mirror of https://github.com/apache/druid.git
77 lines
1.9 KiB
Markdown
77 lines
1.9 KiB
Markdown
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---
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layout: doc_page
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---
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## DimensionSpec
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`DimensionSpec`s define how dimension values get transformed prior to aggregation.
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### DefaultDimensionSpec
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Returns dimension values as is and optionally renames renames the dimension.
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```json
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{ "type" : "default", "dimension" : <dimension>, "outputName": <output_name> }
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```
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### ExtractionDimensionSpec
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Returns dimension values transformed using the given [DimExtractionFn](#toc_3)
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```json
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{
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"type" : "extraction",
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"dimension" : <dimension>,
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"outputName" : <output_name>,
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"dimExtractionFn" : <dim_extraction_fn>
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}
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```
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## DimExtractionFn
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`DimExtractionFn`s define the transformation applied to each dimenion value
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### RegexDimExtractionFn
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Returns the first group matched by the given regular expression. If there is no match it returns the dimension value as is.
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```json
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{ "type" : "regex", "expr", <regular_expression> }
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```
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### PartialDimExtractionFn
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Returns the dimension value as is if there is a match, otherwise returns null.
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```json
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{ "type" : "partial", "expr", <regular_expression> }
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```
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### SearchQuerySpecDimExtractionFn
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Returns the dimension value as is if the given [SearchQuerySpec](SearchQuerySpec.html) matches, otherwise returns null.
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```json
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{ "type" : "searchQuery", "query" : <search_query_spec> }
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```
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### TimeDimExtractionFn
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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](http://icu-project.org/apiref/icu4j/com/ibm/icu/text/SimpleDateFormat.html) format
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```json
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{ "type" : "time", "timeFormat" : <input_format>, "resultFormat" : <output_format> }
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```
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### JavascriptDimExtractionFn
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Returns the dimension value as transformed by the given JavaScript function.
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Example
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```json
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{
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"type" : "javascript",
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"function" : "function(str) { return str.substr(0, 3); }"
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}
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