ABAP 7.40 - limits of MESH? - abap

Question

Are there any know limits of meshes?
I know, that the table-types need to be non-generic.
But can it be, that a 5-key-dbtable as base for local table-type-definition is not ok ??? (I really doubt it).
I simply have a two-level table hierarchy and want to retrieve ALL mesh-results of the second table py passing the key of the main-table. I only have forward-associations, have a look, this is, what I try to achieve (pattern found on some website):
TYPES: lty_types TYPE STANDARD TABLE OF zordertype WITH NON-UNIQUE KEY table_line,
lty_excludes TYPE STANDARD TABLE OF zexcludeorder WITH NON-UNIQUE key table_line.
DATA: lt_types TYPE lty_types,
lt_excludes TYPE lty_excludes.
TYPES:
BEGIN OF MESH ty_type_excludes,
types TYPE lty_types
ASSOCIATION to_excludes
TO excludes ON order_type = order_type,
excludes TYPE lty_excludes,
END OF MESH ty_type_excludes.
DATA: ls_mesh TYPE ty_type_excludes.
START-OF-SELECTION.
SELECT * FROM zordertype
INTO TABLE #lt_types
ORDER BY order_type.
SELECT * FROM zexcludeorder
INTO TABLE #lt_excludes
ORDER BY order_type.
ls_mesh-types = lt_types.
ls_mesh-excludes = lt_excludes.
DATA wf_check TYPE zorder_type VALUE 'CAT'.
DATA(chk) = ls_mesh-types\to_excludes[ wf_check ].
break myuser.
This dumps with "CX_ITAB_LINE_NOT_FOUND".
But I did it exactly, how it was written. And, I think, this must work, because I use this approach to get a subset from another table based on the keyentries of the first table. I tried to add additional association-params, which did not dump anymore, but anyway, just returned only one record of the second table.
I seem to overlook some basic thingy, but which one ?

Answer 1

As stated in the ABAP documentation, a mesh path expression, "the result of a mesh path expression is a row from the last path node of the mesh path".
PS: there are the programs DEMO_MESH_EXPRESSION* to play with mesh path expressions. Here is a shorter standalone demo program, taken from the chapter 12 of blog post ABAP 7.40 Quick Reference :
TYPES: BEGIN OF t_manager,
name TYPE char10,
salary TYPE int4,
END OF t_manager,
tt_manager TYPE SORTED TABLE OF t_manager WITH UNIQUE KEY name.
TYPES: BEGIN OF t_developer,
name TYPE char10,
salary TYPE int4,
manager TYPE char10,
END OF t_developer,
tt_developer TYPE SORTED TABLE OF t_developer WITH UNIQUE KEY name.
TYPES: BEGIN OF MESH m_team,
managers TYPE tt_manager ASSOCIATION my_employees TO developers
ON manager = name,
developers TYPE tt_developer ASSOCIATION my_manager TO managers
ON name = manager,
END OF MESH m_team.
DATA: ls_team TYPE m_team.
LS_TEAM-MANAGERS = value #(
( Name = 'Jason' Salary = 3000 )
( Name = 'Thomas' Salary = 3200 ) ).
LS_TEAM-DEVELOPERS = value #(
( Name = 'Bob' Salary = 2100 manager = 'Jason' )
( Name = 'David' Salary = 2000 manager = 'Thomas' )
( Name = 'Jack' Salary = 1000 manager = 'Thomas' )
( Name = 'Jerry' Salary = 1000 manager = 'Jason' )
( Name = 'John' Salary = 2100 manager = 'Thomas' )
( Name = 'Tom' Salary = 2000 manager = 'Jason' ) ).
" Get details of Jerry's manager
ASSIGN ls_team-developers[ name = 'Jerry' ] TO FIELD-SYMBOL(<ls_jerry>).
DATA(ls_jmanager) = ls_team-developers\my_manager[ <ls_jerry> ].
WRITE: / |Jerry's manager: { ls_jmanager-name }|,30
|Salary: { ls_jmanager-salary }|.
" Get Thomas' developers
SKIP.
WRITE: / |Thomas' developers:|.
ASSIGN ls_team-managers[ name = 'Thomas' ] TO FIELD-SYMBOL(<ls_thomas>).
LOOP AT ls_team-managers\my_employees[ <ls_thomas> ]
ASSIGNING FIELD-SYMBOL(<ls_emp>).
WRITE: / |Employee name: { <ls_emp>-name }|.
ENDLOOP.
" the result of a mesh path expression is a row from the last path node of the mesh path
DATA(thomas_employee) = ls_team-managers\my_employees[ <ls_thomas> ].
SKIP.
WRITE: / |Thomas's "any" Employee name: { thomas_employee-name }|.