OpenEdge Development:<br />Progress 4GL Handbook Passing a temp-table parameter by binding

Starting with OpenEdge Release 10.1A, you can also save the overhead of copying a temp-table’s definition and data on a local call by using the BIND keyword. You use this keyword in both the calling and called routines to tell Progress to bind both temp-table references to the same temp-table instance. In the calling routine, you add the keyword to the parameter in the RUN statement, instead of the BY-REFERENCE keyword:

In the called routine, you specify the keyword as part of the parameter definition:

RUN `internal-procedure-name` IN `procedure-handle` ([ INPUT \| INPUT-OUTPUT \| OUTPUT ] TABLE `temp-table-name` BIND )

DEFINE [ INPUT \| INPUT-OUTPUT \| OUTPUT ] PARAMETER TABLE FOR `temp-table-name` BIND

The most basic case where you would want to use the BIND keyword is when you want to use the called routine’s temp-table instance instead of the calling routine’s instance. For example, you may have a routine in your application that has a cache of useful data, such as all Item values for use in entering an Order, which it has retrieved from the database and stored in a temp-table. Other routines running in the same session might want access to this data, for example to display the list of Items in a selection list. To save the overhead of copying the temp-table to all the other routines that want to share its data, you can bind the callers to the called routine’s temp-table cache.

In the calling routine, define the temp-table as REFERENCE-ONLY. This tells Progress not to instantiate the caller’s temp-table when the routine is first run.

In the calling routine, specify the BIND keyword in the RUN statement that uses the temp-table parameter. This tells Progress to bind both ends of the call to the same temp-table instance.

In the called routine, define the temp-table parameter with the BIND keyword. This confirms to Progress that both ends of the call are to refer to the same instance. You must always specify BIND on both ends of the call.

Define the temp-table parameters in both routines as OUTPUT. This tells Progress to use the called routine’s temp-table instance and change all references within the caller to point to it.

In the called routine, define the temp-table as REFERENCE-ONLY.

In the called routine, define the temp-table parameter with the BIND keyword.

In the calling routine, specify the BIND keyword in the RUN statement that uses the temp-table parameter.

Make sure that the parameter mode matches in both routines. That is, they must both be defined as INPUT-OUTPUT or both be defined as INPUT parameters.

You can use the BIND syntax to change the scope of the temp-table that is passed from caller to called routine. When you use BY-REFERENCE in an internal procedure call, as was described earlier, the scope of the temp-table is limited to that one call. That is, Progress changes the temp-table references (within the internal procedure you run) to refer back to the caller. When the internal procedure completes and returns to the caller, the association ends. In some exceptional cases, you might want to bind the caller’s temp-table to the called routine for their mutual lifetime.

Table 11–1 describes how to decide between passing a temp-table as a parameter using the BY-REFERENCE keyword versus using BIND. This table refers only to those calls that always or sometimes occur between routines in the same session. If you know that the call will always be to routines in different sessions, you should just pass the temp-table parameter by value.

Table 11–1: Passing a temp-table by reference versus by binding
If you want to use this routine’s temp-table data . . .	And you want the binding of the two temp-tables to last until . . .	Then do this in the calling routine . . .	And do this in the called routine . . .
Calling	The call ends.	Define the temp-table In the `RUN` statement, specify the temp-table parameter with the `BY-REFERENCE` modifier.	Define the temp-table as `REFERENCE-ONLY`. Define the temp-table parameter.
Calling	The procedure that contains the calling routine ends or is deleted.	Define the temp-table. In the `RUN` statement, specify the temp-table parameter with the `BIND` modifier.	Define the temp-table as `REFERENCE-ONLY`. Define the temp-table parameter with `BIND`.
Called	The procedure that contains the called routine ends or is deleted.	Define the temp-table as `REFERENCE-ONLY`. In the `RUN` statement, specify the temp-table parameter with the `BIND` modifier and as `OUTPUT` mode.¹	Define the temp-table. Define the temp-table parameter with `BIND` and as `OUTPUT` mode.¹

¹The temp-table parameter must be an OUTPUT parameter for the first call involving the temp-table so that the calling routine’s REFERENCE-ONLY table can point to a valid instantiated table. In subsequent calls, the parameter can be passed as INPUT.