added decimal point truncate to postmaster start time query

[tschuyebuhl]

postgres=# SELECT CAST(extract(epoch from pg_postmaster_start_time()) AS INTEGER) as start_time;
 start_time 
------------
 1667939963
(1 row)

postgres=# SELECT extract(epoch from pg_postmaster_start_time()) as start_time;
    start_time     
-------------------
 1667939963.007028
(1 row)

the current query results in this error spam:

ts=2023-07-07T15:35:20.847Z caller=collector.go:190 level=error msg="collector failed" name=postmaster duration_seconds=0.016613707 err="sql: Scan error on column index 0, name \"pg_postmaster_start_time\": converting driver.Value type time.Time (\"2022-11-08 21:39:23.007028 +0100 CET\") to a float64: invalid syntax"
we probably dont need to use float64 with this change, but i didn't want to make a bigger mess for now
issue ref: #850

[sysadmind]

I just checked locally, this has already been resolved in the master branch. v0.13.1 still has this bug. The error you see was resolved in #828

Also of note, we have opened #830 to track improvements to this collector.

[tschuyebuhl]

Right. We can close this one. I just double checked now and, of course, you are right:

Thank you for your time anyways. Waiting til #828 makes its way downstream.