dongyifeng b06ac54a5e add PrefixFilteredDimensionSpec for multi-value dimensions (#6307)
* add PrefixFilteredDimensionSpec for multi-value dimensions

* add docs for PrefixFilteredDimensionSpec

* remove unnecessary null handling

* add null check to the result of NullHandling
2018-10-12 17:51:09 -07:00
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2018-09-10 09:33:29 -07:00