Incrementing counters

[Collin Sauve]

Hi,

I'm having some trouble incrementing counters properly with the C# driver.  Say I have the following entity:

 
 [Table("test_counter_v1")]
 public class TestCounterEntity1
 {
     [Column("pk")]
     public string PartitionKey { get; set; }

     [Column("counter")]
     [Counter]
     public long Counter { get; set; }
 }

I originally expected I should have to do something like this:

 
 [Test]
 public async Task TestUpdateCounterConstant()
 {
     var paritionKey = Guid.NewGuid().ToString();
     var table = new Table<TestCounterEntity1>(Session);

     await table
         .Where(_ => _.PartitionKey == paritionKey)
         .Select(_ => new TestCounterEntity1
         {
             Counter = _.Counter + 4                 // We will be working with this line...
         })
         .Update()
         .ExecuteAsync();
 }

However I receive this exception:

"System.InvalidOperationException : variable '_' of type 'Nudge.Tests.Core.Cassandra.TestCounterEntity1' referenced from scope '', but it is not defined

Digging through some examples, including the LinqGeneratedUpdateStatementForCounterTest that was created in PR#43, I see I need to change that line to:

   

             Counter = 1

And that works!  However, what if I want to increment by more than 1? ie:

             Counter = 4

This actually only increments it by 1.  Even going back and trying to change the original LinqGeneratedUpdateStatementForCounterTest to have Value = 2 it writes CQL that would only increment by 1.

 Additionally, if I want to increment it by a non-constant, ie

             Counter = x.SomeProperty

I get this exception:

Cassandra.Data.Linq.CqlLinqNotSupportedException : The expression Convert = [Convert(value(Cassandra.Tests.Mapping.Linq.LinqToCqlUnitTests+<>c__DisplayClass12_0).x.Value)] is not supported in SelectBinding parse phase.

So... am I missing some other way of doing this? ie with the Mapper instead of Linq component perhaps?   Should I file a bug / attempt to fix it myself?

    

[Jorge Bay Gondra]

Hi Collin,

It is indeed a bug in the Linq component, I've created a ticket for it: https://datastax-oss.atlassian.net/browse/CSHARP-467

Thanks,

Jorge

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[David Buckle]

I have a similar issue but if the counter record doesn't already exist in the table is doesn't get created using Update().  I thought Update actually did an Upsert() ?

I can't use Insert() since it will throw an exception as it is a counter type.  Really stuck now, and I'm not sure if this is related to the original bug.

I also tried this direct:

"UPDATE test_table set count_value = count_value + 1 WHERE somekey = ?"

But still the record isn't created.  

Any ideas?

[David Buckle]

I just found out seconds after posting this that the original record had been deleted.  If I used another key, it works.  That's pretty confusing.

[David Buckle]

...and I found that it needs to be GC'd.

https://stackoverflow.com/questions/45031924/how-do-you-update-timestamp-field-in-cassandra-with-c-sharp-drive