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Issue 92: Crashes with large data sets if you close before fetching all results
2 people starred this issue and may be notified of changes. Back to list
Status:  WontFix
Owner:  ----
Closed:  Nov 2010


 
Reported by nickreta...@gmail.com, Mar 9, 2010
What steps will reproduce the problem?
1. cursor.execute a query on a vertica table that returns 50k+ rows
2. cursor.fetchmany(1000)
3. cursor.close()

What is the expected output? What do you see instead?
I expected to get the first 1000 rows of the result.  Instead, it crashed 
silently with exit code 245.  Trying this in the repl prints Segmentation 
Fault.

What version of the product are you using? On what operating system?
'2.1.7-beta0'
CentOS
Python 2.6.4
/usr/local/lib/vertica_3.5.9_odbc_3.5_unixodbc_x86_64_linux.so

Please provide any additional information below.
I'm not sure whether this is the fault of pyodbc, unixodbc, or the vertica 
odbc driver, but it's an aggravating problem.  I must support arbitrary 
queries since this is an internal tool and users will be writing queries all the 
time, so I can't rely on people always putting in limits.  I don't want to 
fetch 50k rows.
Mar 9, 2010
#1 nickreta...@gmail.com
Huh, it's worse than I thought.  You can skip step 2 and it'll still crash.  Any time you 
execute with a large result set and then neglect to fetch any or all of the rows, it 
crashes.
Mar 9, 2010
#2 nickreta...@gmail.com
Curious.  Calling rowcount on my query returns 51,214, even though the result set 
should include 1,299,764,619 rows.  Calling my query with a limit of 51,219 works 
properly and returns that many rows, but raising the limit to 51,220+ makes it claim 
only 51,214 rows were returned and then segfault on closing.
Mar 29, 2010
#3 bs1...@gmail.com
Hey Nick,  did you try bringing this up with vertica tech support?  Perhaps the error is in the vertica driver 
implementation?
Aug 24, 2010
Project Member #4 mkleehammer
Any more information on this?  I'm not reproducing it here, but I don't have access to that particular database/driver.
Status: Investigating
Aug 24, 2010
#5 nickreta...@gmail.com
I don't know.  I don't work with that project anymore.  If I still had access to those emails, I could be more specific.

I did bring it up with the Vertica techs.  I think this is related to the other bug I posted, where memory issues happen due to the double size characters in Vertica.  The Vertica techs told me to always configure it to expect double size characters when working with pyodbc, or something.
Nov 21, 2010
Project Member #6 mkleehammer
Since we are unable to reproduce and you are no longer working with this, I'm going to close this.  Feel free to reopen if you encounter this again.

Status: WontFix

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