Re: list of columns
> But then you'd need > re-ahead to check if the column is new, that should be 'read-ahead', sorry. Bill Bill de hOra wrote: Agree with David, it's not there and thinking about how the data is laid out on disk, it can't be done without changing core code or harming something else. > if this is a performance concern It's not, it was to supply an administrative function on SuperColumns, but it would be good to not crush a node. > a separate column family which just contains the column names and > timestamps with empty values. Eventually, you'd want to ask a client library to do this, at the cost of two writes everytime you add a new column. But then you'd need re-ahead to check if the column is new, which would kill write performance. Bill Jonathan Shook wrote: I think you are correct, David. What Bill is asking for specifically is not in the API. Bill, if this is a performance concern (i.e., your column values are/could be vastly larger than your column names, and you need to query the namespace before loading the values), then you might consider keeping a separate column family which just contains the column names and timestamps with empty values. On Sun, May 16, 2010 at 4:37 AM, David Boxenhorn wrote: Bill, I am a new user of Cassandra, so I've been following this discussion with interest. I think the answer is "no", except for the brute force method of looping through all your data. It's like asking for a list of all the files on your C: drive. The term "column" is very misleading, since "columns" are really leaves of a tree structure, not columns of a tabular structure. Anybody want to tell me I'm wrong? BTW, Bill, I think we've corresponded before, here: http://www.dehora.net/journal/2004/04/whats_in_a_name.html On Fri, May 14, 2010 at 2:23 AM, Bill de hOra wrote: A SlicePredicate/SliceRange can't exclude column values afaik. Bill Jonathan Shook wrote: get_slice see: http://wiki.apache.org/cassandra/API under get_slice and SlicePredicate On Thu, May 13, 2010 at 9:45 AM, Bill de hOra wrote: get_count returns the number of columns, not the names of those columns? I should have been specific, by "list the columns", I meant "list the column names". Bill Gary Dusbabek wrote: We have get_count at the thrift level. You supply a predicate and it returns the number of columns that match. There is also multi_get_count, which is the same operation against multiple keys. Gary. On Thu, May 13, 2010 at 04:18, Bill de hOra wrote: Admin question - is there a way to list the columns for a particular key? Bill
Re: list of columns
Agree with David, it's not there and thinking about how the data is laid out on disk, it can't be done without changing core code or harming something else. > if this is a performance concern It's not, it was to supply an administrative function on SuperColumns, but it would be good to not crush a node. > a separate column family which just contains the column names and > timestamps with empty values. Eventually, you'd want to ask a client library to do this, at the cost of two writes everytime you add a new column. But then you'd need re-ahead to check if the column is new, which would kill write performance. Bill Jonathan Shook wrote: I think you are correct, David. What Bill is asking for specifically is not in the API. Bill, if this is a performance concern (i.e., your column values are/could be vastly larger than your column names, and you need to query the namespace before loading the values), then you might consider keeping a separate column family which just contains the column names and timestamps with empty values. On Sun, May 16, 2010 at 4:37 AM, David Boxenhorn wrote: Bill, I am a new user of Cassandra, so I've been following this discussion with interest. I think the answer is "no", except for the brute force method of looping through all your data. It's like asking for a list of all the files on your C: drive. The term "column" is very misleading, since "columns" are really leaves of a tree structure, not columns of a tabular structure. Anybody want to tell me I'm wrong? BTW, Bill, I think we've corresponded before, here: http://www.dehora.net/journal/2004/04/whats_in_a_name.html On Fri, May 14, 2010 at 2:23 AM, Bill de hOra wrote: A SlicePredicate/SliceRange can't exclude column values afaik. Bill Jonathan Shook wrote: get_slice see: http://wiki.apache.org/cassandra/API under get_slice and SlicePredicate On Thu, May 13, 2010 at 9:45 AM, Bill de hOra wrote: get_count returns the number of columns, not the names of those columns? I should have been specific, by "list the columns", I meant "list the column names". Bill Gary Dusbabek wrote: We have get_count at the thrift level. You supply a predicate and it returns the number of columns that match. There is also multi_get_count, which is the same operation against multiple keys. Gary. On Thu, May 13, 2010 at 04:18, Bill de hOra wrote: Admin question - is there a way to list the columns for a particular key? Bill
Re: list of columns
