Package com.netrics.likeit

Class NetricsCompoundReader

java.lang.Object

com.netrics.likeit.NetricsCompoundReader

All Implemented Interfaces:

NetricsBaseRecSrc, NetricsCompoundRecSrc

public class NetricsCompoundReader
extends java.lang.Object
implements NetricsCompoundRecSrc

Read compound records from a set of record sources.

Objects of this class provide a means of reading in compound records. A compound record is a parent record along with a set of zero or more child records. It may also be an orphan child record. This class builds compound records from a set of record sources. One source represents the parent table, zero or more additional sources represent the child tables. Each source is associated with a table name, all table names must be unique.

To build compound records it is assumed that all sources are sorted by the parent record key. The child record sources are not sorted by their own key, they must be sorted by the parent record key. In this way the sources can be read in parallel and merged.

Constructor Summary

Constructors

Constructor	Description
NetricsCompoundReader(java.lang.String parent_tbl_name, NetricsRecSrc parent_recs, boolean return_orphans)	Create a compound record reader.

Method Summary

Modifier and Type	Method	Description
void	addChildTable(java.lang.String child_tbl_name, NetricsRecSrc child_recs)	add a new child table to this compound record reader.
java.util.List<java.lang.String>	getChildTables()	return a list of child table names used.
java.lang.Integer	getCount()	Get the count of records that have been retrieved from the record source.
NetricsCompoundRecord	getNext()	return the next record.
java.lang.String	getParentTable()
int	getPosition()	Deprecated. Use getCount()
boolean	hasNext()	Implement the hasNext method.
void	reset()	Implement the reset method.

Methods inherited from class java.lang.Object

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

Constructor Detail

NetricsCompoundReader

public NetricsCompoundReader(java.lang.String parent_tbl_name,
                             NetricsRecSrc parent_recs,
                             boolean return_orphans)
                      throws java.lang.IllegalArgumentException,
                             NetricsRecSrcException

Create a compound record reader. This creates a compound record reader. It is created with a single parent table. Child tables must be added using the addChildTable method.

Parameters:

parent_tbl_name - the name of the parent table.

parent_recs - a record source that provides parent records. The records MUST be provided in sort order of the record keys.

return_orphans - if this is true orphan child records are returned as a NetricsCompoundRecord with no children. If this is false orphan child records are quietly skipped.

Throws:

java.lang.IllegalArgumentException - if any argument is null or the parent table name is empty (zero length).

NetricsRecSrcException - if there is an error reading the first parent record.

Method Detail

addChildTable

public void addChildTable(java.lang.String child_tbl_name,
                          NetricsRecSrc child_recs)
                   throws java.lang.IllegalArgumentException,
                          NetricsRecSrcException

add a new child table to this compound record reader. This is used to add a child table to this compound record reader. This call should be made before any records are read, but this is not enforced.

Parameters:

child_tbl_name - the name of the child table. This must not be the same as the name of the parent table or any existing child table.

child_recs - this is the source of child records. The records returned by this source should be child records. The records must be returned in sort order of the parent key.

Throws:

java.lang.IllegalArgumentException - if either argument is null, the table name is zero length, the table name is the same as the parent table or an existing child table.

NetricsRecSrcException - if there is an error reading the first record.

getNext

public NetricsCompoundRecord getNext()
                              throws NetricsRecSrcException

return the next record.

Specified by:

getNext in interface NetricsBaseRecSrc

Specified by:

getNext in interface NetricsCompoundRecSrc

Returns:

the next record, null if no more records.

Throws:

NetricsRecSrcException - if there is an error on any of the underlying readers when reading the next record.

hasNext

public boolean hasNext()
                throws NetricsRecSrcException

Implement the hasNext method.

Specified by:

hasNext in interface NetricsBaseRecSrc

Returns:

True if there is another record, false otherwise

Throws:

NetricsRecSrcException - if an error occurs.

reset

public void reset()
           throws NetricsRecSrcException

Implement the reset method.

Specified by:

reset in interface NetricsBaseRecSrc

Throws:

NetricsRecSrcException - if an error occurs, or if the record source does not support resetting.

getPosition

@Deprecated
public int getPosition()

Deprecated.

Use getCount()

Returns:

an indicator of the current position in the scan.

getCount

public java.lang.Integer getCount()

Description copied from interface: NetricsBaseRecSrc

Get the count of records that have been retrieved from the record source.
Sources that don't support a count will return null.

Specified by:

getCount in interface NetricsBaseRecSrc

Returns:

The number of records that have been retrieved from the record source.

getParentTable

public java.lang.String getParentTable()

Specified by:

getParentTable in interface NetricsCompoundRecSrc

Returns:

the parent/primary table name for the compound record.

getChildTables

public java.util.List<java.lang.String> getChildTables()

Description copied from interface: NetricsCompoundRecSrc

return a list of child table names used. This list represents all possible child tables. Any particular compound record returned may not contain child records for all of these tables.

Specified by:

getChildTables in interface NetricsCompoundRecSrc

Returns:

the list of child table names.