Class DB2Dialect

    • Constructor Detail

      • DB2Dialect

        public DB2Dialect()
        Constructs a DB2Dialect
    • Method Detail

      • getLowercaseFunction

        public String getLowercaseFunction()
        Description copied from class: Dialect
        The name of the SQL function that transforms a string to lowercase
        Overrides:
        getLowercaseFunction in class Dialect
        Returns:
        The dialect-specific lowercase function.
      • 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.
      • dropConstraints

        public boolean dropConstraints()
        Description copied from class: Dialect
        Do we need to drop constraints before dropping tables in this dialect?
        Overrides:
        dropConstraints in class Dialect
        Returns:
        True if constraints must be dropped prior to dropping the table; false otherwise.
      • 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.
      • getSelectSequenceNextValString

        public String getSelectSequenceNextValString​(String sequenceName)
                                              throws MappingException
        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.
        Throws:
        MappingException - If sequences are not supported.
      • 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
      • 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.
      • 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
      • 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.
      • supportsVariableLimit

        public boolean supportsVariableLimit()
        Description copied from class: Dialect
        Does this dialect support bind variables (i.e., prepared statement parameters) for its limit/offset?
        Overrides:
        supportsVariableLimit in class Dialect
        Returns:
        True if bind variables can be used; false otherwise.
      • getLimitString

        public String getLimitString​(String sql,
                                     int offset,
                                     int limit)
        Description copied from class: Dialect
        Given a limit and an offset, apply the limit clause to the query.
        Overrides:
        getLimitString in class Dialect
        Parameters:
        sql - The query to which to apply the limit.
        offset - The offset of the limit
        limit - The limit of the limit ;)
        Returns:
        The modified query statement with the limit applied.
      • convertToFirstRowValue

        public int convertToFirstRowValue​(int zeroBasedFirstResult)
        Hibernate APIs explicitly state that setFirstResult() should be a zero-based offset. Here we allow the Dialect a chance to convert that value based on what the underlying db or driver will expect.

        NOTE: what gets passed into Dialect.getLimitString(String,int,int) is the zero-based offset. Dialects which do not Dialect.supportsVariableLimit() should take care to perform any needed first-row-conversion calls prior to injecting the limit values into the SQL string.

        DB2 does have a one-based offset, however this was actually already handled in the limit string building (the '?+1' bit). To not mess up inheritors, I'll leave that part alone and not touch the offset here.

        Overrides:
        convertToFirstRowValue in class Dialect
        Parameters:
        zeroBasedFirstResult - The user-supplied, zero-based first row offset.
        Returns:
        The corresponding db/dialect specific offset.
        See Also:
        Query.setFirstResult(int), Criteria.setFirstResult(int)
      • 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.
      • useMaxForLimit

        public boolean useMaxForLimit()
        Description copied from class: Dialect
        Does the LIMIT clause take a "maximum" row number instead of a total number of returned rows?

        This is easiest understood via an example. Consider you have a table with 20 rows, but you only want to retrieve rows number 11 through 20. Generally, a limit with offset would say that the offset = 11 and the limit = 10 (we only want 10 rows at a time); this is specifying the total number of returned rows. Some dialects require that we instead specify offset = 11 and limit = 20, where 20 is the "last" row we want relative to offset (i.e. total number of rows = 20 - 11 = 9)

        So essentially, is limit relative from offset? Or is limit absolute?

        Overrides:
        useMaxForLimit in class Dialect
        Returns:
        True if limit is relative from offset; false otherwise.
      • supportsOuterJoinForUpdate

        public boolean supportsOuterJoinForUpdate()
        Description copied from class: Dialect
        Does this dialect support FOR UPDATE in conjunction with outer joined rows?
        Overrides:
        supportsOuterJoinForUpdate in class Dialect
        Returns:
        True if outer joined rows can be locked via FOR UPDATE.
      • supportsExistsInSelect

        public boolean supportsExistsInSelect()
        Description copied from class: Dialect
        Does the dialect support an exists statement in the select clause?
        Overrides:
        supportsExistsInSelect in class Dialect
        Returns:
        True if exists checks are allowed in the select clause; false otherwise.
      • supportsLockTimeouts

        public boolean supportsLockTimeouts()
        Description copied from class: Dialect
        Informational metadata about whether this dialect is known to support specifying timeouts for requested lock acquisitions.
        Overrides:
        supportsLockTimeouts in class Dialect
        Returns:
        True is this dialect supports specifying lock timeouts.
      • getSelectClauseNullString

        public String getSelectClauseNullString​(int sqlType)
        Description copied from class: Dialect
        Given a Types type code, determine an appropriate null value to use in a select clause.

        One thing to consider here is that certain databases might require proper casting for the nulls here since the select here will be part of a UNION/UNION ALL.

