ColumnSelectorFactory (druid-processing 28.0.0 API)

All Superinterfaces:

ColumnInspector, Expr.InputBindingInspector

All Known Implementing Classes:

AllNullColumnSelectorFactory, DefaultColumnSelectorFactoryMaker.ColumnAccessorBasedColumnSelectorFactory, FrameColumnSelectorFactory, IndexedTableColumnSelectorFactory, LookupColumnSelectorFactory, MultiColumnSelectorFactory, QueryableIndexColumnSelectorFactory, RowBasedColumnSelectorFactory, VirtualizedColumnSelectorFactory
```
public interface ColumnSelectorFactory
extends ColumnInspector
```
Factory class for MetricSelectors

Method Summary

All Methods Instance Methods Abstract Methods Default Methods
Modifier and Type	Method	Description
`ColumnCapabilities`	`getColumnCapabilities(String column)`	Returns capabilities of a particular column, if known.
`default RowIdSupplier`	`getRowIdSupplier()`	Returns a `RowIdSupplier` that allows callers to detect whether the selectors returned by this factory have moved or not.
`ColumnValueSelector`	`makeColumnValueSelector(String columnName)`	Returns ColumnValueSelector corresponding to the given column name, or `NilColumnValueSelector` if the column with such name is absent.
`DimensionSelector`	`makeDimensionSelector(DimensionSpec dimensionSpec)`

Methods inherited from interface org.apache.druid.segment.ColumnInspector
getColumnCapabilitiesWithDefault, getType

Methods inherited from interface org.apache.druid.math.expr.Expr.InputBindingInspector
areNumeric, areNumeric, areSameTypes, areSameTypes, areScalar, areScalar, canVectorize, canVectorize

- Method Detail
  - makeDimensionSelector
```
DimensionSelector makeDimensionSelector(DimensionSpec dimensionSpec)
```
  - makeColumnValueSelector
```
ColumnValueSelector makeColumnValueSelector(String columnName)
```
    Returns ColumnValueSelector corresponding to the given column name, or NilColumnValueSelector if the column with such name is absent.
  - getColumnCapabilities
```
@Nullable
ColumnCapabilities getColumnCapabilities(String column)
```
    Returns capabilities of a particular column, if known. May be null if the column doesn't exist, or if the column does exist but the capabilities are unknown. The latter is possible with dynamically discovered columns.
    
    Specified by:
    
    getColumnCapabilities in interface ColumnInspector
    
    Parameters:
    
    column - column name
    
    Returns:
    
    capabilities, or null
  - getRowIdSupplier
```
@Nullable
default RowIdSupplier getRowIdSupplier()
```
    Returns a RowIdSupplier that allows callers to detect whether the selectors returned by this factory have moved or not. Useful for selectors that wrap other selectors, such as virtual columns, as it allows them to cache their outputs.