Resource use for C++ UDxs
Your UDxs consume at least a small amount of memory by instantiating classes and creating local variables.
Your UDxs consume at least a small amount of memory by instantiating classes and creating local variables. This basic memory usage by UDxs is small enough that you do not need to be concerned about it.
If your UDx needs to allocate more than one or two megabytes of memory for data structures, or requires access to additional resources such as files, you must inform Vertica about its resource use. Vertica can then ensure that the resources your UDx requires are available before running a query that uses it. Even moderate memory use (10MB per invocation of a UDx, for example) can become an issue if there are many simultaneous queries that call it.
Note
If your UDx allocates its own memory, you must make absolutely sure it properly frees it. Failing to free even a single byte of allocated memory can have significant consequences at scale. Instead of having your code allocate its own memory, you should use the C++vt_alloc macro, which uses Vertica's own memory manager to allocate and track memory. This memory is guaranteed to be properly disposed of when your UDx completes execution. See Allocating resources for UDxs for more information.