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From Joris van der Wel <jo...@jorisvanderwel.com>
Subject Questions about TTL and batch_mutate
Date Sun, 21 Aug 2011 11:38:26 GMT
Hello,

I have a ColumnFamily in which all columns are always set with a TTL,
this would be one of the hottest column families (rows_cached is set
to 1.0). I am wondering if TTL values also follow gc_grace? If they
do, am I correct in thinking it would be best to set gc_grace really
low in this case? (zero?)

Another question:
For a single key I have data in ColumnFamily "CF_A" and ColumnFamily
"CF_B". I set their data in one thrift "batch_mutate".
If I understood correctly, atomicity is then guaranteed (if one
mutation fails, they all fail). But isolation is not. However if for
example the following Mutation takes place:

batch_mutate({
     "mykey": {
          "CF_A": [
                    Mutation {
                         column_or_supercolumn: ColumnOrSuperColumn {
                              column: {
                                   name: "abc",
                                   value: 10,
                                   timestamp: 1313918714729
                              }
                         }
                    }
               ],
          "CF_B": [
                    Mutation {
                         column_or_supercolumn: ColumnOrSuperColumn {
                              column: {
                                   name: "def",
                                   value: 55,
                                   timestamp: 1313918714730
                              }
                         }
                    },
               ]
     }
}, QUORUM)

The mutation against Column Family "CF_B" is placed last.
If:
       get CF_B[def] is 55
Can I then safely assume that
       get CF_A[abc] is 10 OR a newer value


Thanks,
Gr. Joris

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