Question

I have table with 300 000 records (MyISAM). I get record from this table with this function:

public function loadRows() {
    if (!$this->result)
        die("Nothing found!");
    $this->rows = array();
    while ($r = mysql_fetch_array($this->result, MYSQL_ASSOC))
        $this->rows[] = $r;
    //mysql_free_result($this->result);
    return $this->rows;
}

The estimate time for showing 100 records from this table is 6 seconds, very slowly and the MEMORY used from this query is 512 MB. Where I’m wrong?

The query is:

SELECT i.* FROM inv i 
LEFT JOIN (inv_m im) ON (i.m_id = im.id)
LEFT JOIN (inv_f iff) ON (iff.num = i.num)
LEFT JOIN (temp_a ta) ON (ta.num = i.num)
WHERE i.vid = 1
AND iff.num IS NULL
AND ta.num IS NULL
LIMIT 100

For i.vid I show all records.

Declared INDEXES:

i.m_id INDEX

im.id PRIMARY KEY

iff.num INDEX

i.num INDEX

ta.num INDeX

THE EXPLAIN RESULT

id  select_type  table  type     possible_keys  key      key_len  ref                 rows    Extra
1   SIMPLE       i      ref      vid            vid      4        const               85343   Using where
1   SIMPLE       im     eq_ref   PRIMARY        PRIMARY  4        checksys_r1.i.m_id  1 
1   SIMPLE       iff    ref      num            num      182      checksys_r1.i.num   1       Using where
1   SIMPLE       ta     ref      num            num      194      checksys_r1.i.num   1       Using where

Answer 1

Start with running:

EXPLAIN SELECT i.* FROM inv i 
LEFT JOIN (inv_m im) ON (i.m_id = im.id)
LEFT JOIN (inv_f iff) ON (iff.num = i.num)
LEFT JOIN (temp_a ta) ON (ta.num = i.num)
WHERE i.vid = 1
AND iff.num IS NULL
AND ta.num IS NULL
LIMIT 100

look for things like a full row scan, file i/o, etc. Post the results here. Sometimes a table might need repairing as well.

Also, is there any reason you’re using MyISAM over InnoDB?