Class CardinalityCounter
- java.lang.Object
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- org.apache.derby.impl.sql.execute.CardinalityCounter
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- All Implemented Interfaces:
RowLocationRetRowSource
,RowSource
class CardinalityCounter extends java.lang.Object implements RowLocationRetRowSource
This is a decorator (in Design Patterns Terminology) class to enhance the functionality of a RowLocationRetRowSource. It assumes that the rows are coming in sorted order from the row source and it simply keeps track of the cardinality of all the leading columns.
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Field Summary
Fields Modifier and Type Field Description private long[]
cardinality
private long
numRows
private DataValueDescriptor[]
prevKey
private RowLocationRetRowSource
rowSource
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Constructor Summary
Constructors Constructor Description CardinalityCounter(RowLocationRetRowSource rowSource)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description private DataValueDescriptor[]
clone(DataValueDescriptor[] clonee)
void
closeRowSource()
closeRowSource tells the RowSource that it will no longer need to return any rows and it can release any resource it may have.long[]
getCardinality()
return the array of cardinalities that are kept internally.DataValueDescriptor[]
getNextRowFromRowSource()
Gets next row from the row source and update the count of unique values that are returned.long
getRowCount()
get the number of rows seen in the row source thus far.FormatableBitSet
getValidColumns()
getValidColumns describes the DataValueDescriptor[] returned by all calls to the getNextRowFromRowSource() call.void
keepCount(DataValueDescriptor[] currentKey)
boolean
needsRowLocation()
needsRowLocation returns true iff this the row source expects the drainer of the row source to call rowLocation after getting a row from getNextRowFromRowSource.boolean
needsRowLocationForDeferredCheckConstraints()
boolean
needsToClone()
Does the caller of getNextRowFromRowSource() need to clone the row in order to keep a reference to the row past the getNextRowFromRowSource() call which returned the row.void
offendingRowLocation(RowLocation rl, long containdId)
void
rowLocation(RowLocation rl)
rowLocation is a callback for the drainer of the row source to return the rowLocation of the current row, i.e, the row that is being returned by getNextRowFromRowSource.
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Field Detail
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rowSource
private RowLocationRetRowSource rowSource
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prevKey
private DataValueDescriptor[] prevKey
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cardinality
private long[] cardinality
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numRows
private long numRows
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Constructor Detail
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CardinalityCounter
public CardinalityCounter(RowLocationRetRowSource rowSource)
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Method Detail
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needsRowLocation
public boolean needsRowLocation()
Description copied from interface:RowLocationRetRowSource
needsRowLocation returns true iff this the row source expects the drainer of the row source to call rowLocation after getting a row from getNextRowFromRowSource.- Specified by:
needsRowLocation
in interfaceRowLocationRetRowSource
- Returns:
- true iff this row source expects some row location to be returned
- See Also:
RowLocationRetRowSource.needsRowLocation()
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needsRowLocationForDeferredCheckConstraints
public boolean needsRowLocationForDeferredCheckConstraints()
- Specified by:
needsRowLocationForDeferredCheckConstraints
in interfaceRowLocationRetRowSource
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offendingRowLocation
public void offendingRowLocation(RowLocation rl, long containdId) throws StandardException
- Specified by:
offendingRowLocation
in interfaceRowLocationRetRowSource
- Throws:
StandardException
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rowLocation
public void rowLocation(RowLocation rl) throws StandardException
Description copied from interface:RowLocationRetRowSource
rowLocation is a callback for the drainer of the row source to return the rowLocation of the current row, i.e, the row that is being returned by getNextRowFromRowSource. This interface is for the purpose of loading a base table with index. In that case, the indices can be built at the same time the base table is laid down once the row location of the base row is known. This is an example pseudo code on how this call is expected to be used:boolean needsRL = rowSource.needsRowLocation(); DataValueDescriptor[] row; while((row = rowSource.getNextRowFromRowSource()) != null) { RowLocation rl = heapConglomerate.insertRow(row); if (needsRL) rowSource.rowLocation(rl); }
NeedsRowLocation and rowLocation will ONLY be called by a drainer of the row source which CAN return a row location. Drainer of row source which cannot return rowLocation will guarantee to not call either callbacks. Conversely, if NeedsRowLocation is called and it returns true, then for every row return by getNextRowFromRowSource, a rowLocation callback must also be issued with the row location of the row. Implementor of both the source and the drain of the row source must be aware of this protocol.
The RowLocation object is own by the caller of rowLocation, in other words, the drainer of the RowSource. This is so that we don't need to new a row location for every row. If the Row Source wants to keep the row location, it needs to clone it (RowLocation is a ClonableObject).- Specified by:
rowLocation
in interfaceRowLocationRetRowSource
- Throws:
StandardException
- on error- See Also:
RowLocationRetRowSource.rowLocation(org.apache.derby.iapi.types.RowLocation)
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getNextRowFromRowSource
public DataValueDescriptor[] getNextRowFromRowSource() throws StandardException
Gets next row from the row source and update the count of unique values that are returned.- Specified by:
getNextRowFromRowSource
in interfaceRowSource
- Throws:
StandardException
- Standard Derby Error Policy- See Also:
RowSource.getNextRowFromRowSource()
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needsToClone
public boolean needsToClone()
Description copied from interface:RowSource
Does the caller of getNextRowFromRowSource() need to clone the row in order to keep a reference to the row past the getNextRowFromRowSource() call which returned the row. This call must always return the same for all rows in a RowSource (ie. the caller will call this once per scan from a RowSource and assume the behavior is true for all rows in the RowSource).- Specified by:
needsToClone
in interfaceRowSource
- See Also:
RowSource.needsToClone()
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getValidColumns
public FormatableBitSet getValidColumns()
Description copied from interface:RowSource
getValidColumns describes the DataValueDescriptor[] returned by all calls to the getNextRowFromRowSource() call. If getValidColumns returns null, the number of columns is given by the DataValueDescriptor.length where DataValueDescriptor[] is returned by the preceeding getNextRowFromRowSource() call. Column N maps to DataValueDescriptor[N], where column numbers start at zero. If getValidColumns return a non null validColumns FormatableBitSet the number of columns is given by the number of bits set in validColumns. Column N is not in the partial row if validColumns.get(N) returns false. Column N is in the partial row if validColumns.get(N) returns true. If column N is in the partial row then it maps to DataValueDescriptor[M] where M is the count of calls to validColumns.get(i) that return true where i < N. If DataValueDescriptor.length is greater than the number of columns indicated by validColumns the extra entries are ignored.- Specified by:
getValidColumns
in interfaceRowSource
- See Also:
RowSource.getValidColumns()
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closeRowSource
public void closeRowSource()
Description copied from interface:RowSource
closeRowSource tells the RowSource that it will no longer need to return any rows and it can release any resource it may have. Subsequent call to any method on the RowSource will result in undefined behavior. A closed rowSource can be closed again.- Specified by:
closeRowSource
in interfaceRowSource
- See Also:
RowSource.closeRowSource()
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clone
private DataValueDescriptor[] clone(DataValueDescriptor[] clonee)
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keepCount
public void keepCount(DataValueDescriptor[] currentKey) throws StandardException
- Throws:
StandardException
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getCardinality
public long[] getCardinality()
return the array of cardinalities that are kept internally. One value for each leading key; i.e c1, (c1,c2), (c1,c2,c3) etc.- Returns:
- an array of unique values.
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getRowCount
public long getRowCount()
get the number of rows seen in the row source thus far.- Returns:
- total rows seen from the row source.
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