SQL performance problem

[michel.dominique]

Hello !

i've a performance problem with SQL on MySQL 4.1.18-nt (XP) with InnoDb disabled The first time I execute it, it takes about 14 seconds (mysql query browser says SQL 10 rows fetched in 0,05s (13,8 s)). The next execution times are immediate. I can see the same behaviour whatever MySQL client program I use: mysql cli, easyphp interface, mysql browser, a custom program using mysql API, ...

It seems that this is due to DISTINCT clause because when I remove it the execution time is negligible.

Any help will be appreciated.

Thanks.
Michel.

FYI, here is the SQL request I use:
---------------------------------------
select DISTINCT a.CODEFCT, t.TITRE
from hopafct a, hoptext t
where LANGUE='F' and ID=' ' and CODE like 'FCT_%' and
CODEFCT=SUBSTRING(CODE, 5 ,3) and CODEFCT >= 'CTR'
order by a.CODEFCT LIMIT 0,14


and here is a dump of mysql server variables:
----------------------------------------------------

Variable_name Value
back_log 50
basedir C:\\PROGRA~1\\EASYPH~1\\MySql\\
binlog_cache_size 32768
bulk_insert_buffer_size 8388608
character_set_client latin1
character_set_connection latin1
character_set_database latin1
character_set_results latin1
character_set_server latin1
character_set_system utf8
character_sets_dir C:\\PROGRA~1\\EASYPH~1\\MySql\\share\\charsets/
collation_connection latin1_swedish_ci
collation_database latin1_swedish_ci
collation_server latin1_swedish_ci
concurrent_insert ON
connect_timeout 5
datadir C:\\PROGRA~1\\EASYPH~1\\MySql\\data\\
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
expire_logs_days 0
flush OFF
flush_time 1800
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 YES
have_bdb NO
have_blackhole_engine NO
have_compress YES
have_crypt NO
have_csv NO
have_example_engine NO
have_geometry YES
have_innodb DISABLED
have_isam NO
have_ndbcluster NO
have_openssl NO
have_query_cache YES
have_raid NO
have_rtree_keys YES
have_symlink YES
init_connect
init_file
init_slave
innodb_additional_mem_pool_size 1048576
innodb_autoextend_increment 8
innodb_buffer_pool_awe_mem_mb 0
innodb_buffer_pool_size 8388608
innodb_data_file_path
innodb_data_home_dir
innodb_fast_shutdown ON
innodb_file_io_threads 4
innodb_file_per_table OFF
innodb_flush_log_at_trx_commit 1
innodb_flush_method
innodb_force_recovery 0
innodb_lock_wait_timeout 50
innodb_locks_unsafe_for_binlog OFF
innodb_log_arch_dir
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_table_locks ON
innodb_thread_concurrency 8
interactive_timeout 28800
join_buffer_size 131072
key_buffer_size 268435456
key_cache_age_threshold 300
key_cache_block_size 1024
key_cache_division_limit 100
language C:\\PROGRA~1\\EASYPH~1\\MySql\\share\\english\\
large_files_support ON
license GPL
local_infile ON
log OFF
log_bin ON
log_error .\\MLC.err
log_slave_updates OFF
log_slow_queries OFF
log_update OFF
log_warnings 1
long_query_time 10
low_priority_updates OFF
lower_case_file_system OFF
lower_case_table_names 1
max_allowed_packet 1047552
max_binlog_cache_size 4294967295
max_binlog_size 1073741824
max_connect_errors 10
max_connections 100
max_delayed_threads 20
max_error_count 64
max_heap_table_size 16777216
max_insert_delayed_threads 20
max_join_size 4294967295
max_length_for_sort_data 1024
max_relay_log_size 0
max_seeks_for_key 4294967295
max_sort_length 1024
max_tmp_tables 32
max_user_connections 0
max_write_lock_count 4294967295
myisam_data_pointer_size 4
myisam_max_extra_sort_file_size 2147483648
myisam_max_sort_file_size 2147483647
myisam_recover_options OFF
myisam_repair_threads 1
myisam_sort_buffer_size 67108864
myisam_stats_method nulls_unequal
net_buffer_length 16384
net_read_timeout 30
net_retry_count 10
net_write_timeout 60
new OFF
old_passwords ON
open_files_limit 622
pid_file C:\\PROGRA~1\\EASYPH~1\\MySql\\data\\MLC.pid
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 16777216
query_cache_type ON
query_cache_wlock_invalidate OFF
query_prealloc_size 8192
range_alloc_block_size 2048
read_buffer_size 1044480
read_only OFF
read_rnd_buffer_size 4190208
relay_log_purge ON
relay_log_space_limit 0
rpl_recovery_rank 0
secure_auth OFF
shared_memory OFF
shared_memory_base_name MYSQL
server_id 1
skip_external_locking ON
skip_networking OFF
skip_show_database OFF
slave_net_timeout 3600
slave_transaction_retries 0
slow_launch_time 2
sort_buffer_size 1048568
sql_mode
sql_notes ON
sql_warnings ON
storage_engine MyISAM
sync_binlog 0
sync_frm ON
sync_replication 0
sync_replication_slave_id 0
sync_replication_timeout 0
system_time_zone Paris, Madrid
table_cache 256
table_type MyISAM
thread_cache_size 0
thread_stack 196608
time_format %H:%i:%s
time_zone SYSTEM
tmp_table_size 33554432
tmpdir
transaction_alloc_block_size 8192
transaction_prealloc_size 4096
tx_isolation REPEATABLE-READ
version 4.1.18-log
version_comment MySQL Community Edition (GPL)
version_compile_machine ia32
version_compile_os Win32
wait_timeout 28800