[odb-users] Objects without primitive fields & NULL data to BLOB

Alexander Prokhorov prokher at gmail.com
Mon Jan 14 07:24:16 EST 2013

Hi, Boris.

Thanks for your quick fix of polymorphic save/load of large objects in 
odb compiler. Now it works perfectly. However, we have encountered some 
fresh problems.

Some history - we use ODB with Qt profile and Sqlite, on multiple 
platforms. However, in-depth debugging was performed on linux-64 (ubuntu 
10, 11, 12).

1. [clear bug] It took some time to pinpoint exact problem, which is 
this - objects without any primitive fields can't be loaded. So, when 
persistent object contains only collections, load fails with syntax 
error - odb generates broken query like "SELECT FROM ...". Look into 
attached example odb_collections_test. Simple workaround is to add dummy 
primitive field to persistent class.

2. [bug or feature] Another strange thing that was encountered in same 
persistent classes - saving NULL data to "blob" type by custom traits. 
It's unclear, whether such operation is valid, however, I haven't found 
deep traits description that is deep enough to figure it out. It fails 
with 'object already persistent' message, which is, at least, 
perplexing. Message is clearly bad, the question is, can we save NULL 
blob at all? Non-null with zero size is ok. Look into attached example 

Thanks in advance.
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