MERGE

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    A MERGE statement provides the ability to update, insert into, or delete from a keyspace based on the results of a join with another keyspace or subquery. It is possible to specify actions (insert, update, delete) on the keyspace based on a match or no match in the join. Multiple actions can be specified in the same query.

    Couchbase Server supports two types of merge clause, which are described in the sections below: ANSI Merge and Lookup Merge.

    The ANSI merge clause has much more flexible functionality than its earlier legacy equivalent. Since it is standard compliant and more flexible, we recommend you to use ANSI merge exclusively, where possible.

    Privileges

    User executing the MERGE statement must have the following privileges:

    • Query Select privileges on the source keyspace

    • Query Insert, Query Update, or Query Delete privileges on the target keyspace as per the MERGE actions

    • Query Select privileges on the keyspaces referred in the RETURNING clause

    For more details about user roles, refer to Authorization.

    Couchbase Server 6.5.1

    In Couchbase Server 6.5.1, 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

    merge ::= MERGE INTO ( ansi-merge | lookup-merge ) [ limit-clause ] [ returning-clause ]
    'MERGE' 'INTO' ( ansi-merge | lookup-merge ) limit-clause? returning-clause?

    ANSI Merge

    (Introduced in Couchbase Server 6.5)

    merge-target use-clause 'USING' ansi-merge-source ansi-merge-predicate ansi-merge-actions

    ANSI Merge Target

    merge-target ::= keyspace-ref [ [ AS ] alias ]
    ( namespace ':' )? keyspace ( 'AS'? alias )?

    The merge target is the keyspace which you want to update, insert into or delete from.

    Keyspace Reference

    keyspace-ref ::= [ namespace ':' ] keyspace
    from keyspace ref

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

    namespace

    (Optional) The name or identifier of the namespace of the merge target.

    keyspace

    (Required) The name or identifier of the keyspace of the merge target.

    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.

    ANSI Merge Target Hint

    You can use a USE INDEX hint on the merge target to specify that the merge should use a particular index. For details, refer to USE INDEX Clause.

    The USE INDEX hint is the only hint allowed on the target. You cannot specify a USE KEYS hint or a join hint (USE NL or USE HASH) on the target of a merge statement.

    ANSI Merge Source

    ( merge-source-keyspace | merge-source-subquery | expr ( 'AS'? alias )? ) ansi-merge-source-hints?

    The merge source is the recordset that you want to merge with the merge target. It can be a keyspace reference, a subquery, or a generic expression.

    ANSI Merge Keyspace

    merge-source-keyspace ::= keyspace-ref [ [ AS ] alias ]
    ( namespace ':' )? keyspace ( 'AS'? alias )?
    Keyspace Reference
    keyspace-ref ::= [ namespace ':' ] keyspace
    from keyspace ref

    Keyspace reference for the merge source. For details, refer to Keyspace Reference.

    namespace

    (Optional) The name or identifier of the namespace of the merge source.

    keyspace

    (Required) The name or identifier of the keyspace of the merge source.

    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.

    ANSI Merge Subquery

    merge-source-subquery ::= subquery-expr [ AS ] alias
    subquery-expr 'AS'? alias
    Subquery Expression
    subquery-expr ::= '('  select ')'
    subquery expr

    Use parentheses to specify a subquery for the merge source. For details, refer to Subqueries.

    AS Alias

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

    alias

    String to assign an alias.

    You must assign an alias to a subquery on the merge source. However, when you assign an alias to the subquery, the AS keyword may be omitted.

    ANSI Merge Expression

    merge-source-expr ::= expr [ [ AS ] alias ]
    expr ( 'AS'? alias )?
    expr

    A N1QL expression generating JSON documents or objects for the merge source.

    AS Alias

    Assigns another name to the generic expression. For details, refer to AS Clause.

    alias

    String to assign an alias.

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

    ANSI Merge Source Hints

    You can specify ANSI join hints (USE HASH or USE NL) on the source of an ANSI merge. For details, refer to ANSI JOIN Hints.

    If the merge source is a keyspace, you can also specify a USE KEYS or USE INDEX hint on the merge source. For details, refer to Multiple Hints.

