incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Stuart Broad <stu...@moogsoft.com>
Subject Re: Prepared Statement - cache duration (CQL3 - Cassandra 1.2.4)
Date Tue, 23 Apr 2013 10:48:44 GMT
Hi Sylvain,

Thanks for your response.  I am handling the
'PreparedQueryNotFoundException' more for the case of a cassandra re-start
(rather then expecting to build 100000 statements).

I am not familiar with the binary protocol - which class/methods should I
look at?

Regards,

Stuart



On Tue, Apr 23, 2013 at 11:29 AM, Sylvain Lebresne <sylvain@datastax.com>wrote:

> In thrift, a lot of exceptions (like PreparedQueryNotFoundException) are
> simply returned as InvalidRequestException. The reason for that was a mix
> of not wanting to change the thrift API too much and because we didn't knew
> how to return a lot of different exception with thrift without making it
> horrible to work with. So you'll probably have to parse strings here indeed.
>
> This will be cleaner/less fragile if you use the binary protocol as
> exceptions are more fined grained there.
>
> Though taking a step back (and without saying that you shouldn't handle
> the case where a query is not prepared on the node you contact), if you're
> really considering preparing more than 100000 statements, I'd suggest that
> it might be worth benchmarking whether using prepared statements in your
> case is really going to be worth the trouble. Just saying.
>
> --
> Sylvain
>
>
>
> On Tue, Apr 23, 2013 at 12:14 PM, Stuart Broad <stuart@moogsoft.com>wrote:
>
>> Hi Sorin,
>>
>> The PreparedQueryNotFoundException is not thrown from
>> Cassandra.Client>>execute_prepared_cql3_query method.  I created some
>> prepared statements and then re-started cassandra and received the
>> following exception:
>>
>> InvalidRequestException(why: Prepared query with ID 1124421588 not found
>> (either the query was not prepared on this host (maybe the host has been
>> restarted?) or you have prepared more than 100000 queries and queries
>> 1124421588 has been evicted from the internal cache))
>>
>> The best I have been able to come up with is the following:
>>
>>             try {
>>                 client.execute_prepared_cql3_query(psId, bindValues, ..);
>>             } catch (InvalidRequestException invEx) {
>>                 String why = invEx.getWhy();
>>                 CLogger.logger().warning(why);
>>                 if(why.startsWith("Prepared query with ID")) {
>>                     rebuildPreparedStatement(preparedStatement);
>>                     client.execute_prepared_cql3_query(psId, bindValues,
>> ..);
>>                 } else {
>>                     throw invEx;
>>                 }
>>             }
>>
>> Obviously this is pretty fragile and would break if the cassandra message
>> was changed...but it least it works for now!
>>
>> Cheers,
>>
>> Stuart
>>
>>
>> On Sun, Apr 21, 2013 at 11:51 AM, Sorin Manolache <sorinm@gmail.com>wrote:
>>
>>> On 2013-04-19 13:57, Stuart Broad wrote:
>>>
>>>> Hi,
>>>>
>>>> I am using Cassandra.Client
>>>> prepare_cql3_query/execute_**prepared_cql3_query to create and run some
>>>> prepared statements.  It is working well but I am unclear as to how long
>>>> the server side 'caches' the prepared statements.  Should a prepared
>>>> statement be prepared for every new Cassandra.Client?  Based on my
>>>> limited testing it seems like I can create some prepared statements in
>>>> one Cassandra.Client and use in another but I am not sure how
>>>> reliable/lasting this is i.e.  If I called the prepared statement again
>>>> the next day would it still exist?  What about if cassandra was
>>>> re-started?
>>>>
>>>> _Background:_
>>>>
>>>> I am creating prepared statements for batch updates of pre-defined
>>>> lengths (e.g. 10000, 1000, 500, 250, 50, 10, 1) and wanted to know if
>>>> these could just be set up once.  We felt that using the prepared
>>>> statements was easier than escaping values within a CQL statement and
>>>> probably more performant.
>>>>
>>>> Thanks in advance for your help.
>>>>
>>>>
>>> I've looked in Cassandra's code (v1.2.3). The cache of prepared
>>> statements has a size of 100,000. So if you prepare more than 100 thousand
>>> statements, the least recently used ones will vanish. You'll get the
>>> exception PreparedQueryNotFoundException**, code 0x2500.
>>>
>>> Regards,
>>> Sorin
>>>
>>>
>>>
>>
>

Mime
View raw message