Re: row-attribute in EXPLAIN-output doesn't match count(*)

On Thu, Apr 14, 2005 at 06:38:14PM +0200, Andreas Joseph Krogh wrote:
> Hi everybody, I have table which inly has 298 rows in it, but EXPLAIN ANALYZE
> shows that PG thinks it has as much as 160057 rows AFAICT from the
> EXPLAIN-output.

It does have 160057 rows:

> INFO: vacuuming "public.onp_web_index"
> INFO: "onp_web_index": found 0 removable, 160057 nonremovable row versions in
> 206940 pages
> DETAIL: 159759 dead row versions cannot be removed yet.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

You no doubt have a long-running transaction keeping the rows from
being recovered. Look for "idle in transaction" as a first guess.

> DETAIL: 160057 index row versions were removed.
> 0 index pages have been deleted, 0 are currently reusable.
> CPU 2.40s/0.92u sec elapsed 286.41 sec.
>
> Here it says that it removed 160057 rows, doesn't it?

No; that's the index row versions.

> Is this normal, shall I just overlook the "rows=160057" output from EXPLAIN,
> or is something wrong?
> What does the line "DETAIL: 159759 dead row versions cannot be removed yet."
> mean?

It means that those rows were marked invalidated after some existing
transaction started.

A

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