MySQL PDO查询优化

Question

I'm trying to reduce this script execution time. It queries a database with about 2 million records about 1000 times on a loop:

foreach ($ids as $id){
    $stmt=$dbh->query("SELECT SQL_CACHE * FROM `ids` 
                WHERE $id BETWEEN `id_start` AND `id_end`");
    $rows[] = $stmt->fetch();
}

It takes forever on a 4 core 8 GB machine (about 800 seconds!). Id groups do not overlap, ids tend to be from just a few different groups in each execution and I have indexed both (id_start,id_end) and (id_end).

Caching improves very much the situation (running the same 1000 values more than once is just a few seconds), but I would like to know what can I do to speed up non cached queries.

Example output of EXPLAIN:

"id"    "select_type"   "table"     "type"  "possible_keys"     "key"               "key_len"   "ref"   "rows"  "Extra"
"1"     "SIMPLE"        "ids"       "range" "id_start,id_end"   "id_start,id_end"   "5"          ""     "52508" "Using index condition"

EDIT: Instead of "Using index condition" I get "Using where" sometimes (Not sure but I think from id values higher than 840771583) Why?

EDIT 2: Full create code:

CREATE TABLE `ids` (
    `id_start` INT(10) UNSIGNED NULL DEFAULT NULL,
    `id_end` INT(10) UNSIGNED NULL DEFAULT NULL,
    `iso-639-1` VARCHAR(2) NULL DEFAULT NULL COLLATE 'utf8_unicode_ci',
    `country_name` VARCHAR(64) NULL DEFAULT NULL COLLATE 'utf8_unicode_ci',
    `region_name` VARCHAR(64) NULL DEFAULT NULL COLLATE 'utf8_unicode_ci',
    `city_name` VARCHAR(64) NULL DEFAULT NULL COLLATE 'utf8_unicode_ci',
    `area_code` VARCHAR(16) NULL DEFAULT NULL COLLATE 'utf8_unicode_ci',
    `timezone` VARCHAR(6) NULL DEFAULT NULL COLLATE 'utf8_unicode_ci',
    UNIQUE INDEX `id_startid_end` (`id_start`, `id_end`),
    INDEX `id_end` (`id_end`),
    INDEX `country_name` (`country_name`),
    INDEX `region_name` (`region_name`),
    INDEX `city_name` (`city_name`),
    INDEX `area_code` (`area_code`),
    INDEX `iso-639-1` (`iso-639-1`),
    INDEX `timezone` (`timezone`)
)
COLLATE='utf8_unicode_ci'
ENGINE=InnoDB;

Answer 1

Since the intervals do not overlap, try this rewriting of the query:

SELECT * 
FROM ids
WHERE id_start =
      ( SELECT MAX(id_start) 
        FROM ids
        WHERE id_start <= $id
      )
  AND $id <= id_end ;