"Read" with Initial Confirm and Forecast 

 

Reading Units Using the LDQ API ("Read") with Initial Confirm and Forecast

To read a given table of queues, a reader object and unit reader object are created for each queue. For each queue, the system reads the units in blocks of 10 so as just to extract their state information. As soon as a given u_size is reached, the content of the corresponding units is read, and the payload extracted as in the previous scenario. The units are then deleted (“confirmed”) from the database.

 

Flow Chart:

 

 

Design:

 

a) Input parameters:

 

ap_name           TYPE ldq_application_name DEFAULT 'Perf_TEST',

qp_name           TYPE ldq_queue_name DEFAULT 'LDQ_TEST_',

n_queues          TYPE i DEFAULT 5,

n_times           TYPE i DEFAULT 1,

u_size            TYPE i DEFAULT 2.

last_received_seq_nr  TYPE ldq_unit_id.

 

 

 

b) Declarations:

 

DATA: l_ldq_reader      TYPE REF TO if_ldq_reader,

      l_ldq_unit_reader TYPE REF TO if_ldq_unit_reader.

DATA: l_queue_name_tab  TYPE ldq_queue_name_tab,

      l_queue_name      TYPE ldq_queue_name.

DATA: l_xdata           TYPE xstring,

      l_cdata           TYPE string.

DATA: l_size            TYPE i.

DATA: l_content_tab        TYPE ldq_unit_content_reader_tab.

DATA: l_state_tab        TYPE ldq_unit_state_reader_tab.

 

DATA: l_del             TYPE i.

DATA: l_seq nr          TYPE ldq_unit_id.

DATA: l_queue_nr(4)     TYPE n.

DATA: l_lines           TYPE i.

DATA: l_last_lines      TYPE i.

DATA: l_unit            TYPE i.

 

DATA: l_state_wa        TYPE REF TO if_ldq_unit_state_reader,

      l_content_wa      TYPE REF TO if_ldq_unit_content_reader.

DATA: l_format          TYPE ldq_data_format.

DATA: l_next_state_nr  TYPE i.

DATA: l_next_content_nr TYPE i.

data: l_number          type i.

FIELD-SYMBOLS: <l_content_wa> TYPE REF TO if_ldq_unit_content_reader.

FIELD-SYMBOLS: <l_state_wa>   TYPE REF TO if_ldq_unit_state_reader.

*

 

c) Creation of queue names:

*

CLEAR: l_queue_name_tab[], l_content_tab[].

DO n_queues TIMES.

  l_queue_nr = sy-index.

  CONCATENATE qp_name l_queue_nr INTO l_queue_name.

  CONDENSE l_queue_name NO-GAPS.

  APPEND l_queue_name TO l_queue_name_tab.

ENDDO.

 

u_size = u_size * 1000. "in kbytes

LOOP AT l_queue_name_tab INTO l_queue_name.

*

 

d) Creation of LDQ application object:

*

  l_ldq_reader       = cl_ldq_application=>get_reader( ap_name ).

 

 

e) Confirm the read units from previous sessions, up to a given sequence number:

*

  l_ldq_reader->confirm_queue_units( l_queue_name, last_received_seq_nr ).

* Note: This method executes an implicit commit.

*

f) Initialisation of the queue name to retrieve the units:

*

  l_ldq_unit_reader = l_ldq_reader->set_queue_name( l_queue_name ).

 

  DO n_times TIMES. "n_read TIMES.

 

 

 

g) Retrieve as many units as fit into the u_size:

*

    l_next_state_nr = l_lines = 0.

    DO.

      l_next_state_nr = l_next_state_nr + 10.

      l_state_tab = l_ldq_unit_reader->get_next_states( l_next_state_nr ).

      l_last_lines = LINES( l_state_tab ).

      IF l_lines >= l_last_lines.

* not enough units on the database to reach the required u_size

* therfore use the existing one

        l_next_content_nr = l_lines.

        EXIT.

      ELSE.

        l_lines = l_last_lines.

      ENDIF.

 

      l_size = 0.

      LOOP AT l_state_tab ASSIGNING <l_state_wa>.

        l_size = l_size + <l_state_wa>->get_size( ).

        IF l_size >= u_size.

          l_next_content_nr = sy-tabix.

          EXIT.

        ENDIF.

      ENDLOOP.

      IF l_size < u_size.

        CONTINUE.

      ELSE.

* the requested size is reached

        EXIT.

      ENDIF.

    ENDDO.

 

*

h) Get the (maximum) l_next_content_nr contents, i. e. unit state plus its payload, from the queue:

*

    l_content_tab = l_ldq_unit_reader->get_next_contents( l_next_content_nr ).

    l_unit = LINES( l_content_tab ).

 

 

i) Retrieve contained information out of content object:

*

    l_number = l_number + 1.

 

    WRITE: / l_number, 'Qname:', l_queue_name, 'unit number:', l_unit.

    LOOP AT l_content_tab  ASSIGNING <l_content_wa>.

      l_format = <l_content_wa>->get_format( ).

      IF cl_ldq_unit_writer=>co_character_data_type = l_format.

        l_cdata = <l_content_wa>->get_cdata( ).

      ELSE.

        l_xdata = <l_content_wa>->get_xdata( ).

      ENDIF.

      l_sequence number  = <l_content_wa>->get_sequence_number( ).

      l_size = <l_content_wa>->get_size( ).

      WRITE: /13 'sequence number:', l_seq_nr, 'size:', l_size.

    ENDLOOP.

 

i) Persist the read status of LDQ data into the database:

    COMMIT WORK.

 

  ENDDO.

 

ENDLOOP.