Allow macro to return void
--------------------------
Key: PIG-1998
URL: https://issues.apache.org/jira/browse/PIG-1998
Project: Pig
Issue Type: Improvement
Components: impl
Affects Versions: 0.9.0
Reporter: Richard Ding
Assignee: Richard Ding
Fix For: 0.9.0
Pig macro is allowed to not have output alias. But this property isn't clear
from macro definition and macro invocation (macro inline). Here we propose to
make it clear:
1. If a macro doesn't output any alias, it must specify void as return value.
For example:
{code}
define mymacro(...) returns void {
... ...
};
{code}
2. If a macro doesn't output any alias, it must be invoked without return
value. For example, to invoke above macro, just specify:
{code}
mymacro(...);
{code}
3. Any non-void return alias in the macro definition must exist in the macro
body and be prefixed with $. For example:
{code}
define mymacro(...) returns B {
... ...
$B = filter ...;
};
{code}
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