Hi! Just was looking at processlist and thinking "why he cannot optimize such a easy case". I think there is a possible BOOST place (this is common query in many apps): mysql> select count(*) from url; +----------+ | count(*) | +----------+ | 17945916 | +----------+ 1 row in set (0.00 sec) mysql> mysql> show full processlist; +------+------+-----------+-----------+---------+------+----------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Id | User | Host | db | Command | Time | State | Info | +------+------+-----------+-----------+---------+------+----------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | 78 | root | localhost | eeindexer | Query | 141 | Sorting result | INSERT INTO udm_url_tmp SELECT url.rec_id FROM url WHERE next_index_time<=1240742878 ORDER BY hops LIMIT 256 ..... So, it takes HUGE time to find out 256 rows with least hops. How I would make it manually (MySQL engine has internally better ways to do it): mysql> select min(hops) from url; +-----------+ | min(hops) | +-----------+ | 0 | +-----------+ 1 row in set (0.12 sec) mysql> select count(hops) from url where hops=0; +-------------+ | count(hops) | +-------------+ | 1 | +-------------+ 1 row in set (0.00 sec) mysql> select count(hops) from url where hops=1; +-------------+ | count(hops) | +-------------+ | 92 | +-------------+ 1 row in set (0.00 sec) mysql> select count(hops) from url where hops=2; +-------------+ | count(hops) | +-------------+ | 9790 | +-------------+ 1 row in set (0.00 sec) mysql> mysql> SELECT url.rec_id FROM url WHERE hops in (0,1,2,3) ORDER BY hops LIMIT 256; +--------+ | rec_id | +--------+ | 1 | | 82 | | 121 | | 55 | | 63 | | 39 | | 65 | | 100 | | 129 | | 85 | | 25 | | 11 | | 12 | | 54 | | 3 | | 101 | | 7 | | 50 | | 76 | | 77 | | 10 | | 24 | | 14 | | 2 | | 57 | | 46 | | 44 | | 17 | | 122 | | 135 | | 8 | | 51 | | 104 | | 124 | | 35 | | 56 | | 116 | | 62 | | 41 | | 78 | | 126 | | 15 | | 26 | | 40 | | 90 | | 80 | | 13 | | 36 | | 45 | | 70 | | 60 | | 117 | | 47 | | 114 | | 132 | | 19 | | 96 | | 118 | | 74 | | 9 | | 120 | | 95 | | 23 | | 136 | | 71 | | 130 | | 83 | | 33 | | 111 | | 125 | | 81 | | 43 | | 97 | | 28 | | 73 | | 109 | | 98 | | 105 | | 133 | | 128 | | 106 | | 4 | | 102 | | 127 | | 5 | | 30 | | 115 | | 123 | | 27 | | 6 | | 113 | | 93 | | 48 | | 10047 | | 55273 | | 7120 | | 21448 | | 16872 | | 17985 | | 9862 | | 20979 | | 45717 | | 491 | | 16943 | | 18183 | | 1753 | | 21176 | | 16486 | | 7578 | | 2329 | | 9824 | | 1239 | | 400 | | 6470 | | 8052 | | 2752 | | 1258 | | 16039 | | 593 | | 49887 | | 5884 | | 7119 | | 3011 | | 7819 | | 14710 | | 244 | | 6881 | | 16518 | | 240 | | 16445 | | 49988 | | 62181 | | 61227 | | 61651 | | 18118 | | 9951 | | 54964 | | 61197 | | 16361 | | 21452 | | 15361 | | 2840 | | 16479 | | 17006 | | 2768 | | 7917 | | 61198 | | 21556 | | 2650 | | 2525 | | 55022 | | 54911 | | 55672 | | 15326 | | 14763 | | 15493 | | 55156 | | 21435 | | 49959 | | 18242 | | 1887 | | 6437 | | 19407 | | 7593 | | 2355 | | 16908 | | 16102 | | 1275 | | 57868 | | 15943 | | 7977 | | 16079 | | 14712 | | 49874 | | 17269 | | 55851 | | 57783 | | 3442 | | 18085 | | 50913 | | 4067 | | 19402 | | 2785 | | 7920 | | 16456 | | 19143 | | 15141 | | 54895 | | 3578 | | 2905 | | 16623 | | 16802 | | 6472 | | 5894 | | 7004 | | 14711 | | 2545 | | 19184 | | 2994 | | 3297 | | 7993 | | 10034 | | 51738 | | 16854 | | 7007 | | 7583 | | 15967 | | 3720 | | 54940 | | 15299 | | 2343 | | 9896 | | 7016 | | 19668 | | 16128 | | 21624 | | 7529 | | 3521 | | 16602 | | 16089 | | 54821 | | 51589 | | 61828 | | 19690 | | 3608 | | 17946 | | 61146 | | 2265 | | 9809 | | 2509 | | 54729 | | 2426 | | 21617 | | 7543 | | 1841 | | 3700 | | 21391 | | 21442 | | 55155 | | 7532 | | 3490 | | 7821 | | 1891 | | 9876 | | 3677 | | 10019 | | 2862 | | 16186 | | 16299 | | 16528 | | 50641 | | 5926 | | 55135 | | 16800 | | 54734 | | 19375 | +--------+ 256 rows in set (0.09 sec) mysql> So why not to look on index cardinality, limit size (let say, less than 1% of table), min or max value of field ordered by and then exclude big part of table to avoid unnecessary work? Tõnu