@@ -4439,84 +4439,102 @@ Passing the User Name and/or Password in the URL
User-Defined Functions and Stored Procedures
@features_1582_p
In addition to the built-in functions, this database supports user-defined Java functions. In this database, Java functions can be used as stored procedures as well. A function must be declared (registered) before it can be used. Only static Java methods are supported; both the class and the method must be public. Example Java method:
In addition to the built-in functions, this database supports user-defined Java functions. In this database, Java functions can be used as stored procedures as well. A function must be declared (registered) before it can be used. A functions can be defined using source code, or as a reference to a compiled class that is available in the classpath.
@features_1583_p
The Java function must be registered in the database by calling <code>CREATE ALIAS</code>:
@features_1583_h3
Referencing a Compiled Method
@features_1584_p
When referencing a method, the class must already be compiled and included in the classpath where the database is running. Only static Java methods are supported; both the class and the method must be public. Example Java class:
@features_1585_p
The Java function must be registered in the database by calling <code>CREATE ALIAS ... FOR</code>:
@features_1586_p
For a complete sample application, see <code>src/test/org/h2/samples/Function.java</code>.
@features_1585_h3
@features_1587_h3
Declaring Functions as Source Code
@features_1588_p
When defining a function alias with source code, the database tries to compile the source code using the Sun Java compiler (the class <code>com.sun.tools.javac.Main</code>) if the <code>tools.jar</code> is in the classpath. If not, <code>javac</code> is run as a separate process. Only the source code is stored in the database; the class is compiled each time the database is re-opened. Source code is usually passed as dollar quoted text to avoid escaping problems, however single quotes can be used as well. Example:
@features_1589_p
The method name (<code>nextPrime</code> in the example above) is ignored. By default, the three packages <code>java.util, java.math, java.sql</code> are imported. If different import statements are required, they must be declared at the beginning and separated with the tag <code>@CODE</code>:
@features_1590_p
The following template is used to create a complete Java class:
@features_1591_h3
Function Data Type Mapping
@features_1586_p
@features_1592_p
Functions that accept non-nullable parameters such as <code>int</code> will not be called if one of those parameters is <code>NULL</code>. Instead, the result of the function is <code>NULL</code>. If the function should be called if a parameter is <code>NULL</code>, you need to use <code>java.lang.Integer</code> instead.
@features_1587_p
@features_1593_p
SQL types are mapped to Java classes and vice-versa as in the JDBC API. For details, see <a href="datatypes.html">Data Types</a>. There are two special cases: <code>java.lang.Object</code> is mapped to <code>OTHER</code> (a serialized object). Therefore, <code>java.lang.Object</code> can not be used to match all SQL types (matching all SQL types is not supported). The second special case is <code>Object[]</code>: arrays of any class are mapped to <code>ARRAY</code>.
@features_1588_h3
@features_1594_h3
Functions that require a Connection
@features_1589_p
@features_1595_p
If the first parameter of a Java function is a <code>java.sql.Connection</code>, then the connection to database is provided. This connection does not need to be closed before returning. When calling the method from within the SQL statement, this connection parameter does not need to be (can not be) specified.
@features_1590_h3
Functions throwing an Exception
@features_1596_h3
Functions Throwing an Exception
@features_1591_p
@features_1597_p
If a function throws an exception, then the current statement is rolled back and the exception is thrown to the application.
@features_1592_h3
Functions returning a Result Set
@features_1598_h3
Functions Returning a Result Set
@features_1593_p
@features_1599_p
Functions may returns a result set. Such a function can be called with the <code>CALL</code> statement:
@features_1594_h3
@features_1600_h3
Using SimpleResultSet
@features_1595_p
@features_1601_p
A function can create a result set using the <code>SimpleResultSet</code> tool:
@features_1596_h3
@features_1602_h3
Using a Function as a Table
@features_1597_p
@features_1603_p
A function that returns a result set can be used like a table. However, in this case the function is called at least twice: first while parsing the statement to collect the column names (with parameters set to <code>null</code> where not known at compile time). And then, while executing the statement to get the data (maybe multiple times if this is a join). If the function is called just to get the column list, the URL of the connection passed to the function is <code>jdbc:columnlist:connection</code>. Otherwise, the URL of the connection is <code>jdbc:default:connection</code>.
