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  1. Cassandra
  2. CASSANDRA-13409

Materialized Views: View cells are resurrected



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      Consider the following commands, ran against trunk@0f054fee5c:

      echo "create keyspace ks WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 1};" | bin/cqlsh
      echo "create table ks.base (p int primary key, v1 int, v2 int) with gc_grace_seconds = 1;" | bin/cqlsh
      echo "create materialized view ks.my_view as select * from ks.base where p is not null and v1 is not null primary key (v1, p);" | bin/cqlsh
      echo "insert into ks.base (p, v1, v2) values (3, 1, 3) using timestamp 1;" | bin/cqlsh
      bin/nodetool flush ks my_view base
      echo "delete from ks.base using timestamp 2 where p = 3;" | bin/cqlsh
      bin/nodetool flush ks my_view base
      echo "insert into ks.base (p, v1) values (3, 1) using timestamp 3;" | bin/cqlsh
      bin/nodetool flush ks my_view base
      echo "select * from ks.my_view;" | bin/cqlsh
       v1 | p | v2
        1 | 3 |  3
      (1 rows)
      echo "select * from ks.base;" | bin/cqlsh
       p | v1 | v2
       3 |  1 | null
      (1 rows)

      As you can see, this incorrectly brings back cell v2=3.

      There is one definitive problem and a potential one:

      • Merging rows must be commutative. If a shadowable tombstone is applied after a row tombstone, it will replace that tombstone; if a row marker shadows the shadowable tombstone before the row containing the original data is applied, then any dead cells in said data will be resurrected;
      • Shadowable tombstones shouldn't compact away previous row tombstones or even deleted cells; if the relevant tombstones have been GCed from the base table, then a base table update won't carry them anymore (alongside a newer row marker).


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              jasonstack Zhao Yang
              duarten Duarte Nunes
              Zhao Yang
              Alex Petrov
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