggly Bridge".

UPDATE `travel-sample`.inventory.landmark
USE KEYS "landmark_10090"
SET nickname = "Squiggly Bridge"
RETURNING landmark.nickname;

[
  {
    "nickname": "Squiggly Bridge"
  }
]

Example 2. Unset an attribute

This statement removes the nickname attribute from the landmark keyspace for the document with the key landmark_10090.

UPDATE `travel-sample`.inventory.landmark
USE KEYS "landmark_10090"
UNSET nickname
RETURNING landmark.name;

[
  {
    "name": "Tradeston Pedestrian Bridge"
  }
]

Example 3. Set attributes in an array

This statement sets the codeshare attribute for each element in the schedule array for document route_10003 in the route keyspace.

UPDATE `travel-sample`.inventory.route t
USE KEYS "route_10003"
SET s.codeshare = NULL FOR s IN schedule END
RETURNING t;

[
  {
    "t": {
      "airline": "AF",
      "airlineid": "airline_137",
      "destinationairport": "ATL",
      "distance": 654.9546621929924,
      "equipment": "757 739",
      "id": 10003,
      "schedule": [
        {
          "codeshare": null,
          "day": 0,
          "flight": "AF986",
          "utc": "22:26:00"
        },
        {
          "codeshare": null,
          "day": 0,
          "flight": "AF962",
          "utc": "04:25:00"
        },
// ...
      ],
      "sourceairport": "TPA",
      "stops": 0,
      "type": "route"
    }
  }
]

Example 4. Set nested array elements

UPDATE `travel-sample`.inventory.hotel AS h USE KEYS "hotel_10025"
SET i.ratings = OBJECT_ADD(i.ratings, "new", "new_value" ) FOR i IN reviews END
RETURNING h.reviews[*].ratings;

[
  {
    "ratings": [
      {
        "Cleanliness": 5,
        "Location": 4,
        "Overall": 4,
        "Rooms": 3,
        "Service": 5,
        "Value": 4,
        "new": "new_value"
      },
      {
        "Business service (e.g., internet access)": 4,
        "Check in / front desk": 4,
        "Cleanliness": 4,
        "Location": 4,
        "Overall": 4,
        "Rooms": 3,
        "Service": 3,
        "Value": 5,
        "new": "new_value"
      }
    ]
  }
]

Example 5. Access nested arrays

Query

UPDATE `travel-sample`.inventory.hotel AS h USE KEYS "hotel_10025"
UNSET i.new FOR i IN
  (ARRAY j.ratings FOR j IN reviews END)
END
RETURNING h.reviews[*].ratings;

Result

[
  {
    "ratings": [
      {
        "Cleanliness": 5,
        "Location": 4,
        "Overall": 4,
        "Rooms": 3,
        "Service": 5,
        "Value": 4
      },
      {
        "Business service (e.g., internet access)": 4,
        "Check in / front desk": 4,
        "Cleanliness": 4,
        "Location": 4,
        "Overall": 4,
        "Rooms": 3,
        "Service": 3,
        "Value": 5
      }
    ]
  }
]

Example 6. Update a document with the results of a subquery

Query

UPDATE `travel-sample`.inventory.airport AS a
SET hotels =
  (SELECT  h.name, h.id
  FROM  `travel-sample`.inventory.hotel AS h
  WHERE h.city = "Nice")
WHERE a.faa ="NCE"
RETURNING a;

Result

[
  {
    "a": {
      "airportname": "Cote D\\'Azur",
      "city": "Nice",
      "country": "France",
      "faa": "NCE",
      "geo": {
        "alt": 12,
        "lat": 43.658411,
        "lon": 7.215872
      },
      "hotels": [
        {
          "id": 20419,
          "name": "Best Western Hotel Riviera Nice"
        },
        {
          "id": 20420,
          "name": "Hotel Anis"
        },
        {
          "id": 20421,
          "name": "NH Nice"
        },
        {
          "id": 20422,
          "name": "Hotel Suisse"
        },
        {
          "id": 20423,
          "name": "Gounod"
        },
        {
          "id": 20424,
          "name": "Grimaldi Hotel Nice"
        },
        {
          "id": 20425,
          "name": "Negresco"
        }
      ],
      "icao": "LFMN",
      "id": 1354,
      "type": "airport",
      "tz": "Europe/Paris"
    }
  }
]

Example 7. Update a document and set expiration

Update a document and set the expiration to 1 week.

Query

UPDATE `travel-sample`.inventory.route t USE KEYS "route_10003"
SET meta(t).expiration = 7*24*60*60,
s.codeshare = NULL FOR s IN schedule END;

Example 8. Update a document and preserve expiration

Query

UPDATE `travel-sample`.inventory.route t USE KEYS "route_10003"
SET meta(t).expiration = meta(t).expiration,
s.codeshare = NULL FOR s IN schedule END;

Note that in Couchbase Server 7.1 and later, it is possible to preserve the document expiration using the request-level preserve_expiration parameter.

Example 9. Update a document and unset expiration

Set the document expiration to 0 to unset the document expiration. (In this case, the document expiration defaults to be the same as the bucket expiration.)

Query

UPDATE `travel-sample`.inventory.route t USE KEYS "route_10003"
SET meta(t).expiration = 0,
s.codeshare = NULL FOR s IN schedule END;

Alternatively, if the request-level preserve_expiration parameter is set to false, and you update the document without specifying the document expiration, the document expiration defaults to 0.

Query

UPDATE `travel-sample`.inventory.route t USE KEYS "route_10003"
SET s.codeshare = NULL FOR s IN schedule END;