Aerospike C Client Manual ——— user-defined functions-apply UDFs to records

Applying UDFs to records

The Aerospike C Client API provides aerospike_key_apply () to apply a user-defined function to a record in the database.

before using the aerospike_key_apply () operation, the UDF module containing the function being applied must first be registered with the Aerospike server. See the section " registering user-defined Functions " to learn how to register using C API, or read the AQL Handbook to learn how to register with external tools.

The following code references the sample directory from the " Examples/basic_examples/get " , comes with the Aerospike C client installation package.

Please read the section "Creating connections" to understand how to establish a connection to a cluster.

Defining UDFs

The function bin_transform is defined in a module named "Basice_udf".

function bin_transform(record, bin_name, x, y) record[bin_name] = (record[bin_name] * x) + y aerospike:update(record) return record[bin_name]end

This function is a simple algorithm with three parameters, and three parameter names are "Bin_name", "X", "Y", respectively. It performs operations on the bin specified by "Bin_name" and updates the record data, and then returns the result value of the bin's operation.

Initialize record key (key)

Below we create a key for the sample code. The key is the string "Test-key", where the namespace name of the data is called "Test", the set name is called "Test-set"

as_key key;as_key_init_str(&key, "test", "test-set", "test-key");

Passing parameters to the UDF

user-defined function" Bin_transform ", Requires a string argument and two integer (integer) parameters, so a parameter list needs to be populated.

as_arraylist args;as_arraylist_inita(&args, 3);as_arraylist_append_str(&args, "test-bin-2");as_arraylist_append_int64(&args, 4);as_arraylist_append_int64(&args, 400);

Apply a UDF on a record

Using the record key, you can now invoke a user-defined function on the specified record in the database:

as_val * result = NULL;if (aerospike_key_apply(&as, &err, NULL, &key, "mymodule", "add", (as_list *) &args, &result) != AEROSPIKE_OK) { fprintf(stderr, "err(%d) %s at [%s:%d]\n", err.code, err.message, err.file, err.line);}

The return value of the UDF function Bin_trransform () is returned in the Parameter object result.

If the record key does not exist, the UDF function is returned when it is found Aerospike_err_record_not_found, otherwise a UDF run-time error is returned, and the error details are returned in the member domain of As_error.

Clean up resources

When you no longer need the returned results, you should free it and its associated resources:

as_val_destroy(&result);

Also, clean up the parameter list:

as_arraylist_destroy(&args);

The record key here does not need to be explicitly destroyed because it and its members are created on the stack.

original link: http://www.aerospike.com/docs/client/c/usage/udf/apply.html Translator: crooked Neck belly Q  

Aerospike C Client Manual ——— user-defined functions-apply UDFs to records