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QUERY


Revision as of 11:39, 24 March 2015 by KNO (Talk | contribs) (Content query)

IC METACLASS.gif Query
Name QUERY
Namespace System.Query
Internal Name SystemObjects.QUERY
TypeString UBIK.Kernel.MetaClass
RuntimeType UBIK.Kernel.Query
Purpose Configure queries
Version 2+

In UBIK, queries are used for fetching a list of ContentClasses from the database. Queries use data base mechanism for perfomant data access and will deliver a list of objects of a certain Metaclass. Queries can be used in different scenarios:

  • data fetching (n records)
  • finding a single or a set of recordset(s)
  • used as definition of root nodes in a View
IC Hint square.pngThere are specific methods available for this type!

Query and QueryItems

A Query is defined for a single MetaClass, where the MetaClass is defined in the property FILTEROBJECT. Once a query is evaluated it will deliver a list of objects of type ContentClasses (instances), filtered as defined by its QueryItems. The correspondence between Queries and its items is created and stored by a relationship SYSREL QUERY. Therefore a single QueryItem can be used several times for different Queries.

Content query

Objects can be loaded on demand from the server, as storing a huge amount of data permanently on the device would need too much resources.

A content query needs to be

  • an QUERY instance classified as SYSCLS QUERY
  • related either to other content objects (to show up somewhere in the view hierarchy) or placed as root object of a View
  • described by a Query Scopes in the ACM

Further it is nessary to

  • create a HowTo:Create_a_new_ViewItem for the query object itself
  • Set filter object (FILTEROBJECT) similar as for other query
  • Create a proper relation
  • Create a query view item and set the instance as QUERY
  • Create a relation view item and set the according default MetaClass and relation
  • Create and relate a query context scope and set the instance as QUERY
  • For the scope define the MetaProperties, which should be available as filter criteria on the client. Without appropriate query item, equality is used as filter operator (=)
  1. Once the scan is finished, wait until the scanner is closed and an empty browser shows up;
  2. Depending on the network connection and the UBIK® sync mode, different ways of searching will be applied;
  3. During the search, the list might show a searching text before any objects are found;
    Searching for Objects
  4. If any objects are found, they will be added to the list.
    Displaying Objects

Scan query

Usage of DatabaseViews

It is also possible to define a Database View and use this View for the evaluation of Queries (see VirtualContentClass).

See also