H2Dialect (Hibernate JavaDocs)
Date: 2012-04-05

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## org.hibernate.dialect
Class H2Dialect

    java.lang.Object
      org.hibernate.dialect.Dialect
          org.hibernate.dialect.H2Dialect

All Implemented Interfaces:
  ConversionContext

    public class H2Dialect

extends Dialect

A dialect compatible with the H2 database.

Field Summary

Fields inherited from class org.hibernate.dialect.Dialect
`CLOSED_QUOTE, DEFAULT_BATCH_SIZE, LEGACY_LOB_MERGE_STRATEGY, NEW_LOCATOR_LOB_MERGE_STRATEGY, NO_BATCH, QUOTE, STREAM_XFER_LOB_MERGE_STRATEGY`

Constructor Summary
`H2Dialect()`

Method Summary
`boolean` | `bindLimitParametersFirst()` Does the `LIMIT` clause come at the start of the `SELECT` statement, rather than at the end?
`boolean` | `bindLimitParametersInReverseOrder()` ANSI SQL defines the LIMIT clause to be in the form LIMIT offset, limit.
`boolean` | `doesReadCommittedCauseWritersToBlockReaders()` For the underlying database, is READ_COMMITTED isolation implemented by forcing readers to wait for write locks to be released?
`boolean` | `dropTemporaryTableAfterUse()` Do we need to drop the temporary table after use?
`String` | `getAddColumnString()` The syntax used to add a column to a table (optional).
`String` | `getCreateSequenceString(String sequenceName)` Typically dialects which support sequences can create a sequence with a single command.
`String` | `getCreateTemporaryTablePostfix()` Get any fragments needing to be postfixed to the command for temporary table creation.
`String` | `getCreateTemporaryTableString()` Command used to create a temporary table.
`String` | `getCurrentTimestampSelectString()` Retrieve the command used to retrieve the current timestamp from the database.
`String` | `getDropSequenceString(String sequenceName)` Typically dialects which support sequences can drop a sequence with a single command.
`String` | `getForUpdateString()` Get the string to append to SELECT statements to acquire locks for this dialect.
`String` | `getIdentityColumnString()` The syntax used during DDL to define a column as being an IDENTITY.
`String` | `getIdentityInsertString()` The keyword used to insert a generated value into an identity column (or null).
`String` | `getIdentitySelectString()` Get the select command to use to retrieve the last generated IDENTITY value.
`String` | `getLimitString(String sql, boolean hasOffset)` Apply s limit clause to the query.
`String` | `getQuerySequencesString()` Get the select command used retrieve the names of all sequences.
`String` | `getSelectSequenceNextValString(String sequenceName)` Generate the select expression fragment that will retrieve the next value of a sequence as part of another (typically DML) statement.
`String` | `getSequenceNextValString(String sequenceName)` Generate the appropriate select statement to to retrieve the next value of a sequence.
`ViolatedConstraintNameExtracter` | `getViolatedConstraintNameExtracter()`
`boolean` | `isCurrentTimestampSelectStringCallable()` Should the value returned by `Dialect.getCurrentTimestampSelectString()` be treated as callable.
`Boolean` | `performTemporaryTableDDLInIsolation()` Does the dialect require that temporary table DDL statements occur in isolation from other statements? This would be the case if the creation would cause any current transaction to get committed implicitly.
`boolean` | `supportsCurrentTimestampSelection()` Does this dialect support a way to retrieve the database's current timestamp value?
`boolean` | `supportsIdentityColumns()` Does this dialect support identity column key generation?
`boolean` | `supportsIfExistsAfterTableName()`
`boolean` | `supportsLimit()` Does this dialect support some form of limiting query results via a SQL clause?
`boolean` | `supportsLobValueChangePropogation()` Does the dialect support propagating changes to LOB values back to the database? Talking about mutating the internal value of the locator as opposed to supplying a new locator instance...
`boolean` | `supportsPooledSequences()` Does this dialect support "pooled" sequences.
`boolean` | `supportsSequences()` Does this dialect support sequences?
`boolean` | `supportsTemporaryTables()` Does this dialect support temporary tables?
`boolean` | `supportsTupleDistinctCounts()` Does this dialect support `count(distinct a,b)`?
`boolean` | `supportsUnionAll()` Does this dialect support UNION ALL, which is generally a faster variant of UNION?
`boolean` | `supportsUnique()` Does this dialect support the `UNIQUE` column syntax?

