it means the column family uses composite key, which gives you additional capabilities like order by in the where clause
On Wed, Nov 14, 2012 at 5:27 PM, Kevin Burton <rkevinbur...@charter.net> wrote: > I hope I am not bugging you but now what is the purpose of PRIMARY_KEY(id, > item_id)? By expressing the KEY as two values this basically gives the > database a hint that this will be an array? Is there an implicit INDEX on id > and item_id? Thanks again. > > -----Original Message----- > From: aaron morton [mailto:aa...@thelastpickle.com] > Sent: Wednesday, November 14, 2012 4:08 PM > To: user@cassandra.apache.org > Subject: Re: CF metadata syntax for an array > > Like this? > > cqlsh:dev> CREATE TABLE my_orders( > ... id int, > ... item_id int, > ... price decimal, > ... title text, > ... PRIMARY KEY(id, item_id) > ... ); > > cqlsh:dev> insert into my_orders > ... (id, item_id, price, title) > ... values > ... (1, 1, 4, 'this is an example'); > cqlsh:dev> insert into my_orders > ... (id, item_id, price, title) > ... values > ... (1, 2, 8, 'this is another example'); > cqlsh:dev> insert into my_orders > ... (id, item_id, price, title) > ... values > ... (1, 3, 6, 'this is the last example'); > > cqlsh:dev> select * from my_orders where id = 1; id | item_id | price | > title > ----+---------+-------+-------------------------- > 1 | 1 | 4 | this is an example > 1 | 2 | 8 | this is another example > 1 | 3 | 6 | this is the last example > > > > > ----------------- > Aaron Morton > Freelance Cassandra Developer > New Zealand > > @aaronmorton > http://www.thelastpickle.com > > On 15/11/2012, at 10:38 AM, Kevin Burton <rkevinbur...@charter.net> wrote: > >> An array would be a list of groups of items. In my case I want a > list/array of line items. An order has certain characteristics and one of > them is a list of the items that are being ordered. Say ever line item has > an id, price, and description so one such "array" would look like: >> >> 1 $4.00 "This is an example" >> 2 $8.00 "This is another example" >> 3 $6.00 "This is the last example" >> >> So in this case the array would be the three items listed above. So the > "column" is repeated three times for this order. >> >> From: aaron morton [mailto:aa...@thelastpickle.com] >> Sent: Wednesday, November 14, 2012 3:05 PM >> To: user@cassandra.apache.org >> Subject: Re: CF metadata syntax for an array >> >> In both cases the array is the PRIMARY_KEY. >> I'm not sure what you mean by the "array" >> >> The vector_name and list_name columns are used as "variable names" to > identify a particular vector or list. They are the storage engine "row key". >> >> Cheers >> >> ----------------- >> Aaron Morton >> Freelance Cassandra Developer >> New Zealand >> >> @aaronmorton >> http://www.thelastpickle.com >> >> On 14/11/2012, at 5:31 PM, Kevin Burton <rkevinbur...@charter.net> wrote: >> >> >> Does the array have to be a KEY? >> Sorry I don't understand this question. >> >> In the samples you give you specify array as >> >> CREATE COLUMNFAMILY Description ( >> PRIMARY_KEY > (vector_name, index), >> Age text, >> Gender text, >> vector_name text, >> index bigint, >> ... >> >> Or >> CREATE COLUMNFAMILY Description ( >> PRIMARY_KEY > (listr_name, sort_key), >> Age text, >> Gender text, >> sort_key bigint, >> list_name text >> .. >> >> >> In both cases the array is the PRIMARY_KEY. In order for an array to work > does the array have to be a KEY? >> >> From: aaron morton [mailto:aa...@thelastpickle.com] >> Sent: Tuesday, November 13, 2012 10:18 PM >> To: user@cassandra.apache.org >> Subject: Re: CF metadata syntax for an array >> >> >> Would this syntax be the same for CREATE COLUMNFAMILY (as an aside what is > a 'TABLE' in Cassandra)? >> Yes, CQL 2 uses COLUMN FAMILY or Table and CQL 3 uses TABLE >> >> http://www.datastax.com/dev/blog/cql3-evolutions >> >> In other words is this valid: >> Does it work ? Is so it's valid. >> >> Does the array have to be a KEY? >> Sorry I don't understand this question. >> >> Finally, what would be the syntax for inserting data into the CF? >> Depends on what you want to do. >> Docs are a good starting point >> http://www.datastax.com/docs/1.1/references/cql/index >> >> Cheers >> >> ----------------- >> Aaron Morton >> Freelance Developer >> @aaronmorton >> http://www.thelastpickle.com >> >> On 14/11/2012, at 2:42 AM, Kevin Burton <rkevinbur...