H2 Database Engine

H2 Database Engine is an open source, multiplatform and free graphical software implemented in Java and designed to provide users with a very fast JDBC API that features a browser-based console and leaves a very small footprint (around 1 MB).

The application comes with an embedded mode (in-memory databases), which is faster than the client-server mode. It also features support for encrypted databases, an ODBC (Open Database Connectivity) driver, full-text search, as well as multi version concurrency.

Features at a glance

Key features include a very fast database engine, support for standard SQL and JDBC API, clustering support, powerful security options, support for the PostgreSQL ODBC driver, in-memory tables, in-memory databases, disk-based databases, disk-based tables, temporary tables, support for read-only databases, transaction support and table level locking.

In addition, the software features 2-phase-commit support, cost-based optimizer, support for multiple connections, support for result sets that are updatable and scrollable, support for external result sorting, support for large result sets, support for AES (Advanced Encryption Standard) encrypted databases, SSL (Secure Socket Layer) support, as well as support for SHA-256 encrypted passwords.

Among other features worth mentioning, we can easily name support for information schema and multiple schemas, collation support, support for roles and users, lossless data compression, outer and inner joins, inline views, read-only views, subqueries, referential integrity, check constraints, autoincrement columns, computed columns and sequence columns.

Supported database servers

Currently, H2 Database Engine is fully compatible with the well known MySQL, PostgreSQL, IBM DB2, Apache Derby, Microsoft SQL Server, Oracle and HSQLDB database servers/engines.

Under the hood and supported operating systems

Being written in the Java programming language, the H2 Database Engine project is platform-independent and supports any operating system where the Java Runtime Environment (JRE) is available, including GNU/Linux, Microsoft Windows, Mac OS X, Solaris and BSD.

What is new in this release:

• EXPLAIN was incorrect for queries with "ANY" or "SOME" conditions.
• CallableStatement with "out" parameters: running the same statement twice could result in an exception ("parameter not set").
• Union queries: duplicate rows could be returned if the sub-queries contained "order by".
• The GEOMETRY data type now works for user defined functions that return a result set.
• PostgreSQL compatibility: the PgServer was not working properly when the setting database_to_upper was set to false.
• JdbcDataSource: the methods setUrl and getUrl where added as aliases for setURL and getURL. This should solve problems with the HikariCP (Hikari connection pool).
• Issue 537: H2 Console: when loading the schema, incorrect JDBC calls where issued, which caused the exception "Column PRECISION not found".
• Improved Geometry processing (issue 535).
• The collation can now be set in the database URL, even if there are data tables, if the collection is the same as the current collation.
• Improved Oracle compatibility for CASE WHEN and DECODE.
• The statement "drop all objects" did not work if a table depends on a view via a constraint.
• Subqueries or views with "order by" an alias expression could not be executed due to a regression introduced in version 1.3.174.
• Issue 73: MySQL compatibility: support REPLACE, patch by Cemo Koc.
• The spatial index now works in MVCC mode when using the MVStore storage.
• MVStore: concurrency problems have been fixed. The API has been simplified.
• Improve error message when dropping an index that belongs to a constraint, specify constraint in error message.
• Issue 518: java.sql.Connection.commit() freezes after LOB modification with EXCLUSIVE connection
• Issue 517: Create or replace view statement has no effect on the others already existing JDBC connection
• Support 123L syntax as in Java; example: SELECT (2000000000L*2).
• Issue 520: Add support for sequence max value, min value and cycle, patch by Daniel Gredler.
• Issue 521: ScriptReader should implement Closeable
• Issue 524: RunScript.execute does not close its Statement, patch from Gaul.
• Add support for DB2 "WITH UR" clause, patch from litailang
• Added support for ON DUPLICATE KEY UPDATE like MySQL with the values() function to update with the value that was to be inserted. Patch from Jean-Francois Noel.
• Issue 522: Treat empty strings like NULL in Oracle compatibility mode, patch by Daniel Gredler.
• Issue 527: Oracle compatibility mode: incorrect scale behavior, patch by Daniel Gredler.
• Slightly reduce the memory cost of View metadata.
• Extend support of "GRANT ALTER ANY SCHEMA TO " to allow grantee ability to manipulate tables
• Issue 532: Javadoc for ErrorCode.ROLES_AND_RIGHT_CANNOT_BE_MIXED looks wrong
• Issue 528: Add Oracle-compatible TO_CHAR function, patch by Daniel Gredler.
• Issue 534: CREATE ALIAS NOCACHE, Patch by Nicolas Fortin
• Fix an issue with storing Unicode surrogate pairs in CLOB columns.
• H2 console: add SHIFT+ENTER "run selected" functionality
• Fix bug in DB2 syntax "select * from test with ur", patch from litailang
• Fix bug in DROP ALL OBJECTS when dealing with inter-schema dependencies.

