ektravel commented on code in PR #12549: URL: https://github.com/apache/druid/pull/12549#discussion_r1101737118
########## docs/querying/sql-data-types.md: ########## @@ -92,36 +92,39 @@ the `UNNEST` functionality available in some other SQL dialects. Refer to the do > nearly all possible native functionality. ## Arrays -Multi-value dimensions may also be converted to standard SQL arrays, either by explicitly converting them with `MV_TO_ARRAY`, -or implicitly when used within the [array functions](./sql-array-functions.md). `ARRAY` types behave as standard SQL arrays, where -grouping on them will group on the entire array of values instead of the implicit `UNNEST` that occurs when grouping on -multi-value dimensions directly or when used with the multi-value functions. Arrays may also be constructed from multiple -columns using the array functions. +Druid also has support for `ARRAY` types constructed at query time, though currently lacks the ability to store them in +segments. `ARRAY` types behave as standard SQL arrays, where results are grouped by matching entire arrays. This is in +contrast to the implicit `UNNEST` that occurs when grouping on multi-value dimensions directly or when used with the +multi-value functions. You can convert multi-value dimensions to standard SQL arrays either by explicitly converting +them with `MV_TO_ARRAY`, or implicitly when used within the [array functions](./sql-array-functions.md). Arrays may +also be constructed from multiple columns using the array functions. ## Multi-value strings behavior The behavior of Druid [multi-value string dimensions](multi-value-dimensions.md) varies depending on the context of their usage. -When used as `VARCHAR` functions, which are not "aware" that their inputs which claim to be `VARCHAR` might actually have multiple -values such as `CONCAT`, Druid will map the function across all values in the row. If the row is null or empty, the function will -recieve `NULL` as its input, otherwise it will be applied to every row value and continue its life as a multi-value VARCHAR. +When used with standard `VARCHAR` functions which expect a single input value per row, such as `CONCAT`, Druid will map Review Comment: ```suggestion When used with standard `VARCHAR` functions, which expect a single input value per row, Druid maps the function across all values in the row. ``` Do you think we can omit the `CONCAT` example in this case? I think the sentence reads better without it. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
