How to find last inserted value using CQL3

[Rahul Gupta <rg...@dekaresearch.com>]

I am trying to find last value inserted in a Cassandra1.2 table using CQL3 but can't find a solution.

There is WRITETIME(<col name>) but that gives me time when that column was written.


CREATE TABLE "dev"."eventTable" (
  "eventName" text,
  "eventTime" timestamp,
  "rawEvent" text,
  PRIMARY KEY ("eventName", "eventTime")
) WITH CLUSTERING ORDER BY ("eventTime" ASC);


select WRITETIME("rawEvent"), "eventTime", "rawEvent"
from "eventTable"
where "eventName" = 'myevent'
ORDER BY "eventTime" DESC;

This returns bunch of events and their writetime, how to get last (or max) writetime using CQL?

Thanks,
Rahul Gupta


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Re: How to find last inserted value using CQL3

[DuyHai Doan <do...@gmail.com>]

Hello Rahul

 1) If your query pattern is to always request the last events, change your
clustering order to "DESC":  WITH CLUSTERING ORDER BY (*"eventTime"* DESC);

 2) To get the last or N last events, use the LIMIT clause of CQL3:   select*
... *ORDER BY* "eventTime"* DESC LIMIT 1;

 3) I believe the value "eventTime" corresponds to the time the event is
created right ? Would'nt it be sufficient to consider this value also as
the write time for the event ?   Do you really need to distinguish between
event creation time and event write time ?

 If such distinction is not necessary, you may use use eventTime and get
rid of the writetime() function

 Regards

 Duy Hai DOAN





On Thu, Jan 30, 2014 at 7:30 PM, Rahul Gupta <rg...@dekaresearch.com>wrote:

>  I am trying to find last value inserted in a Cassandra1.2 table using
> CQL3 but can't find a solution.
>
>
>
> There is WRITETIME(<col name>) but that gives me time when that column was
> written.
>
>
>
>
>
> CREATE TABLE* "dev"."eventTable"* (
>
> *  "eventName"* text,
>
> *  "eventTime"* timestamp,
>
> *  "rawEvent"* text,
>
>   PRIMARY KEY (*"eventName"*,* "eventTime"*)
>
> ) WITH CLUSTERING ORDER BY (*"eventTime"* ASC);
>
>
>
>
>
> select WRITETIME(*"rawEvent"*),* "eventTime"*,* "rawEvent"*
>
> from* "eventTable"*
>
> where* "eventName"* = 'myevent'
>
> ORDER BY* "eventTime"* DESC;
>
>
>
> This returns bunch of events and their writetime, how to get last (or max)
> writetime using CQL?
>
>
>
> Thanks,
>
> *Rahul Gupta*
>
>
> ------------------------------
> This e-mail and the information, including any attachments, it contains
> are intended to be a confidential communication only to the person or
> entity to whom it is addressed and may contain information that is
> privileged. If the reader of this message is not the intended recipient,
> you are hereby notified that any dissemination, distribution or copying of
> this communication is strictly prohibited. If you have received this
> communication in error, please immediately notify the sender and destroy
> the original message.
>
> Thank you.
>
> Please consider the environment before printing this email.
>