CDS Table Functions

A CDS table function is a CDS view whose body is computed by AMDP (ABAP Managed Database Procedure) running on HANA. It exposes the result of a SQLScript procedure as if it were a CDS view, so you can use it with SELECT from ABAP.

Two artifacts are always required:

DDLS (*.ddls.asddls) — the signature: define table function, return-row columns, pointer to the implementing AMDP method
AMDP class (*.clas.abap) — INTERFACES if_amdp_marker_hdb and a CLASS-METHODS x FOR TABLE FUNCTION <ddls> method implemented BY DATABASE FUNCTION FOR HDB LANGUAGE SQLSCRIPT

→ For the exact XML metadata files (SOURCE_TYPE F, CLSCCINCL X) and boilerplate .asddls / .clas.abap source: abapgit-agent ref --topic abapgit-cds, section “CDS Table Function (DDLS, SOURCE_TYPE F)”.

When to use a table function vs. a view entity

Need	Use
Pure CDS DDL is enough (joins, aggregations, conditions)	View entity (`define view entity`, `SOURCE_TYPE W`)
SQLScript constructs (window functions, recursive CTE, MERGE-like joins, dynamic SQL)	Table function
Access a table in a different / replicated HANA schema via `$ABAP.schema( <logical> )`	Table function (CDS view entities don’t support `$ABAP.schema(...)`)

Logical schema — accessing replicated / foreign schemas

Table functions can read from replicated HANA schemas or schemas of co-deployed ABAP applications via the $ABAP.schema( ... ) macro:

SELECT ...
  FROM "$ABAP.schema( FRA_CORE_ERP )".rbkp

This is the only way to do cross-schema reads from ABAP — CDS view entities and plain ABAP SQL don’t support the macro. The mapping from logical to physical schema is maintained per landscape in transaction DB_SCHEMA_MAP.

→ Full guide (setup, syntax, common errors, end-to-end example): abapgit-agent ref --topic abap-schema-mapping

Return-column types — what to use

Type expression	Use it for
`abap.clnt`	client / MANDT
`abap.char(N)`	fixed CHAR (e.g. BUKRS → `abap.char(4)`, LIFNR → `abap.char(10)`)
`abap.numc(N)`	numeric character (e.g. GJAHR → `abap.numc(4)`)
`abap.dats`	date `YYYYMMDD`
`abap.tims`	time `HHMMSS`
`abap.dec(N,M)`	decimal (e.g. invoice amount → `abap.dec(23,2)`)
`abap.cuky`	currency key (5-char)
`abap.int4`	4-byte integer
`abap.string`	unbounded NVARCHAR
`mandt`, `bukrs`, `lifnr`, …	DDIC data elements — only if active in the same package as the DDLS

⚠️ Data elements from replicated tables are NOT in the local DDIC

abapgit-agent view --objects WERTV8 --type DTEL may say the data element exists somewhere in the system, but the DDLS activator only resolves data elements that are either (a) standard SAP_BASIS types or (b) active in the same ABAP package as your DDLS.

Symptom:

Entity Z_TF_MY_FUNCTION: Data element WERTV8 parameter/field AMOUNT does not exist or not active

Fix — use a primitive abap.* type:

amount : abap.dec(23,2);     // instead of: amount : wertv8;
vendor_reference : abap.char(16);   // instead of: xblnr1

Or — if you want strong typing and reuse — create your own data elements under your project namespace and reference them. (This is what production table function packages typically do: e.g. FRA_ERP_VENDOR, FRA_ERP_DOCUMENT_DATE.)

Activation order — DDLS depends on the AMDP class

The DDLS contains implemented by method ZCL_X=>METHOD, so the DDLS cannot activate until the AMDP class is active. The AMDP class declares CLASS-METHODS m FOR TABLE FUNCTION z_tf_x, but the class compiles against the signature of the DDLS — which exists from the first pull onwards.

Recommended sequence:

git add . && git commit -m "..." && git push
abapgit-agent pull --files src/zcl_tf_x.clas.abap         # class first
abapgit-agent pull --files src/z_tf_x.ddls.asddls         # then DDLS

A single pull --files src/zcl_tf_x.clas.abap,src/z_tf_x.ddls.asddls often works on the second attempt — first pass activates the class, second pass activates the DDLS. Don’t be alarmed by “Activation cancelled” on attempt 1 if a follow-up pull reports 1 activated.

`inspect` is NOT reliable for table-function DDLS

abapgit-agent inspect --files src/z_tf_x.ddls.asddls
✅ DDLS Z_TF_X - Syntax check passed     # ← but activation FAILS

inspect runs a syntactic check on the DDLS source, not a full DDIC activation. Data-element-not-found and $ABAP.schema resolution errors slip through.

