org.apache.cayenne.dba
Class JdbcPkGenerator

java.lang.Object
  extended by org.apache.cayenne.dba.JdbcPkGenerator
All Implemented Interfaces:
PkGenerator
Direct Known Subclasses:
DB2PkGenerator, DerbyPkGenerator, FrontBasePkGenerator, MySQLPkGenerator, OpenBasePkGenerator, OraclePkGenerator, SybasePkGenerator

public class JdbcPkGenerator
extends java.lang.Object
implements PkGenerator

Default primary key generator implementation. Uses a lookup table named "AUTO_PK_SUPPORT" to search and increment primary keys for tables.


Field Summary
protected  JdbcAdapter adapter
           
static int DEFAULT_PK_CACHE_SIZE
           
protected  java.util.Map<java.lang.String,org.apache.cayenne.dba.LongPkRange> pkCache
           
protected  int pkCacheSize
           
 
Constructor Summary
JdbcPkGenerator(JdbcAdapter adapter)
           
 
Method Summary
protected  boolean autoPkTableExists(DataNode node)
          Checks if AUTO_PK_TABLE already exists in the database.
 void createAutoPk(DataNode node, java.util.List<DbEntity> dbEntities)
          Generates necessary database objects to provide automatic primary key support.
 java.util.List<java.lang.String> createAutoPkStatements(java.util.List<DbEntity> dbEntities)
          Returns a list of SQL strings needed to generates database objects to provide automatic primary support for the list of entities.
 void dropAutoPk(DataNode node, java.util.List<DbEntity> dbEntities)
          Drops table named "AUTO_PK_SUPPORT" if it exists in the database.
 java.util.List<java.lang.String> dropAutoPkStatements(java.util.List<DbEntity> dbEntities)
          Returns SQL string needed to drop database objects associated with automatic primary key generation.
protected  java.lang.String dropAutoPkString()
           
 java.lang.Object generatePk(DataNode node, DbAttribute pk)
          Generates a unique and non-repeating primary key for specified dbEntity.
 JdbcAdapter getAdapter()
           
 int getPkCacheSize()
          Returns a size of the entity primary key cache.
protected  long longPkFromDatabase(DataNode node, DbEntity entity)
          Performs primary key generation ignoring cache.
protected  java.lang.String pkCreateString(java.lang.String entName)
           
protected  java.lang.String pkDeleteString(java.util.List<DbEntity> dbEntities)
           
protected  java.lang.String pkSelectString(java.lang.String entName)
           
protected  java.lang.String pkTableCreateString()
           
protected  java.lang.String pkUpdateString(java.lang.String entName)
           
 void reset()
          Resets any cached primary keys forcing generator to go to the database next time id generation is requested.
 int runUpdate(DataNode node, java.lang.String sql)
          Runs JDBC update over a Connection obtained from DataNode.
 void setPkCacheSize(int pkCacheSize)
          Sets the size of the entity primary key cache.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

DEFAULT_PK_CACHE_SIZE

public static final int DEFAULT_PK_CACHE_SIZE
See Also:
Constant Field Values

adapter

protected JdbcAdapter adapter

pkCache

protected java.util.Map<java.lang.String,org.apache.cayenne.dba.LongPkRange> pkCache

pkCacheSize

protected int pkCacheSize
Constructor Detail

JdbcPkGenerator

public JdbcPkGenerator(JdbcAdapter adapter)
Method Detail

getAdapter

public JdbcAdapter getAdapter()

createAutoPk

public void createAutoPk(DataNode node,
                         java.util.List<DbEntity> dbEntities)
                  throws java.lang.Exception
Description copied from interface: PkGenerator
Generates necessary database objects to provide automatic primary key support.

Specified by:
createAutoPk in interface PkGenerator
Parameters:
node - node that provides access to a DataSource.
dbEntities - a list of entities that require primary key auto-generation support
Throws:
java.lang.Exception

createAutoPkStatements

public java.util.List<java.lang.String> createAutoPkStatements(java.util.List<DbEntity> dbEntities)
Description copied from interface: PkGenerator
Returns a list of SQL strings needed to generates database objects to provide automatic primary support for the list of entities. No actual database operations are performed.

Specified by:
createAutoPkStatements in interface PkGenerator

dropAutoPk

public void dropAutoPk(DataNode node,
                       java.util.List<DbEntity> dbEntities)
                throws java.lang.Exception
Drops table named "AUTO_PK_SUPPORT" if it exists in the database.

Specified by:
dropAutoPk in interface PkGenerator
Parameters:
node - node that provides access to a DataSource.
dbEntities - a list of entities whose primary key auto-generation support should be dropped.
Throws:
java.lang.Exception

dropAutoPkStatements

public java.util.List<java.lang.String> dropAutoPkStatements(java.util.List<DbEntity> dbEntities)
Description copied from interface: PkGenerator
Returns SQL string needed to drop database objects associated with automatic primary key generation. No actual database operations are performed.

Specified by:
dropAutoPkStatements in interface PkGenerator

pkTableCreateString

protected java.lang.String pkTableCreateString()

pkDeleteString

protected java.lang.String pkDeleteString(java.util.List<DbEntity> dbEntities)

pkCreateString

protected java.lang.String pkCreateString(java.lang.String entName)

pkSelectString

protected java.lang.String pkSelectString(java.lang.String entName)

pkUpdateString

protected java.lang.String pkUpdateString(java.lang.String entName)

dropAutoPkString

protected java.lang.String dropAutoPkString()

autoPkTableExists

protected boolean autoPkTableExists(DataNode node)
                             throws java.sql.SQLException
Checks if AUTO_PK_TABLE already exists in the database.

Throws:
java.sql.SQLException

runUpdate

public int runUpdate(DataNode node,
                     java.lang.String sql)
              throws java.sql.SQLException
Runs JDBC update over a Connection obtained from DataNode. Returns a number of objects returned from update.

Throws:
java.sql.SQLException - in case of query failure.

generatePk

public java.lang.Object generatePk(DataNode node,
                                   DbAttribute pk)
                            throws java.lang.Exception
Generates a unique and non-repeating primary key for specified dbEntity.

This implementation is naive since it does not lock the database rows when executing select and subsequent update. Adapter-specific implementations are more robust.

Specified by:
generatePk in interface PkGenerator
Throws:
java.lang.Exception
Since:
3.0

longPkFromDatabase

protected long longPkFromDatabase(DataNode node,
                                  DbEntity entity)
                           throws java.lang.Exception
Performs primary key generation ignoring cache. Generates a range of primary keys as specified by "pkCacheSize" bean property.

This method is called internally from "generatePkForDbEntity" and then generated range of key values is saved in cache for performance. Subclasses that implement different primary key generation solutions should override this method, not "generatePkForDbEntity".

Throws:
java.lang.Exception
Since:
3.0

getPkCacheSize

public int getPkCacheSize()
Returns a size of the entity primary key cache. Default value is 20. If cache size is set to a value less or equals than "one", no primary key caching is done.


setPkCacheSize

public void setPkCacheSize(int pkCacheSize)
Sets the size of the entity primary key cache. If pkCacheSize parameter is less than 1, cache size is set to "one".

Note that our tests show that setting primary key cache value to anything much bigger than 20 does not give any significant performance increase. Therefore it does not make sense to use bigger values, since this may potentially create big gaps in the database primary key sequences in cases like application crashes or restarts.


reset

public void reset()
Description copied from interface: PkGenerator
Resets any cached primary keys forcing generator to go to the database next time id generation is requested. May not be applicable for all generator implementations.

Specified by:
reset in interface PkGenerator


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