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get_keys.md

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##Get Keys (getkeys) v2.0

The get keys command is used to fetch all keys from a vbucket.

The request:

  • Can have a key, which will be treated as the start_key.
    • If the key is not specified GET_KEYS will default to returning keys from the default collection
    • If the op is sent on a collection enabled connection, GET_KEYS will work on a per collection basics. This means that if your call GET_KEYS then you may only get keys from one collection at a time. To specify which collection to get keys from, encode the start_key with the collectionID e.g. \bstart_key where the collection id here is 0xb.
  • Can have 4 byte extras (uint32_t), which is treated as max count. The maximum number of keys to return. If this is not specified ep-engine will default to 1000.

The response:

  • Keys are placed in the value section of the response. This is returned in the format of uint32_t which specifies the length of the key in bytes. After this their may be another uint32_t for the next key. This should be repeated to get all the keys returned till the number of bytes observed is equal to total body bytes.

Note that the returned keys are only persisted and committed keys, and as such from a serial sequence of operations, GET_KEYS issued after any write is not guaranteed to include the write as the write may not be persisted before the GET_KEYS.

####Binary Implementation

Get Meta Binary Request

Byte/     0       |       1       |       2       |       3       |
   /              |               |               |               |
  |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
  +---------------+---------------+---------------+---------------+
 0|    0x80       |     0xB8      |     0x00      |     0x09      |
  +---------------+---------------+---------------+---------------+
 4|    0x04       |     0x00      |     0x00      |     0x03      |
  +---------------+---------------+---------------+---------------+
 8|    0x00       |     0x00      |     0x00      |     0x00      |
  +---------------+---------------+---------------+---------------+
12|    0x00       |     0x00      |     0x00      |     0x00      |
  +---------------+---------------+---------------+---------------+
16|    0x00       |     0x00      |     0x00      |     0x00      |
  +---------------+---------------+---------------+---------------+
20|    0x00       |     0x00      |     0x00      |     0x00      |
  +---------------+---------------+---------------+---------------+
24|    0x00       |     0x00      |     0x00      |     0x00      |
  +---------------+---------------+---------------+---------------+
28|    0x0A('s')  |     0x73('t') |     0x74('a') |     0x61('r') |
  +---------------+---------------+---------------+---------------+
32|    0x72('t')  |     0x74('_') |     0x5F('k') |     0x6B('e') |
  +---------------+---------------+---------------+---------------+
36|    0x65('y')  |
  +---------------+

GET_KEYS command
Field        (offset) (value)
Magic        (0)    : 0x80                (Request)
Opcode       (1)    : 0xB8                (Get Keys)
Key length   (2,3)  : 0x0009              (9)
Extra length (4)    : 0x04                (4)
Data type    (5)    : 0x00                (Field not used)
VBucket      (6,7)  : 0x0003              (3)
Total body   (8-11) : 0x00000000          (0)
Opaque       (12-15): 0x00000000          (Field not used)
CAS          (16-23): 0x0000000000000000  (Field not used)
Extras              :
  Count      (24-28): 0x00000002          (2)
Key          (29-38): start_key

Get Keys Binary Response

Byte/     0       |       1       |       2       |       3       |
   /              |               |               |               |
  |0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
  +---------------+---------------+---------------+---------------+
 0|     0x81      |     0xB8      |     0x00      |     0x00      |
  +---------------+---------------+---------------+---------------+
 4|     0x15      |     0x00      |     0x00      |     0x00      |
  +---------------+---------------+---------------+---------------+
 8|     0x00      |     0x00      |     0x00      |     0x1E      |
  +---------------+---------------+---------------+---------------+
12|     0x00      |     0x00      |     0x00      |     0x00      |
  +---------------+---------------+---------------+---------------+
16|     0x00      |     0x00      |     0x00      |     0x00      |
  +---------------+---------------+---------------+---------------+
20|     0x00      |     0x00      |     0x00      |     0x00      |
  +---------------+---------------+---------------+---------------+
24|     0x00      |     0x00      |     0x00      |     0x0A      |
  +---------------+---------------+---------------+---------------+
28|     0x00      |    0x0A('s')  |     0x73('t') |     0x74('a') |
  +---------------+---------------+---------------+---------------+
32|     0x61('r') |    0x72('t')  |     0x74('_') |     0x5F('k') |
  +---------------+---------------+---------------+---------------+
36|     0x6B('e') |     0x65('y') |     0x31('1') |     0x00      |
  +---------------+---------------+---------------+---------------+
40|     0x00      |     0x00      |     0x0A      |     0x00      |
  +---------------+---------------+---------------+---------------+
44|    0x0A('s')  |     0x73('t') |     0x74('a') |     0x61('r') |
  +---------------+---------------+---------------+---------------+
48|    0x72('t')  |     0x74('_') |     0x5F('k') |     0x6B('e') |
  +---------------+---------------+---------------+---------------+
52|    0x65('y')  |     0x32('2') |
  +---------------+---------------+

GET_KEYS command
Field        (offset) (value)
Magic        (0)    : 0x81 (Response)
Opcode       (1)    : 0xB8 (Get Keys)
Key length   (2,3)  : 0x0000
Extra length (4)    : 0x00 (0)
Data type    (5)    : 0x00
Status       (6,7)  : 0x0000 (0)
Total body   (8-11) : 0x0000001E (30)
Opaque       (12-15): 0x00000000
CAS          (16-23): 0x0000000000000000 (0) (Field not used)
Extras              : (Field not used)
Key                 : (Field not used)
Value        (24-34): "0x0000000A\0start_string10x0000000A\0start_string2"

###Status

PROTOCOL_BINARY_RESPONSE_SUCCESS (0x00)

The operation succeeded and the result is in the value of the response

PROTOCOL_BINARY_RESPONSE_EINVAL (0x04)

The data in this packet is malformed or incomplete then this error is returned.

PROTOCOL_BINARY_RESPONSE_NOT_MY_VBUCKET (0x07)

The vbucket does not exist.

PROTOCOL_BINARY_RESPONSE_EACCESS (0x24)

The caller lacks the correct privilege to read documents

PROTOCOL_BINARY_RESPONSE_UNKNOWN_COLLECTION (0x88)

The collection of the start_key does not exist or the client does not have access to the collection. Should only be returned on an collection enabled connection.