Methods inherited from class org.hibernate.dialect.Dialect
`appendIdentitySelectToInsert, appendLockHint, applyLocksToSql, areStringComparisonsCaseInsensitive, buildSQLExceptionConversionDelegate, buildSQLExceptionConverter, closeQuote, convertToFirstRowValue, createCaseFragment, createOuterJoinFragment, doesRepeatableReadCauseReadersToBlockWriters, dropConstraints, forceLimitUsage, forUpdateOfColumns, generateTemporaryTableName, getAddForeignKeyConstraintString, getAddPrimaryKeyConstraintString, getAddUniqueConstraintString, getCascadeConstraintsString, getCaseInsensitiveLike, getCastTypeName, getColumnAliasExtractor, getColumnComment, getCreateMultisetTableString, getCreateSequenceString, getCreateSequenceStrings, getCreateSequenceStrings, getCreateTableString, getCrossJoinSeparator, getCurrentTimestampSQLFunctionName, getDefaultProperties, getDialect, getDialect, getDropForeignKeyString, getDropSequenceStrings, getDropTemporaryTableString, getForUpdateNowaitString, getForUpdateNowaitString, getForUpdateString, getForUpdateString, getForUpdateString, getForUpdateString, getFunctions, getHibernateTypeName, getHibernateTypeName, getIdentityColumnString, getIdentitySelectString, getKeywords, getLimitString, getLobMergeStrategy, getLockingStrategy, getLowercaseFunction, getMaxAliasLength, getNativeIdentifierGeneratorClass, getNoColumnsInsertString, getNullColumnString, getReadLockString, getResultSet, getSelectClauseNullString, getSelectGUIDString, getSqlTypeDescriptorOverride, getTableComment, getTableTypeString, getTypeName, getTypeName, getWriteLockString, hasAlterTable, hasDataTypeInIdentityColumn, hasSelfReferentialForeignKeyBug, isLockTimeoutParameterized, openQuote, qualifyIndexName, quote, registerColumnType, registerColumnType, registerFunction, registerHibernateType, registerHibernateType, registerKeyword, registerResultSetOutParameter, remapSqlTypeDescriptor, replaceResultVariableInOrderByClauseWithPosition, requiresCastingOfParametersInSelectClause, supportsBindAsCallableArgument, supportsCascadeDelete, supportsCaseInsensitiveLike, supportsCircularCascadeDeleteConstraints, supportsColumnCheck, supportsCommentOn, supportsEmptyInList, supportsExistsInSelect, supportsExpectedLobUsagePattern, supportsIfExistsBeforeTableName, supportsInsertSelectIdentity, supportsLimitOffset, supportsLockTimeouts, supportsNotNullUnique, supportsOuterJoinForUpdate, supportsParametersInInsertSelect, supportsResultSetPositionQueryMethodsOnForwardOnlyCursor, supportsRowValueConstructorSyntax, supportsRowValueConstructorSyntaxInInList, supportsSubqueryOnMutatingTable, supportsSubselectAsInPredicateLHS, supportsTableCheck, supportsTupleCounts, supportsUnboundedLobLocatorMaterialization, supportsUniqueConstraintInCreateAlterTable, supportsVariableLimit, toBooleanValueString, toString, transformSelectString, useInputStreamToInsertBlob, useMaxForLimit`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Constructor Detail

### H2Dialect

    public H2Dialect()

Method Detail

### getAddColumnString

    public String getAddColumnString()

  Description copied from class: `Dialect`
  The syntax used to add a column to a table (optional).

  Overrides:
    `getAddColumnString` in class `Dialect`
  Returns:
    The "add column" fragment.

### supportsIdentityColumns

    public boolean supportsIdentityColumns()

  Description copied from class: `Dialect`
  Does this dialect support identity column key generation?

  Overrides:
    `supportsIdentityColumns` in class `Dialect`
  Returns:
    True if IDENTITY columns are supported; false otherwise.

