Class ConcatRowsAndColumns
- java.lang.Object
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- org.apache.druid.query.rowsandcols.ConcatRowsAndColumns
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- All Implemented Interfaces:
RowsAndColumns
public class ConcatRowsAndColumns extends Object implements RowsAndColumns
A RowsAndColumns implementation that effectively concatenates multiple RowsAndColumns objects together.That is, if it is given 3 RowsAndColumns objects, of sizes 4, 2, and 3 respectively, the resulting RowsAndColumns object will have 9 rows where rows 0-to-3 will be from the first object, 4-to-5 from the next and 6-to-8 from the last.
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Constructor Summary
Constructors Constructor Description ConcatRowsAndColumns(ArrayList<RowsAndColumns> racBuffer)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description <T> T
as(Class<T> clazz)
Asks the RowsAndColumns to return itself as a concrete implementation of a specific interface.Column
findColumn(String name)
Finds a column by name.Collection<String>
getColumnNames()
The set of column names available from the RowsAndColumnsint
numRows()
The number of rows in the RowsAndColumns object
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Constructor Detail
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ConcatRowsAndColumns
public ConcatRowsAndColumns(ArrayList<RowsAndColumns> racBuffer)
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Method Detail
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getColumnNames
public Collection<String> getColumnNames()
Description copied from interface:RowsAndColumns
The set of column names available from the RowsAndColumns- Specified by:
getColumnNames
in interfaceRowsAndColumns
- Returns:
- The set of column names available from the RowsAndColumns
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numRows
public int numRows()
Description copied from interface:RowsAndColumns
The number of rows in the RowsAndColumns object- Specified by:
numRows
in interfaceRowsAndColumns
- Returns:
- the integer number of rows
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findColumn
@Nullable public Column findColumn(String name)
Description copied from interface:RowsAndColumns
Finds a column by name. null is returned if the column is not found. The RowsAndColumns object should not attempt to default not-found columns to pretend as if they exist, instead the user of the RowsAndColumns object should decide the correct semantic interpretation of a column that does not exist. It is expected that most locations will choose to believe that the column does exist and is always null, but there are often optimizations that can effect this same assumption without doing a lot of extra work if the calling code knows that it does not exist.- Specified by:
findColumn
in interfaceRowsAndColumns
- Parameters:
name
- the name of the column to find- Returns:
- the Column, if found. null if not found.
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as
@Nullable public <T> T as(Class<T> clazz)
Description copied from interface:RowsAndColumns
Asks the RowsAndColumns to return itself as a concrete implementation of a specific interface. The interface asked for will tend to be a semantically-meaningful interface. This method allows the calling code to interrogate the RowsAndColumns object about whether it can offer a meaningful optimization of the semantic interface. If a RowsAndColumns cannot do anything specifically optimal for the interface requested, it should return null instead of trying to come up with its own default implementation.- Specified by:
as
in interfaceRowsAndColumns
- Type Parameters:
T
- The interface that the calling code wants a concrete implementation of- Parameters:
clazz
- A class object representing the interface that the calling code wants a concrete implementation of- Returns:
- A concrete implementation of the interface, or null if there is no meaningful optimization to be had through a local implementation of the interface.
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