If you  set different TTLs for column families you can run into issues with SELECT count(*) queries not working correctly (depending on which column family is used to store the EMPTY_COLUMN_VALUE).

On Tue, Sep 4, 2018 at 10:56 AM, Sergey Soldatov <sergey.soldatov@gmail.com> wrote:
What is the use case to set TTL only for a single column family? I would say that making TTL table wide is a mostly technical decision because in relational databases we operate with rows and supporting TTL for only some columns sounds a bit strange. 

Thanks,
Sergey 

On Fri, Aug 31, 2018 at 7:43 AM Domen Kren <dk.nexus@gmail.com> wrote:
Hello,

we have situation where we would like to set TTL on a single column family in a table. After getting errors while trying to do that trough a phoenix command i found this issue, https://issues.apache.org/jira/browse/PHOENIX-1409, where it said "TTL - James Taylor and I discussed offline and we decided that for now we will only be supporting for all column families to have the same TTL as the empty column family. This means we error out if a column family is specified while setting TTL property - both at CREATE TABLE and ALTER TABLE time. Also changes were made to make sure that any new column family added gets the same TTL as the empty CF."

If i understand correctly, this was a design decision and not a technical one. So my question is, if i change this configuration trough HBase API or console, could there be potential problems that arise in phoenix?

Thanks you and best regards,
Domen Kren