Ordenación virtual en ABAP: Claves secundarias y rendimiento

" Tabla con claves secundarias
DATA: lt_orders TYPE SORTED TABLE OF ty_order
        WITH UNIQUE KEY order_id
        WITH NON-UNIQUE SORTED KEY by_customer COMPONENTS customer_id
        WITH NON-UNIQUE SORTED KEY by_date COMPONENTS order_date.

" Clave secundaria ordenada
DATA: lt_data TYPE STANDARD TABLE OF ty_data
        WITH EMPTY KEY
        WITH NON-UNIQUE SORTED KEY by_name COMPONENTS name
        WITH NON-UNIQUE SORTED KEY by_amount COMPONENTS amount DESCENDING.

" Acceso por clave secundaria
LOOP AT lt_data INTO DATA(ls_data) USING KEY by_name.
  " Iteración ordenada por nombre
ENDLOOP.

READ TABLE lt_data INTO DATA(ls_found)
  WITH KEY by_name COMPONENTS name = 'Test'.

" Clave secundaria hash (acceso O(1))
DATA: lt_data TYPE STANDARD TABLE OF ty_data
        WITH EMPTY KEY
        WITH UNIQUE HASHED KEY by_id COMPONENTS id.

" Acceso directo por hash
READ TABLE lt_data INTO DATA(ls_found)
  WITH KEY by_id COMPONENTS id = 12345.

TYPES: BEGIN OF ty_order,
         order_id    TYPE i,
         customer_id TYPE i,
         product_id  TYPE string,
         amount      TYPE p DECIMALS 2,
         order_date  TYPE d,
         status      TYPE c LENGTH 1,
       END OF ty_order.

" Definición con múltiples claves
DATA: lt_orders TYPE STANDARD TABLE OF ty_order
        WITH EMPTY KEY
        " Acceso rápido por ID de pedido
        WITH UNIQUE HASHED KEY by_id
          COMPONENTS order_id
        " Búsqueda por cliente ordenada
        WITH NON-UNIQUE SORTED KEY by_customer
          COMPONENTS customer_id order_date
        " Búsqueda por producto
        WITH NON-UNIQUE SORTED KEY by_product
          COMPONENTS product_id
        " Ordenar por importe descendente
        WITH NON-UNIQUE SORTED KEY by_amount
          COMPONENTS amount DESCENDING.

" Llenar tabla
lt_orders = VALUE #(
  ( order_id = 1 customer_id = 100 product_id = 'A' amount = '500.00' order_date = '20241101' status = 'A' )
  ( order_id = 2 customer_id = 200 product_id = 'B' amount = '1500.00' order_date = '20241102' status = 'A' )
  ( order_id = 3 customer_id = 100 product_id = 'A' amount = '300.00' order_date = '20241103' status = 'P' )
  ( order_id = 4 customer_id = 300 product_id = 'C' amount = '2000.00' order_date = '20241104' status = 'A' )
  ( order_id = 5 customer_id = 100 product_id = 'B' amount = '750.00' order_date = '20241105' status = 'A' )
).

" 1. Buscar por ID (hash - O(1))
READ TABLE lt_orders INTO DATA(ls_order)
  WITH KEY by_id COMPONENTS order_id = 3.

" 2. Todos los pedidos de un cliente (ordenados por fecha)
LOOP AT lt_orders INTO ls_order
  USING KEY by_customer
  WHERE customer_id = 100.
  WRITE: / ls_order-order_id, ls_order-order_date.
ENDLOOP.

" 3. Top pedidos por importe
DATA(lv_count) = 0.
LOOP AT lt_orders INTO ls_order USING KEY by_amount.
  lv_count = lv_count + 1.
  IF lv_count > 3.
    EXIT.
  ENDIF.
  WRITE: / 'Top', lv_count, ':', ls_order-amount.
ENDLOOP.

" 4. Pedidos de un producto
LOOP AT lt_orders INTO ls_order
  USING KEY by_product
  WHERE product_id = 'A'.
  WRITE: / ls_order-order_id, ls_order-product_id.
ENDLOOP.

" MALO: Búsqueda lineal O(n)
LOOP AT lt_orders INTO DATA(ls_order)
  WHERE customer_id = 100.
  " ...
ENDLOOP.