What is new in version 1.3.174:

• LIRS cache: bugfix for caches that only contain non-resident entries.
• For in-memory databases, queries with a "group by" column that is also a hash index threw a RuntimeException.
• Improved error message for some syntax errors.
• File system abstraction: if used directly, some file systems did not work correctly with spliced byte buffers (the database engine doesn't use those).
• To use the MVStore storage engine (which is still work in progress), append ";mv_store=true" to the database URL. Using the MVTableEngine when creating the table is no longer recommended.
• To compile user defined functions, the javax.tools.JavaCompiler is now used if available, and no temporary files are created. This should solve problems when multiple H2 database concurrently compile the same user defined functions. To disable, system the system property "h2.javaSystemCompiler" to false.
• Concurrently creating function aliases in different databases could result in the exception "javac: file not found".
• The function "regexp_replace" threw the wrong kind of exception if the replacement string was invalid.
• A checkpoint is now done every MAX_LOG_SIZE / 2 instead of every MAX_LOG_SIZE, so that the transaction log doesn't grow as large.
• MVStore table engine: new setting "retention_time" to configure the time to retain old data. The default is 45 seconds.
• The method TableEngine.createTable() now returns a Table object.
• For read-only databases, for the trace level "debug", the trace info is written to the temp directory.
• Closing the file lock will now wait until the background thread is stopped.
• In version 1.3.172, a performance regression was introduced when fixing the issue 389 (when there is a multi-column primary key, H2 does not seem to always pick the right index). This was related to boosting an index that matches the "order by" column list (the wrong index was used in some cases).
• Improved spatial index and data type.
• Issue 467: OSGi Class Loader (ability to create reference to class in other ClassLoader, for example in another OSGi bundle).
• Queries "group by" that contain a subquery with an aggregate function returned the wrong result in some cases.
• Fix bug in unique and non-unique hash indexes which manifested as incorrect results when the search key was a different cardinal type from the table index key. e.g. where the one was INT and the other was LONG
• Bug: Changes to the database structure did not result in the Session query cache being invalidated.
• New feature from Davide Cavestro - allow using custom Java object serialization engines on a per-DB basis.
• When running the Recover tool on very large (>6G) databases, some statistics were reported with negative numbers.
• Add a CONTAINS_UNCOMMITTED column to the SESSIONS metadata table, to allow detecting when rogue sessions are creating large transactions.
• Some small fixes to the GEOMETRY support, patches by Nicolas Fortin.
• The BNF tool and the autocomplete feature are exported in OSGi, which makes it possible for smart editors to do autocomplete. Patch from Nicolas Fortin.
• Fix DROP ALL OBJECTS and DROP SCHEMA in the presence of tables with computed column dependencies.
• Session-temporary LOB's could sometimes accumulate, increasing the size of the DB file until shutdown. Now they are cleared out at every commit.
• There was a bug where a hash index with more than one column would be silently converted to a regular index. It will now throw an exception.
• Query Statistics: new feature which stores the newest 100 SQL queries executed and their performance data. Useful for tracking down badly performing queries.
• Fix an LOB deadlock between reading and updating LOB columns.
• Support the JDBC DatabaseMetaData#getClientInfoProperties() method, in the sense of returning an empty result, in order to make WebSphere happy.
• Make Server#openBrowser respect the $BROWSER environment variable. Add "chromium" to the list of browsers tried. Patch from Felix Kaiser.
• Fix to org.h2.util.ScriptReader when handling unclosed block comments.
• Make org.h2.util.ScriptReader throw a better exception when handling broken scripts which generate extremely large statements.
• Fix bug with ALLOW_LITERALS=NONE, where the periodic analyze table on insert would throw an exception. A similar problem was fixed in the Console tool.
• Issue 510: Make org.h2.bnf public for consumption by external projects, patch by Nicolas Fortin
• Issue 509: Important fix on ValueGeometry, patch by Nicolas Fortin (with some tweaking) Make ValueGeometry#getDimensionCount more reliable. Add unit test to check for illegal ValueGeometry comparison Add unit test for conversion of Geometry object into Object Add optional export to MANIFEST.MF for JTS Geometry classes Validate that geometry values can be represented in WKB.
• Issue 506: RFE: Include Thread.getName() in case of a deadlock
• Adding support for "GRANT ALTER ANY SCHEMA TO ", patch by John Yates

