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Berkeley DB Java Edition version 3.1.0 |
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java.lang.Objectcom.sleepycat.je.DatabaseConfig
public class DatabaseConfig
Specify the attributes of a database.
Field Summary | |
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static DatabaseConfig |
DEFAULT
An instance created using the default constructor is initialized with the system's default settings. |
Constructor Summary | |
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DatabaseConfig()
An instance created using the default constructor is initialized with the system's default settings. |
Method Summary | |
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DatabaseConfig |
cloneConfig()
Returns a copy of this configuration object. |
boolean |
getAllowCreate()
Return true if the Environment.openDatabase method is configured
to create the database if it does not already exist. |
Comparator |
getBtreeComparator()
Returns the Comparator used for key comparison on this database. |
boolean |
getBtreeComparatorByClassName()
|
boolean |
getDeferredWrite()
Returns the setting for the deferred write option. |
Comparator |
getDuplicateComparator()
Returns the Comparator used for duplicate data item comparison on this database. |
boolean |
getDuplicateComparatorByClassName()
|
boolean |
getExclusiveCreate()
Return true if the Environment.openDatabase method is configured
to fail if the database already exists. |
int |
getNodeMaxDupTreeEntries()
Return the maximum number of children a B+Tree duplicate tree node can have. |
int |
getNodeMaxEntries()
Return the maximum number of children a B+Tree node can have. |
boolean |
getOverrideBtreeComparator()
Returns the override setting for the btree comparator. |
boolean |
getOverrideDuplicateComparator()
Returns the override setting for the duplicate comparator. |
boolean |
getReadOnly()
Return true if the database is configured in read-only mode. |
boolean |
getSortedDuplicates()
Return true if the database is configured to support sorted duplicate data items. |
boolean |
getTransactional()
Return true if the database open is enclosed within a transaction. |
void |
setAllowCreate(boolean allowCreate)
Configure the Environment.openDatabase method to create
the database if it does not already exist. |
void |
setBtreeComparator(Class btreeComparator)
By default, a byte by byte lexicographic comparison is used for btree keys. |
void |
setBtreeComparator(Comparator btreeComparator)
By default, a byte by byte lexicographic comparison is used for btree keys. |
void |
setDeferredWrite(boolean deferredWrite)
Open this database in deferred write mode. |
void |
setDuplicateComparator(Class duplicateComparator)
By default, a byte by byte lexicographic comparison is used for duplicate data items in a duplicate set. |
void |
setDuplicateComparator(Comparator duplicateComparator)
By default, a byte by byte lexicographic comparison is used for duplicate data items in a duplicate set. |
void |
setExclusiveCreate(boolean exclusiveCreate)
Configure the Environment.openDatabase method to fail if
the database already exists. |
void |
setNodeMaxDupTreeEntries(int nodeMaxDupTreeEntries)
Configure the Environment.openDatabase method to have a
B+Tree duplicate tree fanout of nodeMaxDupTreeEntries. |
void |
setNodeMaxEntries(int nodeMaxEntries)
Configure the Environment.openDatabase method to have a
B+Tree fanout of nodeMaxEntries. |
void |
setOverrideBtreeComparator(boolean override)
Set to true if the database exists and the btree comparator specified in this configuration object should override the current comparator. |
void |
setOverrideDuplicateComparator(boolean override)
Set to true if the database exists and the duplicate comparator specified in this configuration object should override the current comparator. |
void |
setReadOnly(boolean readOnly)
Configure the database in read-only mode. |
void |
setSortedDuplicates(boolean sortedDuplicates)
Configure the database to support sorted, duplicate data items. |
void |
setTransactional(boolean transactional)
Enclose the database open within a transaction. |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
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public static final DatabaseConfig DEFAULT
Constructor Detail |
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public DatabaseConfig()
Method Detail |
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public void setAllowCreate(boolean allowCreate)
Environment.openDatabase
method to create
the database if it does not already exist.
allowCreate
- If true, configure the Environment.openDatabase
method to
create the database if it does not already exist.public boolean getAllowCreate()
Environment.openDatabase
method is configured
to create the database if it does not already exist.
This method may be called at any time during the life of the application.
Environment.openDatabase
method is configured
to create the database if it does not already exist.public void setExclusiveCreate(boolean exclusiveCreate)
Environment.openDatabase
method to fail if
the database already exists.
