Method Detail

• getSQLClause

  public static java.lang.String getSQLClause(SQLClauseType type,
                              DSRequest dsRequest)
                                       throws java.lang.Exception

  Returns the text of the generated SQL we will use to implement a clause of the supplied type for the supplied DSRequest. The clause text will be exactly the same as the value of the corresponding $defaultXxxxxClause Velocity variable that you can use when developing your own customSQL queries. Clauses consist of just the variable part and exclude the SQL keywords. The one exception to this is the special clause type "All"; if you specify this clause type, we return a full-formed SQL query suitable for passing straight to the executeQuery() or executeUpdate() method of a JDBC driver or equivalent.

  Note that we ordinarily generate SQL that is self-contained and context-free, so you can store the clauses that this API returns and use them to construct a query for later execution without any dependence on the DSRequest. However, we are not always able to do this; binary columns and CLOBs cannot be assigned inline, so we have to generate SQL containing '?' markers, which can only be executed as parameterized queries. This in turn means that you need to store the values of any such fields in order to provide them as parameters when you come to execute the query.

  Also note that the query clauses produced by SQLDataSource are database-specific and will only work if run against the same database product they were generated for.

  Parameters:

  clauseType - The type of clause to generate and return

  dsRequest - The DSRequest embodying the fetch or update operation

  Returns:

  The text of the generated SQL we will use to implement a clause of clauseType for the supplied dsRequest

  Throws:

  java.lang.Exception

• executeAsBatch

  public static java.util.List executeAsBatch(java.util.List dsRequests)
                                       throws java.lang.Exception

  Convenience implementation of SQLDataSource.executeAsBatch(DSRequest[]), if you prefer to pass and return Lists instead of arrays.

  Parameters:

  dsRequests - List of DSRequests to execute as a batch

  Returns:

  List of update counts, each entry pertains to the corresponding (by ordinal position) DSRequest

  Throws:

  java.lang.Exception

• executeAsBatch

  public static int[] executeAsBatch(DSRequest[] dsRequests)
                              throws java.lang.Exception

  Executes an array of DSRequests in a single JDBC java.sql.Statement.executeBatch() call. The implementation builds up the batch by calling SQLDataSource.getSQLClause(SQLClauseType,DSRequest) to obtain the query text to execute for each DSRequest, and then adding each query with calls to java.sql.Statement.addBatch(). This means that many of the sophistications of DSRequest processing are bypassed. Note the follwoing:

  • No DMI, security checks, or other normal consequences of dsRequest.execute() will occur, because the DSRequests are not executed in the normal way
  • executeAsBatch() allocates and frees its own SQL connection, and does not participate in automatic transctions
  • However, the entire batch is committed or rolled back in a single transaction that is specific to the batch, assuming that the underlying database is capaable of transactions

  This method is intended to be used for edge cases where a large number of records must be updated, and the performance overhead of updating them singly makes normal DSRequest processing impractical. exeuteAsBatch() can give dramatic performance improvements in these circumstances, but at the cost of losing much of the functionality of a DSRequest.

  Parameters:

  dsRequests - Array of DSRequests to execute as a batch

  Returns:

  Array of update counts, each entry pertains to the corresponding (by ordinal position) DSRequest

  Throws:

  java.lang.Exception