Understanding MapR DB Binary Table

                                                  Understanding MapR DB  Binary Table

• A Table - an infinitely large key/value space composed of tablets ( In above diagram table spans from 1-100 key range ). Table data is organized into rows and columns and columns are organized into column families ( CF's ).
  
  
  
  
  
• A Tablet/Region -  4-6GB of data that represents a particular key range. Table comprises of many tablets ( Tablet 1 {key 1~50} and Tablet 2 {key 50~100} ).
  
  
  
  
  
• Partition - It is a mini tablet of up to about 2 GB (partition split in two at 2GB) with zero or one active buckets ( Tablet 1 => Partition 1 [Key 1~25] + Partition 2 [Key 25~50])
• an active bucket is accepting puts
• a second bucket might be flushing (or not exist)
  
  
• Bucket -  It is a file that holds incoming writes unordered up to about 150MB. The keys are kept in in-memory index. If we run low on cache space this will force a bucket flush.
  
  
• Segment - Collection of read only spill files that typically holds 2-4MB of sorted data (just like HBase HFiles) with the row key index at the start of the file
• all of the values for a given row are stored together
• all of the versions for the values are also stored together
  

  

• Spill file - a file that contains sorted additions (called spills) to the corresponding segment. The first spill file can be thought of as a “the initial segment.”
• a segment has no more than 6 spills
• We consider the segment to be composed of the spills so really the first spill is the initial segment data.

  
  

  From Segment we get Spill Map:

  [root@node9 ~]# maprcli debugdb  dump -fid 2182.34.131316 -json

  {

  "timestamp":1489941805408,

  "timeofday":"2017-03-19 09:43:25.408 GMT-0700",

  "status":"OK",

  "total":1,

  "data":[

  {

  "key":"",

  "value":{

  "fid":"<parentCID>.35.131318"

  }

  }

  ]

  }

  
  

  From Spill Map we get Spill (keys)

  
  

  [root@node9 ~]# maprcli debugdb  dump -fid 2182.35.131318 -json

  {

  "timestamp":1489941819033,

  "timeofday":"2017-03-19 09:43:39.033 GMT-0700",

  "status":"OK",

  "total":3,

  "data":[

  {

  "key":0,

  "numRemoteBlocks":0,

  "numSpills":0,

  "numSegments":0,

  "value":{

  "fid":"<parentCID>.36.131320",

  "smeSize":51,

  "keyIdxOffset":12,

  "keyIdxLength":57,

  "ldbIdxLength":20,

  "bloomBitsPerKey":8000,

  "numLogicalBlocks":2,

  "numPhysicalBlocks":5,

  "numRows":1,

  "numRowsWithDelete":0,

  "families":{

  "id":1,

  "offset":524288,

  "length":43,

  "minTimeStamp":1489471080975,

  "maxTimeStamp":1489471080975

  }

  }

  },

  {

  "key":1,

  "numRemoteBlocks":0,

  "numSpills":0,

  "numSegments":0,

  "value":{

  "fid":"<parentCID>.38.131324",

  "smeSize":51,

  "keyIdxOffset":12,

  "keyIdxLength":57,

  "ldbIdxLength":20,

  "bloomBitsPerKey":8000,

  "numLogicalBlocks":2,

  "numPhysicalBlocks":5,

  "numRows":1,

  "numRowsWithDelete":0,

  "families":{

  "id":1,

  "offset":524288,

  "length":43,

  "minTimeStamp":1489471253234,

  "maxTimeStamp":1489471253234

  }

  }

  },

  {

  "key":2,

  "numRemoteBlocks":0,

  "numSpills":0,

  "numSegments":0,

  "value":{

  "fid":"<parentCID>.38.131324",

  "smeSize":52,

  "keyIdxOffset":8204,

  "keyIdxLength":57,

  "ldbIdxLength":20,

  "bloomBitsPerKey":8000,

  "numLogicalBlocks":2,

  "numPhysicalBlocks":5,

  "numRows":1,

  "numRowsWithDelete":0,

  "families":{

  "id":1,

  "offset":589824,

  "length":43,

  "minTimeStamp":1489471657238,

  "maxTimeStamp":1489471657238

  }

  }

  }

  ]

  }