Interactive Grid: Custom Select List on each row

I had a column in an editable interactive grid based on a Select List, which takes valid values from a table that supports “soft delete” – i.e. records could be marked as “deleted” without affecting existing references to those deleted records.

The SQL Query for the LOV was like this (my example is a view on a reference table of school “year levels”):

select name, id from year_levels_vw
where deleted_ind is null
order by sort_order

The problem is that if a year level is marked as deleted, the select list will not include it due to the where clause; since Display Extra Values is set to “Yes”, the item on the page will instead show the internal ID which is not very useful to the user. Instead, I want to show the name but appended with a string to show it has been deleted:

select name
       || case when deleted_ind = 'Y' then ' (DELETED)' end
       as disp_name, id
from year_levels_vw
order by deleted_ind nulls first, sort_order

So now the select list shows the name, even if it has been deleted. However, once users start using this system and they delete some year levels, each select list will include all the deleted values, even if they will never be used again. We’d prefer to only include a deleted value IF it is currently used by the record being viewed; otherwise, we want to omit it from the list.

If this was an APEX item in a single-record edit form, I’d simply change the SQL Query for the LOV to:

select name
       || case when deleted_ind = 'Y' then ' (DELETED)' end
       as disp_name, id
from year_levels_vw
where deleted_ind is null or id = :P1_FROM_YEAR_LEVEL_ID
order by deleted_ind nulls first, sort_order

This way, the select list will only include the deleted year level if the underlying item was already set to that deleted ID. But we are now using an Interactive Grid – there is no page item to refer to.

The method I’ve used to solve this is to take advantage of the Cascading LOV feature in order to allow the query to refer to the value of the column. The SQL Query for the LOV on my Interactive Grid is:

select name
       || case when deleted_ind = 'Y' then ' (DELETED)' end
       as disp_name, id
from year_levels_vw
where deleted_ind is null or id = :FROM_YEAR_LEVEL_ID
order by deleted_ind nulls first, sort_order

Now, we need to make sure that “FROM_YEAR_LEVEL_ID” is available to the query, so we need to put it in the Items to Submit attribute. To make this attribute available, however, we must set Cascading LOV Parent Column(s) to something; I set it to the PK ID of the table, or some other column which doesn’t get changed by the user and isn’t actually referred to in the LOV Query.

Now, records not referring to a deleted value show only valid values:

And records that refer to a deleted value include the deleted value in the list, as desired:

It should be noted that the design of the select list means that the user is allowed to save changes to the record while preserving the reference to the deleted year level. This is desired, in this case; if it wasn’t, however, I’d consider putting a validation on the page to stop the record being saved unless the user changes it to a valid value.

P.S. Concerned parents should note that this example was just testing the ability to delete a record from a database, and I’d just like to make it totally clear that there are no plans by the department to eliminate year 7 from schools. Honest!

ADDENDUM (19/3/2018):

There are two known issues:

  1. If the item is the child of a Cascading LOV, when the parent item is changed, APEX automatically clears out any value in the child before rendering the list of values – which means the column value submitted will be NULL – which means the “deleted” items disappear from the list immediately. This means the user will not be allowed to save the record with a reference to a deleted value from the list.
  2. The column filter list of values is empty – this is due to a known bug in APEX [Doc ID 2289512.1 FILTER NOT WORKING IN INTERACTIVE GRID WITH CASCADING LOV][thanks to Dejan for alerting me to this]

Interactive Grids (APEX 5.1 EA) and TAPIs

DISCLAIMER: this article is based on Early Adopter 1.

event_types_ig

I’ve finally got back to looking at my reference TAPI APEX application. I’ve greatly simplified it (e.g. removed the dependency on Logger, much as I wanted to keep it) and included one dependency (CSV_UTIL_PKG) to make it much simpler to install and try. The notice about compilation errors still applies: it is provided for information/entertainment purposes only and is not intended to be a fully working system. The online demo for APEX 5.0 has been updated accordingly.

I next turned my attention to APEX 5.1 Early Adopter, in which the most exciting feature is the all-new Interactive Grid which may replace IRs and tabular forms. I have installed my reference TAPI APEX application, everything still works fine without changes.

I wanted my sample application to include both the old Tabular Forms as well as the new Interactive Grid, so I started by making copies of some of my old “Grid Edit” (tabular form) pages. You will find these under the “Venues” and “Event Types” menus in the sample application. I then converted the tabular form regions to Interactive Grids, and after some fiddling have found that I need to make a small change to my APEX API to suit them. The code I wrote for the tabular forms doesn’t work for IGs; in fact, the new code is simpler, e.g.:

PROCEDURE apply_ig (rv IN VENUES$TAPI.rvtype) IS
  r VENUES$TAPI.rowtype;
BEGIN
  CASE v('APEX$ROW_STATUS')
  WHEN 'I' THEN
    r := VENUES$TAPI.ins (rv => rv);
    sv('VENUE_ID', r.venue_id);
  WHEN 'U' THEN
    r := VENUES$TAPI.upd (rv => rv);
  WHEN 'D' THEN
    VENUES$TAPI.del (rv => rv);
  END CASE;
END apply_ig;

You may notice a few things here:

(1) APEX$ROW_STATUS for inserted rows is ‘I’ instead of ‘C’; also, it is set to ‘D’ (unlike under tabular forms, where it isn’t set for deleted rows).

