> Assuming we have 1000 columns in 1 row of the column family and about 900 of > them have > > NamedColumn1=1 and of those 900 only 10 of them also have NamedColumn2=1. Am assuming you mean 1,000 rows not columns.
> does Cassandra > optimized this in any way by fetching only the 10 versus the 900 and then > > filtering out the 10 I really need? The most selective term is used first. All the rows that match that term are read (in batches) and then filtered. > How does this affect the internal index column > family and how often will it get compacted? It is compacted when it needs it, not when the parent CF is compacted. > About expirations: if the column in the user defined column family expires > can I > safely assume that its related indexes will also expire? Yes > > http://www.datastax.com/docs/1.1/ddl/indexes > Maintaining Secondary Indexes Emailed to ask for clarification. Cheers ----------------- Aaron Morton Freelance Cassandra Consultant New Zealand @aaronmorton http://www.thelastpickle.com On 20/03/2013, at 5:08 AM, Mayank <4may...@gmail.com> wrote: > Thanks guys. I am working with Andy on this project. > > Further questions on the secondary indexes: > Assuming we have 1000 columns in 1 row of the column family and about 900 of > them have > > NamedColumn1=1 and of those 900 only 10 of them also have NamedColumn2=1. If > I > > query for columns which have NamedColumn1=1 && NamedColumn2=1 does Cassandra > optimized this in any way by fetching only the 10 versus the 900 and then > > filtering out the 10 I really need? > > > We ran some tests that show if only 10 of the 18 NamedColumns were inserted > only > those 10 internal index column families are updated. In this case the size of > the > > user defined column families and the internal index column families will > differ. It > > is then expected that the user defined column family will get compacted more > often > and tombstones removed more often. How does this affect the internal index > column > > family and how often will it get compacted? > > > About expirations: if the column in the user defined column family expires > can I > safely assume that its related indexes will also expire? > > > Here is the link that talks about the rebuild: > > http://www.datastax.com/docs/1.1/ddl/indexes > Maintaining Secondary Indexes > > When a node starts up, Cassandra rebuilds the secondary index of the stored > rows. To perform a hot rebuild of a secondary index, use the nodetool utility > rebuild_index command. > > > We'll look further into Solr but at the moment it may not fit our > need/schedule. > > > - Will that result in Cassandra creating 18 new column families, > > one for each index? > Inserts will be slower, as each insert will potentially result in 18 > additional > inserts. This is just the same as a RDBMS, more indexes == more insert work. > > > - If a given column is not specified in any rows, will Cassandra > > still create an index column family? > Yes > > > - The documentation says that indexes are rebuilt with every > > Cassandra restart. Why is that needed? What does the rebuild do? Does it > > read the whole column family into memory at once? > That is not correct, do you have a link for the docs ? > > As Moshe said, standard cassandra i not a great fit for faceting. Consider > Solr > or Data Stax > http://3.datastax.com/datastax-enterprise.php > > > Cheers > > ----------------- > Aaron Morton > Freelance Cassandra Consultant > New Zealand > > @aaronmorton > > http://www.thelastpickle.com > > > On 17/03/2013, at 10:17 PM, > moshe.kr...@barclays.com > wrote: > > > I do not think this is a good use case for Cassandra alone, assuming the > > queries can be any combination of the 18 columns. > > I would consider using some combination of Cassandra and Solr, where Solr > > provides the indexing/search, and Cassandra provides the bulk store. > > > > From: Andy Stec [ > mailto:andys...@gmail.com > ] > > Sent: Saturday, March 16, 2013 12:10 AM > > To: > user@cassandra.apache.org > > > Subject: Secondary Indexes > > > > We need to provide search capability based on a field that is a bitmap > > combination of 18 possible values. We want to use secondary indexes to > > improve performance. One possible solution is to create a named column for > > each value and have a secondary index for each of the 18 columns. > > Questions we have are: > > > > > > - Will that result in Cassandra creating 18 new column families, > > one for each index? > > > > - If a given column is not specified in any rows, will Cassandra > > still create an index column family? > > > > - The documentation says that indexes are rebuilt with every > > Cassandra restart. Why is that needed? What does the rebuild do? Does it > > read the whole column family into memory at once? > > > > > > > > _______________________________________________ > > > > This message may contain information that is confidential or privileged. 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