    If the merge action is update or delete, you can specify any of the join methods: USE HASH(BUILD), USE HASH(PROBE), or USE NL.

    If the merge action is insert, the only join methods you can specify are USE HASH(PROBE) or USE NL. In this case, if you specify USE HASH(BUILD), the join method will default to USE NL.

    The ANSI join hint is optional. If omitted, the default hint is USE NL.

    If you are using a nested-loop join, i.e. USE NL is specified or no join hint is specified, the target keyspace reference must have an appropriate secondary index defined for the join to work. If such an index cannot be found an error will be returned.

    ANSI Merge Predicate

    ansi-merge-predicate ::= ON expr
    'ON' expr

    The merge predicate enables you to specify an ANSI join between the merge source and the merge target.

    expr

    Boolean expression representing the join condition. This expression may contain fields, constant expressions, or any complex N1QL expression.

    ANSI Merge Actions

    ansi-merge-actions ::= [ merge-update ] [ merge-delete ] [ ansi-merge-insert ]
    merge-update? merge-delete? ansi-merge-insert?

    The merge actions enable you to specify insert, update, and delete actions on the target keyspace, based on a match or no match in the join.

    ANSI Merge Update

    merge-update ::= WHEN MATCHED THEN UPDATE [ set-clause ] ] [ unset-clause ] [ where-clause ]
    'WHEN' 'MATCHED' 'THEN' 'UPDATE' set-clause? unset-clause? where-clause?

    Updates a document that already exists with updated values.

    SET Clause
    set-clause ::= SET path '=' expr [ update-for ] [ ',' path '=' expr [ update-for ] ]*
    'SET' path '=' expr update-for? (',' path '=' expr update-for?)*

    Specifies the value for an attribute to be changed. For more details, refer to SET Clause.

    Couchbase Server 6.5.1

    In Couchbase Server 6.5.1, the SET clause also supports alternative arguments which enable you to set the expiration of the document.

    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? ) )*

    For more details, refer to SET Clause.

    UNSET Clause
    unset-clause ::= UNSET path [ update-for ] [ ',' path [ update-for ] ]*
    'UNSET' path update-for? (',' path update-for?)*

    Removes a specified attribute from the document. For more details, refer to UNSET Clause.

    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 )?

    Iterates over a nested array to SET or UNSET the given attribute for every matching element in the array. For more details, refer to FOR Clause.

    WHERE Clause
    where-clause ::= WHERE cond
    where clause

    Optionally specifies a condition that must be met for data to be updated. For more details, refer to WHERE Clause.

    ANSI Merge Delete

    merge-delete ::= WHEN MATCHED THEN DELETE [ where-clause ]
    'WHEN' 'MATCHED' 'THEN' 'DELETE' where-clause?

    Removes the specified document from the keyspace.

    WHERE Clause
    where-clause ::= WHERE cond
    where clause

    Optionally specifies a condition that must be met for data to be deleted. For more details, refer to WHERE Clause.

    ANSI Merge Insert

    ansi-merge-insert ::= WHEN NOT MATCHED THEN INSERT '(' [ KEY ] key [ ',' [ VALUE ] value ] ')' [ where-clause ]
    'WHEN' 'NOT' 'MATCHED' 'THEN' 'INSERT' '(' 'KEY'? key ( ',' 'VALUE'? value )? ')' where-clause?

    Inserts a new document into the keyspace. Use parentheses to specify the key and value for the inserted document, separated by a comma.

    Use the UUID() function to generate a random, unique document key.
    key

    An expression specifying the key for the inserted document.

    The KEY keyword may be omitted. If it is omitted, the VALUE keyword must be omitted also.

    value

    [Optional] An expression specifying the value for the inserted document. If the value is omitted, an empty document is inserted.

    The VALUE keyword may be omitted. If it is omitted, the KEY keyword must be omitted also.

