Search queries
- Implementation details
  - Strategies
Server configuration
Query context
SearchQuerySpec

Search queries

info

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:

property	description	required?
queryType	This String should always be “search”; this is the first thing Apache Druid looks at to figure out how to interpret the query.	yes
dataSource	A String or Object defining the data source to query, very similar to a table in a relational database. See DataSource for more information.	yes
granularity	Defines the granularity of the query. See Granularities.	no (default to `all`)
filter	See Filters.	no
limit	Defines the maximum number per Historical process (parsed as int) of search results to return.	no (default to 1000)
intervals	A JSON Object representing ISO-8601 Intervals. This defines the time ranges to run the query over.	yes
searchDimensions	The dimensions to run the search over. Excluding this means the search is run over all dimensions.	no
virtualColumns	A JSON list of virtual columns available to use in `searchDimensions`.	no (default none)
query	See SearchQuerySpec.	yes
sort	An 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
context	See Context	no

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.

Server configuration

The following runtime properties apply:

Property	Description	Default
`druid.query.search.searchStrategy`	Default search query strategy.	useIndexes

Query context

The following query context parameters apply:

Property	Description
`searchStrategy`	Overrides 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 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"
}