Leonid,
Are you using some client for doing these operations..? Hector is a java client which provides APIs for adding/deleting columns to a column family in cassandra. I don¹t think you really need to write your wrapper in this format- you are restricting the number of columns it can use etc.I suggest your code can accept user input to get col family name, operation, keys , and operation, and accordingly call the appropriate hector API for adding/deleting data. Regards, Roshni On 11/06/12 7:20 PM, "Leonid Ilyevsky" <lilyev...@mooncapital.com> wrote: >Thanks, I understand what you are telling me. Obviously deleting the >column is the proper way to do this in Cassandra. >What I was looking for, is some convenient wrapper on top of that which >will do it for me. Here is my scenario. > >I have a function that takes a record to be saved in Cassandra (array of >objects, or Map<String, Object>). Let say, it can have up to 8 columns. I >prepare a statement like this: > >Insert into <table> values(?, ?, ?, ?, ?, ?, ?, ?) > >If I somehow could put null when I execute it, it would be enough to >prepare that statement once and execute it multiple times. I would then >expect that when some element is null, the corresponding column is not >inserted (for the new key) or deleted (for the existing key). >The way it is now, in my code I have to examine which columns are present >and which are not, depending on that I have to generate customized >statement, and it is going to be different for the case of existing key >versus case of the new key. >Isn't this too much hassle? > >Related question. I assumed that prepared statement in Cassandra is there >for the same reason as in RDBMS, that is, for efficiency. In the above >scenario, how expensive is it to execute specialized statement for every >record compare to prepared statement executed multiple times? > >If I need to execute those specialized statements, should I still use >prepared statement or should I just generate a string with everything in >ascii format? > >-----Original Message----- >From: Roshni Rajagopal [mailto:roshni.rajago...@wal-mart.com] >Sent: Monday, June 11, 2012 12:58 AM >To: user@cassandra.apache.org >Subject: Re: Setting column to null > >Would you want to view data like this "there was a key, which had this >column , but now it does not have any value as of this time." > >Unless you specifically want this information, I believe you should just >delete the column, rather than have an alternate value for NULL or create >a composite column. > >Because in cassandra that¹s the way deletion is dealt with, putting NULLs >is the way we deal with it in RDBMS because we have a fixed number of >columns which always have to have some value, even if its NULL, and we >have to have the same set of columns for every row. >In Cassandara, we can delete the column, and in most scenarios that¹s >what we should do, unless we specifically want to preserve some history >that this column was turned null at this timeŠEach row can have different >columns. > >Regards, >Roshni > >From: Edward Capriolo ><edlinuxg...@gmail.com<mailto:edlinuxg...@gmail.com>> >Reply-To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" ><user@cassandra.apache.org<mailto:user@cassandra.apache.org>> >To: "user@cassandra.apache.org<mailto:user@cassandra.apache.org>" ><user@cassandra.apache.org<mailto:user@cassandra.apache.org>> >Subject: Re: Setting column to null > >Your best bet is to define the column as a composite column where one >part represents is null and the other part is the data. > >On Friday, June 8, 2012, shashwat shriparv ><dwivedishash...@gmail.com<mailto:dwivedishash...@gmail.com>> wrote: >> What you can do is you can define some specific variable like >>"NULLDATA" some thing like that to update in columns that does have value >> >> >> On Fri, Jun 8, 2012 at 11:58 PM, aaron morton >><aa...@thelastpickle.com<mailto:aa...@thelastpickle.com>> wrote: >> >> You don't nee to set columns to null, delete the column instead. >> Cheers >> ----------------- >> Aaron Morton >> Freelance Developer >> @aaronmorton >> http://www.thelastpickle.com >> On 8/06/2012, at 9:34 AM, Leonid Ilyevsky wrote: >> >> Is it possible to explicitly set a column value to null? >> >> I see that if insert statement does not include a specific column, that >>column comes up as null (assuming we are creating a record with new >>unique key). >> But if we want to update a record, how we set it to null? >> >> Another situation is when I use prepared cql3 statement (in Java) and >>send parameters when I execute it. If I want to leave some column >>unassigned, I need a special statement without that column. >> What I would like is, prepare one statement including all columns, and >>then be able to set some of them to null. I tried to set corresponding >>ByteBuffer parameter to null, obviously got an exception. >> ________________________________ >> This email, along with any attachments, is confidential and may be >>legally privileged or otherwise protected from disclosure. Any >>unauthorized dissemination, copying or use of the contents of this email >>is strictly prohibited and may be in violation of law. If you are not >>the intended recipient, any disclosure, copying, forwarding or >>distribution of this email is strictly prohibited and this email and any >>attachments should be deleted immediately. 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