So, returning to MySQL for a moment, a query (without a WHERE clause), selects the fields to be returned the query output, and constructs a list of matching rows in the output. So, looking at an SQL statement:
When running a query on MySQL, the MySQL server takes the information in the table or tables, and then constructs the list of records (and corresponding fields) to be returned, like this:
On Couchbase, Views construct a list of records from the individual document information, creating an index as a side effect of that process. The result is a list of all the documents generated by the view.
In Couchbase, the generated view is your table, and when you query the view, Couchbase uses the key values (and the associated index that was generated), with the query values that you specify filtering out the returned information to generate the final list of matching records.
This method of specifying the tables that you want to query enables you to simplify and optimize the way you extract information from the database. But it also means you need to give some more thought to how you want to query the information.
Next Time
Now you know how MySQL stores and queries information, and how that knowledge that can be translated when you migrate information to Couchbase Server 2.0. Next time, we’ll start building some queries based on what we’ve learned, and start looking at more advanced queries and the migration process.
楼主: jieforest
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发表于 2013-2-14 05:57