What is new in version 1.3.173:

• This version improves MySQL and PostgreSQL compatibility, improves the MVStore storage engine, and adds the new data type "geometry" for spatial data.

What is new in version 1.3.171:

• Security: the TCP server did not correctly restrict access rights of clients in some cases. This was specially a problem when using the flag "tcpAllowOthers".
• H2 Console: the session timeout can now be configured using the system property "h2.consoleTimeout".
• Issue 431: Improved compatibility with MySQL: support for "ENGINE=InnoDB charset=UTF8" when creating a table.
• Issue 249: Improved compatibility with MySQL in the MySQL mode: now the methods DatabaseMetaData methods stores*Case*Identifiers return the same as MySQL when using the MySQL mode.
• Issue 434: H2 Console didn't work in the Chrome browser due to a wrong viewport argument.
• There was a possibility that the .lock.db file was not deleted when the database was closed, which could slow down opening the database.
• The SQL script generated by the "script" command contained inconsistent newlines on Windows.
• When using trace level 4 (SLF4J) in the server mode, a directory "trace.db" and an empty file was created on the client side. This is no longer made.
• Optimize IN(...) queries: there was a bug in version 1.3.170 if the type of the left hand side didn't match the type of the right hand side. Fixed.
• Optimize IN(...) queries: there was a bug in version 1.3.170 for comparison of the type "X IN(NULL, NULL)". Fixed.
• Timestamps with timezone that were passed as a string were not always converted correctly. For example "2012-11-06T23:00:00.000Z" was converted to "2012-11-06" instead of to "2012-11-07" in the timezone CET. Thanks a lot to Steve Hruda for reporting the problem!
• New table engine "org.h2.mvstore.db.MVTableEngine" that internally uses the MVStore to persist data. To try it out, append ";DEFAULT_TABLE_ENGINE=org.h2.mvstore.db.MVTableEngine" to the database URL. This is still very experimental, and many features are not supported yet. The data is stored in a file with the suffix ".mv.db".
• New connection setting "DEFAULT_TABLE_ENGINE" to use a specific table engine if none is set explicitly. This is to simplify testing the MVStore table engine.
• MVStore: encrypted stores are now supported. Only standardized algorithms are used: PBKDF2, SHA-256, XTS-AES, AES-128.
• MVStore: improved API thanks to Simo Tripodi.
• MVStore: maps can now be renamed.
• MVStore: store the file header also at the end of each chunk, which results in a further reduced number of write operations.
• MVStore: a map implementation that supports concurrent operations.
• MVStore: unified exception handling; the version is included in the messages.
• MVStore: old data is now retained for 45 seconds by default.
• MVStore: compress is now disabled by default, and can be enabled on request.
• Support ALTER TABLE ADD ... AFTER. Patch from Andrew Gaul (argaul at gmail.com). Fixes issue 401.
• Improved OSGi support. H2 now registers itself as a DataSourceFactory service. Fixes issue 365.
• Add a DISK_SPACE_USED system function. Fixes issue 270.
• Fix a compile-time ambiguity when compiling with JDK7, thanks to a patch from Lukas Eder.
• Supporting dropping an index for Lucene full-text indexes.
• Optimized performance for SELECT ... ORDER BY X LIMIT Y OFFSET Z queries for in-memory databases using partial sort (by Sergi Vladykin).
• Experimental off-heap memory storage engine "nioMemFS:" and "nioMemLZF:", suggestion from Mark Addleman.
• Issue 438: JdbcDatabaseMetaData.getSchemas() is no longer supported as of 1.3.169.
• MySQL compatibility: support for ALTER TABLE tableName MODIFY [COLUMN] columnName columnDef. Patch from Ville Koskela.
• Issue 404: SHOW COLUMNS FROM tableName does not work with ALLOW_LITERALS=NUMBERS.
• Throw an explicit error to make it clear we don't support the TRIGGER combination of SELECT and FOR EACH ROW.
• Issue 439: Utils.sortTopN does not handle single-element arrays.

