sql: timestamps are truncated to precision 0 after 19.2 upgrade

[thoszhang]

Start a cluster running 19.1.5 and create a table with a timestamp column:

root@localhost:26257/defaultdb> create table t (a timestamp);
CREATE TABLE

Insert a value (just for comparison's sake):

root@localhost:26257/defaultdb> insert into t values ('2016-01-25 10:10:10.555555');
INSERT 1

Then upgrade to 19.2.0-rc.2.

Now when timestamps are inserted, they get truncated:

root@localhost:26257/defaultdb> insert into t values ('2016-01-25 10:10:10.555555');
INSERT 1

root@localhost:26257/defaultdb> select * from t;
                 a
+----------------------------------+
  2016-01-25 10:10:10.555555+00:00
  2016-01-25 10:10:11+00:00
(2 rows)

This was introduced in #37920. The problem is that the Precision field for the timestamp types were unset, and the precision was always 6 (i.e. microseconds) by default. After the change, a Precision of 0 is now taken to mean precision 0 (i.e. seconds).

[RaduBerinde]

Cool find! I filed #42309 to track adding a test along these lines.

[solongordon]

Fixed by #42286.