BUG #7853: Incorrect statistics in table with many dead rows.

The following bug has been logged on the website:

Bug reference:      7853
Logged by:          James Skaggs
Email address:      jimbob@seagate.com
PostgreSQL version: 8.4.14
Operating system:   RHEL6
Description:        =


After "analyze verbose", the table shows 158 million rows. A select count(1)
yields 13.8 million rows.

INFO:  analyzing "public.stream_file"
INFO:  "stream_file": scanned 30000 of 2123642 pages, containing 184517 live
rows and 2115512 dead rows; 30000 rows in sample, 158702435 estimated total
rows

Here are the table statistics.

Sequential Scans    81853    =

Sequential Tuples Read    578848425234    =

Index Scans    1976513672    =

Index Tuples Fetched    2183339860    =

Tuples Inserted    65122575    =

Tuples Updated    308883671    =

Tuples Deleted    51238760    =

Tuples HOT Updated    2242897    =

Live Tuples    163981972    =

Dead Tuples    7056493    =

Heap Blocks Read    43483331819    =

Heap Blocks Hit    43121456487    =

Index Blocks Read    134539277    =

Index Blocks Hit    13606451182    =

Toast Blocks Read        =

Toast Blocks Hit        =

Toast Index Blocks Read        =

Toast Index Blocks Hit        =

Last Vacuum    2013-02-04 10:06:44.058743-07    =

Last Autovacuum    2013-02-04 16:11:34.289823-07    =

Last Analyze    2013-02-04 14:22:27.848547-07    =

Last Autoanalyze    2013-02-01 17:37:29.855553-07    =

Table Size    17 GB    =

Toast Table Size    none    =

Indexes Size    34 GB
Query returned successfully with no result in 4094 ms.


Bad statistics led to a bad plan.  We will cluster the table today to see if
that fixes it, but I think statistics should be correct, regardless of the
state of a table.  BTW, Coverity product requries 8.x, and we'll upgrade to
8.4.15 today. Didn't see anything about better statistics in the 8.4.15
changelog.