Package org.hibernate.dialect

Class DB2Dialect

java.lang.Object
org.hibernate.dialect.Dialect
org.hibernate.dialect.DB2Dialect
Direct Known Subclasses:
DB2390Dialect, DB2400Dialect, DerbyDialect
public class DB2Dialect extends Dialect
An SQL dialect for DB2.

  • Constructor Details

    • DB2Dialect

      public DB2Dialect()

  • Method Details

    • 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.

    • 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.

    • 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

    • 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.

    • 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.

    • 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.

    • 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

    • 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:

    • 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:

    • 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

    • convertToFirstRowValue

      public int convertToFirstRowValue(int zeroBasedFirstResult)
      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 offset
      Returns:
      zeroBasedFirstResult
      See Also:

    • 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.

    • supportsNotNullUnique

      public boolean supportsNotNullUnique()
      Overrides:
      supportsNotNullUnique in class Dialect

    • 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.

    • main

      public static void main(String[] args)

    • 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 an OUT parameter which will be returning a ResultSet. How this is accomplished varies greatly from DB to DB, hence its inclusion (along with Dialect.getResultSet(java.sql.CallableStatement)) here.
      Overrides:
      registerResultSetOutParameter in class Dialect
      Parameters:
      statement - The callable statement.
      col - The bind position at which to register the OUT param.
      Returns:
      The number of (contiguous) bind positions used.
      Throws:
      SQLException - Indicates problems registering the OUT param.

    • getResultSet

      public ResultSet getResultSet(CallableStatement ps) throws SQLException
      Description copied from class: Dialect
      Given a callable statement previously processed by Dialect.registerResultSetOutParameter(java.sql.CallableStatement, int), extract the ResultSet from the OUT parameter.
      Overrides:
      getResultSet in class Dialect
      Parameters:
      ps - The callable statement.
      Returns:
      The extracted result set.
      Throws:
      SQLException - Indicates problems extracting the result set.

    • supportsCommentOn

      public boolean supportsCommentOn()
      Overrides:
      supportsCommentOn 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.

    • generateTemporaryTableName

      public String generateTemporaryTableName(String baseTableName)
      Description copied from class: Dialect
      Generate a temporary table name given the base table.
      Overrides:
      generateTemporaryTableName in class Dialect
      Parameters:
      baseTableName - The table name from which to base the temp table name.
      Returns:
      The generated temp table name.

    • 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.

    • 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.

    • supportsParametersInInsertSelect

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

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

      Overrides:
      supportsParametersInInsertSelect in class Dialect
      Returns:
      True.

    • requiresCastingOfParametersInSelectClause

      public boolean requiresCastingOfParametersInSelectClause()
      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.

    • supportsResultSetPositionQueryMethodsOnForwardOnlyCursor

      public boolean supportsResultSetPositionQueryMethodsOnForwardOnlyCursor()
      Description copied from class: Dialect
      Does this dialect support asking the result set its positioning information on forward only cursors. Specifically, in the case of scrolling fetches, Hibernate needs to use ResultSet.isAfterLast() and ResultSet.isBeforeFirst(). Certain drivers do not allow access to these methods for forward only cursors.

      NOTE : this is highly driver dependent!

      Overrides:
      supportsResultSetPositionQueryMethodsOnForwardOnlyCursor in class Dialect
      Returns:
      True if methods like ResultSet.isAfterLast() and ResultSet.isBeforeFirst() are supported for forward only cursors; false otherwise.

    • getCrossJoinSeparator

      public String getCrossJoinSeparator()
      Description copied from class: Dialect
      Get 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:

    • 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.

    • 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.

    • 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 disintct tuples; false otherwise.