Odd out of memory problem. - Mailing list pgsql-hackers

I'm not sure if this is a bug, but I have wrestling with this problem 
for a client.

Platform is Windows Servers 2003 64 bit, PostgreSQL 8.4.8., 4Gb RAM, 
running on an Amazon VM.

Shared buffers: 512Mb, work_mem: 25Mb. There are only a handful of 
connections to the database, and no other activity.

We are seeing the error shown below. The table in question has two 
columns (Oid, int) and roughly 43m rows. The only other thing remarkable 
about the settings is that effective_cache_size is set to 5Gb, which is 
clearly too high, but surely that shouldn't cause a memory error.

I'm really perplexed as to why this fairly simple query should cause an 
out of memory error:
   select loid, max(pageno) from ldata group by loid order by 2 desc   limit 10;

I can't see what I might be missing.


cheers

andrew
   TopMemoryContext: 49816 total in 6 blocks; 5384 free (7 chunks);   44432 used      TopTransactionContext: 8192 total
in1 blocks; 7696 free (0   chunks); 496 used      Record information cache: 8192 total in 1 blocks; 1800 free (0
chunks);6392 used      Type information cache: 8192 total in 1 blocks; 1800 free (0   chunks); 6392 used      Operator
classcache: 8192 total in 1 blocks; 3848 free (0   chunks); 4344 used      Operator lookup cache: 24576 total in 2
blocks;14072 free (6   chunks); 10504 used      MessageContext: 40960 total in 3 blocks; 29920 free (6 chunks);   11040
used     smgr relation table: 8192 total in 1 blocks; 2816 free (0   chunks); 5376 used      TransactionAbortContext:
32768total in 1 blocks; 32752 free (0   chunks); 16 used      Portal hash: 8192 total in 1 blocks; 3912 free (0
chunks);4280 used      PortalMemory: 8192 total in 1 blocks; 8040 free (0 chunks); 152 used        PortalHeapMemory:
1024total in 1 blocks; 920 free (0 chunks);   104 used          ExecutorState: 8192 total in 1 blocks; 2144 free (1
chunks);  6048 used            TupleSort: 40984 total in 3 blocks; 24208 free (10 chunks);   16776 used
ExprContext:0 total in 0 blocks; 0 free (0 chunks); 0 used            AggContext: 864018432 total in 127 blocks; 3400
free(110   chunks); 864015032 used              TupleHashTable: 619175960 total in 95 blocks; 821528 free   (331
chunks);618354432 used            ExprContext: 0 total in 0 blocks; 0 free (0 chunks); 0 used            ExprContext: 0
totalin 0 blocks; 0 free (0 chunks); 0 used            ExprContext: 0 total in 0 blocks; 0 free (0 chunks); 0 used
Relcacheby OID: 8192 total in 1 blocks; 3376 free (0 chunks);   4816 used      CacheMemoryContext: 667696 total in 20
blocks;169960 free (2   chunks); 497736 used        pg_shdepend_reference_index: 1024 total in 1 blocks; 240 free   (0
chunks);784 used        pg_depend_depender_index: 1024 total in 1 blocks; 152 free (0   chunks); 872 used
pg_depend_reference_index:1024 total in 1 blocks; 152 free (0   chunks); 872 used        pg_largeobject_loid_pn_index:
1024total in 1 blocks; 280 free   (0 chunks); 744 used        pg_database_datname_index: 1024 total in 1 blocks; 344
free(0   chunks); 680 used        pg_index_indrelid_index: 1024 total in 1 blocks; 304 free (0   chunks); 720 used
 pg_opclass_am_name_nsp_index: 1024 total in 1 blocks; 152 free   (0 chunks); 872 used
pg_foreign_data_wrapper_name_index:1024 total in 1 blocks; 344   free (0 chunks); 680 used        pg_enum_oid_index:
1024total in 1 blocks; 344 free (0 chunks);   680 used        pg_class_relname_nsp_index: 1024 total in 1 blocks; 240
free(0   chunks); 784 used        pg_foreign_server_oid_index: 1024 total in 1 blocks; 344 free   (0 chunks); 680 used
     pg_statistic_relid_att_index: 1024 total in 1 blocks; 240 free   (0 chunks); 784 used
pg_cast_source_target_index:1024 total in 1 blocks; 240 free   (0 chunks); 784 used        pg_language_name_index: 1024
totalin 1 blocks; 344 free (0   chunks); 680 used        pg_authid_oid_index: 1024 total in 1 blocks; 304 free (0
chunks);720 used        pg_amop_fam_strat_index: 1024 total in 1 blocks; 88 free (0   chunks); 936 used
pg_index_indexrelid_index:1024 total in 1 blocks; 304 free (0   chunks); 720 used        pg_ts_template_tmplname_index:
