Wrapper Configuration Properties¶

Wrapper Configuration Properties allow indicating specific characteristics of the underlying data sources such as their distributed transaction support capacity or whether inserting operations are permitted. The section Data Source Configuration Properties indicated the configuration properties of the data sources. This section describes the configurable properties in each wrapper, depending on the type of data source they have come from.

The properties of each wrapper can be configured in the wrapper creation statement by adding parameter/value pairs or from the Virtual DataPort Administration Tool. The configurable properties are as follows:

• Allow Insert (ALLOWINSERT). Configurable in JDBC and ODBC wrappers. It indicates whether the underlying data source supports INSERT operations and whether the wrapper will process them. The possible values are:

  • default: assigns the default value, which depends on the source.

  • true: the wrapper will process INSERT operations.

  • false: the wrapper will not process INSERT operations.

• Allow Delete (ALLOWDELETE). Configurable in JDBC and ODBC wrappers. It indicates whether the underlying data source supports DELETE operations and whether the wrapper will process them. The possible values are:

  • default: assigns the default value, which depends on the source.

  • true: the wrapper will process DELETE operations.

  • false: the wrapper will not process DELETE operations.

• Allow Update (ALLOWUPDATE). Configurable in JDBC and ODBC wrappers. It indicates whether the underlying data source supports UPDATE operations and whether the wrapper will process them. The possible values are:

  • default: assigns the default value, which depends on the source.

  • true: the wrapper will process UPDATE operations.

  • false: the wrapper will not process UPDATE operations.

• Delegate SQL sentence as subquery (DELEGATESQLSENTENCEASSUBQUERY ) Configurable in JDBC wrappers. If its value is yes and the base view has been created from a SQL query, at runtime, Virtual DataPort will be able to delegate more operations over the base view, to the database. To achieve this, the SQL query of the base view will be delegated as a subquery in the FROM clause.

  The section View Configuration Properties of the Administration Guide explains this property in more detail.

• Delegate SQL sentence variables as parameters (DELEGATESQLSENTENCEVARIABLESASPARAMETERS ) Configurable in the wrapper source configuration of base views. If its value is yes and the base view has been created from a SQL query, at runtime, Virtual DataPort will be able to delegate SQL sentence interpolation variables as parameters over the base view, to the database.

  Default value: no.

• Supports Distributed Transactions (SUPPORTSDISTRIBUTEDTRANSACTIONS). Configurable in JDBC and ODBC wrappers. It indicates whether the underlying data source can take part in an XA distributed transaction. It is applicable to relational databases (accessible via JDBC and ODBC) and CUSTOM wrappers. The possible values are:

  • default: assigns the default value, which depends on the source.

  • true: the data source meets the XA specification.

  • false: the data source does not meet the XA specification.

• Fields by which the data is sorted in the source (DATAINORDERFIELDSLIST). Configurable in all the wrappers except Custom ones. This property indicates the fields by which the data is ordered. The syntax of this property is the following: <field name> { ASC | DESC } [, <field name> { ASC | DESC }]*

  E.g., let us say that we have a Web service base view with the fields F1 and F2. We know that the results of querying the Web service are ordered in ascendant order by the field F1 and then, by descendant order by the field F2. By setting this property to F1 ASC, F2 DESC, we are telling Virtual DataPort the order of the result and it may be able to perform certain optimizations such as selecting a most efficient join algorithm.

• Delegate Operators List (DELEGATEOPERATORSLIST). This property determines the list of operators that can be delegated to the data source. This list allows Virtual DataPort to optimize the query plan by delegating part of the processing to the source. While the Server carries out this action automatically on relational databases, other types of sources do not provide this information about their metadata.

Example: In the following example we create a DF wrapper indicating that the data of the file is ordered by the column id (property DATAINORDERFIELDSLIST). By adding this property, a base view created over this wrapper can participate in a MERGE JOIN. Otherwise it cannot.

CREATE WRAPPER DF w_internet_inc
    DATASOURCENAME = df_ds_internet_inc
    OUTPUTSCHEMA (
        id (OPT),
        summary (OPT),
        ttime (OPT),
        taxid = 'taxId' (OPT),
        specific_field1 (OPT),
        specific_field2 (OPT)
    )
    SOURCECONFIGURATION (
    DATAINORDERFIELDSLIST = (id ASC)
);