Package org.apache.druid.segment

Interface VectorColumnProcessorFactory<T>

All Known Implementing Classes:

CardinalityVectorProcessorFactory, GroupByVectorColumnProcessorFactory, VectorValueMatcherColumnProcessorFactory

public interface VectorColumnProcessorFactory<T>

Class that encapsulates knowledge about how to create vector column processors. Used by ColumnProcessors.makeVectorProcessor(java.lang.String, org.apache.druid.segment.VectorColumnProcessorFactory<T>, org.apache.druid.segment.vector.VectorColumnSelectorFactory). Column processors can be any type "T". The idea is that a ColumnProcessorFactory embodies the logic for wrapping and processing selectors of various types, and so enables nice code design, where type-dependent code is not sprinkled throughout. Unlike ColumnProcessorFactory, this interface does not have a "defaultType" method, because vector column types are always known, so it isn't necessary.

See Also:

the non-vectorized version

Method Summary

Modifier and Type	Method	Description
T	makeArrayProcessor(ColumnCapabilities capabilities, VectorObjectSelector selector)	Called when TypeSignature.getType() is ARRAY.
T	makeDoubleProcessor(ColumnCapabilities capabilities, VectorValueSelector selector)	Called when TypeSignature.getType() is DOUBLE.
T	makeFloatProcessor(ColumnCapabilities capabilities, VectorValueSelector selector)	Called when TypeSignature.getType() is FLOAT.
T	makeLongProcessor(ColumnCapabilities capabilities, VectorValueSelector selector)	Called when TypeSignature.getType() is LONG.
T	makeMultiValueDimensionProcessor(ColumnCapabilities capabilities, MultiValueDimensionVectorSelector selector)	Called only if TypeSignature.getType() is STRING and the underlying column may have multiple values per row.
T	makeObjectProcessor(ColumnCapabilities capabilities, VectorObjectSelector selector)	Called when TypeSignature.getType() is COMPLEX.
T	makeSingleValueDimensionProcessor(ColumnCapabilities capabilities, SingleValueDimensionVectorSelector selector)	Called only if TypeSignature.getType() is STRING and the underlying column always has a single value per row.
default boolean	useDictionaryEncodedSelector(ColumnCapabilities capabilities)	The processor factory can influence the decision on whether or not to prefer a dictionary encoded column value selector over a an object selector by examining the ColumnCapabilities.

Method Detail

makeSingleValueDimensionProcessor

T makeSingleValueDimensionProcessor(ColumnCapabilities capabilities,
                                    SingleValueDimensionVectorSelector selector)

Called only if TypeSignature.getType() is STRING and the underlying column always has a single value per row. Note that for STRING-typed columns where the dictionary does not exist or is not expected to be useful, makeObjectProcessor(org.apache.druid.segment.column.ColumnCapabilities, org.apache.druid.segment.vector.VectorObjectSelector) may be called instead. To handle all string inputs properly, processors must implement all three methods (single-value, multi-value, object).

makeMultiValueDimensionProcessor

T makeMultiValueDimensionProcessor(ColumnCapabilities capabilities,
                                   MultiValueDimensionVectorSelector selector)

Called only if TypeSignature.getType() is STRING and the underlying column may have multiple values per row. Note that for STRING-typed columns where the dictionary does not exist or is not expected to be useful, makeObjectProcessor(org.apache.druid.segment.column.ColumnCapabilities, org.apache.druid.segment.vector.VectorObjectSelector) may be called instead. To handle all string inputs properly, processors must implement all three methods (single-value, multi-value, object).

makeFloatProcessor

T makeFloatProcessor(ColumnCapabilities capabilities,
                     VectorValueSelector selector)

Called when TypeSignature.getType() is FLOAT.

makeDoubleProcessor

T makeDoubleProcessor(ColumnCapabilities capabilities,
                      VectorValueSelector selector)

Called when TypeSignature.getType() is DOUBLE.

makeLongProcessor

T makeLongProcessor(ColumnCapabilities capabilities,
                    VectorValueSelector selector)

Called when TypeSignature.getType() is LONG.

makeArrayProcessor

T makeArrayProcessor(ColumnCapabilities capabilities,
                     VectorObjectSelector selector)

Called when TypeSignature.getType() is ARRAY.

makeObjectProcessor

T makeObjectProcessor(ColumnCapabilities capabilities,
                      VectorObjectSelector selector)

Called when TypeSignature.getType() is COMPLEX. May also be called for STRING typed columns in cases where the dictionary does not exist or is not expected to be useful.

See Also:

for details on what can appear here when type is STRING

useDictionaryEncodedSelector

default boolean useDictionaryEncodedSelector(ColumnCapabilities capabilities)

The processor factory can influence the decision on whether or not to prefer a dictionary encoded column value selector over a an object selector by examining the ColumnCapabilities. By default, all processor factories prefer to use a dictionary encoded selector if the column has a dictionary available (ColumnCapabilities.isDictionaryEncoded() is true), and there is a unique mapping of dictionary id to value (ColumnCapabilities.areDictionaryValuesUnique() is true), but this can be overridden if there is more appropriate behavior for a given processor. For processors, this means by default only actual dictionary encoded string columns (likely from real segments) will use SingleValueDimensionVectorSelector and MultiValueDimensionVectorSelector, while processors on things like string expression virtual columns will prefer to use VectorObjectSelector. In other words, it is geared towards use cases where there is a clear opportunity to benefit to deferring having to deal with the actual string value in exchange for the increased complexity of dealing with dictionary encoded selectors.