(2) After inserting a new record, the session state for the Primary Key column(s) must be set if the insert might have set them – including if the “Primary Key” in the region is ROWID. Otherwise, Apex 5.1 raises No Data Found when it tries to retrieve the new row.

(3) I did not have to make any changes to my TAPI at all 🙂

Here’s the example from my Event Types table, which doesn’t have a surrogate key, so we use ROWID instead:

PROCEDURE apply_ig (rv IN EVENT_TYPES$TAPI.rvtype) IS
  r EVENT_TYPES$TAPI.rowtype;
BEGIN
  CASE v('APEX$ROW_STATUS')
  WHEN 'I' THEN
    r := EVENT_TYPES$TAPI.ins (rv => rv);
    sv('ROWID', r.p_rowid);
  WHEN 'U' THEN
    r := EVENT_TYPES$TAPI.upd (rv => rv);
  WHEN 'D' THEN
    EVENT_TYPES$TAPI.del (rv => rv);
  END CASE;
END apply_ig;

Converting Tabular Form to Interactive Grid

The steps needed to convert a Tabular Form based on my APEX API / TAPI system are relatively straightforward, and only needed a small change to my APEX API.

  1. Select the Tabular Form region
  2. Change Type from “Tabular Form [Legacy]” to “Interactive Grid”
  3. Delete any Region Buttons that were associated with the Tabular form, such as CANCEL, MULTI_ROW_DELETE, SUBMIT, ADD
  4. Set the Page attribute Advanced > Reload on Submit = “Only for Success”
  5. Under region Attributes, set Edit > Enabled to “Yes”
  6. Set Edit > Lost Update Type = “Row Version Column”
  7. Set Edit > Row Version Column = “VERSION_ID”
  8. Set Edit > Add Row If Empty = “No”
  9. If your query already included ROWID, you will need to remove this (as the IG includes the ROWID automatically).
  10. If the table has a Surrogate Key, set the following attributes on the surrogate key column:
    Identification > Type = “Hidden”
    Source > Primary Key = “Yes”
  11. Also, if the table has a Surrogate Key, delete the generated ROWID column. Otherwise, leave it (it will be treated as the Primary Key by both the Interactive Grid as well as the TAPI).
  12. Set any columns Type = “Hidden” where appropriate (e.g. for Surrogate Key columns and VERSION_ID).
  13. Under Validating, create a Validation:
    Editable Region = (your interactive grid region)
    Type = “PL/SQL Function (returning Error Text)”
    PL/SQL = (copy the suggested code from the generated Apex API package) e.g.

        RETURN VENUES$TAPI.val (rv =>
          VENUES$TAPI.rv
            (venue_id     => :VENUE_ID
            ,name         => :NAME
            ,map_position => :MAP_POSITION
            ,version_id   => :VERSION_ID
            ));
        
  14. Under Processing, edit the automatically generated “Save Interactive Grid Data” process:
    Target Type = PL/SQL Code
    PL/SQL = (copy the suggested code from the generated Apex API package) e.g.

        VENUES$APEX.apply_ig (rv =>
          VENUES$TAPI.rv
            (venue_id     => :VENUE_ID
            ,name         => :NAME
            ,map_position => :MAP_POSITION
            ,version_id   => :VERSION_ID
            ));
        

I like how the new Interactive Grid provides all the extra knobs and dials needed to interface cleanly with an existing TAPI implementation. For example, you can control whether it will attempt to Lock each Row for editing – and even allows you to supply Custom PL/SQL to implement the locking. Note that the lock is still only taken when the page is submitted (unlike Oracle Forms, which locks the record as soon as the user starts editing it) – which is why we need to prevent lost updates:

Preventing Lost Updates

The Interactive Grid allows the developer to choose the type of Lost Update protection (Row Values or Row Version Column). The help text for this attribute should be required reading for any database developer. In my case, I might choose to turn this off (by setting Prevent Lost Updates = “No” in the Save Interactive Grid Data process) since my TAPI already does this; in my testing, however, it didn’t hurt to include it.

Other little bits and pieces

I found it interesting that the converted Interactive Grid includes some extra columns automatically: APEX$ROW_SELECTOR (Type = Row Selector), APEX$ROW_ACTION (Type = Actions Menu), and ROWID. These give greater control over what gets included, and you can delete these if they are not required.

Another little gem is the new Column attribute Heading > Alternative Label: “Enter the alternative label to use in dialogs and in the Single Row View. Use an alternative label when the heading contains extra formatting, such as HTML tags, which do not display properly.”.

Demo

If you’d like to play with a working version of the reference application, it’s here (at least, until the EA is refreshed) (login as demo / demo):

http://apexea.oracle.com/pls/apex/f?p=SAMPLE560&c=JK64

I’ve checked in an export of this application to the bitbucket repository (f9674_ea1.sql).