On 03/09/2015 09:19 AM, Joshua D. Drake wrote:
On 03/09/2015 08:57 AM, Adrian Klaver wrote:
On 03/09/2015 08:49 AM, Kevin Grittner wrote:
pinker <pinker@xxxxxxx> wrote:
INFO: vacuuming "my_table"
INFO: "my_table": found 0 removable, 3043947 nonremovable row
versions in 37580 pages
DETAIL: 0 dead row versions cannot be removed yet.
So there are no longer any dead rows being left behind, right?
Why are we still discussing this? Do you have some other question?
Well from the original post:
"I have deleted a large number of records from my_table, which
originally had 288 MB. Then I ran vacuum full to make the table size
smaller. After this operation size of the table remains the same,
despite of the fact that table contains now only 241 rows and after
rewriting it in classic way: CREATE TABLE new_table AS SELECT * FROM
old_table - new_table size is 24kB. "
So I think the question remains how is 241 rows = 3043947 nonremovable
row versions? And that number is an increase from the original number
which was 2989662 nonremovable row versions.
TGL has answered this before:
http://www.postgresql.org/message-id/14512.1282137722@xxxxxxxxxxxxx
There are a number of things that can cause this but they are all about
making sure that all versions of the tuple are completely and utterly of
no use before vacuum will remove them.
And that is what this thread is trying to determine. As others and I
suspect, there is good reason to believe there is some sort of data
corruption at work. This awaits a clearer understanding of what 'It was
flash copy snapshot' means. Also per Kevin Grittner and Tom Lane there
is a Nabble issue at work where the list here is not seeing all the
information. Example:
On this list I saw:
"In other words detail the steps you took to get the snapshot.
I would like to know as well. Sysadmin team manage it, I'll ask them, but
as far I know it's matrix feature...."
on Nabble I see:
"> In other words detail the steps you took to get the snapshot.
First, they call pg_start_backup, then flash copy is done for blocks,
that were changed. Flash copy is made on another filesystem.
If this matters - xmaxes for all rows are 0.
"
Also per Kevin Grittner we are looking at a moving target, so some sort
of information about current state would be helpful.
JD
--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx
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