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Get current date in cassandra cql select

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问题 In SQL, I am able to do: select getdate(), getdate() - 7 Which returns the current date as well as current date - 7 days. I want to achieve the same in Cassandra CQL. I tried: select dateof(now()) But that does not work. It works only on insert and not in select. How can I get the same? Any help would be appreciated. 回答1: select dateof(now()) On its own, you are correct, that does not work. But if you have a table that you know only has one row (like system.local ): aploetz@cqlsh

Iterating through Cassandra wide row with CQL3

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How can I pull in a range of Composite columns with CQL3? Consider the following: CREATE TABLE Stuff ( a int, b text, c text, d text, PRIMARY KEY (a,b,c) ); In Cassandra what this effectively does is creates a ColumnFamily with integer rows (values of a) and with CompositeColumns composed of the values of b and c and the literal string 'd'. Of course this is all covered up by CQL3 so that we will think that we're inserting into individual database rows... but I digress. And consider the following set of inputs: INSERT INTO Stuff (a,b,c,d) VALUES (1,'A','P','whatever0'); INSERT INTO Stuff (a,b

Cassandra alter column type: which types are compatible?

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问题 There's some patchy information on the interwebs about some examples when column type can't be changed. For example, on the DataStax site there's a mention: Changing the type of a clustering column. Changing columns on which an index is defined. Or, for example, here is mentioned that you can't convert uuid to timeuuid . And from my personal experience, I can't change text to timestamp (we store dates in ISO8601 format as text, an unfortunate decision early in the project timeline). However,

Where and Order By Clauses in Cassandra CQL

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问题 I am new to NoSQL database and have just started using apache Cassandra. I created a simple table "emp" with primary key on "empno" column. This is a simple table as we always get in Oracle's default scott schema. Now I loaded data using the COPY command and issued query Select * from emp order by empno but I was surprised that CQL did not allow Order by on empno column (which is PK). Also when I used Where condition, it did not allow any inequality operations on empno column (it said only EQ

alter composite primary key in cassandra CQL 3.0

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问题 I'm in a situation where I need to change the the composite primary key as follows: Old Primary Key: (id, source, attribute_name, updated_at); New Primary Key I want: (source, id, attribute_name, updated_at); I issued the following (mysql like) command: ALTER TABLE general_trend_table DROP PRIMARY KEY, ADD PRIMARY KEY(source, id, attribute_name, updated_at); I got the following error: Bad Request: line 1:38 no viable alternative at input 'PRIMARY' any idea how to get around this problem? more

Range query on secondary index in cassandra

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问题 I am using cassandra 2.1.10. So First I will clear that I know secondary index are anti-pattern in cassandra.But for testing purpose I was trying following: CREATE TABLE test_topology1.tt ( a text PRIMARY KEY, b timestamp ) WITH bloom_filter_fp_chance = 0.01 AND caching = '{"keys":"ALL", "rows_per_partition":"NONE"}' AND comment = '' AND compaction = {'class': 'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy'} AND compression = {'sstable_compression': 'org.apache.cassandra.io

Apache Cassandra delete from counter

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I'm developing a little web application for studying Apache Cassandra and Java EE 6. Cassandra version is 1.1.6. Have a problem driving me mad... I created a table with a counter (using cqlsh v. 3.0.0) CREATE TABLE test ( author varchar PRIMARY KEY, tot counter ) and put some values this way: update test set tot = tot +1 where author = 'myAuthor'; the column family is perfectly updated author | tot ----------+----- myAuthor | 1 BUT, if you try to delete this row and then update again (with the same key), then nothing happens! The table is no more updated and I can't figure why: it seems to me

How to rename table in Cassandra CQL3

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问题 I'm trying to rename table created via CQLSH. E.g. rename table "AAA" to "BBB". Can't find any command to do so. Any ideas? Using [cqlsh 3.1.6 | Cassandra 1.2.8 | CQL spec 3.0.0 | Thrift protocol 19.36.0] 回答1: I don't believe you can rename tables or keyspaces, there's no CQL3 operation to do it, and nothing in the old Thirft interfaces either, if I remember correctly. One reason why you can't is that it would be an extremely hard thing for Cassandra to do due to its distributed nature, the

Cassandra cql: how to select the LAST n rows from a table

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I want to verify that rows are getting added to the table. What cql statement would show the last n rows from the table below? Table description below: cqlsh:timeseries> describe table option_data; CREATE TABLE option_data ( ts bigint, id text, strike decimal, callask decimal, callbid decimal, maturity timestamp, putask decimal, putbid decimal, PRIMARY KEY ((ts), id, strike) ) WITH bloom_filter_fp_chance=0.010000 AND caching='KEYS_ONLY' AND comment='' AND dclocal_read_repair_chance=0.100000 AND gc_grace_seconds=864000 AND index_interval=128 AND read_repair_chance=0.000000 AND replicate_on

How do I set the consistency level of an individual CQL query in CQL3?

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问题 In the earlier beta releases of CQL, there was a command I could use to set the read / write consistency of an individual CQL operation. It looked like this: SELECT * FROM users WHERE state='TX' USING CONSISTENCY QUORUM; I use CQL3 regularly and have a use-case where I need to be able to perform a read with a higher consistency level than the rest of our application. I looked through the CQL3 reference and didn't find any mention of any CQL syntax that allows me to change the consistency