org.apache.druid.segment

Class NestedDataColumnMerger

java.lang.Object

org.apache.druid.segment.NestedDataColumnMerger

All Implemented Interfaces:

DimensionMerger, DimensionMergerV9

public class NestedDataColumnMerger
extends Object
implements DimensionMergerV9

Field Summary

Fields

Modifier and Type	Field and Description
static Comparator<com.google.common.collect.PeekingIterator<Double>>	DOUBLE_MERGING_COMPARATOR
static Comparator<com.google.common.collect.PeekingIterator<Long>>	LONG_MERGING_COMPARATOR
static Comparator<com.google.common.collect.PeekingIterator<String>>	STRING_MERGING_COMPARATOR

Constructor Summary

Constructors

Constructor and Description
NestedDataColumnMerger(String name, IndexSpec indexSpec, SegmentWriteOutMedium segmentWriteOutMedium, Closer closer)

Method Summary

Modifier and Type	Method and Description
ColumnValueSelector	convertSortedSegmentRowValuesToMergedRowValues(int segmentIndex, ColumnValueSelector source) Creates a value selector, which converts values with per-segment, _sorted order_ (see DimensionIndexer.convertUnsortedValuesToSorted(org.apache.druid.segment.ColumnValueSelector)) encoding from the given selector to their equivalent representation in the merged set of rows.
boolean	hasOnlyNulls() Returns true if this dimension has no data besides nulls.
ColumnDescriptor	makeColumnDescriptor() Return a ColumnDescriptor containing ColumnPartSerde objects appropriate for this DimensionMerger's value metadata, sequence of row values, and index structures.
void	processMergedRow(ColumnValueSelector selector) Process a column value(s) (potentially multi-value) of a row from the given selector and update the DimensionMerger's internal state.
void	writeIndexes(List<IntBuffer> segmentRowNumConversions) Internally construct any index structures relevant to this DimensionMerger.
void	writeMergedValueDictionary(List<IndexableAdapter> adapters) Given a list of segment adapters: - Read _sorted order_ (e.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

STRING_MERGING_COMPARATOR

public static final Comparator<com.google.common.collect.PeekingIterator<String>> STRING_MERGING_COMPARATOR

LONG_MERGING_COMPARATOR

public static final Comparator<com.google.common.collect.PeekingIterator<Long>> LONG_MERGING_COMPARATOR

DOUBLE_MERGING_COMPARATOR

public static final Comparator<com.google.common.collect.PeekingIterator<Double>> DOUBLE_MERGING_COMPARATOR

Constructor Detail

NestedDataColumnMerger

public NestedDataColumnMerger(String name,
                              IndexSpec indexSpec,
                              SegmentWriteOutMedium segmentWriteOutMedium,
                              Closer closer)

Method Detail

writeMergedValueDictionary

public void writeMergedValueDictionary(List<IndexableAdapter> adapters)
                                throws IOException

Description copied from interface: DimensionMerger

Given a list of segment adapters: - Read _sorted order_ (e. g. see IncrementalIndexAdapter.getDimValueLookup(String)) dictionary encoding information from the adapters - Merge those sorted order dictionary into a one big sorted order dictionary and write this merged dictionary. The implementer should maintain knowledge of the "index number" of the adapters in the input list, i.e., the position of each adapter in the input list. This "index number" will be used to refer to specific segments later in DimensionMerger.convertSortedSegmentRowValuesToMergedRowValues(int, org.apache.druid.segment.ColumnValueSelector).

Specified by:

writeMergedValueDictionary in interface DimensionMerger

Parameters:

adapters - List of adapters to be merged.

Throws:

IOException

See Also:

DimensionIndexer.convertUnsortedValuesToSorted(org.apache.druid.segment.ColumnValueSelector)

convertSortedSegmentRowValuesToMergedRowValues

public ColumnValueSelector convertSortedSegmentRowValuesToMergedRowValues(int segmentIndex,
                                                                          ColumnValueSelector source)

Description copied from interface: DimensionMerger

Creates a value selector, which converts values with per-segment, _sorted order_ (see DimensionIndexer.convertUnsortedValuesToSorted(org.apache.druid.segment.ColumnValueSelector)) encoding from the given selector to their equivalent representation in the merged set of rows. This method is used by the index merging process to build the merged sequence of rows. The implementing class is expected to use the merged value metadata constructed during DimensionMerger.writeMergedValueDictionary(List), if applicable. For example, an implementation of this function for a dictionary-encoded String column would convert the segment-specific, sorted order dictionary values within the row to the common merged dictionary values determined during DimensionMerger.writeMergedValueDictionary(List).

Specified by:

convertSortedSegmentRowValuesToMergedRowValues in interface DimensionMerger

Parameters:

segmentIndex - indicates which segment the row originated from, in the order established in DimensionMerger.writeMergedValueDictionary(List)

source - the selector from which to take values to convert

Returns:

a selector with converted values

processMergedRow

public void processMergedRow(ColumnValueSelector selector)
                      throws IOException

Description copied from interface: DimensionMerger

Process a column value(s) (potentially multi-value) of a row from the given selector and update the DimensionMerger's internal state. After constructing a merged sequence of rows across segments, the index merging process will iterate through these rows and on each iteration, for each column, pass the column value selector to the corresponding DimensionMerger. This allows each DimensionMerger to build its internal view of the sequence of merged rows, to be written out to a segment later.

Specified by:

processMergedRow in interface DimensionMerger

Throws:

IOException

writeIndexes

public void writeIndexes(@Nullable
                         List<IntBuffer> segmentRowNumConversions)

Description copied from interface: DimensionMerger

Internally construct any index structures relevant to this DimensionMerger. After receiving the sequence of merged rows via iterated DimensionMerger.processMergedRow(org.apache.druid.segment.ColumnValueSelector) calls, the DimensionMerger can now build any index structures it needs. For example, a dictionary encoded String implementation would create its bitmap indexes for the merged segment during this step. The index merger will provide a list of row number conversion IntBuffer objects. Each IntBuffer is associated with one of the segments being merged; the position of the IntBuffer in the list corresponds to the position of segment adapters within the input list of DimensionMerger.writeMergedValueDictionary(List). For example, suppose there are two segments A and B. Row 24 from segment A maps to row 99 in the merged sequence of rows, The IntBuffer for segment A would have a mapping of 24 -> 99.

Specified by:

writeIndexes in interface DimensionMerger

Parameters:

segmentRowNumConversions - A list of row number conversion IntBuffer objects.

hasOnlyNulls

public boolean hasOnlyNulls()

Description copied from interface: DimensionMerger

Returns true if this dimension has no data besides nulls. See NullColumnPartSerde for how null-only columns are stored in the segment.

Specified by:

hasOnlyNulls in interface DimensionMerger

makeColumnDescriptor

public ColumnDescriptor makeColumnDescriptor()

Description copied from interface: DimensionMergerV9

Return a ColumnDescriptor containing ColumnPartSerde objects appropriate for this DimensionMerger's value metadata, sequence of row values, and index structures.

Specified by:

makeColumnDescriptor in interface DimensionMergerV9

Returns:

ColumnDescriptor that IndexMergerV9 will use to build a column.