Multiple row inserts as fast as possible - php

Question

I've seen multiple threads discussing this but there always has been totally different conclusion in the answers. Especially I wonder whether it is really necessary to create a own prepared statement (with the right amount of placeholders) in order to insert it as single query. I expected that when I use beginTransaction and endTransaction before and after my for loop, that pdo/php waits with the transaction until all data is collected and it will send these data's as a single query once the server hits the line endTransaction.
How would I need to rewrite such a for loop insert with multiple inserts in order to reach the best performance (it has between 1 and 300 rows usually but it also could reach 2000 rows).
for($i=0; $i<$baseCount; $i++)
{
$thLevel = $bases[$i]["ThLevel"];
$gold = $bases[$i]["Gold"];
$elixir = $bases[$i]["Elixir"];
$darkElixir = $bases[$i]["DarkElixir"];
$dateFound = $elixir = $bases[$i]["TimeFound"];
$query = $db->prepare("INSERT INTO bot_attacks_searchresults (attack_id, available_gold, available_elixir, available_dark_elixir, date_found, opponent_townhall_level)
VALUES (:attack_id, :available_gold, :available_elixir, :available_dark_elixir, :date_found, :opponent_townhall_level)");
$query->bindValue(':attack_id', $attackId);
$query->bindValue(':available_gold', $gold);
$query->bindValue(':available_elixir', $elixir);
$query->bindValue(':available_dark_elixir', $darkElixir);
$query->bindValue(':date_found', $dateFound);
$query->bindValue(':opponent_townhall_level', $thLevel);
$query->execute();
}

Answer 1

Prepare the statement once. MySQL lexes it once, so any subsequent call to the query will be quick since it's already lexed and juts needs parameters.
Start the transaction before the loop. This is done so your hard drive can write down all the rows in one input output operation. The default mode is that 1 insert query = 1 I/O of the hdd.
Create the loop, bind your parameters there and call the $query->execute();
Exit the loop and commit() the transaction.
Full code:
$db->beginTransaction();
$query = $db->prepare("INSERT INTO bot_attacks_searchresults (attack_id, available_gold, available_elixir, available_dark_elixir, date_found, opponent_townhall_level)
VALUES (:attack_id, :available_gold, :available_elixir, :available_dark_elixir, :date_found, :opponent_townhall_level)");
for($i = 0; $i < $baseCount; $i++)
{
$thLevel = $bases[$i]["ThLevel"];
$gold = $bases[$i]["Gold"];
$elixir = $bases[$i]["Elixir"];
$darkElixir = $bases[$i]["DarkElixir"];
$dateFound = $elixir = $bases[$i]["TimeFound"];
$query->bindValue(':attack_id', $attackId);
$query->bindValue(':available_gold', $gold);
$query->bindValue(':available_elixir', $elixir);
$query->bindValue(':available_dark_elixir', $darkElixir);
$query->bindValue(':date_found', $dateFound);
$query->bindValue(':opponent_townhall_level', $thLevel);
$query->execute();
}
$db->commit();

Answer 2

Here's a very crude proof of concept:
<?php
$values = array();
for($i=0;$i<10;$i++)
{
$values[] = "($i)";
}
$values = implode($values,',');
$query = "INSERT INTO my_table VALUES $values";
echo $query;
?>
outputs INSERT INTO my_table VALUES (0),(1),(2),(3),(4),(5),(6),(7),(8),(9)
You would need to restructure this slightly to work with prepare (PHP is not my forte), but the principle is the same; i.e. you build the query inside the loop, but execute it only once.