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From Edward Capriolo <edlinuxg...@gmail.com>
Subject Re: Prepared Statement - cache duration (CQL3 - Cassandra 1.2.4)
Date Tue, 23 Apr 2013 15:05:53 GMT
Thrift has a prepare_cql call which returns an ID. Then it has an
exececute_cql call which takes the id and a map or variable bindings.


On Tue, Apr 23, 2013 at 10:29 AM, Stuart Broad <stuart@moogsoft.com> wrote:

> Hi all,
>
> I just realised that the binary protocol is the low-level thrift api that
> I was originally using (Cassandra.Client>> get / insert ...).  How can a
> prepared statement be called through the thrift api (i.e. not the cql
> methods)?
>
> Cheers,
>
> Stuart
>
>
> On Tue, Apr 23, 2013 at 11:48 AM, Stuart Broad <stuart@moogsoft.com>wrote:
>
>> 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
>>>>>
>>>>>
>>>>>
>>>>
>>>
>>
>

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