Couchbase API数据访问Guide

jieforest

WRITING AND UPDATING DATA

Add Operations

The add method adds a value to the database with the specified key, but will fail (Couchbase::Error::KeyExists) if the key already exists in the database.

1. client.add(key, value, options = {})
   
2. client.add[key, options = {}] = value

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Replace Operations

The replace method will replace an existing key with a new value but will fail (Couchbase::Error::NotFound) if the key does not exist in the database.

1. client.replace(key, value, options = {})
   
2. client.replace[key, options = {}] = value

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jieforest

Set Operations

The set method stores a value to the database with a specified key, overwriting existing content if it exists (see add/replace above).

1. client.set(key, value, options = {})
   
2. client.set[key, options = {}] = value

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options:

1. :ttl     [Fixnum, Integer] Time to Live in seconds [optional]
   
2. :flags   [Fixnum] Flags that you want to store/retrieve [optional]
   
3. :cas     [Fixnum] Optimistic locking for update control, must match the document cas in Couchbase to succeed
   
4. :format  [:document, :plain, :marshal] Explicit format setting, :plain for strings, :document for Hash(JSON), :marshal to use Marshal. load and Marshal.dump; format is :document by default
   

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Asynchronous Store Example (Block)

1. client.run do
   
2.   client.add(“foo” => “val1”, “bar” => “val2”) do |ret|
   
3.     ret.operation #=> :add
   
4.     ret.success? #=> true
   
5.     ret.keys #=> “foo”, “bar” in separate calls
   
6.     ret.cas
   
7.     ret.flags
   
8.   end
   
9. end

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jieforest

READING DATA

The Get method is versatile, allowing for both optimistic and pessimistic locking, multiple gets, and hash-like syntax.

Simple Get Operations

1. val = client.get(key, options = {})
   
2. val = client[“key”]
   

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Extended Tuple Get Operations

1. val, flags, cas = client.get(key, :extended => true)
   
2. val, flags, cas = client[“key”, :extended => true]
   

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jieforest

Multi-Get Operations

1. val_array = client.get(keys)
   
2. val_hash = client.get(keys, :assemble_hash => true)

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options:

1. :extended     [String, Symbol] Key used to reference the value
   
2. :quiet        [true, false] Return nil for missing keys default, or false to Return Couchbase::Error::KeyNotFound for missing key
   
3. :ttl          [Fixnum, Integer] Get and Touch, :ttl will also reset the TTL at the same time as the get (seconds)
   
4. :lock         Lock the document, true to use default lock timeout, or integer for number of seconds to lock
   
5. :format       [:document, :plain, :marshal] Explicit format setting, :plain for strings, :document for Hash(JSON), :marshal to use Marshal.load and Marshal.dump
   
6. :assemble_hash [true, false] For Multi-Get, will return a Hash keyed on the document keys instead of default of array

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jieforest

GETTING STATS FROM COUCHBASE

Obtain stats from all servers for the connection (bucket)

1. client.stats
   
2. client.stats[“stats”]

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To fetch memory stats

1. client.stats(:memory)

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Parameters:

1. stat        Individual stat string (i.e. "curr_items")

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rocyang

mark

jieforest

DELETING AND UPDATING DATA

To delete keys/values

1. client.delete(key)

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Atomic Counter Operations

Atomic Counters are only atomic per cluster, but are useful for many different patterns and numeric data. They are unsigned positive integers.

You cannot use atomic operations on floats or objects or arrays.

1. client.incr(key, delta, options = {})
   
2. client.decr(key, delta, options = {})

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jieforest

options:

1. delta            [Fixnum] Amount to incr/decr, default is 1, can be up to 64 bits
   
2. :create         [true, false] If set to true, if key doesn’t exist, initializes to zero but doesn’t increment, can be combined with :initial
   
3. :initial           [Fixnum, Unsigned Integer] Sets initial value if key doesn’t exist, doesn’t increment the initial value!
   
4. :extended    [true, false] Returns [value, cas] tuple instead of just value
   
5. :ttl                [Fixnum, Integer] Sets TTL, doesn’t alter existing TTL, will only be applied to a new item created via :create and/or :initial
   

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Touch Operations

Reset the TTL expiration on one or more keys explicitly with the touch command, can also be done with a get command.

1. client.touch(key, ttl)
   
2. client.touch({“key1”=> ttl1, “key2” => ttl2})

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jieforest

Durability Requirements

Observe the state of the keys on all the nodes or using :replicated and ersisted it allows to set up the waiting rule.

1. client.observe(*keys, options = {})
   
2. client.observe_and_wait(*keys, options = {})
   

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Non-JSON Operations

For non-json values, prepend and append can concatenate to existing values accordingly. Defaults tolain format for encoder/decoder.

1. client.prepend(key, value)
   
2. client.append(key, value)

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jieforest

QUERYING DATA

With Couchbase Server 2.0, you can create Indexes through Map/Reduce functions. http://www.couchbase.com/docs/co ... ouchbase-views.html

Create Design Doc Object

Refer to the design_doc by name, the Views are an array of view names, as well as functions defined by name.

1. ddoc = client.design_docs[‘design_doc_name’]
   
2. ddoc.views #=> [‘view_name’, ‘view_name_2’, …]
   

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Use dot notation for accessing the view by your defined view name and pass in options for query parameters:

1. ddoc.view_name(params = {}).each do |doc|
   
2. # do stuff with docs
   
3. end

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