fetchall

I have been working on speeding up a query I'm using for about a week now and asked several questions about it here ( How can I speed up fetching the results after running an sqlite query? , Is it normal that sqlite.fetchall() is so slow? , How to use min() and max() in an efficient way? ). With the very useful help from the answers given there I managed to get the time down to the sqlite query taking 100.95 seconds and fetchall taking: 1485.43 . This was still not enough, so after trying out some different indexes I managed to get the query time down to 0.08 seconds for one sample and the

Imagine I have a mysql cursor and data read. The amount of data might be very big that I want to deal with one line each time. An easy and straight forward way might be like this: while True: row = cursor.fetchone() if not row: break ..... but this doesn't look good, so I wonder whether this way works as imagined: for row in iter(cursor.fetchall()) the thing I want to know is: if I use the iter(cursor.fetchall()) way, does it fetch all the data first or it just fetch one row at a time? Any idea is appreciated. thx The MySQLdb cursor class implements the iterator protocol , so you can simply do

As an answer on my question: Is it normal that sqlite.fetchall() is so slow? it seems that fetch-all and fetch-one can be incredibly slow for sqlite. As I mentioned there, I have the following query: time0 = time.time() self.cursor.execute("SELECT spectrum_id, feature_table_id "+ "FROM spectrum AS s "+ "INNER JOIN feature AS f "+ "ON f.msrun_msrun_id = s.msrun_msrun_id "+ "INNER JOIN (SELECT feature_feature_table_id, min(rt) AS rtMin, max(rt) AS rtMax, min(mz) AS mzMin, max(mz) as mzMax "+ "FROM convexhull GROUP BY feature_feature_table_id) AS t "+ "ON t.feature_feature_table_id = f.feature

I am using psycopg2 module in python to read from postgres database, I need to some operation on all rows in a column, that has more than 1 million rows. I would like to know would cur.fetchall() fail or cause my server to go down? (since my RAM might not be that big to hold all that data) q="SELECT names from myTable;" cur.execute(q) rows=cur.fetchall() for row in rows: doSomething(row) what is the smarter way to do this? fetchall() fetches up to the arraysize limit, so to prevent a massive hit on your database you can either fetch rows in manageable batches, or simply step through the cursor

I'm having trouble getting my data from fetchAll to print selectively. In normal mysql I do it this way: $rs = mysql_query($sql); while ($row = mysql_fetch_array($rs)){ $id = $row['id']; $n = $row['n']; $k = $row['k']; } In PDO, I'm having trouble. I bound the params, then I'm saving the fetched data into $rs like above, with the purpose of looping through it the same way.. $sth->execute(); $rs = $query->fetchAll(); Now comes the trouble part. What do I do PDO-wise to get something matching the while loop above?! I know I can use print_r() or dump_var, but that's not what I want. I need to do

I have problems with PHP in Ubuntu 10.04. When I try use mysqli_result::fetch_all this error appears: Call to undefined method mysqli_result::fetch_all() However, it works in Windows XP. The Code: $result = $this->dbh->query('SELECT [...] '); return $result->fetch_all(MYSQLI_ASSOC); I don't want to use fetch_assoc with a loop because I send the result to another layer for processing. I'm using PHP 5.4.4. and with php -m | grep mysql the mysqlnd module it doesn't appear. How can I install it? Could that be the problem? Ibrahim Azhar Armar mysqli_result::fetch_all() requires MySQL Native Driver