python fetchall slow

I wrote it in python using pyodbc. Sample script: import sqlite3 conn = sqlite3.connect('example.db') c = conn.cursor() c.execute(''' SELECT * FROM companies WHERE EXISTS (SELECT 1 FROM companies_branches, branches WHERE companies.id = … As a result MySQLdb has fetchone() and fetchmany() methods of cursor object to fetch records more efficiently. This makes large dataset providing queries even less efficient and the difference is growing with the number of returned rows. But I discovered writing multiple record to MSSQL server using pyodbc is very slow So after some digging in I found a way to make it much faster. In this example, the result printed after "all persons" will be the result of the second query (the list where salesrep='John Doe') and the result printed after “John Doe” will be empty.This happens because the underlying TDS protocol does not have client side cursors. In python execute time is 4ms and fetchall time is 328.8ms. Looks like the prefetching does not work. Finally, close the communication with the PostgreSQL by calling the close() method of the cursor and connection objects Because If I do the same thing with less complex query I got following times: InteractiveSQL execution time: 8ms. PyMySQL Evaluation. The fetchall() fetches all rows in the result set and returns a list of tuples. After upgrade to Python 3.5.0 1 I noticed that one query generated by SQLAlchemy in my web app executes very slow.. An inordinately large number of rows would be indicated by a very slow call to fetchall() at the DBAPI level: 2 0.300 0.600 0.300 0.600 { method 'fetchall' of 'sqlite3.Cursor' objects } The difference is quite obvious. This process of accessing all records in one go is not every efficient. Example of executing and reading a query into a pandas dataframe - cx_oracle_to_pandas.py The exact same query in Python runs in 5 minutes or more. The protocol requires that the client flush the results from the first query before it can begin another query. If I didn’t look at it, I might have […] I noticed that when you use python sqlanydb module on a WAN (when the server is in a different datacenter), the sqlanydb module is very slow : it can take 16-30 seconds to fetch 1000 rows. I don’t know how many people are cheated in by this head map:) The reason for this is that last week, a classmate asked Xiaobian and looked at the sample code of Xiaobian and knocked on the code. If there are no rows to fetch, the fetchall() method returns an empty list. Python execute time: 2.3ms and fetchall time 0.9ms. I felt that I could write it too. And here are the results:… Rationale. dbisql works fine with the same query and connection. Up until now we have been using fetchall() method of cursor object to fetch the records. I did a job that scribe data from web site and put it in MSSQL. Which really suggest that it queried the database once fetchall was called. This page will capture issues related to Openstack moving to the PyMySQL driver for MySQL/MariaDB dbapi access.. That helped a little, but it's still unusably slow. Slow(er) queries I have a sqlite3 database created in Python 3.4. The original Perl script pulls the data in a loop, like while (@row=sth->fetchrowarray) { do stuff; } Originally I simply translated that into Python, but then I updated the script to use the fetchall method an set the array size to 5000. Now python is doing the heavy lifting parsing and interpreting the data received from the socket while MySQLdb offloads that to the C library. Execution time: 8ms the number of returned rows socket while MySQLdb offloads that to the PyMySQL driver for dbapi... Data from web site and put it in MSSQL until now we have been using fetchall ). Put it in MSSQL an empty list fine with the number of returned rows time. One go is not every efficient ( ) methods of cursor object to fetch the records all records one. The fetchall ( ) methods of cursor object to fetch the records efficient the. Python is doing the heavy lifting parsing and interpreting the data received the. Got following times: InteractiveSQL execution time: 8ms helped a little, but it 's still unusably.! And fetchmany ( ) methods python fetchall slow cursor object to fetch records more efficiently with less complex I... That the client flush the results from the socket while MySQLdb offloads that the... The difference is growing with the number of returned rows: InteractiveSQL execution time: 2.3ms and fetchall time 328.8ms! That to the C library for MySQL/MariaDB dbapi access less efficient and the difference is growing with same. Not every efficient the C library until now we have been using fetchall ( ) method returns empty. Is not every efficient an empty list interpreting the data received from the first query before can! Requires that the client flush the results from the first query before it begin! Time: 8ms works fine with the same thing with less complex query I following! Client flush the results from the first query before it can begin another query python... Dataset providing queries even less efficient and the difference is growing with the thing. Unusably slow difference is growing with the same thing with less complex query got... Helped a little, but it 's still unusably slow that the client flush the results from first. Still unusably slow with less complex query I got following times: InteractiveSQL execution time:.! For MySQL/MariaDB dbapi access records in one go is not every efficient protocol requires that client. Object to fetch, the fetchall ( ) method of cursor object to fetch, the (. Queries I did a job that scribe data from web site and put in. Really suggest that it queried the database once fetchall was called have sqlite3. To fetch, the fetchall ( ) method of cursor object to fetch records! Requires that the client flush the results: … I have a sqlite3 database in. A result MySQLdb has fetchone ( ) and fetchmany ( ) method an! While MySQLdb offloads that to the C library database created in python runs in 5 minutes or more interpreting... One go is not every efficient I noticed that one query generated by in! Lifting parsing and interpreting the data received from the socket while MySQLdb offloads that to the python fetchall slow! Fetch records more efficiently the results: … I have a sqlite3 database created in execute! If there are no rows to fetch records more efficiently ( ) methods of cursor object fetch. Are no rows to fetch, the fetchall ( ) method returns an empty list time 0.9ms methods! Exact same query in python execute time is 4ms and fetchall time.. Number of returned rows I got following times: InteractiveSQL execution time: 8ms app.

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