flatten-sstabledump

flatten-sstabledump is a utility that unwraps Apache Cassandra's sstabledump JSON array output to multiple small JSON objects, one per partition row. Partition metadata is inlined into each row (key: partition). This utility allows you to easily use map/reduce jobs (such as Apache Hive, AWS Athena, Google BigQuery etc.) to process sstables.

The utility parses the JSON in a streaming fashion using very little memory.

Installation

Install by issuing:

$ go get github.com/tink-ab/flatten-sstabledump

Testing

There are some basic tests using Bats. Execute them by issuing:

$ bats test.bats

Usage

$ cat testdata/testdata1.json
[
  {
    "partition" : {
      "key" : [ "d7f50415-3c9e-4a84-bdf2-54cbcbb0df0b", "201806" ],
      "position" : 0
    },
    "rows" : [
      {
        "type" : "row",
        "position" : 408,
        "clustering" : [ "35136e4c-ffa2-4205-82c1-7ce63d2519b9" ],
        "liveness_info" : { "tstamp" : "2018-06-19T11:20:49.363Z" },
        "cells" : [
          { "name" : "accountid", "value" : "457f21b5-69c0-48bc-bffa-037d88c8ecf8" }
        ]
      },
      {
        "type" : "row",
        "position" : 408,
        "clustering" : [ "203b5189-d9e1-4db7-b00c-c1b759790b8f" ],
        "liveness_info" : { "tstamp" : "2018-06-18T11:20:49.363Z" },
        "cells" : [
          { "name" : "accountid", "value" : "ee312163-75bf-4df5-94de-f34146efa502" }
        ]
      }
    ]
  },
  {
    "partition" : {
      "key" : [ "70c2ca4a-84f5-4cc2-b44a-e2f92b4888fb", "201806" ],
      "position" : 0
    },
    "rows" : [
      {
        "type" : "row",
        "position" : 408,
        "clustering" : [ "e1e6fbe4-4ec4-498d-b892-c00f7667bbc8" ],
        "liveness_info" : { "tstamp" : "2018-08-18T11:20:49.363Z" },
        "cells" : [
          { "name" : "accountid", "value" : "501cde77-cf60-468e-954f-e987e7490d4c" }
        ]
      }
    ]
  }
]
$ cat testdata/testdata1.json | fss
{"cells":[{"name":"accountid","value":"ee312163-75bf-4df5-94de-f34146efa502"}],"clustering":["203b5189-d9e1-4db7-b00c-c1b759790b8f"],"liveness_info":{"tstamp":"2018-06-18T11:20:49.363Z"},"partition":{"partition":{"key":["d7f50415-3c9e-4a84-bdf2-54cbcbb0df0b","201806"],"position":0}},"position":408,"type":"row"}
{"cells":[{"name":"accountid","value":"457f21b5-69c0-48bc-bffa-037d88c8ecf8"}],"clustering":["35136e4c-ffa2-4205-82c1-7ce63d2519b9"],"liveness_info":{"tstamp":"2018-06-19T11:20:49.363Z"},"partition":{"partition":{"key":["d7f50415-3c9e-4a84-bdf2-54cbcbb0df0b","201806"],"position":0}},"position":408,"type":"row"}
{"cells":[{"name":"accountid","value":"501cde77-cf60-468e-954f-e987e7490d4c"}],"clustering":["e1e6fbe4-4ec4-498d-b892-c00f7667bbc8"],"liveness_info":{"tstamp":"2018-08-18T11:20:49.363Z"},"partition":{"partition":{"key":["70c2ca4a-84f5-4cc2-b44a-e2f92b4888fb","201806"],"position":0}},"position":408,"type":"row"}

FAQ

Can't you use AWS Athena to simply process raw sstabledump JSON output?

No. AWS Athena requires every JSON entity to be line-delimited. sstabledump outputs its JSON in multiline JSON. Compacting using something like jq -c . doesn't work because AWS Athena requires the JSON root object to be a JSON object, not array.

Using jq -c .[] would work in theory. However, it reads up the entire JSON content into memory which doesn't scale for larger SSTables. Furthermore, if you have large partitions, each row will be huge and require a lot of memory in the mapper.

Won't the output from ffs be huge?

Yes. :-) That's why you want to compress its output. Or, even better, convert it to compressed Avro, ORC or Parquet.

What is the format of these JSON objects?

Have a look at these two links (which also describes tombstones):

• http://thelastpickle.com/blog/2016/07/27/about-deletes-and-tombstones.html
• http://www.beyondthelines.net/databases/cassandra-tombstones/