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From "Sylvain Lebresne (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (CASSANDRA-5563) The CQL3 binary protocol does not allow a user to bind an empty buffer to signify the start of the token range
Date Tue, 09 Jul 2013 15:05:48 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-5563?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Sylvain Lebresne resolved CASSANDRA-5563.
-----------------------------------------

       Resolution: Cannot Reproduce
    Fix Version/s:     (was: 1.2.7)

I'm not able to reproduce this. I've just tested it and binding an empty buffer to a bind
marker that is the argument to token() works fine. And as far as I can tell, the native protocol
has always allowed to bind empty byte buffers so I'm not sure that has ever be a problem,
but if it was, it's fixed now as far as I can tell.

I'll note that the fact that the token of an empty buffer happens to return the minimum token
is a bit of an implementation detail of our IPartitioner.getToken() methods. And in particular,
with composite partition key you won't really be able to provide a empty byte buffer for the
whole partition key, so you will have to use more than a single prepared statement to page
in that case.

As for allowing null as argument to token(), I'm not a fan because:
# I don't find {{token(null)}} particularly logical/clean.
# This doesn't really transpose well to composite partition key (for which the token() method
really expect multiple arguments).
# With the native protocol 2.0 supporting a much simpler way to do paging, I don't see a point
in bothering here.
                
> The CQL3 binary protocol does not allow a user to bind an empty buffer to signify the
start of the token range
> --------------------------------------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-5563
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-5563
>             Project: Cassandra
>          Issue Type: Bug
>          Components: API
>    Affects Versions: 1.2.0
>            Reporter: Steven Lowenthal
>            Assignee: Sylvain Lebresne
>            Priority: Minor
>
> Using CQL2 or CQL3 over thrift, one can issue a query which starts at the beginning of
the table by binding an empty buffer.  The same is true for CQL2 using calls like get_range_slice.
  This is not allowed with the binary protocol.  Here is working sample code for CQL3 over
thrift:
> {code}
>     CqlPreparedResult stmt = _client.prepare_cql3_query(ByteBuffer.wrap("SELECT \" Sequence
number\" from \"nhanes52simple\" where TOKEN (\" Sequence number\") > TOKEN(?) limit 15".getBytes()),
Compression.NONE);
>     // Bind empty buffer to get query to start at the beginning of 
>     // the table
>     ByteBuffer b = ByteBuffer.wrap(new byte[0]);
>     bindVars.add(b);
>     int cnt = 0;
>     CqlResult result;
>     do {
>       result =  _client.execute_prepared_cql3_query(stmt.itemId, bindVars, ConsistencyLevel.ONE);
>       // Set up the next chunk, by setting the bind var to the last received key
>       bindVars.set(0, ByteBuffer.wrap(result.getRows()
>               .get(result.getRows().size() - 1).getColumns().get(0).getValue()));
>       // Count rows
>       cnt += result.getRows().size();
>       if (cnt > 100)
>         Assert.fail("Running past the end of the table: cnt = " + cnt + ", size() = 
" + result.getRows().size());
>     } while (result.getRows().size() >= CHUNK_SIZE);
>     Assert.assertEquals("Wrong count", 100, cnt);
>   } 
> {code}

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