Package org.apache.druid.segment
Class NestedDataColumnMergerV4
- java.lang.Object
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- org.apache.druid.segment.NestedDataColumnMergerV4
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- All Implemented Interfaces:
DimensionMerger
,DimensionMergerV9
public class NestedDataColumnMergerV4 extends Object implements DimensionMergerV9
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Field Summary
Fields Modifier and Type Field 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
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Constructor Summary
Constructors Constructor Description NestedDataColumnMergerV4(String name, IndexSpec indexSpec, SegmentWriteOutMedium segmentWriteOutMedium, Closer closer)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description ColumnValueSelector
convertSortedSegmentRowValuesToMergedRowValues(int segmentIndex, ColumnValueSelector source)
Creates a value selector, which converts values with per-segment, _sorted order_ (seeDimensionIndexer.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.
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Field Detail
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STRING_MERGING_COMPARATOR
public static final Comparator<com.google.common.collect.PeekingIterator<String>> STRING_MERGING_COMPARATOR
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LONG_MERGING_COMPARATOR
public static final Comparator<com.google.common.collect.PeekingIterator<Long>> LONG_MERGING_COMPARATOR
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DOUBLE_MERGING_COMPARATOR
public static final Comparator<com.google.common.collect.PeekingIterator<Double>> DOUBLE_MERGING_COMPARATOR
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Constructor Detail
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NestedDataColumnMergerV4
public NestedDataColumnMergerV4(String name, IndexSpec indexSpec, SegmentWriteOutMedium segmentWriteOutMedium, Closer closer)
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Method Detail
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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. seeIncrementalIndexAdapter.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 inDimensionMerger.convertSortedSegmentRowValuesToMergedRowValues(int, org.apache.druid.segment.ColumnValueSelector)
.- Specified by:
writeMergedValueDictionary
in interfaceDimensionMerger
- Parameters:
adapters
- List of adapters to be merged.- Throws:
IOException
- See Also:
DimensionIndexer.convertUnsortedValuesToSorted(org.apache.druid.segment.ColumnValueSelector)
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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_ (seeDimensionIndexer.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 duringDimensionMerger.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 duringDimensionMerger.writeMergedValueDictionary(List)
.- Specified by:
convertSortedSegmentRowValuesToMergedRowValues
in interfaceDimensionMerger
- Parameters:
segmentIndex
- indicates which segment the row originated from, in the order established inDimensionMerger.writeMergedValueDictionary(List)
source
- the selector from which to take values to convert- Returns:
- a selector with converted values
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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 interfaceDimensionMerger
- Throws:
IOException
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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 iteratedDimensionMerger.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 ofDimensionMerger.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 interfaceDimensionMerger
- Parameters:
segmentRowNumConversions
- A list of row number conversion IntBuffer objects.
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hasOnlyNulls
public boolean hasOnlyNulls()
Description copied from interface:DimensionMerger
Returns true if this dimension has no data besides nulls. SeeNullColumnPartSerde
for how null-only columns are stored in the segment.- Specified by:
hasOnlyNulls
in interfaceDimensionMerger
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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 interfaceDimensionMergerV9
- Returns:
- ColumnDescriptor that IndexMergerV9 will use to build a column.
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