We are trying to store lots of attributes for a particular profile_id inside a table (using CQL3) and cannot wrap our heads around which approach is the best:
a. create table mytable (profile_id, a1 int, a2 int, a3 int, a4 int ... a3000 int) primary key (profile_id);
OR
b. create MANY tables, eg.
create table mytable_a1(profile_id, value int) primary key (profile_id);
create table mytable_a2(profile_id, value int) primary key (profile_id);
...
create table mytable_a3000(profile_id, value int) primary key (profile_id);
OR
c. create table mytable (profile_id, a_all text) primary key (profile_id);
and just store 3000 "columns" inside a_all, like:
insert into mytable (profile_id, a_all) values (1, "a1:1,a2:5,a3:55, .... a3000:5");
OR
d. none of the above
The type of query we would be running on this table:
select * from mytable where profile_id in (1,2,3,4,5423,44)
We tried the first approach and the queries keep timing out and sometimes even kill cassandra nodes.
The answer would be to use a clustering column. A clustering column allows you to create dynamic columns that you could use to hold the attribute name (col name) and it's value (col value).
The table would be
create table mytable (
profile_id text,
attr_name text,
attr_value int,
PRIMARY KEY(profile_id, attr_name)
)
This allows you to add inserts like
insert into mytable (profile_id, attr_name, attr_value) values ('131', 'a1', 3);
insert into mytable (profile_id, attr_name, attr_value) values ('131', 'a2', 1031);
.....
insert into mytable (profile_id, attr_name, attr_value) values ('131', 'an', 2);
This would be the optimal solution.
Because you then want to do the following
'The type of query we would be running on this table: select * from mytable where profile_id in (1,2,3,4,5423,44)'
This would require 6 queries under the hood but cassandra should be able to do this in no time especially if you have a multi node cluster.
Also if you use the DataStax Java Driver you can run this requests asynchronously and concurrently on your cluster.
For more on data modelling and the DataStax Java Driver check out DataStax's free online training. Its worth a look
http://www.datastax.com/what-we-offer/products-services/training/virtual-training
Hope it helps.
Related
I need to alter the table to add a new column after a particular column or as last column, I have been through the document but no luck.
Let's say I'm starting with a table that has this definition:
CREATE TABLE mykeyspace.letterstable (
column_n TEXT,
column_b TEXT,
column_c TEXT,
column_z TEXT,
PRIMARY KEY (column_n));
1- Adding a column is a simple matter.
ALTER TABLE mykeyspace.letterstable ADD column_j TEXT;
2- After adding the new column, my table definition will look like this:
desc table mykeyspace.letterstable;
CREATE TABLE mykeyspace.letterstable (
column_n TEXT,
column_b TEXT,
column_c TEXT,
column_j TEXT,
column_z TEXT,
PRIMARY KEY (column_n));
This is because columns in Cassandra are stored by ASCII-betical order, after the keys (so column_n will always be first, because it is the only key). I can't tell Cassandra that I want my new column_j to go after column_z. It's going to put it between column_c and column_z on its own.
Cassandra will store table data based on partition & clustering key.
Standard CQL for adding column:
ALTER TABLE keyspace.table ADD COLUMN column1 columnType;
Running DESC table for a given table via CQLSH does not portray how the data is stored. It will always list the partition key & clustering key first; then the remaining columns in alphabetical order.
https://docs.datastax.com/en/cql/3.1/cql/cql_reference/alter_table_r.html
Cassandra create table won't keep column order
Have a table
REATE TABLE IF NOT EXISTS tabletest (uuid text, uuidHotel text, uuidRoom text, uuidGuest text, bookedTimeStampSet set<text>, PRIMARY KEY (uuidHotel, uuidRoom));
Tried to select with IN:
select * from tabletest where uuidhotel = 'uuidHotel' and bookedtimestampset IN ('1460710800000');
Got
'bookedtimestampset' (set<text>) cannot be restricted by a 'IN' relation"
Can I select elements by IN Set filter?
Can I select elements by IN Set filter?
