jihoonson

Latency Comparison Numbers (~2012)
----------------------------------
L1 cache reference                           0.5 ns
Branch mispredict                            5   ns
L2 cache reference                           7   ns                      14x L1 cache
Mutex lock/unlock                           25   ns
Main memory reference                      100   ns                      20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy             3,000   ns        3 us
Send 1K bytes over 1 Gbps network       10,000   ns       10 us
Read 4K randomly from SSD*             150,000   ns      150 us          ~1GB/sec SSD

jihoonson

Anchors in Markdown

To create an anchor to a heading in github flavored markdown. Add - characters between each word in the heading and wrap the value in parens (#some-markdown-heading) so your link should look like so:

[create an anchor](#anchors-in-markdown)

jihoonson

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Build from Source

You can build Druid directly from source. Please note that these instructions are for building the latest stable of Druid. For building the latest code in master, follow the instructions here.

jihoonson

#!/bin/bash -eux

#
# Backports patches from master to a release branch.
#
# Usage:
#  export GIT_TOKEN=...
#  druid-backport [branch] [pr-number], like: "druid-backport 0.12.1 5706"
#
# Bugs:

jihoonson

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groupBy Queries

These types of queries take a groupBy query object and return an array of JSON objects where each object represents a grouping asked for by the query.

Note: If you are doing aggregations with time as your only grouping, or an ordered groupBy over a single dimension,

jihoonson

{
  "queryType": "groupBy",
  "dataSource": "tpch_lineitem_1g",
  "granularity": {
    "period": "P1D",
    "timeZone": "CET",
    "type": "period"
  },
  "aggregations": [
    { "type": "count", "name": "countSum", "fieldName": "count" }

jihoonson

{
  "type" : "index_hadoop",
  "spec" : {
    "ioConfig" : {
      "type" : "hadoop",
      "inputSpec" : {
        "type" : "static",
        "paths" : "/tpch/1g/lineitem/lineitem.tbl"
      }
    },