Needs to refactor Query::each()

[Tigrov]

Query::each() returns data reader to get data row by row.

foreach ($query->each() as $row) {}

Current realization of the data reader reads batch of rows then read each row from the rows.

db/src/Query/BatchQueryResult.php

Lines 70 to 85 in e380ae2

	if ($this->batch === null || !$this->each || (next($this->batch) === false)) {
	$this->batch = $this->fetchData();
	reset($this->batch);
	}
	if ($this->each) {
	$this->value = current($this->batch);
	if ($this->query->getIndexBy() !== null) {
	$this->key = key($this->batch);
	} elseif (key($this->batch) !== null) {
	$this->key = $this->key === null ? 0 : (int) $this->key + 1;
	} else {
	$this->key = null;
	}
	} else {

If read the result of query row by row (instead of batch of rows), this will be more efficient and will use less memory.