No, but you can put a secondary index on bookedtimestampset and use the CONTAINS operator:
aploetz#cqlsh:stackoverflow> CREATE INDEX timeset_idx ON tabletest(bookedtimestampset);
aploetz#cqlsh:stackoverflow> SELECT uuidhotel,uuidroom FROM tabletest
WHERE uuidhotel = 'uuidHotel1' and bookedtimestampset CONTAINS '1460710800000';
uuidhotel | uuidroom
------------+----------
uuidHotel1 | uuidroom1
(1 rows)
Normally I wouldn't recommend a secondary index, but as long as you are filtering by a partition key (uuidhotel) it should perform ok.
Can I select elements by IN Set filter?
you can't use clause IN with your primary key. It is highly important to understand how significantly data model influences on query performance. Of course, you can add secondary index for column bookedtimestampset but in this case be ready to for performance degradation.
CREATE TABLE IF NOT EXISTS tabletest (uuid text, uuidHotel text, uuidRoom text, uuidGuest text, bookedTimeStampSet set, PRIMARY KEY (uuidHotel, uuidRoom));
your compound primary key consists of one partition key uuidHotel and one clustering key uuidRoom which means that all your hotels and rooms would physically stored on same node in order as result retrieval of rows is very efficient. bookedTimeStampSet is different column which would be spread through whole cluster and it is just impossible to restrict by this column without secondary indexing one.
Consequently. I would recommend you to create primary key according to your future queries even if you need to duplicate some data which is common practice for NoSql database such Cassandra is.
e.q.
CREATE TABLE IF NOT EXISTS tabletest (uuid text, uuidHotel text,
uuidRoom text, uuidGuest text, bookedTimeStamp timestamp, PRIMARY KEY
(uuidHotel, bookedTimeStamp , uuidRoom))
it allows you to make a query like
select * from tabletest where uuidhotel = 'uuidHotel' and
bookedtimestamp > '1460710800000 and bookedtimestamp < '1460710900000'
Say I have a cassandra table xyz with the following schema :
create table xyz(
xyzid uuid,
name text,
fileid int,
sid int,
PRIMARY KEY(xyzid));
I create index on columns fileid , sid:
CREATE INDEX file_index ON xyz (fileid);
CREATE INDEX sid_index ON xyz (sid);
I insert data :
INSERT INTO xyz (xyzid, name , fileid , sid ) VALUES ( now(), 'p120' , 1, 100);
INSERT INTO xyz (xyzid, name , fileid , ssid ) VALUES ( now(), 'p120' , 1, 101);
INSERT INTO xyz (xyzid, name , fileid , sid ) VALUES ( now(), 'p122' , 2, 101);
I want to delete data using the indexed columns :
DELETE from xyz WHERE fileid=1 and sid=101;
Why do I get this error ?
InvalidRequest: code=2200 [Invalid query] message="Non PRIMARY KEY fileid found in where clause"
Is it mandatory to specify the primary key in the where clause for delete queries ?
Does Cassandra supports deletes using secondary index s ?
What has to be done to delete data using secondary index s ?
Any suggestions that could help .
I am using Data Stax Community Cassandra 2.1.8 but I also want to know whether delete using indexed columns is supported by Data Stax Community Cassandra 3.2.1
Thanks
Let me try and answer your questions in order:
1) Yes, if you are going to use a where clause in a CQL statement then the PARTITION KEY must be an equality operator in the where clause. Other than that you are only allowed to filter on clustering columns specified in your primary key. (Unless you have a secondary index)
2) No it does not. See this post for some more information as it is essentially the same problem.
Why can cassandra "select" on secondary key, but not update using secondary key? (1.2.8+)
3) Why not add sid as a clustering column in your primary key. This would allow you to do the delete or query using both as you have shown.
create table xyz(
xyzid uuid,
name text,
fileid int,
sid int,
PRIMARY KEY(xyzid, sid));
4) In general using secondary indexes is considered an anti-pattern (a bit less so with SASI indexes in C* 3.4) so my question is can you add these fields as clustering columns to your primary key? How are you querying these secondary indexes?