@features_1598_h2
@features_1604_h2
Triggers
@features_1599_p
@features_1605_p
This database supports Java triggers that are called before or after a row is updated, inserted or deleted. Triggers can be used for complex consistency checks, or to update related data in the database. It is also possible to use triggers to simulate materialized views. For a complete sample application, see <code>src/test/org/h2/samples/TriggerSample.java</code>. A Java trigger must implement the interface <code>org.h2.api.Trigger</code>. The trigger class must be available in the classpath of the database engine (when using the server mode, it must be in the classpath of the server).
@features_1600_p
@features_1606_p
The connection can be used to query or update data in other tables. The trigger then needs to be defined in the database:
@features_1601_p
@features_1607_p
The trigger can be used to veto a change by throwing a <code>SQLException</code>.
@features_1602_h2
@features_1608_h2
Compacting a Database
@features_1603_p
@features_1609_p
Empty space in the database file is re-used automatically. To re-build the indexes, the simplest way is to delete the <code>.index.db</code> file while the database is closed. However in some situations (for example after deleting a lot of data in a database), one sometimes wants to shrink the size of the database (compact a database). Here is a sample function to do this:
@features_1604_p
@features_1610_p
See also the sample application <code>org.h2.samples.Compact</code>. The commands <code>SCRIPT / RUNSCRIPT</code> can be used as well to create a backup of a database and re-build the database from the script.
@features_1605_h2
@features_1611_h2
Cache Settings
@features_1606_p
@features_1612_p
The database keeps most frequently used data and index pages in the main memory. The amount of memory used for caching can be changed using the setting <code>CACHE_SIZE</code>. This setting can be set in the database connection URL (<code>jdbc:h2:~/test;CACHE_SIZE=131072</code>), or it can be changed at runtime using <code>SET CACHE_SIZE size</code>.
@features_1607_p
@features_1613_p
Also supported is a second level soft reference cache. Rows in this cache are only garbage collected on low memory. By default the second level cache is disabled. To enable it, use the prefix <code>SOFT_</code>. Example: <code>jdbc:h2:~/test;CACHE_TYPE=SOFT_LRU</code>.
@features_1608_p
@features_1614_p
To get information about page reads and writes, and the current caching algorithm in use, call <code>SELECT * FROM INFORMATION_SCHEMA.SETTINGS</code>. The number of pages read / written is listed for the data and index file.
#To restore the cluster, you first need to delete the database that failed, then restart the server that was stopped, and re-run the <code>CreateCluster</code> tool.
@advanced_1095_h3
#Detect Which Cluster Instances are Running #クラスタリングアルゴリズムと制限
#Detect Which Cluster Instances are Running
@advanced_1096_p
# To find out which cluster nodes are currently running, execute the following SQL statement:
...
...
@@ -461,13 +461,13 @@ test
# relative or absolute path are not supported in the database name.
@advanced_1154_td
# By default, the database is stored in the current working directory #Server
# By default, the database is stored in the current working directory
@advanced_1155_td
# where the Server is started except when the -baseDir setting is used. #localhost
# where the Server is started except when the -baseDir setting is used.
@advanced_1156_td
# The name must be at least 3 characters. #サーバー名、またはIPアドレス
# The name must be at least 3 characters.
@advanced_1157_td
Server
...
...
@@ -839,7 +839,7 @@ ZERO() 関数を使用する
# File encryption slows down the performance of the database engine. Compared to unencrypted mode, database operations take about 2.2 times longer when using XTEA, and 2.5 times longer using AES (embedded mode).
@advanced_1280_h3
#Wrong Password / User Name Delay #HTTPS 接続
#Wrong Password / User Name Delay
@advanced_1281_p
# To protect against remote brute force password attacks, the delay after each unsuccessful login gets double as long. Use the system properties <code>h2.delayWrongPasswordMin</code> and <code>h2.delayWrongPasswordMax</code> to change the minimum (the default is 250 milliseconds) or maximum delay (the default is 4000 milliseconds, or 4 seconds). The delay only applies for those using the wrong password. Normally there is no delay for a user that knows the correct password, with one exception: after using the wrong password, there is a delay of up to (randomly distributed) the same delay as for a wrong password. This is to protect against parallel brute force attacks, so that an attacker needs to wait for the whole delay. Delays are synchronized. This is also required to protect against parallel attacks.