### getIdentityColumnString

    public String getIdentityColumnString()

  Description copied from class: `Dialect`
  The syntax used during DDL to define a column as being an IDENTITY.

  Overrides:
    `getIdentityColumnString` in class `Dialect`
  Returns:
    The appropriate DDL fragment.

### getIdentitySelectString

    public String getIdentitySelectString()

  Description copied from class: `Dialect`
  Get the select command to use to retrieve the last generated IDENTITY value.

  Overrides:
    `getIdentitySelectString` in class `Dialect`
  Returns:
    The appropriate select command

### getIdentityInsertString

    public String getIdentityInsertString()

  Description copied from class: `Dialect`
  The keyword used to insert a generated value into an identity column (or null). Need if the dialect does not support inserts that specify no column values.

  Overrides:
    `getIdentityInsertString` in class `Dialect`
  Returns:
    The appropriate keyword.

### getForUpdateString

    public String getForUpdateString()

  Description copied from class: `Dialect`
  Get the string to append to SELECT statements to acquire locks for this dialect.

  Overrides:
    `getForUpdateString` in class `Dialect`
  Returns:
    The appropriate `FOR UPDATE` clause string.

### supportsUnique

    public boolean supportsUnique()

  Description copied from class: `Dialect`
  Does this dialect support the `UNIQUE` column syntax?

  Overrides:
    `supportsUnique` in class `Dialect`
  Returns:
    boolean

### supportsLimit

    public boolean supportsLimit()

  Description copied from class: `Dialect`
  Does this dialect support some form of limiting query results via a SQL clause?

  Overrides:
    `supportsLimit` in class `Dialect`
  Returns:
    True if this dialect supports some form of LIMIT.

### getLimitString

    public String getLimitString(String sql,
                                 boolean hasOffset)

  Description copied from class: `Dialect`
  Apply s limit clause to the query.

  Typically dialects utilize `variable` limit clauses when they support limits. Thus, when building the select command we do not actually need to know the limit or the offest since we will just be using placeholders.

  Here we do still pass along whether or not an offset was specified so that dialects not supporting offsets can generate proper exceptions. In general, dialects will override one or the other of this method and `Dialect.getLimitString(String, int, int)`.

  Overrides:
    `getLimitString` in class `Dialect`
  Parameters:
    `sql` - The query to which to apply the limit.
    `hasOffset` - Is the query requesting an offset?
  Returns:
    the modified SQL

### bindLimitParametersInReverseOrder

    public boolean bindLimitParametersInReverseOrder()

  Description copied from class: `Dialect`
  ANSI SQL defines the LIMIT clause to be in the form LIMIT offset, limit. Does this dialect require us to bind the parameters in reverse order?

  Overrides:
    `bindLimitParametersInReverseOrder` in class `Dialect`
  Returns:
    true if the correct order is limit, offset

### bindLimitParametersFirst

    public boolean bindLimitParametersFirst()

  Description copied from class: `Dialect`
  Does the `LIMIT` clause come at the start of the `SELECT` statement, rather than at the end?

  Overrides:
    `bindLimitParametersFirst` in class `Dialect`
  Returns:
    true if limit parameters should come before other parameters

### supportsIfExistsAfterTableName

    public boolean supportsIfExistsAfterTableName()

  Overrides:
    `supportsIfExistsAfterTableName` in class `Dialect`

### supportsSequences

    public boolean supportsSequences()

  Description copied from class: `Dialect`
  Does this dialect support sequences?

  Overrides:
    `supportsSequences` in class `Dialect`
  Returns:
    True if sequences supported; false otherwise.

### supportsPooledSequences

    public boolean supportsPooledSequences()

  Description copied from class: `Dialect`
  Does this dialect support "pooled" sequences. Not aware of a better name for this. Essentially can we specify the initial and increment values?

  Overrides:
    `supportsPooledSequences` in class `Dialect`
  Returns:
    True if such "pooled" sequences are supported; false otherwise.
  See Also:
    `Dialect.getCreateSequenceStrings(String, int, int)`, `Dialect.getCreateSequenceString(String, int, int)`

### getCreateSequenceString

    public String getCreateSequenceString(String sequenceName)

  Description copied from class: `Dialect`
  Typically dialects which support sequences can create a sequence with a single command. This is convenience form of `Dialect.getCreateSequenceStrings(java.lang.String)` to help facilitate that.

