Gian Merlino 6edee7f434 Expressions work better with strings. (#4394) ... * Expressions work better with strings. - ExpressionObjectSelector able to read from string columns, and able to return strings. - ExpressionVirtualColumn able to offer string (and long for that matter) as its native type. - ExpressionPostAggregator able to return strings. - groupBy, topN: Allow post-aggregators to accept dimensions as inputs, making ExpressionPostAggregator more useful. - topN: Use DimExtractionTopNAlgorithm for STRING columns that do not have dictionaries, allowing it to work with STRING-type expression virtual columns. - Adjusts null handling to better match the rest of Druid: null and empty string treated the same; nulls implicitly treated as zeroes in numeric context. * Code review comments. * More code review. * Fix test. * Adjust annotations.		2017-06-14 14:50:18 -07:00
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src	Expressions work better with strings. (#4394)	2017-06-14 14:50:18 -07:00
pom.xml	Make @Override annotation obligatory (#4274)	2017-05-16 13:30:30 -05:00