@charter.net> wrote: >> >> >> >> Sorry to be so slow but I am just learning CQL. Would this syntax be the > same for CREATE COLUMNFAMILY (as an aside what is a 'TABLE' in Cassandra)? > In other words is this valid: >> >> CREATE COLUMNFAMILY Description ( >> PRIMARY_KEY > (vector_name, index), >> Age text, >> Gender text, >> vector_name text, >> index bigint, >> ... >> >> Or >> CREATE COLUMNFAMILY Description ( >> PRIMARY_KEY > (listr_name, sort_key), >> Age text, >> Gender text, >> sort_key bigint, >> list_name text >> .. >> >> >> >> Does the array have to be a KEY? Finally, what would be the syntax for > inserting data into the CF? >> >> Thanks again. >> >> From: aaron morton [mailto:aa...@thelastpickle.com] >> Sent: Tuesday, November 13, 2012 4:09 AM >> To: user@cassandra.apache.org >> Subject: Re: CF metadata syntax for an array >> >> While this solves the problem for an array of 'primitive' types. What if I > want an array or collection of an arbitrary type like list<foo>, where foo > is a user defined type? >> Do you mean a custom Cassandra data type that sub classes AbstractType? I > dont think CQL can support those, I may be wrong though. >> >> If you mean a basic client side data type you could serialise it and store > as a string or byte buffer in a CQL collection. >> >> What are the options to solve this type of array? >> ... >> >> >> >> arbitrary type like list<foo>, >> Do you mean an array such as int[] or do you mean the equivalent of a java > List<T> with functions like remove that actually delete items and from the > list? >> >> If it's the former a CQL table such as below would work >> >> CREATE TABLE vectors ( >> vector_name text, >> index bigint, >> object_property_1 text, >> object_property_2 text, >> PRIMARY_KEY (vector_name, index) ); >> >> The problem is, if you delete a element at (vector, index) the remaining > indexes will be off. >> >> If it's the later, a List<T>, then it depends a little on what >> features you want to support. If you want a sorted list of objects the >> table is roughly the same >> >> CREATE TABLE List ( >> list_name text, >> sort_key bigint, >> object_property_1 text, >> object_property_2 text, >> PRIMARY_KEY (list_name, sort_key) ); >> >> Hope that helps. >> >> ----------------- >> Aaron Morton >> Freelance Developer >> @aaronmorton >> http://www.thelastpickle.com >> >> ----------------- >> Aaron Morton >> Freelance Developer >> @aaronmorton >> http://www.thelastpickle.com >> >> On 13/11/2012, at 9:46 AM, Kevin Burton <rkevinbur...@charter.net> wrote: >> >> >> >> >> While this solves the problem for an array of 'primitive' types. What if I > want an array or collection of an arbitrary type like list<foo>, where foo > is a user defined type? I am guessing that this cannot be done with > 'collections'. What are the options to solve this type of array? >> >> On Nov 12, 2012, at 2:28 PM, aaron morton <aa...@thelastpickle.com> wrote: >> >> This may help http://www.datastax.com/dev/blog/cql3_collections >> >> I have gotten as far as feeling a need to understand a 'super-column' >> You can happily ignore them. >> >> >> Cheers >> >> ----------------- >> Aaron Morton >> Freelance Developer >> @aaronmorton >> http://www.thelastpickle.com >> >> On 12/11/2012, at 8:35 PM, Kevin Burton <rkevinbur...@charter.net> wrote: >> >> >> >> >> I am sorry if this is an FAQ. But I was wondering what the syntax for > describing an array? I have gotten as far as feeling a need to understand a > 'super-column' but I fail after that. Once I have the metadata in place to > describe an array how do I insert data into the array? Get data from the > array? Thank you. >> >> > >