    Couchbase Server 6.5.1

    In Couchbase Server 6.5.1, the ANSI Merge Insert syntax supports an optional third keyword OPTIONS and an associated argument options.

    ansi-merge-insert ::= WHEN NOT MATCHED THEN INSERT '(' [ KEY ] key [ ',' [ VALUE ] value ] [ ',' [ OPTIONS ] options ] ')' [ where-clause ]
    'WHEN' 'NOT' 'MATCHED' 'THEN' 'INSERT' '(' 'KEY'? key ( ',' 'VALUE'? value )? ( ',' 'OPTIONS'? options )? ')' where-clause?
    options

    [Optional] An object representing the metadata to be set for the inserted document. Only the expiration attribute has any effect; any other attributes are ignored.

    expiration

    An integer, or an expression resolving to an integer, representing the document expiration in seconds.

    If the document expiration is not specified, it defaults to 0, meaning the document expiration is the same as the bucket expiration.

    The OPTIONS keyword may be omitted. If it is omitted, the KEY and VALUE keywords must be omitted also.

    WHERE Clause
    where-clause ::= WHERE cond
    where clause

    Optionally specifies a condition that must be met for data to be inserted. For more details, refer to WHERE clause.

    Lookup Merge

    merge-target 'USING' lookup-merge-source lookup-merge-predicate lookup-merge-actions

    Lookup Merge Target

    Keyspace reference for the merge target. The syntax is the same as for an ANSI merge. Refer to ANSI Merge Target.

    Lookup Merge Source

    from-keyspace ('AS'? alias)? use-clause? | '(' select ')' 'AS'? alias | expr ('AS'? alias)?

    The merge source is the recordset that you want to merge with the merge target. It can be a keyspace reference, a subquery, or a generic expression.

    Lookup Merge Keyspace

    Keyspace reference for the merge source. The syntax is the same as for an ANSI merge. Refer to ANSI Merge Keyspace.

    Lookup Merge Source Hint

    If the merge source is a keyspace, you can specify a USE KEYS or USE INDEX hint on the merge source. For details, refer to USE clause.

    Lookup Merge Subquery

    Specifies a subquery for the merge source. The syntax is the same as for an ANSI merge. Refer to ANSI Merge Subquery.

    Lookup Merge Expression

    Specifies a generic expression for the merge source. The syntax is the same as for an ANSI merge. Refer to ANSI Merge Expression.

    Lookup Merge Predicate

    lookup-merge-predicate ::= ON [ PRIMARY ] KEY expr
    'ON' 'PRIMARY'? 'KEY' expr

    The merge predicate produces a document key for the target of the lookup merge.

    expr

    [Required] String or expression representing the primary key of the documents for the target keyspace.

    Lookup Merge Actions

    lookup-merge-actions ::= [ merge-update ] [ merge-delete ] [ lookup-merge-insert ]
    merge-update? merge-delete? lookup-merge-insert?

    The merge actions enable you to specify insert, update, and delete actions on the target keyspace, based on a match or no match in the join.

    Lookup Merge Update

    Updates a document that already exists with updated values. The syntax is the same as for an ANSI merge. Refer to ANSI Merge Update.

    Lookup Merge Delete

    Removes the specified document from the keyspace. The syntax is the same as for an ANSI merge. Refer to ANSI Merge Delete for details.

    Lookup Merge Insert

    lookup-merge-insert ::= WHEN NOT MATCHED THEN INSERT expr [ where-clause ]
    'WHEN' 'NOT' 'MATCHED' 'THEN' 'INSERT' expr where-clause?

    Inserts a new document into the keyspace. The key specified in the Lookup Merge Predicate is used as the key for the newly inserted document.

    expr

    An expression specifying the value for the inserted document.

    Couchbase Server 6.5.1

    In Couchbase Server 6.5.1, the Lookup Merge Insert syntax does not enable you to specify the document expiration. If you need to specify the document expiration, rewrite the query using the ANSI Merge Insert syntax.

    WHERE Clause
    where-clause ::= WHERE cond
    where clause

    Optionally specifies a condition that must be met for data to be inserted. For more details, refer to WHERE clause.

    Common Clauses

    The following clauses are common to both ANSI Merge and Lookup Merge.

    LIMIT Clause

    limit-clause ::= LIMIT expr
    limit clause

    Specifies the minimum number of records to be processed. For more details, refer to LIMIT Clause.

    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

    Example 1. ANSI merge with expression source

    This example updates the vacancy field based on the source expression.

