BUG #4793: Segmentation fault when doing vacuum analyze

The following bug has been logged online:

Bug reference: 4793
Logged by: Dennis Noordsij
Email address: dennis(dot)noordsij(at)helsinki(dot)fi
PostgreSQL version: snapshot/beta1
Operating system: 64bit arch Linux
Description: Segmentation fault when doing vacuum analyze
Details:

Seen on both 8.4beta1 and daily snapshot downloaded 5 May 2009.

Table used (effects also seen on similar tables):

osm=# \d way_tags
Table "public.way_tags"
Column | Type | Modifiers
--------+--------+-----------
way | bigint | not null
key | text | not null
value | text |
Indexes:
"way_tags_pkey" PRIMARY KEY, btree (way, key)
"way_tag_kv_idx" btree (key, value)
"way_tag_wkv_idx" btree (way, key, value)

osm=# select count(*) from way_tags;
count
---------
4154315
(1 row)

osm=# select count(*) from (select distinct key from way_tags) as foo;
count
-------
322
(1 row)

osm=# select count(*) from (select distinct value from way_tags) as foo;
count
---------
1124909
(1 row)

Statement:
alter table way_tags alter column way set statistics 5000;
alter table way_tags alter column key set statistics 5000;
vacuum analyze;

results in a segmentation fault with the following backtrace:

(gdb) bt
#0 0x00000000004eecf7 in compute_scalar_stats (stats=0x1abd878,
fetchfunc=0x4f0f30 <std_fetch_func>, samplerows=<value optimized out>,
totalrows=4154315)
at analyze.c:2321
#1 0x00000000004efbf5 in analyze_rel (relid=16484, vacstmt=0x1aaf140,
bstrategy=<value optimized out>, update_reltuples=1 '\001') at
analyze.c:433
#2 0x0000000000538681 in vacuum (vacstmt=0x1aaf140, relid=<value optimized
out>,
do_toast=1 '\001', bstrategy=<value optimized out>, for_wraparound=0
'\0',
isTopLevel=<value optimized out>) at vacuum.c:466
#3 0x00000000005e8bc7 in PortalRunUtility (portal=0x1ae00c0,
utilityStmt=0x1aaf140,
isTopLevel=64 '@', dest=0xabc160, completionTag=0x7fff39e7f0e0 "") at
pquery.c:1192
#4 0x00000000005e9d0d in PortalRunMulti (portal=0x1ae00c0,
isTopLevel=<value optimized out>,
dest=0xabc160, altdest=0xabc160, completionTag=0x7fff39e7f0e0 "") at
pquery.c:1297
#5 0x00000000005ea482 in PortalRun (portal=0x1ae00c0,
count=9223372036854775807,
isTopLevel=1 '\001', dest=0xabc160, altdest=0xabc160,
completionTag=0x7fff39e7f0e0 "")
at pquery.c:823
#6 0x00000000005e5807 in exec_simple_query (query_string=0x1aae880 "vacuum
analyze way_tags;\n")
at postgres.c:991
#7 0x00000000005e6dc7 in PostgresMain (argc=1, argv=<value optimized out>,
username=0x1a07560 "dennis") at postgres.c:3606
#8 0x00000000005676af in main (argc=5, argv=0x1a05b70) at main.c:186

Note if I vacuum analyze between the alter table statements then everything
completes fine.

After the segfault, restarting and then running "vacuum analyze way_tags" is
enough to trigger the segfault again.