SAP技术 - How to create a CDS redirect view for a given database table

Scenario

Suppose we have a database table A, and then we create a CDS redirect view B for it, then every time the READ OPEN SQL is done on table A, ABAP kernel will direct this request to view B, and serve the request with content from B.

Prerequisite

In order to make view B qualified as redirect view for table A, both A and B must have the same fields with exactly the same order and tehcnical name.

How to

1. In order to demonstrate the logic, I create a Z table in ER9/001 with four fields as below.

Write a simple report to test:

DATA: lt_table TYPE STANDARD TABLE OF zcomm_product.
SELECT * INTO TABLE lt_table FROM zcomm_product.

WRITE: / sy-dbcnt.

Since this table is just created, so there is no content inside it, 0 is expected for output.

2. Create a new CDS view with following source code:

@AbapCatalog.sqlViewName: 'zmara_cds'
@AbapCatalog.compiler.compareFilter: true
@AccessControl.authorizationCheck: #CHECK
@EndUserText.label: 'Redirect ZCOMM_PRODUCT to MARA'
define view Zp_Mara_Redirect as select from mara {
   mara.matnr as PRODUCT_ID,
   case
     when (mara.mtart = 'HAWA' or mara.mtart = 'INTR')
      then '01'
     when (mara.mtart = 'DIEN' or mara.mtart = 'COUP')
      then '02'
     else ''  
   end as product_Type,
   mara.mtart as object_family
}

Note: since this is just a example, the mapping between ZCOMM_PRODUCT.PRODUCT_TYPE to MARA.MTART does not make sense from business point of view, I just use it to illustrate how a field from database table could be mapped to a CDS view ( field name and technical type must be equal ).
Once CDS view is done, activate it and assign the view to database table via menu in SE11:

Once done, execute the report once again. This time, you could see the SELECT OPEN SQL on empty table ZCOMM_PRODUCT is actually redirected to MARA table - lots of entries returned.

Redirect is also automatically done when you browse the content of ZCOMM_PRODUCT from tcode SE16:

How does redirect work under the hood

If you perform a ST05 trace, you can observe the redirect is automatically done by ABAP runtime, no action from application side is needed.

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