Hello, this link might also be helpful to you for querying table schema.
Link: https://docs.datastax.com/en/cql/3.3/cql/cql_using/useQuerySystemTable.html Best, Iriiza On Tue, Feb 6, 2018 at 9:55 PM, Oliver Ruebenacker <[email protected]> wrote: > > Hello, > > Is there a describe query in CQL? I don't see one on > http://cassandra.apache.org/doc/latest/cql/index.html. > > I also can't find such a query in the DataStax Java driver API. > > Thanks! > > Best, Oliver > > On Tue, Feb 6, 2018 at 11:48 AM, Irtiza Ali <[email protected]> wrote: > >> Hello. >> >> Another thing that you can try is the use the describe table query to get >> the table schema and parse it. Once done you can check whether column >> exists or not. >> >> >> With Regards >> Irtiza Ali >> >> On 6 Feb 2018 21:35, "Oliver Ruebenacker" <[email protected]> wrote: >> >>> Thanks for the response! >>> >>> So, the best solution I can come up with is catching the >>> InvalidQueryException and check whether its message contains the phrase >>> "conflicts with an existing column". Seems to work, but super-ugly. >>> >>> I do assume that in general, if a request fails, it does not >>> permanently change the data in Cassandra, right? >>> >>> It would be great if alter-add could have an if-not-exists clause. >>> Would that be hard to implement? >>> >>> I could not find a standard CQL way of asking what columns exist. Did >>> I miss it? Would it be hard to implement? >>> >>> I get that we're only eventually consistent anyway. >>> >>> Thanks! >>> >>> Best, Oliver >>> >>> On Mon, Feb 5, 2018 at 5:12 PM, Rahul Singh < >>> [email protected]> wrote: >>> >>>> Yeah, you can handle the exception — what i meant that it wouldnt cause >>>> harm to the DB >>>> >>>> -- >>>> Rahul Singh >>>> [email protected] >>>> >>>> Anant Corporation >>>> >>>> On Feb 5, 2018, 5:07 PM -0500, Oliver Ruebenacker <[email protected]>, >>>> wrote: >>>> >>>> Well, it does throw an InvalidQueryException if the column already >>>> exists. >>>> >>>> On Mon, Feb 5, 2018 at 4:44 PM, Rahul Singh < >>>> [email protected]> wrote: >>>> >>>>> Since CQL != SQL, there’s isnt a syntatical way. Just run the alter >>>>> table command and it shouldn't be an issue if its there. >>>>> >>>>> -- >>>>> Rahul Singh >>>>> [email protected] >>>>> >>>>> Anant Corporation >>>>> >>>>> On Feb 5, 2018, 4:15 PM -0500, Oliver Ruebenacker <[email protected]>, >>>>> wrote: >>>>> >>>>> >>>>> Hello, >>>>> >>>>> What's the easiest way to add a column to a table but only if it >>>>> does not exist? Thanks! >>>>> >>>>> Best, Oliver >>>>> >>>>> -- >>>>> Oliver Ruebenacker >>>>> Senior Software Engineer, Diabetes Portal >>>>> <http://www.type2diabetesgenetics.org/>, Broad Institute >>>>> <http://www.broadinstitute.org/> >>>>> >>>>> >>>> >>>> >>>> -- >>>> Oliver Ruebenacker >>>> Senior Software Engineer, Diabetes Portal >>>> <http://www.type2diabetesgenetics.org/>, Broad Institute >>>> <http://www.broadinstitute.org/> >>>> >>>> >>> >>> >>> -- >>> Oliver Ruebenacker >>> Senior Software Engineer, Diabetes Portal >>> <http://www.type2diabetesgenetics.org/>, Broad Institute >>> <http://www.broadinstitute.org/> >>> >>> > > > -- > Oliver Ruebenacker > Senior Software Engineer, Diabetes Portal > <http://www.type2diabetesgenetics.org/>, Broad Institute > <http://www.broadinstitute.org/> > >
