Can not fetch all records from Oracle table

[86mm86]

Hi!

I am trying to retrieve 300k records from an Oracle table with 119 columns.
I can easily connect to the database but when I try to fetch the records I get only ca. half of them. Surprisingly:

1. I do not receive any error message;
2. upon re-executing the following Python script

import cx_Oracle
import pandas as pd

sql_query = 'select * from ...'

con = cx_Oracle.connect(user='...', password='...', dsn='...')

df = pd.read_sql(sql_query, con)

df.shape[0]

I do not get the same number of records (that is, I get different values for df.shape[0]).

Any clue on what the problem might be?

Here are some possibly useful info:

1. What is your version of Python? Is it 32-bit or 64-bit?
   Python 3.7.0 64-bit

2. What is your cx_Oracle version?
   7.2.2

3. What error(s) you are seeing?
   None

4. What OS (and version) is Python executing on?
   Windows 10

5. What is your Oracle Database version?
   Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production

6. What Oracle environment variables did you set? How exactly did you set them?
   None

[cjbj]

Start by simplifying the testcase and removing all use of Pandas. Can you query the data using pure cx_Oracle?

[86mm86]

Yes, I can query the data using only cx_Oracle. Nevertheless, when I run the following script

import cx_Oracle

con = cx_Oracle.connect(user='...',  password='...',  dsn='...')

cur = con.cursor()

sql_query = 'select * from ...'

cur.execute(sql_query)

result = cur.fetchall()

num_rows = len(result)

print(num_rows)

cur.close()
con.close() 

the number of records num_rows is smaller than the 'real' total number of records in my Oracle table. Remarks: it is not a memory problem, I do not receive any error message and the value of row_counter is non-deterministic as it changes (slightly increases!) every time I execute the script above.

PS: Using R software (and specifically the ROracle library), I can fetch all records, so it is not a problem with the database.

[cjbj]

Give numbers. What data sizes are we talking about? How do you check the amount of memory? What version of the Oracle Client libraries are you using?

[86mm86]

Data size: 300k rows * 119 columns

Memory is checked just via task manager while running the script above

Oracle Client Version: 11.2.0.4.0

[cjbj]

Details matter.

Show us the output of a select count(*) from the table and the value of num_rows.

[86mm86]

I have just realized this issue has nothing to do with cx_Oracle. There was a typo in a WHERE clause of my select statement. Indeed details matter! :)