Fwd: Cassandra Query

[Hareesh Veduraj <ha...@gmail.com>]

Hi Team,

I have a new requirement , where I need to copy all the rows from one table
to another table in Cassandra, where the second table contains one extra
column.

I have written a python script, which reads each row and inserts . But the
problem is in stage environment I'm observing the select count query is
returning different result each time I execute, so the row count is
varying.

The base  table contains 6 lakhs rows.The stage cluster is of 5 instances
with a replication factor of 3.

I'm able to successfully run the query in dev cluster with the same data,
where 3 instances are there and replication factor is 3.

Can anyone help me out what is the best way to achieve this?Also, what is
the reason for the variation in select count query?

Below is the Python script snippet:

cql='select key, column1, column2, column3, column4, value from table1
limit 1000000';
insert_table2_query = session.prepare('INSERT INTO table2 (key, column1,
column2, column3, column4, column5, value) VALUES (?, ?, ?, ?, ?, ?, ?)');

def insert_into_table2():
    counter =1;
    for row in session.execute(cql):
        try:
            val1=row.column4;
            val2 = row.value;
            if(len(val1)==0 or val1 == None) :
                 val1="";
            session.execute(insert_table2_query,(row.key,row.column1,
row.column2,row.column3,val1,val2,val2))
            print("processed row count : "+str(counter));
            counter = counter + 1;
        except Exception as e:
            counter = counter + 1;
            print 'failed to insert the row ';


Appreciating any help.

Thanks,
Hareesh.A.V
Mob: +7022643519

Re: Cassandra Query

[Erick Ramirez <fl...@gmail.com>]

That is one of the most asked questions that it prompted me to write a blog
post last month --
https://academy.datastax.com/support-blog/counting-keys-might-well-be-counting-stars

On Mon, Nov 13, 2017 at 6:55 PM, Hareesh Veduraj <ha...@gmail.com>
wrote:

> Hi Team,
>
> I have a new requirement , where I need to copy all the rows from one
> table to another table in Cassandra, where the second table contains one
> extra column.
>
> I have written a python script, which reads each row and inserts . But the
> problem is in stage environment I'm observing the select count query is
> returning different result each time I execute, so the row count is
> varying.
>
> The base  table contains 6 lakhs rows.The stage cluster is of 5 instances
> with a replication factor of 3.
>
> I'm able to successfully run the query in dev cluster with the same data,
> where 3 instances are there and replication factor is 3.
>
> Can anyone help me out what is the best way to achieve this?Also, what is
> the reason for the variation in select count query?
>
> Below is the Python script snippet:
>
> cql='select key, column1, column2, column3, column4, value from table1
> limit 1000000';
> insert_table2_query = session.prepare('INSERT INTO table2 (key, column1,
> column2, column3, column4, column5, value) VALUES (?, ?, ?, ?, ?, ?, ?)');
>
> def insert_into_table2():
>     counter =1;
>     for row in session.execute(cql):
>         try:
>             val1=row.column4;
>             val2 = row.value;
>             if(len(val1)==0 or val1 == None) :
>                  val1="";
>             session.execute(insert_table2_query,(row.key,row.column1,row
> .column2,row.column3,val1,val2,val2))
>             print("processed row count : "+str(counter));
>             counter = counter + 1;
>         except Exception as e:
>             counter = counter + 1;
>             print 'failed to insert the row ';
>
>
> Appreciating any help.
>
> Thanks,
> Hareesh.A.V
> Mob: +7022643519
>
>