        Overrides:
        getSelectClauseNullString in class Dialect
        Parameters:
        sqlType - The Types type code.
        Returns:
        The appropriate select clause value fragment.
      • 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.
      • registerResultSetOutParameter

        public int registerResultSetOutParameter​(CallableStatement statement,
                                                 int col)
                                          throws SQLException
        Description copied from class: Dialect
        Registers a parameter (either OUT, or the new REF_CURSOR param type available in Java 8) capable of returning ResultSet *by position*. Pre-Java 8, registering such ResultSet-returning parameters varied greatly across database and drivers; hence its inclusion as part of the Dialect contract.
        Overrides:
        registerResultSetOutParameter in class Dialect
        Parameters:
        statement - The callable statement.
        col - The bind position at which to register the output param.
        Returns:
        The number of (contiguous) bind positions used.
        Throws:
        SQLException - Indicates problems registering the param.
      • supportsCommentOn

        public boolean supportsCommentOn()
        Description copied from class: Dialect
        Does this dialect/database support commenting on tables, columns, etc?
        Overrides:
        supportsCommentOn in class Dialect
        Returns:
        true if commenting is supported
      • 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.
      • 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.
      • supportsParametersInInsertSelect

        public boolean supportsParametersInInsertSelect()
        Does this dialect support parameters within the SELECT clause of INSERT ... SELECT ... statements?

        NOTE : DB2 is know to support parameters in the SELECT clause, but only in casted form (see requiresCastingOfParametersInSelectClause()).

        Overrides:
        supportsParametersInInsertSelect in class Dialect
        Returns:
        True if this is supported; false otherwise.
      • requiresCastingOfParametersInSelectClause

        public boolean requiresCastingOfParametersInSelectClause()
        Does this dialect require that parameters appearing in the SELECT clause be wrapped in cast() calls to tell the db parser the expected type.

        DB2 in fact does require that parameters appearing in the select clause be wrapped in cast() calls to tell the DB parser the type of the select value.

        Overrides:
        requiresCastingOfParametersInSelectClause in class Dialect
        Returns:
        True if select clause parameter must be cast()ed
      • getCrossJoinSeparator

        public String getCrossJoinSeparator()
        Description copied from class: Dialect
        Returns the separator to use for defining cross joins when translating HQL queries.

        Typically this will be either [ cross join ] or [, ]

        Note that the spaces are important!

        Overrides:
        getCrossJoinSeparator in class Dialect
        Returns:
        The cross join separator
      • supportsEmptyInList

        public boolean supportsEmptyInList()
        Description copied from class: Dialect
        Does this dialect support empty IN lists?

        For example, is [where XYZ in ()] a supported construct?

        Overrides:
        supportsEmptyInList in class Dialect
        Returns:
        True if empty in lists are supported; 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.
      • 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.
      • buildSQLExceptionConversionDelegate

        public SQLExceptionConversionDelegate buildSQLExceptionConversionDelegate()
        Description copied from class: Dialect
        Build an instance of a SQLExceptionConversionDelegate for interpreting dialect-specific error or SQLState codes.

        When Dialect.buildSQLExceptionConverter() returns null, the default SQLExceptionConverter is used to interpret SQLState and error codes. If this method is overridden to return a non-null value, the default SQLExceptionConverter will use the returned SQLExceptionConversionDelegate in addition to the following standard delegates:

        1. a "static" delegate based on the JDBC 4 defined SQLException hierarchy;
        2. a delegate that interprets SQLState codes for either X/Open or SQL-2003 codes, depending on java.sql.DatabaseMetaData#getSQLStateType

        It is strongly recommended that specific Dialect implementations override this method, since interpretation of a SQL error is much more accurate when based on the a vendor-specific ErrorCode rather than the SQLState.

        Specific Dialects may override to return whatever is most appropriate for that vendor.

        Overrides:
        buildSQLExceptionConversionDelegate in class Dialect
        Returns:
        The SQLExceptionConversionDelegate for this dialect
      • getUniqueDelegate

        public UniqueDelegate getUniqueDelegate()
        Description copied from class: Dialect
        Get the UniqueDelegate supported by this dialect
        Overrides:
        getUniqueDelegate in class Dialect
        Returns:
        The UniqueDelegate
      • getNotExpression

        public String getNotExpression​(String expression)
        Description copied from class: Dialect
        Negate an expression
        Overrides:
        getNotExpression in class Dialect
        Parameters:
        expression - The expression to negate
        Returns:
        The negated expression
      • getLimitHandler

        public LimitHandler getLimitHandler()
        Description copied from class: Dialect
        Returns the delegate managing LIMIT clause.
        Overrides:
        getLimitHandler in class Dialect
        Returns:
        LIMIT clause delegate.
      • renderOrderByElement

        public String renderOrderByElement​(String expression,
                                           String collation,
                                           String order,
                                           NullPrecedence nullPrecedence)
        Handle DB2 "support" for null precedence...
        Overrides:
        renderOrderByElement in class Dialect
        Parameters:
        expression - The SQL order expression. In case of @OrderBy annotation user receives property placeholder (e.g. attribute name enclosed in '{' and '}' signs).
        collation - Collation string in format collate IDENTIFIER, or null if expression has not been explicitly specified.
        order - Order direction. Possible values: asc, desc, or null if expression has not been explicitly specified.
        nullPrecedence - Nulls precedence. Default value: NullPrecedence.NONE.
        Returns:
      • supportsPartitionBy

        public boolean supportsPartitionBy()
        Description copied from class: Dialect
        Does the underlying database support partition by
        Overrides:
        supportsPartitionBy in class Dialect
        Returns:
        boolean