  Dialects which support sequences and can create a sequence in a single command need *only* override this method. Dialects which support sequences but require multiple commands to create a sequence should instead override `Dialect.getCreateSequenceStrings(java.lang.String)`.

  Overrides:
    `getCreateSequenceString` in class `Dialect`
  Parameters:
    `sequenceName` - The name of the sequence
  Returns:
    The sequence creation command

### getDropSequenceString

    public String getDropSequenceString(String sequenceName)

  Description copied from class: `Dialect`
  Typically dialects which support sequences can drop a sequence with a single command. This is convenience form of `Dialect.getDropSequenceStrings(java.lang.String)` to help facilitate that.

  Dialects which support sequences and can drop a sequence in a single command need *only* override this method. Dialects which support sequences but require multiple commands to drop a sequence should instead override `Dialect.getDropSequenceStrings(java.lang.String)`.

  Overrides:
    `getDropSequenceString` in class `Dialect`
  Parameters:
    `sequenceName` - The name of the sequence
  Returns:
    The sequence drop commands

### getSelectSequenceNextValString

    public String getSelectSequenceNextValString(String sequenceName)

  Description copied from class: `Dialect`
  Generate the select expression fragment that will retrieve the next value of a sequence as part of another (typically DML) statement.

  This differs from `Dialect.getSequenceNextValString(String)` in that this should return an expression usable within another statement.

  Overrides:
    `getSelectSequenceNextValString` in class `Dialect`
  Parameters:
    `sequenceName` - the name of the sequence
  Returns:
    The "nextval" fragment.

### getSequenceNextValString

    public String getSequenceNextValString(String sequenceName)

  Description copied from class: `Dialect`
  Generate the appropriate select statement to to retrieve the next value of a sequence.

  This should be a "stand alone" select statement.

  Overrides:
    `getSequenceNextValString` in class `Dialect`
  Parameters:
    `sequenceName` - the name of the sequence
  Returns:
    String The "nextval" select string.

### getQuerySequencesString

    public String getQuerySequencesString()

  Description copied from class: `Dialect`
  Get the select command used retrieve the names of all sequences.

  Overrides:
    `getQuerySequencesString` in class `Dialect`
  Returns:
    The select command; or null if sequences are not supported.
  See Also:
    `SchemaUpdate`

### getViolatedConstraintNameExtracter

    public ViolatedConstraintNameExtracter getViolatedConstraintNameExtracter()

  Specified by:
    `getViolatedConstraintNameExtracter` in interface `ConversionContext`
  Overrides:
    `getViolatedConstraintNameExtracter` in class `Dialect`

### supportsTemporaryTables

    public boolean supportsTemporaryTables()

  Description copied from class: `Dialect`
  Does this dialect support temporary tables?

  Overrides:
    `supportsTemporaryTables` in class `Dialect`
  Returns:
    True if temp tables are supported; false otherwise.

### getCreateTemporaryTableString

    public String getCreateTemporaryTableString()

  Description copied from class: `Dialect`
  Command used to create a temporary table.

  Overrides:
    `getCreateTemporaryTableString` in class `Dialect`
  Returns:
    The command used to create a temporary table.

### getCreateTemporaryTablePostfix

    public String getCreateTemporaryTablePostfix()

  Description copied from class: `Dialect`
  Get any fragments needing to be postfixed to the command for temporary table creation.

  Overrides:
    `getCreateTemporaryTablePostfix` in class `Dialect`
  Returns:
    Any required postfix.

### performTemporaryTableDDLInIsolation

    public Boolean performTemporaryTableDDLInIsolation()

  Description copied from class: `Dialect`
  Does the dialect require that temporary table DDL statements occur in isolation from other statements? This would be the case if the creation would cause any current transaction to get committed implicitly.

  JDBC defines a standard way to query for this information via the `DatabaseMetaData.dataDefinitionCausesTransactionCommit()` method. However, that does not distinguish between temporary table DDL and other forms of DDL; MySQL, for example, reports DDL causing a transaction commit via its driver, even though that is not the case for temporary table DDL.

