Edit

Search queries

Apache Druid supports two query languages: Druid SQL and native queries. This document describes a query type that is only available in the native language.

A search query returns dimension values that match the search specification.

{
  "queryType": "search",
  "dataSource": "sample_datasource",
  "granularity": "day",
  "searchDimensions": [
    "dim1",
    "dim2"
  ],
  "query": {
    "type": "insensitive_contains",
    "value": "Ke"
  },
  "sort" : {
    "type": "lexicographic"
  },
  "intervals": [
    "2013-01-01T00:00:00.000/2013-01-03T00:00:00.000"
  ]
}

There are several main parts to a search query:

propertydescriptionrequired?
queryTypeThis String should always be "search"; this is the first thing Apache Druid looks at to figure out how to interpret the query.yes
dataSourceA String or Object defining the data source to query, very similar to a table in a relational database. See DataSource for more information.yes
granularityDefines the granularity of the query. See Granularities.yes
filterSee Filters.no
limitDefines the maximum number per Historical process (parsed as int) of search results to return.no (default to 1000)
intervalsA JSON Object representing ISO-8601 Intervals. This defines the time ranges to run the query over.yes
searchDimensionsThe dimensions to run the search over. Excluding this means the search is run over all dimensions.no
querySee SearchQuerySpec.yes
sortAn object specifying how the results of the search should be sorted.
Possible types are "lexicographic" (the default sort), "alphanumeric", "strlen", and "numeric".
See Sorting Orders for more details.		no
contextSee Contextno

The format of the result is:

[
  {
    "timestamp": "2013-01-01T00:00:00.000Z",
    "result": [
      {
        "dimension": "dim1",
        "value": "Ke$ha",
        "count": 3
      },
      {
        "dimension": "dim2",
        "value": "Ke$haForPresident",
        "count": 1
      }
    ]
  },
  {
    "timestamp": "2013-01-02T00:00:00.000Z",
    "result": [
      {
        "dimension": "dim1",
        "value": "SomethingThatContainsKe",
        "count": 1
      },
      {
        "dimension": "dim2",
        "value": "SomethingElseThatContainsKe",
        "count": 2
      }
    ]
  }
]

Implementation details

Strategies

Search queries can be executed using two different strategies. The default strategy is determined by the "druid.query.search.searchStrategy" runtime property on the Broker. This can be overridden using "searchStrategy" in the query context. If neither the context field nor the property is set, the "useIndexes" strategy will be used.

  • "useIndexes" strategy, the default, first categorizes search dimensions into two groups according to their support for bitmap indexes. And then, it applies index-only and cursor-based execution plans to the group of dimensions supporting bitmaps and others, respectively. The index-only plan uses only indexes for search query processing. For each dimension, it reads the bitmap index for each dimension value, evaluates the search predicate, and finally checks the time interval and filter predicates. For the cursor-based execution plan, please refer to the "cursorOnly" strategy. The index-only plan shows low performance for the search dimensions of large cardinality which means most values of search dimensions are unique.

  • "cursorOnly" strategy generates a cursor-based execution plan. This plan creates a cursor which reads a row from a queryableIndexSegment, and then evaluates search predicates. If some filters support bitmap indexes, the cursor can read only the rows which satisfy those filters, thereby saving I/O cost. However, it might be slow with filters of low selectivity.

  • "auto" strategy uses a cost-based planner for choosing an optimal search strategy. It estimates the cost of index-only and cursor-based execution plans, and chooses the optimal one. Currently, it is not enabled by default due to the overhead of cost estimation.

Server configuration

The following runtime properties apply:

PropertyDescriptionDefault
druid.query.search.searchStrategyDefault search query strategy.useIndexes

Query context

The following query context parameters apply:

PropertyDescription
searchStrategyOverrides the value of druid.query.search.searchStrategy for this query.

SearchQuerySpec

insensitive_contains

If any part of a dimension value contains the value specified in this search query spec, regardless of case, a "match" occurs. The grammar is:

{
  "type"  : "insensitive_contains",
  "value" : "some_value"
}

fragment

If any part of a dimension value contains all of the values specified in this search query spec, regardless of case by default, a "match" occurs. The grammar is:

{
  "type" : "fragment",
  "case_sensitive" : false,
  "values" : ["fragment1", "fragment2"]
}

contains

If any part of a dimension value contains the value specified in this search query spec, a "match" occurs. The grammar is:

{
  "type"  : "contains",
  "case_sensitive" : true,
  "value" : "some_value"
}

regex

If any part of a dimension value contains the pattern specified in this search query spec, a "match" occurs. The grammar is:

{
  "type"  : "regex",
  "pattern" : "some_pattern"
}
← ScanTimeBoundary →