    MERGE INTO `travel-sample` t
    USING [
      {"id":"21728", "vacancy": true},
      {"id":"21730", "vacancy": true}
    ] source
    ON meta(t).id = "hotel_" || source.id
    WHEN MATCHED THEN
      UPDATE SET t.old_vacancy = t.vacancy,
                 t.vacancy = source.vacancy
    RETURNING meta(t).id, t.old_vacancy, t.vacancy;
    Example 2. ANSI merge with keyspace source

    This example finds all BA routes whose source airport is in France. If any flights are using equipment 319, they are updated to use 797.

    MERGE INTO `travel-sample` AS route
    USING `travel-sample` AS airport
    ON route.sourceairport = airport.faa
    WHEN MATCHED THEN
      UPDATE SET route.old_equipment = route.equipment,
                 route.equipment = "797",
                 route.updated = true
    WHERE airport.country = "France"
      AND route.airline = "BA"
      AND CONTAINS(route.equipment, "319");
    Example 3. ANSI merge with updates and inserts

    This example compares a source set of airport data with the travel-sample airport data. If the airport already exists in travel-sample, the record is updated. If the airport does not exist in travel-sample, a new record is created.

    MERGE INTO `travel-sample` AS target
    USING [
      {"iata":"DSA", "name": "Doncaster Sheffield Airport"},
      {"iata":"VLY", "name": "Anglesey Airport / Maes Awyr Môn"}
    ] AS source
    ON target.faa = source.iata
    WHEN MATCHED THEN
      UPDATE SET target.old_name = target.airportname,
                 target.airportname = source.name,
                 target.updated = true
    WHEN NOT MATCHED THEN
      INSERT (KEY UUID(),
              VALUE {"faa": source.iata,
                     "airportname": source.name,
                     "type": "airport",
                     "inserted": true} );
    Example 4. ANSI merge with expiration

    Couchbase Server 6.5.1

    This example compares a source set of airport data with the travel-sample airport data. If the airport already exists in travel-sample, the record is updated, and the existing document expiration is preserved. If the airport does not exist in travel-sample, a new record is created with an expiration of one week.

    MERGE INTO `travel-sample` AS target
    USING [
      {"iata":"DSA", "name": "Doncaster Sheffield Airport"},
      {"iata":"VLY", "name": "Anglesey Airport / Maes Awyr Môn"}
    ] AS source
    ON target.faa = source.iata
    WHEN MATCHED THEN
      UPDATE SET target.old_name = target.airportname,
                 target.airportname = source.name,
                 target.updated = true,
                 meta(target).expiration = meta(target).expiration
    WHEN NOT MATCHED THEN
      INSERT (KEY UUID(),
              VALUE {"faa": source.iata,
                     "airportname": source.name,
                     "type": "airport",
                     "inserted": true},
              OPTIONS {"expiration": 7*24*60*60} );
    Example 5. Lookup merge with expression source

    Lookup merge version of Example 1.

    MERGE INTO `travel-sample` t
    USING [
      {"id":"21728", "vacancy": true},
      {"id":"21730", "vacancy": true}
    ] source
    ON KEY "hotel_"|| source.id
    WHEN MATCHED THEN
      UPDATE SET t.old_vacancy = t.vacancy, t.vacancy = source.vacancy
    RETURNING meta(t).id, t.old_vacancy, t.vacancy;
    Example 6. Lookup merge with keyspace source

    The following statement updates product based on orders.

    MERGE INTO product p USING orders o ON KEY o.productId
    WHEN MATCHED THEN
      UPDATE SET p.lastSaleDate = o.orderDate
    WHEN MATCHED THEN
      DELETE WHERE p.inventoryCount  <= 0;
    Example 7. Lookup merge with updates and inserts

    The following statement merges two datasets containing employee information. It then updates all_empts on match with emps_deptb and inserts when there is no match.

    MERGE INTO all_empts a USING emps_deptb b ON KEY b.empId
    WHEN MATCHED THEN
      UPDATE SET a.depts = a.depts + 1
      a.title = b.title || ", " || b.title
    WHEN NOT MATCHED THEN
      INSERT { "name": b.name, "title": b.title, "depts": b.depts, "empId": b.empId, "dob": b.dob };