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Cassandra secondary index

  • A primary index is global, although a secondary index is local.
  • To query a users by their secondary indexed value or their email every machine has to query its self target of users.
  • One query, five reads from disk.
what is secondary index in cassandra

Using a secondary index

  • Using SQL,after defining a table you can create an index on a column.
  • You can also index a collection column.
  • Secondary indexes are used to query a table using a column that is not general query table.
  • Secondary indexes are difficult to use and can impact performance greatly.
  • The index table is stored on every node in a cluster, so a query involving a secondary index if multiple nodes are accessed it can quickly become a performance nightmare.
  • A general rule of thumb is to index a column with low cardinality of few data.
  • Before creating an index, be aware of when and when not to create an index.
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