Subject How to determine whether a column is computed?
Author Christian G├╝tter
Hi,

I am trying to determine whether a given column is a COMPUTED BY
column. As far as I can see, the are several ways to do this.

The first (and easy) way could be to check whether the
RDB$COMPUTED_SOURCE field in RDB$FIELDS contains a value (i.e.
it is not blank/not NULL). This seems to be true for all
computed columns. But I am not sure if this always works.

There must be another way to determine this by the use of the
table RDB$TYPES. There is a column RDB$TYPES.RDB$FIELD_NAME that
contains the value "RDB$OBJECT_TYPE" and the corresponding field
RDB$TYPES.TYPE_NAME contains the description "COMPUTED_FIELD".
So there must be a place where a field is defined as "COMPUTED_FIELD",
but I cannot find it. I tried to look it up in the IB 6 beta docs,
but no success. I am sure someone can give me a hint on this ;-)

For now, I will use the RDB$COMPUTED_SOURCE field. Please tell me
if this an inappropriate hack.

Thanks in advance,


Christian