What is new in version 1.3.170:

• Issue 407: The TriggerAdapter didn't work with CLOB and BLOB columns.
• PostgreSQL compatibility: support for data types BIGSERIAL and SERIAL as an alias for AUTO_INCREMENT.
• Issue 417: H2 Console: the web session timeout didn't work, resulting in a memory leak. This was only a problem if the H2 Console was run for a long time and many sessions were opened.
• Issue 412: Running the Server tool with just the option "-browser" will now log a warning.
• Issue 411: CloseWatcher registration was not concurrency-safe.
• MySQL compatibility: support for CONCAT_WS. Thanks a lot to litailang for the patch!
• PostgreSQL compatibility: support for EXTRACT(WEEK FROM dateColumn). Thanks to Prashant Bhat for the patch!
• Fix for a bug where we would sometimes use the wrong unique constraint to validate foreign key constraints.
• Support BOM at the beginning of files for the RUNSCRIPT command
• Fix in calling SET @X = IDENTITY() where it would return NULL incorrectly
• Fix ABBA deadlock between adding a constraint and the H2-Log-Writer thread.
• Optimize IN(...) queries where the values are constant and of the same type.
• Restore tool: the parameter "quiet" was not used and is now removed.
• Fix ConcurrentModificationException when creating tables and executing SHOW TABLES in parallel. Reported by Viktor Voytovych.
• Serialization is now pluggable using the system property "h2.javaObjectSerializer". Thanks to Sergi Vladykin for the patch!

What is new in version 1.3.169:

• The default jar file is now compiled for Java 6.
• The new jar file will probably not end up in the central Maven repository in the next few weeks because Sonatype has disabled automatic synchronization from SourceForge (which they call 'legacy sync' now). It will probably take some time until this is sorted out. The H2 jar files are deployed to http://h2database.com/m2-repo/com/h2database/h2/maven-metadata.xml and http://hsql.sourceforge.net/m2-repo/com/h2database/h2/maven-metadata.xml as usual.
• A part of the documentation and the H2 Console has been changed to support the Apple retina display.
• The CreateCluster tool could not be used if the source database contained a CLOB or BLOB. The root cause was that the TCP server did not synchronize on the session, which caused a problem when using the exclusive mode.
• Statement.getQueryTimeout(): only the first call to this method will query the database. If the query timeout was changed in another way than calling setQueryTimeout, this method will always return the last value. This was changed because Hibernate calls getQueryTimeout() a lot.
• Issue 416: PreparedStatement.setNString throws AbstractMethodError. All implemented JDBC 4 methods that don't break compatibility with Java 5 are now included in the default jar file.
• Issue 414: for some functions, the parameters were evaluated twice (for example "char(nextval(..))" ran "nextval(..)" twice).
• The ResultSetMetaData methods getSchemaName and getTableName could return null instead of "" (an empty string) as specified in the JDBC API.
• Added compatibility for "SET NAMES" query in MySQL compatibility mode.