" MALO: Ordenar cada vez
SORT lt_orders BY amount DESCENDING.
" Esto modifica el orden físico y pierde otros órdenes

" BIEN: Búsqueda binaria O(log n)
LOOP AT lt_orders INTO DATA(ls_order)
  USING KEY by_customer
  WHERE customer_id = 100.
  " ...
ENDLOOP.

" BIEN: Acceso ordenado sin modificar datos
LOOP AT lt_orders INTO ls_order
  USING KEY by_amount.
  " Ordenado por amount sin SORT
ENDLOOP.

DATA: lt_sales TYPE STANDARD TABLE OF ty_sales
        WITH EMPTY KEY
        WITH NON-UNIQUE SORTED KEY by_region_date
          COMPONENTS region sales_date
        WITH NON-UNIQUE SORTED KEY by_product_region
          COMPONENTS product_id region.

" Acceso con clave parcial
LOOP AT lt_sales INTO DATA(ls_sale)
  USING KEY by_region_date
  WHERE region = 'EUROPE'.  " Solo primer componente
  " Iteración de todas las ventas de Europa, ordenadas por fecha
ENDLOOP.

" UNIQUE: No permite duplicados en la combinación de componentes
DATA: lt_unique TYPE STANDARD TABLE OF ty_data
        WITH UNIQUE HASHED KEY by_id COMPONENTS id.

" INSERT fallará si el ID ya existe
INSERT VALUE #( id = 1 name = 'Duplicado' ) INTO TABLE lt_unique.
IF sy-subrc <> 0.
  " Clave duplicada
ENDIF.


" NON-UNIQUE: Permite duplicados
DATA: lt_non_unique TYPE STANDARD TABLE OF ty_data
        WITH NON-UNIQUE SORTED KEY by_category COMPONENTS category.

" Múltiples entradas con la misma categoría permitidas

" Las claves secundarias se actualizan automáticamente
INSERT VALUE #( order_id = 6 customer_id = 100 amount = '999.00' )
  INTO TABLE lt_orders.
" Todas las claves secundarias se actualizan

" MODIFY también actualiza las claves
MODIFY TABLE lt_orders FROM VALUE #(
  order_id = 1
  amount = '600.00'  " Cambio de amount
) USING KEY by_id.
" La clave by_amount se reordena automáticamente

" No se pueden usar en SORTED/HASHED TABLE con clave primaria conflictiva
" INCORRECTO:
DATA: lt_bad TYPE SORTED TABLE OF ty_data
        WITH UNIQUE KEY id
        WITH UNIQUE SORTED KEY also_id COMPONENTS id.  " Redundante

CLASS zcl_order_index DEFINITION PUBLIC FINAL CREATE PUBLIC.
  PUBLIC SECTION.
    TYPES: BEGIN OF ty_order,
             order_id    TYPE i,
             customer_id TYPE i,
             status      TYPE c LENGTH 1,
             amount      TYPE p DECIMALS 2,
           END OF ty_order.

    TYPES: ty_orders TYPE STANDARD TABLE OF ty_order
             WITH EMPTY KEY
             WITH UNIQUE HASHED KEY by_id COMPONENTS order_id
             WITH NON-UNIQUE SORTED KEY by_customer COMPONENTS customer_id
             WITH NON-UNIQUE SORTED KEY by_status COMPONENTS status.

    METHODS: get_by_id
      IMPORTING iv_id           TYPE i
      RETURNING VALUE(rs_order) TYPE ty_order.

    METHODS: get_by_customer
      IMPORTING iv_customer_id    TYPE i
      RETURNING VALUE(rt_orders)  TYPE ty_orders.

    METHODS: get_by_status
      IMPORTING iv_status        TYPE c
      RETURNING VALUE(rt_orders) TYPE ty_orders.

  PRIVATE SECTION.
    DATA: mt_orders TYPE ty_orders.
ENDCLASS.

CLASS zcl_order_index IMPLEMENTATION.
  METHOD get_by_id.
    READ TABLE mt_orders INTO rs_order
      WITH KEY by_id COMPONENTS order_id = iv_id.
  ENDMETHOD.

  METHOD get_by_customer.
    rt_orders = VALUE #(
      FOR order IN mt_orders USING KEY by_customer
      WHERE ( customer_id = iv_customer_id )
      ( order )
    ).
  ENDMETHOD.

  METHOD get_by_status.
    rt_orders = VALUE #(
      FOR order IN mt_orders USING KEY by_status
      WHERE ( status = iv_status )
      ( order )
    ).
  ENDMETHOD.
ENDCLASS.