...
...
@@ -1010,31 +1010,31 @@ SSL/TLS 接続
AES-128
@advanced_1337_td
#A block encryption algorithm. See also: <a href="http://en.wikipedia.org/wiki/Advanced_Encryption_Standard">Wikipedia: AES</a> #Digest
#A block encryption algorithm. See also: <a href="http://en.wikipedia.org/wiki/Advanced_Encryption_Standard">Wikipedia: AES</a>
@advanced_1338_td
Birthday Paradox
@advanced_1339_td
#Describes the higher than expected probability that two persons in a room have the same birthday. Also valid for randomly generated UUIDs. See also: <a href="http://en.wikipedia.org/wiki/Birthday_paradox">Wikipedia: Birthday Paradox</a> #GCJ
#Describes the higher than expected probability that two persons in a room have the same birthday. Also valid for randomly generated UUIDs. See also: <a href="http://en.wikipedia.org/wiki/Birthday_paradox">Wikipedia: Birthday Paradox</a>
@advanced_1340_td
Digest
@advanced_1341_td
#Protocol to protect a password (but not to protect data). See also: <a href="http://www.faqs.org/rfcs/rfc2617.html">RFC 2617: HTTP Digest Access Authentication</a> #HTTPS
#Protocol to protect a password (but not to protect data). See also: <a href="http://www.faqs.org/rfcs/rfc2617.html">RFC 2617: HTTP Digest Access Authentication</a>
@advanced_1342_td
GCJ
@advanced_1343_td
#Compiler for Java. <a href="http://gcc.gnu.org/java">GNU Compiler for the Java</a> and <a href="http://www.dobysoft.com/products/nativej">NativeJ (commercial)</a> #Modes of Operation
#Compiler for Java. <a href="http://gcc.gnu.org/java">GNU Compiler for the Java</a> and <a href="http://www.dobysoft.com/products/nativej">NativeJ (commercial)</a>
@advanced_1344_td
HTTPS
@advanced_1345_td
#A protocol to provide security to HTTP connections. See also: <a href="http://www.ietf.org/rfc/rfc2818.txt">RFC 2818: HTTP Over TLS</a> #Salt
#A protocol to provide security to HTTP connections. See also: <a href="http://www.ietf.org/rfc/rfc2818.txt">RFC 2818: HTTP Over TLS</a>
@advanced_1346_td
Modes of Operation
...
...
@@ -1046,25 +1046,25 @@ Modes of Operation
Salt
@advanced_1349_td
#Random number to increase the security of passwords. See also: <a href="http://en.wikipedia.org/wiki/Key_derivation_function">Wikipedia: Key derivation function</a> #SQLインジェクション
#Random number to increase the security of passwords. See also: <a href="http://en.wikipedia.org/wiki/Key_derivation_function">Wikipedia: Key derivation function</a>
#A security vulnerability where an application embeds SQL statements or expressions in user input. See also: <a href="http://en.wikipedia.org/wiki/SQL_injection">Wikipedia: SQL Injection</a> #SSL/TLS
#A security vulnerability where an application embeds SQL statements or expressions in user input. See also: <a href="http://en.wikipedia.org/wiki/SQL_injection">Wikipedia: SQL Injection</a>
@advanced_1354_td
Watermark Attack (透かし攻撃)
@advanced_1355_td
#Security problem of certain encryption programs where the existence of certain data can be proven without decrypting. For more information, search in the internet for 'watermark attack cryptoloop' #XTEA
#Security problem of certain encryption programs where the existence of certain data can be proven without decrypting. For more information, search in the internet for 'watermark attack cryptoloop'
# In addition to the built-in functions, this database supports user-defined Java functions. In this database, Java functions can be used as stored procedures as well. A function must be declared (registered) before it can be used. Only static Java methods are supported; both the class and the method must be public. Example Java method:
# In addition to the built-in functions, this database supports user-defined Java functions. In this database, Java functions can be used as stored procedures as well. A function must be declared (registered) before it can be used. A functions can be defined using source code, or as a reference to a compiled class that is available in the classpath.
