/**
* Performs the actual optimization. In this case the optimizer looks
* at the size of the column and the size of the value. If the value size is
* smaller than the column size it tries to convert the column to a smaller
* size. Next, it counts if there is any different between the smaller column
* and the original column. If no differences are found the original column
* gets replaced.
* Like the other optimizers, this optimizer returns TRUE if it thinks
* further optimizations can happen, FALSE otherwise.
*
* @return boolean $yesNo advance to next optimizer
*/
public function optimize()
{
//get the type of the current value
$type = $this->writer->scanType($this->value);
//get all the fields in the table
$fields = $this->writer->getColumns($this->table);
//If the column for some reason does not occur in fields, return
if (!in_array($this->column, array_keys($fields))) {
return false;
}
//get the type we got in the field of the table
$typeInField = $this->writer->code($fields[$this->column]);
//Is the type too wide?
if ($type < $typeInField) {
try {
@$this->adapter->exec("alter table " . $this->writer->safeTable($this->table) . " drop __test");
} catch (Exception $e) {
}
//Try to re-fit the entire column; by testing it.
$type = $this->writer->typeno_sqltype[$type];
//Add a test column.
@$this->adapter->exec("alter table " . $this->writer->safeTable($this->table) . " add __test " . $type);
//Copy the values and see if there are differences.
@$this->adapter->exec("update " . $this->writer->safeTable($this->table) . " set __test=" . $this->writer->safeColumn($this->column) . "");
$rows = $this->adapter->get("select " . $this->writer->safeColumn($this->column) . " as a, __test as b from " . $this->writer->safeTable($this->table));
$diff = 0;
foreach ($rows as $row) {
$diff += $row["a"] != $row["b"];
}
if (!$diff) {
//No differences; shrink column.
@$this->adapter->exec("alter table " . $this->writer->safeTable($this->table) . " change " . $this->writer->safeColumn($this->column) . " " . $this->writer->safeColumn($this->column) . " " . $type);
}
//Throw away test column; we don't need it anymore!
@$this->adapter->exec("alter table " . $this->writer->safeTable($this->table) . " drop __test");
}
return false;
}
/**
* Performs the actual optimization. In this case the optimizer looks
* at the size of the column and the size of the value. If the value size is
* smaller than the column size it tries to convert the column to a smaller
* size. Next, it counts if there is any different between the smaller column
* and the original column. If no differences are found the original column
* gets replaced.
* Like the other optimizers, this optimizer returns TRUE if it thinks
* further optimizations can happen, FALSE otherwise.
*
* @return boolean $yesNo advance to next optimizer
*/
public function optimize() {
$type = $this->writer->scanType($this->value);
$fields = $this->writer->getColumns($this->table);
if (!in_array($this->column,array_keys($fields))) return false;
$typeInField = $this->writer->code($fields[$this->column]);
if ($type < $typeInField) {
try {
@$this->adapter->exec("alter table ".$this->writer->noKW($this->table)." drop __test");
}catch(Exception $e) {}
$type = $this->writer->typeno_sqltype[$type];
@$this->adapter->exec("alter table ".$this->writer->noKW($this->table)." add __test ".$type);
@$this->adapter->exec("update ".$this->writer->noKW($this->table)." set __test=".$this->writer->noKW($this->column)."");
$rows = $this->adapter->get("select ".$this->writer->noKW($this->column)." as a, __test as b from ".$this->writer->noKW($this->table));
$diff = 0;
foreach($rows as $row) {
$diff += ($row["a"]!=$row["b"]);
}
if (!$diff) {
@$this->adapter->exec("alter table ".$this->writer->noKW($this->table)." change ".$this->writer->noKW($this->column)." ".$this->writer->noKW($this->column)." ".$type);
}
@$this->adapter->exec("alter table ".$this->writer->noKW($this->table)." drop __test");
}
return false;
}
