[jira] [Created] (IMPALA-5939) StringConcatUpdate() UDA example uses StringVal::CopyFrom() incorrectly.

["Tim Armstrong (JIRA)" <ji...@apache.org>]

Tim Armstrong created IMPALA-5939:
-------------------------------------

             Summary: StringConcatUpdate() UDA example uses StringVal::CopyFrom() incorrectly.
                 Key: IMPALA-5939
                 URL: https://issues.apache.org/jira/browse/IMPALA-5939
             Project: IMPALA
          Issue Type: Bug
          Components: Backend
    Affects Versions: Impala 2.10.0
            Reporter: Tim Armstrong


http://community.cloudera.com/t5/Interactive-Short-cycle-SQL/Memory-handling-in-Impala-UDA-functions/m-p/59877#M3574?eid=1&aid=1 pointed out that StringConcatUpdate() uses a local allocation to store the intermediate value (returned from StringVal::CopyFrom()) when it show be using a non-local allocation from Allocate().

{code}
void StringConcatUpdate(FunctionContext* context, const StringVal& arg1,
    const StringVal& arg2, StringVal* val) {
  if (val->is_null) {
    val->is_null = false;
    *val = StringVal::CopyFrom(context, arg1.ptr, arg1.len);
  } else {
    int new_len = val->len + arg1.len + arg2.len;
    StringVal new_val(context, new_len);
    if (!new_val.is_null) {
      memcpy(new_val.ptr, val->ptr, val->len);
      memcpy(new_val.ptr + val->len, arg2.ptr, arg2.len);
      memcpy(new_val.ptr + val->len + arg2.len, arg1.ptr, arg1.len);
    }
    *val = new_val;
  }
}
{code}

The bug was fixed in a different repo years ago.
https://github.com/cloudera/impala-udf-samples/commit/3fce648fddb6c41e09572e0de89d3a83b394d47a



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