For information on converting to InterSystems IRIS,
see the InterSystems IRIS Adoption Guide
and the InterSystems IRIS In-Place Conversion Guide,
both available on the WRC Distributions page (login required).
Simpler index functions such as BSCAN, expect the file variable to track the last index
access. In order to allow this, we store these in an array, subscripted by index name.
The top level is used to track when BSCAN walks over the global itself, instead of
property %FireTriggers as %Integer [ InitialExpression = 0 ];
This boolean flag indicates that the MVFIO routines must process trigger calls
when it is set to TRUE. The trigger routine itself will clear this flag to call
back in to MVFIO to process the operation then set it back to TRUE when the
operation is complete. This allows Pre and Post operations to exist for an
MVFIO function without interfering with the indexing routine calls.
property %IndexCollation as %Integer [ InitialExpression = 0 ];
A select list can represent an index. An index stores the actual keys
as oppposed to the key values returned by READNEXT in collated encoding
sequence such as MV R or SPACE (equivlant to MV L) etc.
This property defines the collation in use for the index.
When the file variable is produced as a result of OPENINDEX
then the index that was opened is stored here for future use by any select
lists. Note that at the moment index storage is restricted to the default
of ^INDEXGLOBAL("indexName",... and we may need to review this, though it
is unlikely to be an issue
property %TriggerOperations as %Integer [ InitialExpression = 0 ];
This integer flag stores a number of bits indicating which, if any MVFIO
operations must operate trigger subroutines. If the bit corresponding to the
operation at hand is set, and the trigger processing is not currently executing
then a specific COS routine entry point will be be queued up by the MVFIO C
routine and the processing function will DISP to it.
Stores the name of the generated COS routine (including namespace) that must be
called if this file descriptor is subject to any of the file trigger processing
options described below.
How this works is that when a file is opened the FireTriggers flag is set
(if there are ANY triggers). When any MVFIO routine is called it checks to see
if this flag is set and if it is, then it checks to see if there are triggers
for this specific operation (may do this the other way around). If both tests
pass then control is transferred to the named COS routine TriggerRoutine.
The first thing the entry point for the particular IO function does is turn
that flag off. It is then free to call the BASIC subroutines pre and post
operation and call back in to the MVFIO system to do the actual operation
(which will this time not fire the COS routine).