MYSQL variables to tweak for queries fetching huge datasets

SHOW varaible o/p
auto_increment_increment 1
auto_increment_offset 1
automatic_sp_privileges ON
back_log 50
basedir /usr/
binlog_cache_size 32768
bulk_insert_buffer_size 8388608
character_set_client latin1
character_set_connection latin1
character_set_database latin1
character_set_filesystem binary
character_set_results latin1
character_set_server latin1
character_set_system utf8
character_sets_dir /usr/share/mysql/charsets/
collation_connection latin1_swedish_ci
collation_database latin1_swedish_ci
collation_server latin1_swedish_ci
completion_type 0
concurrent_insert 1
connect_timeout 15
datadir /var/lib/mysql/
date_format %Y-%m-%d
datetime_format %Y-%m-%d %H:%i:%s
default_week_format 0
delay_key_write ON
delayed_insert_limit 100
delayed_insert_timeout 300
delayed_queue_size 1000
div_precision_increment 4
keep_files_on_create OFF
engine_condition_pushdown OFF
expire_logs_days 0
flush OFF
flush_time 0
ft_boolean_syntax + -><()~*:""&|
ft_max_word_len 84
ft_min_word_len 4
ft_query_expansion_limit 20
ft_stopword_file (built-in)
group_concat_max_len 1024
have_archive NO
have_bdb NO
have_blackhole_engine NO
have_compress YES
have_community_features NO
have_profiling NO
have_crypt YES
have_csv NO
have_dynamic_loading YES
have_example_engine NO
have_federated_engine NO
have_geometry YES
have_innodb YES
have_isam NO
have_merge_engine YES
have_ndbcluster NO
have_openssl NO
have_ssl NO
have_query_cache YES
have_raid NO
have_rtree_keys YES
have_symlink YES
hostname scbcaappz200
innodb_additional_mem_pool_size 1048576
innodb_autoextend_increment 8
innodb_buffer_pool_awe_mem_mb 0
innodb_buffer_pool_size 8388608
innodb_checksums ON
innodb_commit_concurrency 0
innodb_concurrency_tickets 500
innodb_data_file_path ibdata1:10M:autoextend
innodb_adaptive_hash_index ON
innodb_doublewrite ON
innodb_fast_shutdown 1
innodb_file_io_threads 4
innodb_file_per_table OFF
innodb_flush_log_at_trx_commit 1
innodb_force_recovery 0
innodb_lock_wait_timeout 50
innodb_locks_unsafe_for_binlog OFF
innodb_log_archive OFF
innodb_log_buffer_size 1048576
innodb_log_file_size 5242880
innodb_log_files_in_group 2
innodb_log_group_home_dir ./
innodb_max_dirty_pages_pct 90
innodb_max_purge_lag 0
innodb_mirrored_log_groups 1
innodb_open_files 300
innodb_rollback_on_timeout OFF
innodb_support_xa ON
innodb_sync_spin_loops 20
innodb_table_locks ON
innodb_thread_concurrency 8
innodb_thread_sleep_delay 10000
innodb_use_legacy_cardinality_algorithm ON
interactive_timeout 28800
join_buffer_size 131072
key_buffer_size 2147483648
key_cache_age_threshold 300
key_cache_block_size 1024
key_cache_division_limit 100
language /usr/share/mysql/english/
large_files_support ON
large_page_size 0
large_pages OFF
lc_time_names en_US
license GPL
local_infile ON
locked_in_memory OFF
log OFF
log_bin OFF
log_bin_trust_function_creators OFF
log_queries_not_using_indexes OFF
log_slave_updates OFF
log_slow_queries OFF
log_warnings 1
long_query_time 10
low_priority_updates OFF
lower_case_file_system OFF
lower_case_table_names 0
max_allowed_packet 1073741824
max_binlog_cache_size 18446744073709547520
max_binlog_size 1073741824
max_connect_errors 10
max_connections 500
max_delayed_threads 20
max_error_count 64
max_heap_table_size 16777216
max_insert_delayed_threads 20
max_join_size 18446744073709551615
max_length_for_sort_data 1024
max_prepared_stmt_count 16382
max_relay_log_size 0
max_seeks_for_key 18446744073709551615
max_sort_length 1024
max_sp_recursion_depth 0
max_tmp_tables 32
max_user_connections 0
max_write_lock_count 18446744073709551615
multi_range_count 256
myisam_data_pointer_size 6
myisam_max_sort_file_size 9223372036853727232
myisam_mmap_size 18446744073709551615
myisam_recover_options OFF
myisam_repair_threads 1
myisam_sort_buffer_size 8388608
myisam_stats_method nulls_unequal
net_buffer_length 8192
net_read_timeout 60
net_retry_count 10
net_write_timeout 60
new OFF
old_passwords OFF
open_files_limit 2500
optimizer_prune_level 1
optimizer_search_depth 62
pid_file /var/lib/mysql/
port 3306
preload_buffer_size 32768
protocol_version 10
query_alloc_block_size 8192
query_cache_limit 1048576
query_cache_min_res_unit 4096
query_cache_size 0
query_cache_type ON
query_cache_wlock_invalidate OFF
query_prealloc_size 8192
range_alloc_block_size 4096
read_buffer_size 262144
read_only OFF
read_rnd_buffer_size 524288
relay_log_purge ON
relay_log_space_limit 0
rpl_recovery_rank 0
secure_auth OFF
server_id 1
skip_external_locking ON
skip_networking OFF
skip_show_database OFF
slave_compressed_protocol OFF
slave_load_tmpdir /var/lib/mysql/.tmp/
slave_net_timeout 3600
slave_skip_errors OFF
slave_transaction_retries 10
slow_launch_time 2
socket /var/lib/mysql/mysql.sock
sort_buffer_size 524288
sql_big_selects ON
sql_notes ON
sql_warnings OFF
storage_engine MyISAM
sync_binlog 0
sync_frm ON
system_time_zone EDT
table_cache 64
table_lock_wait_timeout 50
table_type MyISAM
thread_cache_size 0
thread_stack 524288
time_format %H:%i:%s
time_zone SYSTEM
timed_mutexes OFF
tmp_table_size 33554432
tmpdir /var/lib/mysql/.tmp/
transaction_alloc_block_size 8192
transaction_prealloc_size 4096
tx_isolation REPEATABLE-READ
updatable_views_with_limit YES
version 5.0.95
version_comment SUSE MySQL RPM
version_compile_machine x86_64
version_compile_os suse-linux-gnu
wait_timeout 28800

For memory concern, the query result could either be buffered on the client side or on the server side. By default, results are sent to client as they are generated and get buffered on the client side. The C API function for that is mysql_store_result(). If the client doesn’t have sufficient memory, you can buffer data on the server instead and fetch it row by row, that is what mysql_use_result() does. In this mode, it is better to have simple processing for each row to avoid tying up the server for too long. If you are using mysql program as the client, use the -q option to turn off caching on the client side. If you using some connector, check the corresponding functions.

Also use the same max_allowed_packet for the client.