These settings are available in system.settings and are autogenerated from source.
Fraction of a WebAssembly UDF instance’s linear memory that one call’s serialized input may occupy. Must be at least 0 and at most 1; the default leaves the other half to the guest for its own working set beside the input buffer.
The margin below 1 is what makes the batching safe: the guest’s own data, stack and allocator share that memory and are invisible to the host. A ratio close to 1 leaves nothing for them, so a call sized against it can still fail inside the guest’s allocator.
Read only for ABI BUFFERED_V1, and it sizes the calls only while webassembly_udf_max_input_block_size is 0 - a non-zero block size caps the rows per call instead.
A batch is never taken below a single row, so a row whose own serialized size is past the budget is passed on its own, and one too large for the module’s linear memory fails inside the guest’s allocator.
Set to 0 to leave the input unsplit: the whole pipeline block is passed in one call.
webassembly_udf_max_fuel
Fuel limit per WebAssembly UDF instance execution. Each WebAssembly instruction consumes some amount of fuel. The value is scaled by 1024 before being passed to the runtime, so webassembly_udf_max_fuel = 1 corresponds to approximately 1024 fuel units. Set to 0 for no finite limit. Applies only to functions whose per-function setting webassembly_udf_enable_fuel is true, which is the default.
Maximum number of rows passed to a WebAssembly UDF in a single call. A non-zero value caps the rows per call and applies to every ABI.
Set to 0 to size the calls by their serialized input instead. That applies to ABI BUFFERED_V1 alone, the only ABI that serializes a whole input block into guest memory: its blocks are split so that a call’s input stays within webassembly_udf_input_split_memory_ratio of the module’s linear memory. ROW_DIRECT passes its arguments as WebAssembly values and ASSEMBLYSCRIPT builds one object per row, so neither has a serialized input to size a call by, and 0 leaves their pipeline block whole.
webassembly_udf_max_instances
Maximum number of WebAssembly UDF instances that can run in parallel per function.
webassembly_udf_max_memory
Memory limit in bytes per WebAssembly UDF instance. Last modified on September 9, 2026