The exclusiveCreate mode is only meaningful if specified with the allowCreate mode.
exclusiveCreate
- If true, configure the Environment.openDatabase
method to
fail if the database already exists.public boolean getExclusiveCreate()
Environment.openDatabase
method is configured
to fail if the database already exists.
This method may be called at any time during the life of the application.
Environment.openDatabase
method is configured
to fail if the database already exists.public boolean getSortedDuplicates()
This method may be called at any time during the life of the application.
public void setReadOnly(boolean readOnly)
Any attempt to modify items in the database will fail, regardless of the actual permissions of any underlying files.
readOnly
- If true, configure the database in read-only mode.public boolean getReadOnly()
This method may be called at any time during the life of the application.
public void setSortedDuplicates(boolean sortedDuplicates)
Insertion when the key of the key/data pair being inserted already exists in the database will be successful. The ordering of duplicates in the database is determined by the duplicate comparison function.
If the application does not specify a duplicate data item comparison function, a default lexical comparison will be used.
If a primary database is to be associated with one or more secondary databases, it may not be configured for duplicates.
Calling this method affects the database, including all threads of control accessing the database.
If the database already exists when the database is opened, any database configuration specified by this method must be the same as the existing database or an error will be returned.
sortedDuplicates
- If true, configure the database to support duplicate data items.
A value of false is illegal to this method, that is, once set, the
configuration cannot be cleared.public void setTransactional(boolean transactional)
If the call succeeds, the open operation will be recoverable. If the call fails, no database will have been created.
All future operations on this database, which are not explicitly enclosed in a transaction by the application, will be enclosed in in a transaction within the library.
transactional
- If true, enclose the database open within a transaction.public boolean getTransactional()
This method may be called at any time during the life of the application.
public DatabaseConfig cloneConfig()
public void setNodeMaxEntries(int nodeMaxEntries)
Environment.openDatabase
method to have a
B+Tree fanout of nodeMaxEntries.
The nodeMaxEntries parameter is only meaningful if specified with the allowCreate mode.
nodeMaxEntries
- The maximum children per B+Tree node.public void setNodeMaxDupTreeEntries(int nodeMaxDupTreeEntries)
Environment.openDatabase
method to have a
B+Tree duplicate tree fanout of nodeMaxDupTreeEntries.
The nodeMaxDupTreeEntries parameter is only meaningful if specified with the allowCreate mode.
nodeMaxDupTreeEntries
- The maximum children per duplicate B+Tree node.public int getNodeMaxEntries()
This method may be called at any time during the life of the application.
public int getNodeMaxDupTreeEntries()
This method may be called at any time during the life of the application.
public void setBtreeComparator(Class btreeComparator)
Note that there are two ways to set the comparator: by specifying the class
or by specifying a serializable object. This method is used to specify a
Comparator class. The comparator class must implement java.util.Comparator
and must have a public zero-parameter constructor. JE will store the class
name and instantiate the Comparator by class name (using
Class.forName
and newInstance
) when subsequently
opening the database. Because the Comparator is instantiated using its
default constructor, it should not be dependent on other constructor
parameters.
Because records are stored in the order determined by the Comparator, the Comparator's behavior must not change over time and therefore should not be dependent on any state that may change over time. In addition, although it is possible to change the comparator for an existing database, care must be taken that the new comparator provides compatible results with the previous comparator, or database corruption will occur.
The Comparator.compare() method is passed the byte arrays that are stored in the database. If you know how your data is organized in the byte array, then you can write a comparison routine that directly examines the contents of the arrays. Otherwise, you have to reconstruct your original objects, and then perform the comparison. See the Getting Started Guide for examples.
JE uses comparators internally in a wide variety of circumstances, so custom comparators must be sure to return valid values for any two arbitrary keys. The user must not make any assumptions about the range of key values that might be compared. For example, it's possible for the comparator may may be used against previously deleted values.
The comparator for an existing database will not be overridden unless setOverrideBtreeComparator() is set to true.
public void setBtreeComparator(Comparator btreeComparator)
Note that there are two ways to set the comparator: by specifying the class or by specifying a serializable object. This method is used to specify a serializable object. The comparator class must implement java.util.Comparator and must be serializable. JE will serialize the Comparator and deserialize it when subsequently opening the database.
Because records are stored in the order determined by the Comparator, the Comparator's behavior must not change over time and therefore should not be dependent on any state that may change over time. In addition, although it is possible to change the comparator for an existing database, care must be taken that the new comparator provides compatible results with the previous comparator, or database corruption will occur.
