ABAP_to_the_Future

15
ABAP Programming for SAP HANA
way.) Another restriction is that in a method that is to be implemented as an AMDP,
you cannot have returning parameters, and all parameters have to be passed as values.
The ABAP in Eclipse aspect of this is unlikely to ever change, but I wouldn’t be shocked
if the other restrictions were lifted at some point in the future. For example, before
ABAP 7.4 SP 8, you couldn’t have CHANGING parameters in a method that was going to
be implemented as an AMDP; now you can. In the same way, before SP 8, any sort of
exception caused a short dump; after SP 8, the exception can be caught by CATCH cx_
admp_error.
In a stored procedure, you have two choices when retrieving data from the database:
SQL statements or calculation engine (CE) functions. A year ago, SAP’s position
was that you should use CE functi ons whenever possible. Now, the instruction
is not to touch them with a 10-fo ot bargepole. CE functions were once
supposed to perform faster for basic operations, but over time the performance of
real SQL statements has improved to th e extent that the overhead of wrapping
them in a CE function is not worth it.
In any event, the important thing is to keep the two (SQL statements and CE functions)
apart. As an example, you may have encountered a dual-stack SAP Process
Integration (PI) system in which half of the code was in ABAP and half in Java.
The ABAP code ran fast, the Java code not quite so fast but okay, but the performance
killer was when data had to keep moving between the two stacks. In the
same way, if you have both SQL statemen ts and CE functions in one stored procedure,
then the poor old database is thrown into a tizzy, and the performance is
much worse than if you had used only one or the other.
An SQL statement in SQLScript does not look that radically different from its
ABAP equivalent; you just have lots more options available and the syntax (punctuation
marks) changes slightly. You saw this just now when we talked about CDS
views. The change here is that CDS views manage the client for you; in an AMDP,
you have to specify the client.
In Listing 15.13, you’ll see some SQLScript code to do a database SELECT from
within an AMDP method implementation.
METHOD get_people_scared_today BY DATABASE PROCEDURE
FOR HDB
LANGUAGE SQLScript
OPTIONS READ-ONLY
USING zt_monsters zt_scary_event_header zt_scary_event_items.
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