Eclipse BIRT Report Object Model (ROM)

DataSet Element

# Element Overview

Parent of simple data set and joint data set.

### Details

Display Name: | Data Set
Since: | 2.1
XML Element: | `None`
Extends: | ReportElement
Extendable: | No
Abstract: | Yes
Name Space: | Data Sets
Name Requirement: | Required
Allows User Properties: | Yes
Has Style: | No

### Property Summary

cachedMetaData
  Cached derived data attributes of a data set.
columnHints
  Defines the report-related data attributes of the result set�s columns.
computedColumns
  User-defined columns in the result set.
filter
  An optional set of filters to apply to the result set before any other data transforms.
needsCache
parameters
resultSetHints
rowFetchLimit

### Inherited Properties

comments, customXml, displayName, displayNameID, eventHandlerClass, extends, name, newHandlerOnEachEvent, propertyMasks, userProperties, viewAction

### Description

# Property Detail

## cachedMetaData Property

Cached derived data attributes of a data set.

### Details

Type: | CachedMetaData Structure
Since: | 1.0
Required: | No
Display Name: | Cached metadata
JavaScript Type: |
Default Value: | None
Inherited: | Yes
Runtime Settable: | Yes
Property Sheet Visibility: | Hidden
Property Sheet Group: | Top

### Description

Defines the cached derived data attributes of a data set. The BIRT designer uses the cached information until the user initiates refresh and reconciles with the latest derived data attributes provided by the connected data source. This property is used during report design time only; its content is maintained by the BIRT designer tool.

### See Also

`CachedMetaData structure`

## columnHints Property

Defines the report-related data attributes of the result set�s columns.

### Details

Type: | List of ColumnHint Structures
Since: | 1.0
Required: | No
Display Name: | Column hints
JavaScript Type: |
Default Value: | None
Inherited: | Yes
Runtime Settable: | Yes
Property Sheet Visibility: | Hidden
Property Sheet Group: | Top

### Description

In BIRT, a result set column can be defined with an alias. Aliases are useful in cases where a column name is awkward, or is used by multiple columns in a result set.

BIRT reports provide a rich viewing experience. The user can search the report, extract data to a file, export data to an OLAP system, and more. Such operations work on the actual data set�s result set instead of on the presentation of the data. Column hints let the report developer customize the search and data extract experience.

The column hint element provides a number of "hints" about result set columns. The hints override BIRT defaults for how columns are handled during viewing. Hints can be provided for both retrieved and computed columns.

Column hints are keyed to the data set�s primary result set using names. The user must understand how to keep the hints in sync with the data set when either the data set definition, or underlying data source, changes.

BIRT uses the column hints in the following cases:

- The report references a column using the alias defined in the column hint.
- The report references a column (retrieved or computed) that is also referenced by the column hint.
- The column hint has the Export attribute set to "always".

In each case, BIRT checks whether the data set provides the requested column. If so, it continues processing the report. If not, it issues a fatal runtime error.

### See Also

`ColumnHint structure`

## computedColumns Property

User-defined columns in the result set.

### Details

Type: | List of ComputedColumn Structures
Since: | 1.0
Required: | No
Display Name: | Computed columns
JavaScript Type: |
Default Value: | None
Inherited: | Yes
Runtime Settable: | Yes
Property Sheet Visibility: | Hidden
Property Sheet Group: | Top

### Description

A computed column is a user-defined column produced as an expression of other columns within the data set�s primary result set. It is not of the columns retrieved directly from the underlying data provider.

### See Also

`ComputedColumn structure`

## filter Property

An optional set of filters to apply to the result set before any other data transforms.

### Details

Type: | List of FilterCondition Structures
Since: | 1.0
Required: | No
Display Name: | Filter
JavaScript Type: |
Default Value: | None
Inherited: | Yes
Runtime Settable: | No
Property Sheet Visibility: | Hidden
Property Sheet Group: | Top

### Description

An optional set of filters that apply to the data set�s primary result set. A data set�s filter is applied to each row of the retrieved result set before any other data transforms. The filter expression should thus not contain any aggregation functions. It usually references at least one column from a data row, and may also reference a report parameter or other scripting variable.

### See Also

`Filter Criteria structure`

Listing `filter` property

ListingGroup `filter` property

## needsCache Property

### Details

Type: | boolean
Since: | 2.3
Required: | No
Display Name: | Needs cache for data-engine
JavaScript Type: |
Default Value: | false
Inherited: | Yes
Runtime Settable: | No
Property Sheet Visibility: | Visible
Property Sheet Group: | Top

## parameters Property

### Details

Type: | List of DataSetParam Structures
Since: | 1.0
Required: | No
Display Name: | Data set parameters
JavaScript Type: |
Default Value: | None
Inherited: | Yes
Runtime Settable: | Yes
Property Sheet Visibility: | Hidden
Property Sheet Group: | Top

## resultSetHints Property

### Details

Type: | List of ResultSetColumn Structures
Since: | 2.1
Required: | No
Display Name: | Result set hints
JavaScript Type: |
Default Value: | None
Inherited: | Yes
Runtime Settable: | Yes
Property Sheet Visibility: | Hidden
Property Sheet Group: | Top

## rowFetchLimit Property

### Details

Type: | integer
Since: | 2.2
Required: | No
Display Name: | Max number of rows to fetch from data set
JavaScript Type: |
Default Value: | None
Inherited: | Yes
Runtime Settable: | Yes
Property Sheet Visibility: | Visible
Property Sheet Group: | Top