To see the real activation error, use one of these:

Recommended — read the pull log in JSON:
```
abapgit-agent pull --files src/z_tf_x.ddls.asddls --json
```
Look at the LOG_MESSAGES array.
Activate manually in ADT (right-click → activate). The error popup is the most detailed.
SE80 → DDLS → activate log.

Common errors and fixes

Error message	Cause	Fix
`Data element X parameter/field Y does not exist or not active`	DTEL X is not in the local DDIC	Replace with `abap.<primitive>(...)` (see type table above)
`'Z_TF_X' is not a table function` (from a runner / SELECT)	The DDLS is inactive	Pull the AMDP class first, then the DDLS
`Annotation for AbapCatalog.dataMaintenance does not exist`	Wrong `SOURCE_TYPE` in the DDLS XML	Set `<SOURCE_TYPE>F</SOURCE_TYPE>`
`Compilation was canceled` for the AMDP class	Class compiles against a DDLS signature that hasn’t been deserialized yet	Re-pull — the second attempt picks up the now-deserialized DDLS
`Error updating where-used list` after pulling the AMDP class	The DDLS the class refers to is missing or inactive	Make sure the `.ddls.asddls` file is in the same commit and re-pull both
Class shows `create private` on the server after pull	The source line `class zcl_x implementation.` uses lowercase name — abapGit can’t match it to the serializer output	Write the implementation header in UPPERCASE: `CLASS ZCL_X IMPLEMENTATION.`
Pull `--sync-xml` wipes the DDLS XML to a minimal stub	`--sync-xml` was run after a pull that failed to deserialize the DDLS; the serializer output is empty, and you overwrote your good XML	Never use `--sync-xml` after a failed pull. Restore the XML from git history first, fix the underlying activation error, re-pull, then `--sync-xml`

Example — duplicate vendor invoice detector

A complete two-file table function over a replicated RBKP table:

src/z_tf_duplicate_invoices.ddls.asddls:

@EndUserText.label: 'Duplicate Vendor Invoices'
@ClientHandling.type: #CLIENT_DEPENDENT
define table function Z_TF_DUPLICATE_INVOICES
returns {
  client            : abap.clnt;
  company_code      : abap.char(4);
  document_number   : abap.char(10);
  fiscal_year       : abap.numc(4);
  vendor            : abap.char(10);
  vendor_reference  : abap.char(16);
  amount            : abap.dec(23,2);
  currency          : abap.cuky;
  dup_count         : abap.int4;
}
implemented by method ZCL_TF_DUPLICATE_INVOICES=>GET_DUPLICATES;

src/zcl_tf_duplicate_invoices.clas.abap (excerpt):

METHOD get_duplicates BY DATABASE FUNCTION FOR HDB
                      LANGUAGE SQLSCRIPT
                      OPTIONS READ-ONLY.

  RETURN SELECT
           r.mandt                  AS client,
           r.bukrs                  AS company_code,
           r.belnr                  AS document_number,
           r.gjahr                  AS fiscal_year,
           r.lifnr                  AS vendor,
           r.xblnr                  AS vendor_reference,
           r.rmwwr                  AS amount,
           r.waers                  AS currency,
           CAST( d.cnt AS INTEGER ) AS dup_count
         FROM "$ABAP.schema( FRA_CORE_ERP )".rbkp AS r INNER JOIN
              ( SELECT mandt, lifnr, xblnr, rmwwr, waers,
                       COUNT(*) AS cnt
                FROM "$ABAP.schema( FRA_CORE_ERP )".rbkp
                WHERE xblnr <> '' AND mandt = SESSION_CONTEXT( 'CLIENT' )
                GROUP BY mandt, lifnr, xblnr, rmwwr, waers
                HAVING COUNT(*) > 1 ) AS d
            ON r.mandt = d.mandt AND
               r.lifnr = d.lifnr AND
               r.xblnr = d.xblnr AND
               r.rmwwr = d.rmwwr AND
               r.waers = d.waers
         WHERE r.mandt = SESSION_CONTEXT( 'CLIENT' );

ENDMETHOD.

Call it from regular ABAP:

SELECT vendor, vendor_reference, amount, currency, dup_count
  FROM z_tf_duplicate_invoices( )
  INTO TABLE @DATA(lt_dups)
  UP TO 100 ROWS.

Workflow recap

Create/modify table function?
  └── ✅ Use:
        edit .ddls.asddls + .clas.abap (no syntax — inspect is unreliable for TFs)
        → [abaplint]
        → commit → push
        → pull --files <clas>.clas.abap        (activates AMDP)
        → pull --files <ddls>.ddls.asddls --sync-xml   (activates DDLS)
        → (verify) abapgit-agent run --class <runner_class>