@features_1583_p
# The Java function must be registered in the database by calling <code>CREATE ALIAS</code>:
@features_1583_h3
#Referencing a Compiled Method
@features_1584_p
# When referencing a method, the class must already be compiled and included in the classpath where the database is running. Only static Java methods are supported; both the class and the method must be public. Example Java class:
@features_1585_p
# The Java function must be registered in the database by calling <code>CREATE ALIAS ... FOR</code>:
@features_1586_p
# For a complete sample application, see <code>src/test/org/h2/samples/Function.java</code>.
@features_1585_h3
@features_1587_h3
#Declaring Functions as Source Code
@features_1588_p
# When defining a function alias with source code, the database tries to compile the source code using the Sun Java compiler (the class <code>com.sun.tools.javac.Main</code>) if the <code>tools.jar</code> is in the classpath. If not, <code>javac</code> is run as a separate process. Only the source code is stored in the database; the class is compiled each time the database is re-opened. Source code is usually passed as dollar quoted text to avoid escaping problems, however single quotes can be used as well. Example:
@features_1589_p
# The method name (<code>nextPrime</code> in the example above) is ignored. By default, the three packages <code>java.util, java.math, java.sql</code> are imported. If different import statements are required, they must be declared at the beginning and separated with the tag <code>@CODE</code>:
@features_1590_p
# The following template is used to create a complete Java class:
@features_1591_h3
データタイプマッピング関数
@features_1586_p
@features_1592_p
# Functions that accept non-nullable parameters such as <code>int</code> will not be called if one of those parameters is <code>NULL</code>. Instead, the result of the function is <code>NULL</code>. If the function should be called if a parameter is <code>NULL</code>, you need to use <code>java.lang.Integer</code> instead.
@features_1587_p
@features_1593_p
# SQL types are mapped to Java classes and vice-versa as in the JDBC API. For details, see <a href="datatypes.html">Data Types</a>. There are two special cases: <code>java.lang.Object</code> is mapped to <code>OTHER</code> (a serialized object). Therefore, <code>java.lang.Object</code> can not be used to match all SQL types (matching all SQL types is not supported). The second special case is <code>Object[]</code>: arrays of any class are mapped to <code>ARRAY</code>.
@features_1588_h3
@features_1594_h3
接続を必要とする関数
@features_1589_p
@features_1595_p
# If the first parameter of a Java function is a <code>java.sql.Connection</code>, then the connection to database is provided. This connection does not need to be closed before returning. When calling the method from within the SQL statement, this connection parameter does not need to be (can not be) specified.
@features_1590_h3
例外を投げる関数
@features_1596_h3
#Functions Throwing an Exception
@features_1591_p
@features_1597_p
# If a function throws an exception, then the current statement is rolled back and the exception is thrown to the application.
@features_1592_h3
Result Setを返す関数
@features_1598_h3
#Functions Returning a Result Set
@features_1593_p
@features_1599_p
# Functions may returns a result set. Such a function can be called with the <code>CALL</code> statement:
@features_1594_h3
@features_1600_h3
SimpleResultSetを使用する
@features_1595_p
@features_1601_p
# A function can create a result set using the <code>SimpleResultSet</code> tool:
@features_1596_h3
@features_1602_h3
関数をテーブルとして使用する
@features_1597_p
@features_1603_p
# A function that returns a result set can be used like a table. However, in this case the function is called at least twice: first while parsing the statement to collect the column names (with parameters set to <code>null</code> where not known at compile time). And then, while executing the statement to get the data (maybe multiple times if this is a join). If the function is called just to get the column list, the URL of the connection passed to the function is <code>jdbc:columnlist:connection</code>. Otherwise, the URL of the connection is <code>jdbc:default:connection</code>.
@features_1598_h2
@features_1604_h2
トリガー
@features_1599_p
@features_1605_p
# This database supports Java triggers that are called before or after a row is updated, inserted or deleted. Triggers can be used for complex consistency checks, or to update related data in the database. It is also possible to use triggers to simulate materialized views. For a complete sample application, see <code>src/test/org/h2/samples/TriggerSample.java</code>. A Java trigger must implement the interface <code>org.h2.api.Trigger</code>. The trigger class must be available in the classpath of the database engine (when using the server mode, it must be in the classpath of the server).
