Introduction to Couchbase for Oracle Developers and Experts: Part 2 - Database Objects

CREATE BUCKET:

You create a bucket either via Couchbase web console or via REST API. In the web console, you provide the information below.

 The user provides the following:
Name of a bucket.
Location of an existing data storage. Couchbase creates a directory with the bucket name underneath the specified directly. In this case, the CUSTOMER directory is created under/my/data. This directory /my/data should exist on every node of the Couchbase cluster with data (key-value) service. This is fixed and unchangeable.
Memory is used in megabytes. This is the fixed amount of memory used to cache the data as you insert/load the data. The actual data in memory depends on your application access pattern. Usual LRU, MRU algorithms are used to determine which documents are kept in memory and which ones are evicted. For additional information on key eviction, see the link:
http://bit.ly/2ngKUZk
Bucket Type
Couchbase: JSON and key-value databases
Memcached: Memcache
Ephemeral: just like the Couchbase bucket, except for all the data, the index is only in memory.
Replica: By default, there is one copy of the data in the cluster. You can have up to three copies of the data within the cluster. Under the CAP theorem rules. There are plenty of papers and talks on CAP theorem and its application to NoSQL databases in the public domain.Couchbase Bucket is a CP system. That means Couchbase chooses consistency over availability (C over A). Supporting partition tolerance is a requirement for these multi-node scale-out systems.
See Couchbase documentation for full details on all the parameters and examples.
http://bit.ly/2GrbMOw

Example document INSERT via N1QL:

CREATE SCOPE mybucket.myscope;

CREATE COLLECTION mybucket.myscope.mycustomers

INSERT INTO mybucket.myscope.mycustomers
VALUES("CX:3424", {
"Name": "Jane Smith",
"DOB": "1990-01-30",
"Billing": [
{

      "type": "visa",
"cardnum": "5827-2842-2847-3909",
"expiry": "2019-03"
},
{
"type": "master",
"cardnum": "6274-2842-2847-3909",
"expiry": "2019-03"
}
],
"Connections": [
{
"CustId": "XYZ987",
"Name": "Joe Smith"
},
{
"CustId": "PQR823",
"Name": "Dylan Smith"
},
{
"CustId": "PQR823",
"Name": "Dylan Smith"
}
],
"Purchases": [
{
"id": 12,
"item": "mac",
"amt": 2823.52
},
{
"id": 19,
"item": "ipad2",
"amt": 623.52
}
]
});

The INSERT statement looks similar to Oracle's INSERT statement except you specify the data in a slightly different way: You specify the document key and give the whole JSON document to insert.  The table is automatically sharded (uses consistent hash partitioning) -- nothing for the user to do. 

Couchbase SDKs also provide a simpler way to INSERT, UPDATE, UPSERT individual documents directly in each of the SDKs.  Here's the Java SDK example.

Example: 

{“fullname”: “Joe Smith”}
{“name: { “fname”:”Joe”, “lname”:”Smith”}
{“hobbies”: [“lego”,”robotics”, “ski”]}

In these documents, “name” is a key, also known as an attribute. Its value can be scalar (full name) or an object (name) or array (hobbies).

In Oracle, when you create the table, you specify column names and their data types.

In Couchbase, you simply insert JSON documents.  Each document self-describes the attribute (column) names. This gives you the flexibility to evolve the schema without having to lockdown the table. The data types are simply interpreted from the value itself: String, number, null, true, false, object or an array.

• 
  
• Primary Index
• Named primary index
• Secondary index
• Composite Secondary Index
• Functional index
• Array Index
• ALL array
• ALL DISTINCT array
• Partial Index
• Adaptive Index
• Duplicate Indices
• Covering Index
• Flex indexes