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From "Stu Hood (JIRA)" <>
Subject [jira] Commented: (CASSANDRA-749) Secondary indices for column families
Date Sat, 13 Feb 2010 23:34:27 GMT


Stu Hood commented on CASSANDRA-749:

Thoughts on incrementally updated views:

In a first version a View CF could be defined with a normal column family definition, plus
a function that transforms a mutation against a 'base' column family into zero or more mutations
against the 'view' column family.

At mutation time, inserts can immediately be transformed into inserts to the view. But, an
insert that overwrites an older value implies deletion from the base, and therefore a potential
deletion from the view.

One disadvantage/advantage Cassandra has is that an entire row is not available at mutation
time, so we need to defer all deletes to the view until read time. To handle deletes, all
columns in the view cf should be tagged with the column_key from the base cf that caused their

At read time, the base cf column_keys that are tagging the columns in the view need to be
queried and the view function re-applied. If the output of the view function no longer causes
an insert to the column in question in the view, the column can be deleted from the view.

Definitely need to think of ways to efficiently account for deletes, and minimize the number
of reads to the base cf that need to occur at read time for the view cf.

> Secondary indices for column families
> -------------------------------------
>                 Key: CASSANDRA-749
>                 URL:
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Core
>            Reporter: Gary Dusbabek
>            Assignee: Gary Dusbabek
>            Priority: Minor
>             Fix For: 0.7
>         Attachments: 0001-simple-secondary-indices.patch

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