@features_1600_p
@features_1606_p
# The connection can be used to query or update data in other tables. The trigger then needs to be defined in the database:
@features_1601_p
@features_1607_p
# The trigger can be used to veto a change by throwing a <code>SQLException</code>.
@features_1602_h2
@features_1608_h2
データベースをコンパクトにする
@features_1603_p
@features_1609_p
# Empty space in the database file is re-used automatically. To re-build the indexes, the simplest way is to delete the <code>.index.db</code> file while the database is closed. However in some situations (for example after deleting a lot of data in a database), one sometimes wants to shrink the size of the database (compact a database). Here is a sample function to do this:
@features_1604_p
@features_1610_p
# See also the sample application <code>org.h2.samples.Compact</code>. The commands <code>SCRIPT / RUNSCRIPT</code> can be used as well to create a backup of a database and re-build the database from the script.
@features_1605_h2
@features_1611_h2
キャッシュの設定
@features_1606_p
@features_1612_p
# The database keeps most frequently used data and index pages in the main memory. The amount of memory used for caching can be changed using the setting <code>CACHE_SIZE</code>. This setting can be set in the database connection URL (<code>jdbc:h2:~/test;CACHE_SIZE=131072</code>), or it can be changed at runtime using <code>SET CACHE_SIZE size</code>.
@features_1607_p
@features_1613_p
# Also supported is a second level soft reference cache. Rows in this cache are only garbage collected on low memory. By default the second level cache is disabled. To enable it, use the prefix <code>SOFT_</code>. Example: <code>jdbc:h2:~/test;CACHE_TYPE=SOFT_LRU</code>.
@features_1608_p
@features_1614_p
# To get information about page reads and writes, and the current caching algorithm in use, call <code>SELECT * FROM INFORMATION_SCHEMA.SETTINGS</code>. The number of pages read / written is listed for the data and index file.
@@ -1478,33 +1478,39 @@ features_1578_p=\ This example requires Java 1.6. When using Swing, use <code>ja
features_1579_h3=Passing the User Name and/or Password in the URL
features_1580_p=\ Instead of passing the user name as a separate parameter as in <code> Connection conn \=DriverManager. getConnection("jdbc\:h2\:~/test", "sa", "123"); </code> the user name (and/or password) can be supplied in the URL itself\:<code> Connection conn \=DriverManager. getConnection("jdbc\:h2\:~/test;USER\=sa;PASSWORD\=123"); </code> The settings in the URL override the settings passed as a separate parameter.
features_1581_h2=User-Defined Functions and Stored Procedures
features_1582_p=\ In addition to the built-in functions, this database supports user-defined Java functions. In this database, Java functions can be used as stored procedures as well. A function must be declared (registered) before it can be used. Only static Java methods are supported; both the class and the method must be public. Example Java method\:
features_1583_p=\ The Java function must be registered in the database by calling <code>CREATE ALIAS</code>\:
features_1584_p=\ For a complete sample application, see <code>src/test/org/h2/samples/Function.java</code>.
features_1585_h3=Function Data Type Mapping
features_1586_p=\ Functions that accept non-nullable parameters such as <code>int</code> will not be called if one of those parameters is <code>NULL</code>. Instead, the result of the function is <code>NULL</code>. If the function should be called if a parameter is <code>NULL</code>, you need to use <code>java.lang.Integer</code> instead.
features_1587_p=\ SQL types are mapped to Java classes and vice-versa as in the JDBC API. For details, see <a href\="datatypes.html">Data Types</a>. There are two special cases\:<code>java.lang.Object</code> is mapped to <code>OTHER</code> (a serialized object). Therefore, <code>java.lang.Object</code> can not be used to match all SQL types (matching all SQL types is not supported). The second special case is <code>Object[]</code>\:arrays of any class are mapped to <code>ARRAY</code>.
features_1588_h3=Functions that require a Connection
features_1589_p=\ If the first parameter of a Java function is a <code>java.sql.Connection</code>, then the connection to database is provided. This connection does not need to be closed before returning. When calling the method from within the SQL statement, this connection parameter does not need to be (can not be) specified.
features_1590_h3=Functions throwing an Exception
features_1591_p=\ If a function throws an exception, then the current statement is rolled back and the exception is thrown to the application.
