新版apache druid（0.18） 支持 Joins 及 sql 可以查詢 thetaSketch

apache druid 目前版本迭代非常頻繁，功能也有很大的升級，基本保持着 2個月左右就出現一次版本升級。

關聯查詢一般是nosql數據庫難以實現的功能，但apache druid 最新版本中已經開始 支持 Joins。

支持Joins

-- Joins "sales" with "countries" (using "store" as the join key) to get sales by country.
SELECT
  store_to_country.v AS country,
  SUM(sales.revenue) AS country_revenue
FROM
  sales
  INNER JOIN lookup.store_to_country ON sales.store = store_to_country.k
GROUP BY
  countries.v

語法

<o1> [ INNER | LEFT [OUTER] ] JOIN <o2> ON <condition>

 

{
  "queryType": "scan",
  "dataSource": {
    "type": "union",
    "dataSources": ["<tableDataSourceName1>", "<tableDataSourceName2>", "<tableDataSourceName3>"]
  },
  "columns": ["column1", "column2"],
  "intervals": ["0000/3000"]
}

Sql 支持 thetaSketch

THETA_SKETCH_ESTIMATE(expr)	Returns the distinct count estimate from a theta sketch. expr must return a theta sketch.
THETA_SKETCH_ESTIMATE_WITH_ERROR_BOUNDS(expr, errorBoundsStdDev)	Returns the distinct count estimate and error bounds from a theta sketch. expr must return a theta sketch.
THETA_SKETCH_UNION([size], expr0, expr1, ...)	Returns a union of theta sketches, where each input expression must return a theta sketch. The size can be optionally specified as the first parameter.
THETA_SKETCH_INTERSECT([size], expr0, expr1, ...)	Returns an intersection of theta sketches, where each input expression must return a theta sketch. The size can be optionally specified as the first parameter.
THETA_SKETCH_NOT([size], expr0, expr1, ...)	Returns a set difference of theta sketches, where each input expression must return a theta sketch. The size can be optionally specified as the first parameter.

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