For example , If I create a simple user CF and I try to insert a new row, how can I add an increment key in MySQL?
I have seen many examples, you only need to replace the username with a unique ID, but what if I want users to have duplicate usernames?
In addition, how can I understand that cassandra does not support the> operator, so something like select *something from the user> something2 does not work.
Probably the most important question Is it grouping? Do I need to retrieve all the data and then filter it in any language I use? I think this will slow down my system.
So basically I need some short instructions on how to start Cassanda.
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Key:
>They are used in Cassandra as the unit of the distribution ring. So your key will be taken Be clear, and assign an “owner” in the ring. Use RandomPartitioner to ensure even distribution
>Assuming you use RandomPartitioner (you should), the keys are not sorted. This means you can’t ask for a series of keys. However, you It is possible to request a list of keys in a single query. The
> keys are relevant in some models but not in others. If your model needs to be queried one by one, you can use any unique value known to the application (e.g. UUID). Sometimes the key is a sentinel value, such as the Unix epoch that represents the beginning of the day. This allows Cassandra to give a bunch of known keys to some known keys, and then arrange a series of data by column (see below).
About query predicates:
>You can get a correctly modeled data range to answer your query.
>Since the columns are written in sorted order, you can use slices Query (which is very fast) to query the range from column A to column n. You can also abstract this mechanism using compound columns.
>You can use secondary indexes on columns with lower cardinality – this will provide a value-by-value query Function.
>You can create your own index, where the data is sorted the way you need.
About grouping:
I think you mean creating aggregations. If you If you need real-time data, you will need to use some external mechanisms (such as Storm) to track the data and continuously update the related aggregates into CF. If you are creating aggregates as part of the batch process, Cassandra has excellent integration with Hadoop. Lets you directly use your language to write map/reduction assignments in Pig, Hive.
I am trying to understand Cassandra and how to build my column family (CF), but Because I am used to the relational number According to the database, it is difficult.
For example, if I create a simple user CF and I try to insert a new row, how can I add an increment key in MySQL?
I have seen many examples, you only need to replace the username with a unique ID, but what if I want users to have duplicate usernames?
In addition, how can I understand that cassandra does not support the> operator, so something like select *something from the user> something2 does not work.
Probably the most important question Is it grouping? Do I need to retrieve all the data and then filter it in any language I use? I think this will slow down my system.
So basically I need some short instructions on how to start Cassanda.
Your The problem is quite common, but let me stab me. First, you need to model the data based on the query. With RDBMS, you can model the data in some normalized form and then optimize for specific queries. You can’t use Cassandra like this Do you have to write the data the way you intend to read it. Usually this means more than just writing one way. Generally speaking, if you want to work effectively with Cassandra, this helps to completely get rid of your RDBMS thinking .
Key:
>They are used in Cassandra as the unit of the distribution ring. So your key will be figured out and an “owner” will be assigned in the ring Use RandomPartitioner to ensure even distribution
>Assuming you use RandomPartitioner (you should), the keys are not sorted. This means you can’t ask for a series of keys. However, you can request a list of keys in a single query.
> The >> key is related in some models but not in others. If your model needs to be queried one by one, you can use any unique value known to the application (e.g. UUID). Sometimes the key is a sentinel value, e.g. for one day The beginning of the Unix epoch. This allows Cassandra to give a bunch of known keys to some known keys, and then arrange a series of data through columns (see below).
About query predicates:< /p>
>You can get a correctly modeled data range to answer your query.
>Since the columns are written in sorted order, you can use a slice query (which is very fast) to query from column A to The range of column n. You can also use compound columns to abstract this mechanism.
>You can use secondary indexes on columns with lower cardinality – this will provide a value-by-value query function.
>You can create your own index , Where the data is sorted the way you need it.
About grouping:
I think you mean creating aggregates. If you need real-time data, you will need to use some external mechanisms (Such as Storm) to track data and constantly update related aggregates into CF. If you are creating aggregates as part of the batch process, Cassandra has excellent integration with Hadoop, allowing you to directly use your language in Pig, Hive Write map/reduce operations.
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