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Version: 4.x

UNGROUP operator

danger

At the moment, the UNGROUP operator is not implemented.

The UNGROUP operator creates a property that implements distribution in an extended form.

Syntax​

UNGROUP 
propertyId [BY groupExpr1, ..., groupExprM] 
distributionType exPropertyId [BY exGroupExpr1, ..., exGroupExprM]
[ORDER [DESC] orderExpr1, ..., orderExprK]
[WHERE whereExpr]

where distributionType can be described in several ways:

PROPORTION [STRICT] ROUND(digits)
LIMIT [STRICT]

Description​

The UNGROUP operator creates a property that distributes a certain value among object collections of the same group on a "many-to-many" basis.

The first block, BY, describes groups that the set of object collections will be broken into. If the BY block is not specified, all object collections are considered to belong to the same group.

The second BY block describes additional groups that the result will be grouped by for checking constraints / calculating proportions. If the second block BY is not specified, all object collections are considered to belong to the same group.

The ORDER block defines the order in which distribution will be done. The defined order must be uniquely determined.

The WHERE block defines a condition under which an object collection will participate in distribution operation.

Parameters​

  • propertyId

    ID of the distributed property. The value of this property must be numeric, and the number of parameters must be equal to the number of groups in the BY block. When calculating the values of group/partition expressions will be passed to this property as an input.

  • groupExpr1, ..., groupExprM

    List of group expressions.

  • distributionType

    Distribution type. These are of the following types:

    • PROPORTION

      Keyword specifying the use of proportional distribution. In this case, the value of the distributed property for a particular group is distributed proportionally among the object collections belonging to the group. The proportion is defined by the expr expression that is specified after the distribution type.

      • STRICT

        When this keyword is specified, the value of the distributed property must be exactly (without a remainder) distributed between the object collections belonging to the group. If after distribution there is a remainder (which may also be negative), it is added to the first object collection in accordance with the order defined in the ORDER block.

      • ROUND(digits)

        Specifies the number of decimal places the value will be rounded to.

    • LIMIT

      A keyword specifying the use of distribution with specified limits. In this case, the value of the distributed property is initially set for the first object collection. If the limit is exceeded for this set, the limit is set for the first object collection, and the rest of the value of the distributed property is assigned to the second set of objects. It is then checked for exceeding the limit for the second object collection, and so on. The limit is defined by the expr expression specified after specifying of the distribution type.

      • STRICT

        When this keyword is specified, the value of the distributed property must be exactly (without a remainder) distributed between the object collections belonging to the group. If after distribution there is a remainder, it is added to the last object collection in accordance with the order specified in the ORDER block.

  • exPropertyId

    ID of the property that defines a proportion for PROPORTION type distributions, and defines limits for LIMIT type distributions. The value of this property must be numeric, and the number of parameters must be equal to the number of groups in the BY block.

  • exGroupExpr1, ..., exGroupExprM

    List of additional group expressions.

  • DESC

    Keyword. Specifies a reverse iterate order for object collections.

  • orderExpr1, ..., orderExprK

    A list of expressions that determine the order in which object collections will be iterated when calculating the aggregate function or during distribution. To determine the order, first the value of the first expression is used; then, if equal, the value of the second one is used, etc.

  • whereExpr

    Filtering expression. Only object groups for which the value of the filtering expression is not NULL will participate in the grouping.

Examples​