bug: vertical sharding aggregation with absent displays shard by label

[yeya24]

Describe the bug

    query_fuzz_test.go:169: case 0 results mismatch.
        instant query: count_values without (job) ("value", absent({series="7"}))
        res1: {series="7", value="1"} => 1 @[1678393035.187]
        res2: {__CORTEX_SHARD_BY__="CAEQAiIDam9i", series="7", value="1"} => 1 @[1678393035.187]
        {__CORTEX_SHARD_BY__="EAIiA2pvYg==", series="7", value="1"} => 1 @[1678393035.187]

Got this bug when running the PromQLsmith test.

Ran a query count_values without (job) ("value", absent({series="7"})). Here {series="7"} couldn't match anything so absent() is expected to return a series.

res1 is from non vertical sharding Cortex and it gives expected result. res2 runs vertical sharding Cortex and it gave me bad results and additional __CORTEX_SHARD_BY__ label.

[yeya24]

Seems the count_values aggregation doesn't matter here.

    query_fuzz_test.go:168: case 17 results mismatch.
        instant query: max without (series) (absent({__name__="test_series"}))
        res1: 
        res2: {__CORTEX_SHARD_BY__="CAEQAiIGc2VyaWVz"} => 1 @[1678393609.301]

Got another case with max and absent that displays the additional shard label.

[yeya24]

Probably we should just disable absent and absent_over_time for vertical sharding and then this can be resolved.

[yeya24]

Should be solved by thanos-io/thanos#6201