well, one hairy problem I had was migrating a legacy enterprise behemoth from a 4g language to Java (it was early 2000)
now 4g languages let you do anything easy, so nobody really put thought in anything really. result: everything was soft code and the database grew to around 4 thousand tables. the database itself wasn't even that big, running at around 10gb.
The sheer number of tables made impossible to use an orm layer, because back in the day Hibernate and the others had no other option but to map everything at startup time from xml files or annotation and have all the metadata about tables and relationships loaded in memory. Just the metadata was using about 5gb of memory.
However as part of the migration we managed to build all the UI straight from the 4gl definition, so we really really needed a way to create queries out of the UI metadata using object introspection.
We ended up writing our own object query language and the translation layer to build SQL queries out of it. It sounds bad but in the end wan't impossible even for a small 3 man team - we needed not to support the full spectrum of possible way to interact, only what the UI needed to load the data (and yes this was a thick client)
now 4g languages let you do anything easy, so nobody really put thought in anything really. result: everything was soft code and the database grew to around 4 thousand tables. the database itself wasn't even that big, running at around 10gb.
The sheer number of tables made impossible to use an orm layer, because back in the day Hibernate and the others had no other option but to map everything at startup time from xml files or annotation and have all the metadata about tables and relationships loaded in memory. Just the metadata was using about 5gb of memory.
However as part of the migration we managed to build all the UI straight from the 4gl definition, so we really really needed a way to create queries out of the UI metadata using object introspection.
We ended up writing our own object query language and the translation layer to build SQL queries out of it. It sounds bad but in the end wan't impossible even for a small 3 man team - we needed not to support the full spectrum of possible way to interact, only what the UI needed to load the data (and yes this was a thick client)