BPS80

Result Set Sharing

This project aims to enable multiple BIRT report items to share the same data binding definition and result set.

Specification Leads

Gary Xue, Actuate Corp.

Rima Kanguri, Actuate Corp.

Revision History

2007-4-11 [Gary Xue]: Initial draft

Introduction

This feature enables multiple report items in a BIRT report to share a single result set. A result set is the runtime data calculated based on a set of data binding definitions, which include:

• A data set (for tabular result set) or a cube (for cross-tab result set) as the source of data

• Grouping definition (tabular result set only)

• Calculations and aggregations based on data set/cube data

• Filters

• Sorts

Sharing of result sets permits two or more report items to present different views of the same data, without constraints on the physical placements of these elements. This contrasts with subqueries, which achieves the same effect to a lesser extent, but requires physical containment relationship of related report elements. Result set sharing also permits changes made to the data definition of one report elements to be reflected in other elements sharing the same data. For example, a filter added to a table will also apply to a chart that shares the table’s result set.

Overview of Changes

1. Filter, sort and group definition in Model will be consolidated into a Data Binding Definition structure. All data-enabled report items (including extended items) will contain this structure.
2. A report item can reference another report item’s data bindings in lieu of defining its own, thus enabling sharing of the other item’s result set.
3. Current model’s Group Definition (which only applies to listing items) will be split into two parts: the data group definition (part of Data Binding Definition), and group layout definition (applies to listing items).

Model and Design Engine API Changes

New structure DataGroup

This structure contains properties in the existing ListingGroup element which defines the data aspects of a group.

Property Name	Type	Description
keyExpr	Expression	Group key expression
sort	SortKey	Group sort condition
filter	FilterCondition	Group filter
groupName	String	Name of group
intervelBase	String	Group interval base value
interval	interval	Group interval type
intervalRange	float	Ranged-based interval range value
sortDirection	sortDirection	Simple sort direction
sortType	sortType	complex sort type

Changes to ListingGroup

The ListingGroup element will deprecate all properties that have been moved to DataGroup, except for the groupName property. groupName is the key that associated a ListingGroup element with the corresponding DataGroup element in the DataBinding structure (see below).

When a deprecated property is accessed in ListingGroup, DE will look up the corresponding DataGroup in the DataBinding structure associated with the listing item (by matching their groupName), and read/write that property instead.

New structure DataBinding

This structure defines the data binding definition of a report item that can access data.

Property Name	Type	Description
dataSet	elementRef	Reference to a data set; for tabular items
cube	elementRef	Reference to a cube; for x-tab items
paramBindings	ParamBinding	Data set/cube parameter binding
boundColumns	List of ComputedColumn	Result set bound column list
sort	SortKey	Group sort condition for result set
groups	List of DataGroup	Data group definition for result set
filter	List of FilterCondition	Filter definition for result set

Changes to ReportItem and its subclasses

The following new properties will be added to ReportItem:

Property Name	Type	Description
dataBinding	DataBinding	Report item’s own data binding definition
dataBindingRef	elementRef	Reference to another report item. This report item will use the referenced item’s data binding definition. If dataBindingRef is set, dataBinding property must be empty.

Properties in ReportItem and its derived elements (such as ListingItem) that have been moved to Databinding will be deprecated.

Engine and Data Engine API Changes

Data Engine API: the IQueryResults and ICubeQueryResults interfaces will introduce new methods to obtain a new iterator for the current query result. This will enable Engine to operate multiple concurrent cursors on the same (shared) result set.

Engine changes: Engine will call DTE API to prepare and execute each shared DataBinding only once. It will request a new iterator on the same query result for each report item that uses the shared binding.

Designer UI Changes

Designer needs to introduce the following features (details TBD):

1. Allow a report item to refer to another report item in its data binding definition
2. Warn the user that any edits to shared bindings will affect multiple report items
3. Allow un-sharing of bindings (in which case the shared bindings will be copied to the referring report item).