Most Update Processor commands work the same whether or not dictionary attributes are in control. Certain commands function differently when certain conditions are met. These commands provide the functionality for browsing on indexes. The cruising commands can be used in a double-clutching fashion by specifying the index for the current file and a second index for another file. CTRL+U and CTRL+Y cruise on legal instances in the pointed to file staying in the same item. CTRL+F and CTRL+D cruise on other items in the same file using the index for the attribute as a guide.
Command |
Description |
CTRL+GG |
The ability to move through a defined door to another file. Once in the other file, the user has the option to cruise from item to item in the new file, return to the original file, or zoom through a door into yet another file. When in an attribute that indexes to another file or has a translate code in the input processing code, this command pushes the current process one level and calls the Update Processor again with the item pointed to in the new file as the argument. If the macro attribute (attribute 15) in the primary file attribute definition item is used, this list is appended to the update statement. This is known as zooming. Zooming is only available when done through the Update Processor and involves the use of the i (index, remote) processing code. |
CTRL+F |
In an indexed attribute, the sentence forward command goes to the next sequential index and gets the corresponding item into the Update Processor workspace. |
CTRL+D |
In an attribute with an index, the sentence backward command goes to the previous sequential index and gets the corresponding item into the Update Processor workspace. |
CTRL+U |
If the attribute indexes to another file, the word forward command gets the next sequential item from the pointed to file as the value for this attribute. |
CTRL+Y |
If the attribute indexes to another file, the word backward command gets the previous sequential item from the pointed to file as the value for this attribute. |
The table lookup command (CTRL+U) performs a table-like lookup of items in the remote index using either a full or partial key. Press the key followed by a CTRL+U to call up the first match. If no match is found, the next item in the remote list is called up.
Double-clutching refers to the combined abilities of searching a remote file index for valid values and also searching the local (current) file index for specific items.
Double-clutching provides a unique feature when the local index is specified before the remote index in the input-conversion of an attribute definition. On a new screen, if a new value is entered at the attribute specified for double-clutching, and an item already exists on file containing this same value, that item is automatically retrieved by the Update Processor. For example, consider an Update Processor entity screen where the phone attribute displays first. If this attribute is set up as described above, and a user enters a phone number that is already on file, that item is retrieved. In this example, this feature prevents the entry of the same phone number for two different people.
This feature is only activated on new, unchanged items.
NOTE |
Specifying the remote index before the local index disables this feature. |
The key to cruising is understanding the Balanced Tree (B-tree) indexing feature of D3. A B-tree is a structure used to keep an ordered list, such as names, and provides the ability to search through the list quickly with a minimal number of disk I/Os. Any attribute in a file can contain an index. Indexes are defined using a-correlatives. Once the B-tree has been defined, the system automatically maintains the index.
When the cursor is positioned in a cell belonging to an indexed attribute, the commands CTRL+D and CTRL+F can be used to display the data associated with the item containing an adjacent value in the indexed attribute. The command CTRL+F causes the data associated with the next value in the index to be displayed. The command CTRL+D causes the data associated with the previous value in the index to be displayed.
For example, if an item containing customer name and order number indexed attributes is being displayed on the screen and the cursor is at the order number prompt, the CTRL+F command displays the data associated with the next order number in the order number index. If the cursor is residing adjacent to customer name, CTRL+F displays the data associated with the next customer name in the index and customer name is the key. All of the data in the new item associated with the attribute names displayed on the screen displays.
When the input-conversion attribute in an attribute-defining item specifies an index pointing to another file, that file can be accessed (zoomed to) by using the CTRL+G command. This command pushes the current process one level and accesses the item-ID in the pointed-to file matching the current value in the cell where the cursor resides. Attributes to be displayed with that item-ID must be specified in attribute 15 of the original attribute-defining item. Several logical views may be defined as macros in attribute 15 of the D-pointer.
A FlashBASIC program may be called to specify the actual logical view to use for the current data item. It does this by assigning the logical view number into the pseudo variable AQL (18). If no attributes are specified, the entire item displays. After viewing the new item, the original item can be returned to the screen by a file exit command such as CTRL+XE.
When the input-conversion attribute in an attribute-defining item specifies a second index as well as one pointing to another file, the commands CTRL+U and CTRL+Y allow the user to cruise on indexes in the pointed-to file. The attribute pointed-to in the second file must have been previously indexed by the create-index command. CTRL+U shows the next attribute value in the pointed-to file. Only this value is updated and it is shown in the cell where the cursor is residing. What displays is subject to the conversions specified in the dictionary of the first file. The command CTRL+Y shows the preceding item-ID in the pointed-to file. In order for the Update Processor to function in this manner, the attribute-defining items must contain the proper index processing codes. The input conversion attribute (attribute 14) of the attribute-defining item in the file dictionary is where they are specified.
See Also
i (Local Index) Processing Code