Quanlong Huang has posted comments on this change. ( 
http://gerrit.cloudera.org:8080/16861 )

Change subject: IMPALA-10388: [DOCS] add limitations on mask functions
......................................................................


Patch Set 2:

(1 comment)

http://gerrit.cloudera.org:8080/#/c/16861/2/docs/topics/impala_authorization.xml
File docs/topics/impala_authorization.xml:

http://gerrit.cloudera.org:8080/#/c/16861/2/docs/topics/impala_authorization.xml@711
PS2, Line 711:           <li>This example shows how to use the overload 
mask(FLOAT) that is not yet implemented in
             :             Impala. If you want to mask float/double/decimal to 
NULLs, you can use a more efficient
             :             Nullify policy (MASK_NULL) for the same purpose. Do 
not use Redact(MASK) on
             :             float/double/decimal types as Hive always returns 
NULL for them since it is not
             :             redact.</li>
This is not an example "shows how to use the overload mask(FLOAT) that is not 
yet implemented in Impala"...

What I want to say is mask(FLOAT), mask(DOUBLE), mask(DECIMAL) are missing in 
Impala currently. If users use Redact(MASK) column masking policy on 
float/double/decimal columns, they will hit an error like "No matching function 
with signature: mask..." in Impala.

Then I explain that it doesn't make sense to use Redact(MASK) column masking 
policy on float/double/decimal columns. The reason is Hive's mask function 
always returns NULLs on these types. The actually meaning of "Redact" is 
replacing the content with mask characters, e.g. transforming "ABCDabcd-1234" 
to "XXXXxxxx-nnnn". So transforming 3.14 to NULL doesn't mean "Redact" 
actually. "Redact" will transform "3.14" to "n.nn".

If users do want to mask float/double/decimal types to NULLs, they should use 
the Nullify policy. I think you understand this part correctly. :)

The missing overloads are not just mask(FLOAT), mask(DOUBLE) and mask(DECIMAL). 
This is an example explaining why they are missing (because it doesn't make 
sense to use them), and providing a workaround if users do want to use them.

I think if it's hard to explain these, we can remove this paragraph.



--
To view, visit http://gerrit.cloudera.org:8080/16861
To unsubscribe, visit http://gerrit.cloudera.org:8080/settings

Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: I37f0bcf4cf586cc5cfd03e4df68443967b6bb88f
Gerrit-Change-Number: 16861
Gerrit-PatchSet: 2
Gerrit-Owner: Shajini Thayasingh <sthayasi...@cloudera.com>
Gerrit-Reviewer: Impala Public Jenkins <impala-public-jenk...@cloudera.com>
Gerrit-Reviewer: Quanlong Huang <huangquanl...@gmail.com>
Gerrit-Comment-Date: Fri, 18 Dec 2020 13:20:29 +0000
Gerrit-HasComments: Yes

Reply via email to