  Possible return values and their meanings:
  - `Boolean.TRUE` - Unequivocally, perform the temporary table DDL in isolation.
  - `Boolean.FALSE` - Unequivocally, do not perform the temporary table DDL in isolation.
  - null - defer to the JDBC driver response in regards to `DatabaseMetaData.dataDefinitionCausesTransactionCommit()`

  Overrides:
    `performTemporaryTableDDLInIsolation` in class `Dialect`
  Returns:
    see the result matrix above.

### dropTemporaryTableAfterUse

    public boolean dropTemporaryTableAfterUse()

  Description copied from class: `Dialect`
  Do we need to drop the temporary table after use?

  Overrides:
    `dropTemporaryTableAfterUse` in class `Dialect`
  Returns:
    True if the table should be dropped.

### supportsCurrentTimestampSelection

    public boolean supportsCurrentTimestampSelection()

  Description copied from class: `Dialect`
  Does this dialect support a way to retrieve the database's current timestamp value?

  Overrides:
    `supportsCurrentTimestampSelection` in class `Dialect`
  Returns:
    True if the current timestamp can be retrieved; false otherwise.

### isCurrentTimestampSelectStringCallable

    public boolean isCurrentTimestampSelectStringCallable()

  Description copied from class: `Dialect`
  Should the value returned by `Dialect.getCurrentTimestampSelectString()` be treated as callable. Typically this indicates that JDBC escape syntax is being used...

  Overrides:
    `isCurrentTimestampSelectStringCallable` in class `Dialect`
  Returns:
    True if the `Dialect.getCurrentTimestampSelectString()` return is callable; false otherwise.

### getCurrentTimestampSelectString

    public String getCurrentTimestampSelectString()

  Description copied from class: `Dialect`
  Retrieve the command used to retrieve the current timestamp from the database.

  Overrides:
    `getCurrentTimestampSelectString` in class `Dialect`
  Returns:
    The command.

### supportsUnionAll

    public boolean supportsUnionAll()

  Description copied from class: `Dialect`
  Does this dialect support UNION ALL, which is generally a faster variant of UNION?

  Overrides:
    `supportsUnionAll` in class `Dialect`
  Returns:
    True if UNION ALL is supported; false otherwise.

### supportsLobValueChangePropogation

    public boolean supportsLobValueChangePropogation()

  Description copied from class: `Dialect`
  Does the dialect support propagating changes to LOB values back to the database? Talking about mutating the internal value of the locator as opposed to supplying a new locator instance...

  For BLOBs, the internal value might be changed by: `Blob.setBinaryStream(long)`, `Blob.setBytes(long, byte[])`, `Blob.setBytes(long, byte[], int, int)`, or `Blob.truncate(long)`.

  For CLOBs, the internal value might be changed by: `Clob.setAsciiStream(long)`, `Clob.setCharacterStream(long)`, `Clob.setString(long, String)`, `Clob.setString(long, String, int, int)`, or `Clob.truncate(long)`.

  NOTE : I do not know the correct answer currently for databases which (1) are not part of the cruise control process or (2) do not `Dialect.supportsExpectedLobUsagePattern()`.

  Overrides:
    `supportsLobValueChangePropogation` in class `Dialect`
  Returns:
    True if the changes are propagated back to the database; false otherwise.

### supportsTupleDistinctCounts

    public boolean supportsTupleDistinctCounts()

  Description copied from class: `Dialect`
  Does this dialect support `count(distinct a,b)`?

  Overrides:
    `supportsTupleDistinctCounts` in class `Dialect`
  Returns:
    True if the database supports counting distinct tuples; false otherwise.

### doesReadCommittedCauseWritersToBlockReaders

    public boolean doesReadCommittedCauseWritersToBlockReaders()

  Description copied from class: `Dialect`
  For the underlying database, is READ_COMMITTED isolation implemented by forcing readers to wait for write locks to be released?

  Overrides:
    `doesReadCommittedCauseWritersToBlockReaders` in class `Dialect`
  Returns:
    True if writers block readers to achieve READ_COMMITTED; false otherwise.

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