delete fails with out of memory

Hello

I have a large database and I'm trying to execute delete on a table which
has some related tables. The query fails with following error:
ERROR: out of memory
DETAIL: Failed on request of size 1048576.

I'm new to postgresql and I'm currently trying to figure out what to do by
myself, but it would be great if somebody could tell me how to solve it.

Here is the log:

2009-10-17 17:02:09 PDTLOG: database system was shut down at 2009-10-17
17:02:07 PDT
2009-10-17 17:02:09 PDTLOG: database system is ready to accept connections
2009-10-17 17:02:09 PDTLOG: autovacuum launcher started
TopMemoryContext: 93376 total in 9 blocks; 10376 free (6 chunks); 83000 used
TopTransactionContext: 8192 total in 1 blocks; 7632 free (0 chunks); 560
used
AfterTriggerEvents: 872443512 total in 839 blocks; 9152 free (5 chunks);
872434360 used
Operator class cache: 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; 29544 free (71 chunks); 11416
used
smgr relation table: 8192 total in 1 blocks; 2816 free (0 chunks); 5376
used
TransactionAbortContext: 32768 total 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: 1024 total in 1 blocks; 936 free (0 chunks); 88 used
ExecutorState: 581688 total in 5 blocks; 40936 free (14 chunks);
540752 used
TIDBitmap: 8380416 total in 10 blocks; 360696 free (34 chunks);
8019720 used
ExprContext: 0 total in 0 blocks; 0 free (0 chunks); 0 used
Relcache by OID: 8192 total in 1 blocks; 3376 free (0 chunks); 4816 used
CacheMemoryContext: 667696 total in 20 blocks; 200064 free (0 chunks);
467632 used
idx_att_data_source: 1024 total in 1 blocks; 344 free (0 chunks); 680
used
idx_att_typeid: 1024 total in 1 blocks; 344 free (0 chunks); 680 used
idx_att_nodeid: 1024 total in 1 blocks; 344 free (0 chunks); 680 used
idx_att_id: 1024 total in 1 blocks; 304 free (0 chunks); 720 used
bn_attributes_pkey: 1024 total in 1 blocks; 344 free (0 chunks); 680
used
pg_attrdef_adrelid_adnum_index: 1024 total in 1 blocks; 240 free (0
chunks); 784 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; 192 free (0
chunks); 832 used
pg_foreign_data_wrapper_name_index: 1024 total in 1 blocks; 344 free (0
chunks); 680 used
pg_enum_oid_index: 1024 total 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 total in 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: 1024 total 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: 1024 total 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 total in 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 in 1 blocks; 344 free (0 chunks);
680 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: 1024 total 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: 1024 total 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; 280 free (0 chunks);
744 used
pg_opfamily_oid_index: 1024 total in 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 total in 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 total in 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; 280 free (0
chunks); 744 used
pg_conversion_oid_index: 1024 total 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; 5200 free (0 chunks); 2992 used
LOCALLOCK hash: 8192 total in 1 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
2009-10-17 17:05:41 PDTERROR: out of memory
2009-10-17 17:05:41 PDTDETAIL: Failed on request of size 1048576.
2009-10-17 17:05:41 PDTSTATEMENT: delete from bn_attributes where
id>309279169

Thanks in advance, Yulia