I think you are correct, David. What Bill is asking for specifically is not in the API. Bill, if this is a performance concern (i.e., your column values are/could be vastly larger than your column names, and you need to query the namespace before loading the values), then you might consider keeping a separate column family which just contains the column names and timestamps with empty values. On Sun, May 16, 2010 at 4:37 AM, David Boxenhorn wrote: > Bill, I am a new user of Cassandra, so I've been following this discussion > with interest. I think the answer is "no", except for the brute force method > of looping through all your data. It's like asking for a list of all the > files on your C: drive. The term "column" is very misleading, since > "columns" are really leaves of a tree structure, not columns of a tabular > structure. > > Anybody want to tell me I'm wrong? > > BTW, Bill, I think we've corresponded before, here: > http://www.dehora.net/journal/2004/04/whats_in_a_name.html > > On Fri, May 14, 2010 at 2:23 AM, Bill de hOra wrote: >> >> A SlicePredicate/SliceRange can't exclude column values afaik. >> >> Bill >> >> Jonathan Shook wrote: >>> >>> get_slice >>> >>> see: http://wiki.apache.org/cassandra/API under get_slice and >>> SlicePredicate >>> >>> On Thu, May 13, 2010 at 9:45 AM, Bill de hOra wrote: get_count returns the number of columns, not the names of those columns? I should have been specific, by "list the columns", I meant "list the column names". Bill Gary Dusbabek wrote: > > We have get_count at the thrift level. You supply a predicate and it > returns the number of columns that match. There is also > multi_get_count, which is the same operation against multiple keys. > > Gary. > > > On Thu, May 13, 2010 at 04:18, Bill de hOra wrote: >> >> Admin question - is there a way to list the columns for a particular >> key? >> >> Bill >> >> > >
Re: list of columns
Bill, I am a new user of Cassandra, so I've been following this discussion with interest. I think the answer is "no", except for the brute force method of looping through all your data. It's like asking for a list of all the files on your C: drive. The term "column" is very misleading, since "columns" are really leaves of a tree structure, not columns of a tabular structure. Anybody want to tell me I'm wrong? BTW, Bill, I think we've corresponded before, here: http://www.dehora.net/journal/2004/04/whats_in_a_name.html On Fri, May 14, 2010 at 2:23 AM, Bill de hOra wrote: > A SlicePredicate/SliceRange can't exclude column values afaik. > > Bill > > > Jonathan Shook wrote: > >> get_slice >> >> see: http://wiki.apache.org/cassandra/API under get_slice and >> SlicePredicate >> >> On Thu, May 13, 2010 at 9:45 AM, Bill de hOra wrote: >> >>> get_count returns the number of columns, not the names of those columns? >>> I >>> should have been specific, by "list the columns", I meant "list the >>> column >>> names". >>> >>> Bill >>> >>> Gary Dusbabek wrote: >>> We have get_count at the thrift level. You supply a predicate and it returns the number of columns that match. There is also multi_get_count, which is the same operation against multiple keys. Gary. On Thu, May 13, 2010 at 04:18, Bill de hOra wrote: > Admin question - is there a way to list the columns for a particular > key? > > Bill > > >>> >
Re: list of columns
A SlicePredicate/SliceRange can't exclude column values afaik. Bill Jonathan Shook wrote: get_slice see: http://wiki.apache.org/cassandra/API under get_slice and SlicePredicate On Thu, May 13, 2010 at 9:45 AM, Bill de hOra wrote: get_count returns the number of columns, not the names of those columns? I should have been specific, by "list the columns", I meant "list the column names". Bill Gary Dusbabek wrote: We have get_count at the thrift level. You supply a predicate and it returns the number of columns that match. There is also multi_get_count, which is the same operation against multiple keys. Gary. On Thu, May 13, 2010 at 04:18, Bill de hOra wrote: Admin question - is there a way to list the columns for a particular key? Bill
Re: list of columns
get_slice see: http://wiki.apache.org/cassandra/API under get_slice and SlicePredicate On Thu, May 13, 2010 at 9:45 AM, Bill de hOra wrote: > get_count returns the number of columns, not the names of those columns? I > should have been specific, by "list the columns", I meant "list the column > names". > > Bill > > Gary Dusbabek wrote: >> >> We have get_count at the thrift level. You supply a predicate and it >> returns the number of columns that match. There is also >> multi_get_count, which is the same operation against multiple keys. >> >> Gary. >> >> >> On Thu, May 13, 2010 at 04:18, Bill de hOra wrote: >>> >>> Admin question - is there a way to list the columns for a particular key? >>> >>> Bill >>> > >
Re: list of columns
get_count returns the number of columns, not the names of those columns? I should have been specific, by "list the columns", I meant "list the column names". Bill Gary Dusbabek wrote: We have get_count at the thrift level. You supply a predicate and it returns the number of columns that match. There is also multi_get_count, which is the same operation against multiple keys. Gary. On Thu, May 13, 2010 at 04:18, Bill de hOra wrote: Admin question - is there a way to list the columns for a particular key? Bill
Re: list of columns
We have get_count at the thrift level. You supply a predicate and it returns the number of columns that match. There is also multi_get_count, which is the same operation against multiple keys. Gary. On Thu, May 13, 2010 at 04:18, Bill de hOra wrote: > Admin question - is there a way to list the columns for a particular key? > > Bill >
list of columns
Admin question - is there a way to list the columns for a particular key? Bill