1024total in 1 blocks; 280 free   (0 chunks); 744 used        pg_ts_config_map_index: 1024 total in 1 blocks; 192 free
(0  chunks); 832 used        pg_opclass_oid_index: 1024 total in 1 blocks; 304 free (0   chunks); 720 used
pg_foreign_data_wrapper_oid_index:1024 total in 1 blocks; 344   free (0 chunks); 680 used
pg_auth_members_member_role_index:1024 total in 1 blocks; 280   free (0 chunks); 744 used        pg_ts_dict_oid_index:
1024total in 1 blocks; 344 free (0   chunks); 680 used        pg_conversion_default_index: 1024 total in 1 blocks; 128
free  (0 chunks); 896 used        pg_operator_oprname_l_r_n_index: 1024 total in 1 blocks; 88   free (0 chunks); 936
used       pg_trigger_tgrelid_tgname_index: 1024 total in 1 blocks; 240   free (0 chunks); 784 used
pg_enum_typid_label_index:1024 total in 1 blocks; 280 free (0   chunks); 744 used        pg_ts_config_oid_index: 1024
totalin 1 blocks; 344 free (0   chunks); 680 used        pg_user_mapping_oid_index: 1024 total in 1 blocks; 344 free (0
 chunks); 680 used        pg_opfamily_am_name_nsp_index: 1024 total in 1 blocks; 192 free   (0 chunks); 832 used
pg_type_oid_index:1024 total in 1 blocks; 304 free (0 chunks);   720 used        pg_aggregate_fnoid_index: 1024 total
in1 blocks; 304 free (0   chunks); 720 used        pg_constraint_oid_index: 1024 total in 1 blocks; 344 free (0
chunks);680 used        pg_rewrite_rel_rulename_index: 1024 total in 1 blocks; 280 free   (0 chunks); 744 used
pg_ts_parser_prsname_index:1024 total in 1 blocks; 280 free (0   chunks); 744 used        pg_ts_config_cfgname_index:
1024total in 1 blocks; 280 free (0   chunks); 744 used        pg_ts_parser_oid_index: 1024 total in 1 blocks; 344 free
(0  chunks); 680 used        pg_operator_oid_index: 1024 total in 1 blocks; 304 free (0   chunks); 720 used
pg_namespace_nspname_index:1024 total in 1 blocks; 304 free (0   chunks); 720 used        pg_ts_template_oid_index:
1024total in 1 blocks; 344 free (0   chunks); 680 used        pg_amop_opr_fam_index: 1024 total in 1 blocks; 240 free
(0  chunks); 784 used        pg_ts_dict_dictname_index: 1024 total in 1 blocks; 280 free (0   chunks); 744 used
pg_auth_members_role_member_index:1024 total in 1 blocks; 280   free (0 chunks); 744 used
pg_type_typname_nsp_index:1024 total in 1 blocks; 240 free (0   chunks); 784 used        pg_opfamily_oid_index: 1024
totalin 1 blocks; 344 free (0   chunks); 680 used        pg_class_oid_index: 1024 total in 1 blocks; 304 free (0
chunks);720 used        pg_proc_proname_args_nsp_index: 1024 total in 1 blocks; 152   free (0 chunks); 872 used
pg_attribute_relid_attnum_index:1024 total in 1 blocks; 240   free (0 chunks); 784 used        pg_proc_oid_index: 1024
totalin 1 blocks; 304 free (0 chunks);   720 used        pg_language_oid_index: 1024 total in 1 blocks; 344 free (0
chunks);680 used        pg_namespace_oid_index: 1024 total in 1 blocks; 344 free (0   chunks); 680 used
pg_database_oid_index:1024 total in 1 blocks; 304 free (0   chunks); 720 used        pg_amproc_fam_proc_index: 1024
totalin 1 blocks; 88 free (0   chunks); 936 used        pg_authid_rolname_index: 1024 total in 1 blocks; 304 free (0
chunks);720 used        pg_foreign_server_name_index: 1024 total in 1 blocks; 344 free   (0 chunks); 680 used
pg_attribute_relid_attnam_index:1024 total in 1 blocks; 240   free (0 chunks); 784 used        pg_conversion_oid_index:
1024total in 1 blocks; 344 free (0   chunks); 680 used        pg_user_mapping_user_server_index: 1024 total in 1
blocks;280   free (0 chunks); 744 used        pg_conversion_name_nsp_index: 1024 total in 1 blocks; 280 free   (0
chunks);744 used      MdSmgr: 8192 total in 1 blocks; 4240 free (0 chunks); 3952 used      LOCALLOCK hash: 8192 total
in1 blocks; 3912 free (0 chunks);   4280 used      Timezones: 79320 total in 2 blocks; 5968 free (0 chunks); 73352 used
    ErrorContext: 8192 total in 1 blocks; 8176 free (0 chunks); 16 used   2012-03-25 17:18:01 EDT ERROR:  out of memory
 2012-03-25 17:18:01 EDT DETAIL:  Failed on request of size 20.   2012-03-25 17:18:01 EDT STATEMENT:  select loid,
max(pageno)from   ldata group by loid order by 2 desc limit 10;