The Comparator.compare() method is passed the byte arrays that are stored in the database. If you know how your data is organized in the byte array, then you can write a comparison routine that directly examines the contents of the arrays. Otherwise, you have to reconstruct your original objects, and then perform the comparison. See the Getting Started Guide for examples.
JE uses comparators internally in a wide variety of circumstances, so custom comparators must be sure to return valid values for any two arbitrary keys. The user must not make any assumptions about the range of key values that might be compared. For example, it's possible for the comparator may may be used against previously deleted values.
The comparator for an existing database will not be overridden unless setOverrideBtreeComparator() is set to true.
public Comparator getBtreeComparator()
public boolean getBtreeComparatorByClassName()
public void setOverrideBtreeComparator(boolean override)
override
- Set to true to override the existing comparator.public boolean getOverrideBtreeComparator()
public boolean getDuplicateComparatorByClassName()
public void setDuplicateComparator(Class duplicateComparator)
Note that there are two ways to set the comparator: by specifying the class
or by specifying a serializable object. This method is used to specify a
Comparator class. The comparator class must implement java.util.Comparator
and must have a public zero-parameter constructor. JE will store the class
name and instantiate the Comparator by class name (using
Class.forName
and newInstance
) when subsequently
opening the database. Because the Comparator is instantiated using its
default constructor, it should not be dependent on other constructor
parameters.
Because records are stored in the order determined by the Comparator, the Comparator's behavior must not change over time and therefore should not be dependent on any state that may change over time. In addition, although it is possible to change the comparator for an existing database, care must be taken that the new comparator provides compatible results with the previous comparator, or database corruption will occur.
The Comparator.compare() method is passed the byte arrays that are stored in the database. If you know how your data is organized in the byte array, then you can write a comparison routine that directly examines the contents of the arrays. Otherwise, you have to reconstruct your original objects, and then perform the comparison. See the Getting Started Guide for examples.
JE uses comparators internally in a wide variety of circumstances, so custom comparators must be sure to return valid values for any two arbitrary keys. The user must not make any assumptions about the range of key values that might be compared. For example, it's possible for the comparator may may be used against previously deleted values.
The comparator for an existing database will not be overridden unless setOverrideDuplicateComparator() is set to true.
public void setDuplicateComparator(Comparator duplicateComparator)
Note that there are two ways to set the comparator: by specifying the class or by specifying a serializable object. This method is used to specify a serializable object. The comparator class must implement java.util.Comparator and must be serializable. JE will serialize the Comparator and deserialize it when subsequently opening the database.
Because records are stored in the order determined by the Comparator, the Comparator's behavior must not change over time and therefore should not be dependent on any state that may change over time. In addition, although it is possible to change the comparator for an existing database, care must be taken that the new comparator provides compatible results with the previous comparator, or database corruption will occur.
The Comparator.compare() method is passed the byte arrays that are stored in the database. If you know how your data is organized in the byte array, then you can write a comparison routine that directly examines the contents of the arrays. Otherwise, you have to reconstruct your original objects, and then perform the comparison. See the Getting Started Guide for examples.
JE uses comparators internally in a wide variety of circumstances, so custom comparators must be sure to return valid values for any two arbitrary keys. The user must not make any assumptions about the range of key values that might be compared. For example, it's possible for the comparator may may be used against previously deleted values.
The comparator for an existing database will not be overridden unless setOverrideDuplicateComparator() is set to true.
public Comparator getDuplicateComparator()
public void setOverrideDuplicateComparator(boolean override)
override
- Set to true to override the existing comparator.public boolean getOverrideDuplicateComparator()
public void setDeferredWrite(boolean deferredWrite)
Note that although deferred write databases can page to disk if the cache is not large enough to hold the databases, they are much more efficient if the database remains in memory. See the JE FAQ in the Berkeley DB Developer's Zone for information on how to estimate the cache size needed by a given database. In the current implementation, a deferred write database which is synced or pages to the disk may also add additional log cleaner overhead to the environment. See the je.deferredWrite.temp property in <JEHOME>/example.properties for tuning information on how to ameliorate this cost.
deferredWrite
- if true, this database has been opened in deferred
write mode.public boolean getDeferredWrite()
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Berkeley DB Java Edition version 3.1.0 |
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