features_1592_h3=Functions returning a Result Set
features_1593_p=\ Functions may returns a result set. Such a function can be called with the <code>CALL</code> statement\:
features_1594_h3=Using SimpleResultSet
features_1595_p=\ A function can create a result set using the <code>SimpleResultSet</code> tool\:
features_1596_h3=Using a Function as a Table
features_1597_p=\ A function that returns a result set can be used like a table. However, in this case the function is called at least twice\:first while parsing the statement to collect the column names (with parameters set to <code>null</code> where not known at compile time). And then, while executing the statement to get the data (maybe multiple times if this is a join). If the function is called just to get the column list, the URL of the connection passed to the function is <code>jdbc\:columnlist\:connection</code>. Otherwise, the URL of the connection is <code>jdbc\:default\:connection</code>.
features_1598_h2=Triggers
features_1599_p=\ This database supports Java triggers that are called before or after a row is updated, inserted or deleted. Triggers can be used for complex consistency checks, or to update related data in the database. It is also possible to use triggers to simulate materialized views. For a complete sample application, see <code>src/test/org/h2/samples/TriggerSample.java</code>. A Java trigger must implement the interface <code>org.h2.api.Trigger</code>. The trigger class must be available in the classpath of the database engine (when using the server mode, it must be in the classpath of the server).
features_1600_p=\ The connection can be used to query or update data in other tables. The trigger then needs to be defined in the database\:
features_1601_p=\ The trigger can be used to veto a change by throwing a <code>SQLException</code>.
features_1602_h2=Compacting a Database
features_1603_p=\ Empty space in the database file is re-used automatically. To re-build the indexes, the simplest way is to delete the <code>.index.db</code> file while the database is closed. However in some situations (for example after deleting a lot of data in a database), one sometimes wants to shrink the size of the database (compact a database). Here is a sample function to do this\:
features_1604_p=\ See also the sample application <code>org.h2.samples.Compact</code>. The commands <code>SCRIPT / RUNSCRIPT</code> can be used as well to create a backup of a database and re-build the database from the script.
features_1605_h2=Cache Settings
features_1606_p=\ The database keeps most frequently used data and index pages in the main memory. The amount of memory used for caching can be changed using the setting <code>CACHE_SIZE</code>. This setting can be set in the database connection URL (<code>jdbc\:h2\:~/test;CACHE_SIZE\=131072</code>), or it can be changed at runtime using <code>SET CACHE_SIZE size</code>.
features_1607_p=\ Also supported is a second level soft reference cache. Rows in this cache are only garbage collected on low memory. By default the second level cache is disabled. To enable it, use the prefix <code>SOFT_</code>. Example\:<code>jdbc\:h2\:~/test;CACHE_TYPE\=SOFT_LRU</code>.
features_1608_p=\ To get information about page reads and writes, and the current caching algorithm in use, call <code>SELECT * FROM INFORMATION_SCHEMA.SETTINGS</code>. The number of pages read / written is listed for the data and index file.
features_1582_p=\ In addition to the built-in functions, this database supports user-defined Java functions. In this database, Java functions can be used as stored procedures as well. A function must be declared (registered) before it can be used. A functions can be defined using source code, or as a reference to a compiled class that is available in the classpath.
features_1583_h3=Referencing a Compiled Method
features_1584_p=\ When referencing a method, the class must already be compiled and included in the classpath where the database is running. Only static Java methods are supported; both the class and the method must be public. Example Java class\:
features_1585_p=\ The Java function must be registered in the database by calling <code>CREATE ALIAS ... FOR</code>\:
features_1586_p=\ For a complete sample application, see <code>src/test/org/h2/samples/Function.java</code>.
features_1587_h3=Declaring Functions as Source Code
features_1588_p=\ When defining a function alias with source code, the database tries to compile the source code using the Sun Java compiler (the class <code>com.sun.tools.javac.Main</code>) if the <code>tools.jar</code> is in the classpath. If not, <code>javac</code> is run as a separate process. Only the source code is stored in the database; the class is compiled each time the database is re-opened. Source code is usually passed as dollar quoted text to avoid escaping problems, however single quotes can be used as well. Example\:
features_1589_p=\ The method name (<code>nextPrime</code> in the example above) is ignored. By default, the three packages <code>java.util, java.math, java.sql</code> are imported. If different import statements are required, they must be declared at the beginning and separated with the tag <code>@CODE</code>\:
features_1590_p=\ The following template is used to create a complete Java class\:
features_1591_h3=Function Data Type Mapping
features_1592_p=\ Functions that accept non-nullable parameters such as <code>int</code> will not be called if one of those parameters is <code>NULL</code>. Instead, the result of the function is <code>NULL</code>. If the function should be called if a parameter is <code>NULL</code>, you need to use <code>java.lang.Integer</code> instead.