What is new in version 1.3.168:

• The message "Transaction log could not be truncated" was sometimes written to the .trace.db file even if there was no problem truncating the transaction log.
• New system property "h2.serializeJavaObject" (default: true) that allows to disable serializing Java objects, so that the objects compareTo and toString methods can be used.
• Dylan has translated the H2 Console tool to Korean. Thanks a lot!
• Executing the statement CREATE INDEX IF ALREADY EXISTS if the index already exists no longer fails for a read only database.
• MVCC: concurrently updating a row could result in the row to appear deleted in the second connection, if there are multiple unique indexes (or a primary key and at least one unique index). Thanks a lot to Teruo for the patch!
• Fulltext search: in-memory Lucene indexes are now supported.
• Fulltext search: UUID primary keys are now supported.
• Apache Tomcat 7.x will now longer log a warning when unloading the web application, if using a connection pool.
• H2 Console: support the Midori browser (for Debian / Raspberry Pi)
• When opening a remote session, don't open a temporary file if the trace level is set to zero
• Use HMAC for authenticating remote LOB id's, removing the need for maintaining a cache, and removing the limit on the number of LOBs per result set.
• H2 Console: HTML and XML documents can now be edited in an updatable result set. There is (limited) support for editing multi-line documents.

What is new in version 1.3.164:

• Updating a result set in a trigger is now supported.

What is new in version 11.3.162:

• The following system properties are no longer supported: h2.allowBigDecimalExtensions, h2.emptyPassword, h2.minColumnNameMap, h2.returnLobObjects, h2.webMaxValueLength.
• When using a VPN, starting a H2 server did not work (for some VPN software).
• Oracle compatibility: support for DECODE(...).
• Lucene fulltext search: creating an index is now faster if the table already contains data. Thanks a lot to Angel Leon from the FrostWire Team for the patch!
• Update statements with a column list in brackets did not work if the list only contains one column. Example: update test set (id)=(id).
• Read-only databases in a zip file did not work when using the -baseDir option.
• Issue 334: SimpleResultSet.getString now also works for Clob columns.
• Subqueries with an aggregate did not always work. Example: select (select count(*) from test where a = t.a and b = 0) from test t group by a
• Server: in some (theoretical) cases, exceptions while closing the connection were ignored.
• Server.createTcpServer, createPgServer, createWebServer: invalid arguments are now detected.
• The selectivity of LOB columns is no longer calculated because indexes on LOB columns are not supported (however this should have little effect on performance, as the selectivity is calculated from the hash code and not the data).
• New experimental system property "h2.modifyOnWrite": when enabled, the database file is only modified when writing to the database. When enabled, the serialized file lock is much faster for read-only operations.
• A NullPointerException could occur in TableView.isDeterministic for invalid views.
• Issue 180: when deserializing objects, the context class loader is used instead of the default class loader if the system property "h2.useThreadContextClassLoader" is set. Thanks a lot to Noah Fontes for the patch!
• When using the exclusive mode, LOB operations could cause the thread to block. This also affected the CreateCluster tool (when using BLOB or CLOB data).
• The optimization for "group by" was not working correctly if the group by column was aliased in the select list.
• Issue 326: improved support for case sensitive (mixed case) identifiers without quotes when using DATABASE_TO_UPPER=FALSE.

Requirements:

• Java 2 Standard Edition Runtime Environment