I suppose you can perform delete in two steps:
Select data by secondary index and get primary index column values
(xyzid) from query result
Perform delete by primary index values.
I have a column family and syntax like this:
CREATE TABLE sr_number_callrecord (
id int,
callerph text,
sr_number text,
callid text,
start_time text,
plan_id int,
PRIMARY KEY((sr_number), start_time, callerph)
);
I want to do the query like :
a) select * from dummy where sr_number='+919xxxx8383'
and start_time >='2014-12-02 08:23:18' limit 10;
b) select * from dummy where sr_number='+919xxxxxx83'
and start_time >='2014-12-02 08:23:18'
and callerph='+9120xxxxxxxx0' limit 10;
First query works fine but second query is giving error like
Bad Request: PRIMARY KEY column "callerph" cannot be restricted
(preceding column "start_time" is either not restricted or by a non-EQ
relation)
If I get the result in first query, In second query I am just adding one
more cluster key to get filter result and the row will be less
Just like you cannot skip PRIMARY KEY components, you may only use a non-equals operator on the last component that you query (which is why your 1st query works).
If you do need to serve both of the queries you have listed above, then you will need to have separate query tables for each. To serve the second query, a query table (with the same columns) will work if you define it with a PRIMARY KEY like this:
PRIMARY KEY((sr_number), callerph, start_time)
That way you are still specifying the parts of your PRIMARY KEY in order, and your non-equals condition is on the last PRIMARY KEY component.
There are certain restrictions in the way the primary key columns are to be used in the where clause http://docs.datastax.com/en/cql/3.1/cql/cql_reference/select_r.html
One solution that will work in your situation is to change the order of clustering columns in the primary key
CREATE TABLE sr_number_callrecord (
id int,
callerph text,
sr_number text,
callid text,
start_time text,
plan_id int,
PRIMARY KEY((sr_number), callerph, start_time,)
);
Now you can use range query on the last column as
select * from sr_number_callrecord where sr_number = '1234' and callerph = '+91123' and start_time >= '1234';
I have a cassandra table defined like this:
CREATE TABLE test.test(
id text,
time bigint,
tag text,
mstatus boolean,
lonumb int,
PRIMARY KEY (id, time, tag)
)
And I want to select one column using select.
I tried:
select * from test where lonumb = 4231;
It gives:
code=2200 [Invalid query] message="No indexed columns present in by-columns clause with Equal operator"
Also I cannot do
select * from test where mstatus = true;
Doesn't cassandra support where as a part of CQL? How to correct this?
You can only use WHERE on the indexed or primary key columns. To correct your issue you will need to create an index.
CREATE INDEX iname
ON keyspacename.tablename(columname)
You can see more info here.
But you have to keep in mind that this query will have to run against all nodes in the cluster.
Alternatively you might rethink your table structure if the lonumb is something you'll do the most queries on.
Jny is correct in that WHERE is only valid on columns in the PRIMARY KEY, or those where a secondary index has been created for. One way to solve this issue is to create a specific query table for lonumb queries.
CREATE TABLE test.testbylonumb(
id text,
time bigint,
tag text,
mstatus boolean,
lonumb int,
PRIMARY KEY (lonumb, time, id)
)
Now, this query will work:
select * from testbylonumb where lonumb = 4231;
It will return all CQL rows where lonumb = 4231, sorted by time. I put id on the PRIMARY KEY to ensure uniqueness.
select * from test where mstatus = true;
This one is trickier. Indexes and keys on low-cardinality columns (like booleans) are generally considered a bad idea. See if there's another way you could model that. Otherwise, you could experiment with a secondary index on mstatus, but only use it when you specify a partition key (lonumb in this case), like this:
select * from testbylonumb where lonumb = 4231 AND mstatus = true;
Maybe that wouldn't perform too badly, as you are restricting it to a specific partition. But I definitely wouldn't ever do a SELECT * on mstatus.