features_1593_p=\ SQL types are mapped to Java classes and vice-versa as in the JDBC API. For details, see <a href\="datatypes.html">Data Types</a>. There are two special cases\:<code>java.lang.Object</code> is mapped to <code>OTHER</code> (a serialized object). Therefore, <code>java.lang.Object</code> can not be used to match all SQL types (matching all SQL types is not supported). The second special case is <code>Object[]</code>\:arrays of any class are mapped to <code>ARRAY</code>.
features_1594_h3=Functions that require a Connection
features_1595_p=\ If the first parameter of a Java function is a <code>java.sql.Connection</code>, then the connection to database is provided. This connection does not need to be closed before returning. When calling the method from within the SQL statement, this connection parameter does not need to be (can not be) specified.
features_1596_h3=Functions Throwing an Exception
features_1597_p=\ If a function throws an exception, then the current statement is rolled back and the exception is thrown to the application.
features_1598_h3=Functions Returning a Result Set
features_1599_p=\ Functions may returns a result set. Such a function can be called with the <code>CALL</code> statement\:
features_1600_h3=Using SimpleResultSet
features_1601_p=\ A function can create a result set using the <code>SimpleResultSet</code> tool\:
features_1602_h3=Using a Function as a Table
features_1603_p=\ A function that returns a result set can be used like a table. However, in this case the function is called at least twice\:first while parsing the statement to collect the column names (with parameters set to <code>null</code> where not known at compile time). And then, while executing the statement to get the data (maybe multiple times if this is a join). If the function is called just to get the column list, the URL of the connection passed to the function is <code>jdbc\:columnlist\:connection</code>. Otherwise, the URL of the connection is <code>jdbc\:default\:connection</code>.
features_1604_h2=Triggers
features_1605_p=\ This database supports Java triggers that are called before or after a row is updated, inserted or deleted. Triggers can be used for complex consistency checks, or to update related data in the database. It is also possible to use triggers to simulate materialized views. For a complete sample application, see <code>src/test/org/h2/samples/TriggerSample.java</code>. A Java trigger must implement the interface <code>org.h2.api.Trigger</code>. The trigger class must be available in the classpath of the database engine (when using the server mode, it must be in the classpath of the server).
features_1606_p=\ The connection can be used to query or update data in other tables. The trigger then needs to be defined in the database\:
features_1607_p=\ The trigger can be used to veto a change by throwing a <code>SQLException</code>.
features_1608_h2=Compacting a Database
features_1609_p=\ Empty space in the database file is re-used automatically. To re-build the indexes, the simplest way is to delete the <code>.index.db</code> file while the database is closed. However in some situations (for example after deleting a lot of data in a database), one sometimes wants to shrink the size of the database (compact a database). Here is a sample function to do this\:
features_1610_p=\ See also the sample application <code>org.h2.samples.Compact</code>. The commands <code>SCRIPT / RUNSCRIPT</code> can be used as well to create a backup of a database and re-build the database from the script.
features_1611_h2=Cache Settings
features_1612_p=\ The database keeps most frequently used data and index pages in the main memory. The amount of memory used for caching can be changed using the setting <code>CACHE_SIZE</code>. This setting can be set in the database connection URL (<code>jdbc\:h2\:~/test;CACHE_SIZE\=131072</code>), or it can be changed at runtime using <code>SET CACHE_SIZE size</code>.
features_1613_p=\ Also supported is a second level soft reference cache. Rows in this cache are only garbage collected on low memory. By default the second level cache is disabled. To enable it, use the prefix <code>SOFT_</code>. Example\:<code>jdbc\:h2\:~/test;CACHE_TYPE\=SOFT_LRU</code>.
features_1614_p=\ To get information about page reads and writes, and the current caching algorithm in use, call <code>SELECT * FROM INFORMATION_SCHEMA.SETTINGS</code>. The number of pages read / written is listed for the data and index file.
