druid/docs/content/DimensionSpecs.md

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DimensionSpec

DimensionSpecs define how dimension values get transformed prior to aggregation.

DefaultDimensionSpec

Returns dimension values as is and optionally renames renames the dimension.

{ "type" : "default", "dimension" : <dimension>, "outputName": <output_name> }

ExtractionDimensionSpec

Returns dimension values transformed using the given DimExtractionFn

{
  "type" : "extraction",
  "dimension" : <dimension>,
  "outputName" :  <output_name>,
  "dimExtractionFn" : <dim_extraction_fn>
}

DimExtractionFn

DimExtractionFns define the transformation applied to each dimenion value

RegexDimExtractionFn

Returns the first group matched by the given regular expression. If there is no match it returns the dimension value as is.

{ "type" : "regex", "expr", <regular_expression> }

PartialDimExtractionFn

Returns the dimension value as is if there is a match, otherwise returns null.

{ "type" : "partial", "expr", <regular_expression> }

SearchQuerySpecDimExtractionFn

Returns the dimension value as is if the given SearchQuerySpec matches, otherwise returns null.

{ "type" : "searchQuery", "query" : <search_query_spec> }

TimeDimExtractionFn

Parses dimension values as timestamps using the given input format, and returns them formatted using the given output format. Time formats follow the com.ibm.icu.text.SimpleDateFormat format

{ "type" : "time", "timeFormat" : <input_format>, "resultFormat" : <output_format> }

JavascriptDimExtractionFn

Returns the dimension value as transformed by the given JavaScript function.

Example

{
  "type" : "javascript",
  "function" : "function(str) { return str.substr(0, 3); }"
}