Tracking drop column progress in Oracle - sql

Question

I have issued following statement in Oracle on a huge table (1.8 TB size):
alter table drop unused columns checkpoint
It has been running for almost 10 days now, crashing a couple of times due to lack of memory.
I resumed it with :
alter table drop columns continue
How can I track the progress and possibly get an estimate of the finish time?
I tried querying v$session_longops but there are no records for this session.

Answer 1

I know this is an old question, but given that nobody actually ever answered it, here's what I came up with when I ran into the same problem:
select v.*, to_char(100*"Processed"/"# of Blocks", '990D000000') "% Complete"
from (select sid, serial#, status, event, p1text, p1, p2text, p2, p3text, p3, x.segment_name, x.extent_id,
(select sum(case
when p2 not between block_id and block_id + blocks - 1 then blocks
else p2 - block_id
end)
from dba_extents x2
where x2.segment_name = x.segment_name
and extent_id <= x.extent_id) "Processed",
(select sum(blocks)
from dba_extents
where segment_name = x.segment_name) "# of Blocks"
from v$session s
left join dba_extents x on p1 = file_id and p2 between block_id and block_id + blocks - 1
where (sid, serial#) in ((15,40610))
) v
Basically, I'm taking the P2 value (Block #) from the wait event on the session doing the drop, and identifying where within the table's list of segments the process is at.
There is some work left to the reader here, as this assumes that
You know the session and serial#
That "db file sequential read" activities are, in fact sequential.
That the session isn't swapping between multiple files
That the tablespace the table resides in isn't split across multiple files
One could probably also only look at which extent the session was in compared to the total number of extents in the segment to give a rough estimate of progress as well...
Hopefully somebody else can find this helpful, even if only as a breadcrumb to building a better solution.
Cheers

Answer 2

Good query above. I modified the query a bit:
select
v.*,
Round(100*"Processed"/"# of Blocks", 2) "% Complete"
from (
select
sid,
serial#,
status,
event,
p1text,
p1,
p2text,
p2,
p3text,
p3,
x.segment_name,
x.partition_name,
x.extent_id,
( select
sum(
case
when p2.partition_position < p.partition_position
then x2.blocks
when ( x2.partition_name is null or
p2.partition_position = p.partition_position) and
x2.file_id < x.file_id
then x2.blocks
when ( x2.partition_name is null or
p2.partition_position = p.partition_position) and
x2.file_id = x.file_id and
x2.block_id < x.block_id
then x2.blocks
when ( x2.partition_name is null or
p2.partition_position = p.partition_position) and
x2.file_id = x.file_id and
x2.block_id = x.block_id and
s.p2 < x2.block_id + x2.blocks
then s.p2 - x2.block_id
end
)
from DBA_EXTENTS x2
left join DBA_TAB_PARTITIONS p2
on p2.table_owner = x2.owner and
p2.table_name = x2.segment_name and
p2.partition_name = x2.partition_name
where x2.segment_name = x.segment_name
) as "Processed",
( select
sum(x2.blocks)
from DBA_EXTENTS x2
where x2.segment_name = x.segment_name
) as "# of Blocks"
from V$SESSION s
left join DBA_EXTENTS x
on s.p1 = x.file_id and
s.p2 between x.block_id and x.block_id + x.blocks - 1
left join DBA_TAB_PARTITIONS p
on p.table_owner = x.owner and
p.table_name = x.segment_name and
p.partition_name = x.partition_name
where
--(sid, serial#) in ((84,23431)) or
s.event = 'db file scattered read'
) v