I'm seeing some strange behaviour when building 3 distinct rowsets
in a single page. It appears that each rowset and its map methods
is being called more times than there are records selected.
For example take the following code:
$map := """
imageURL: `idp.utils.GetThumbnailURlForImage`;
imageRecnum: `record number([Images])`;
"""
C_longint($rowSet)
$imageRowSet := RowSet.newFromSelection(->[Images];$map) `
Don't need callback
So despite only 2 image records being loaded, the image map method
gets called 13 times. Catalogue Entry gets called 3 times but for
only 1 record. Bibliography gets called 5 times for 3 records.
There are a few things happening here:
- When a newFromSelection RowSet is created, the row getter is called
to fill the row cache with the values for an empty record. I have to
do this because there is no way for me to know what the type is for a
column expression without executing it. That accounts for one extra
call to the column expression.
- If you are using RowSet.next to iterate through the RowSet, the
last call to next will move to the record after the last, again
loading empty values into the row cache. That accounts for one more
extra call. So that explains the second two cases.
If you want to avoid the extra call at the end, don't use
RowSet.next, instead use a for loop and call gotoRow.
As for why idp.utils.GetThumbnailURlForImage is being called so many
times, the only explanation I can offer is that you must be iterating
over the RowSet more than once. Are you using findRow?
Regards,
Aparajita
www.aparajitaworld.com
"If you dare to fail, you are bound to succeed."
- Sri Chinmoy | www.srichinmoylibrary.com
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