vtlim commented on code in PR #15670: URL: https://github.com/apache/druid/pull/15670#discussion_r1470082875
########## docs/querying/sql-aggregations.md: ########## @@ -87,9 +87,9 @@ In the aggregation functions supported by Druid, only `COUNT`, `ARRAY_AGG`, and |`STDDEV_SAMP(expr)`|Computes standard deviation sample of `expr`. See [stats extension](../development/extensions-core/stats.md) documentation for additional details.|`null` or `0` if `druid.generic.useDefaultValueForNull=true` (legacy mode)| |`STDDEV(expr)`|Computes standard deviation sample of `expr`. See [stats extension](../development/extensions-core/stats.md) documentation for additional details.|`null` or `0` if `druid.generic.useDefaultValueForNull=true` (legacy mode)| |`EARLIEST(expr, [maxBytesPerValue])`|Returns the earliest value of `expr`.<br />If `expr` comes from a relation with a timestamp column (like `__time` in a Druid datasource), the "earliest" is taken from the row with the overall earliest non-null value of the timestamp column.<br />If the earliest non-null value of the timestamp column appears in multiple rows, the `expr` may be taken from any of those rows. If `expr` does not come from a relation with a timestamp, then it is simply the first value encountered.<br /><br />If `expr` is a string or complex type `maxBytesPerValue` amount of space is allocated for the aggregation. Strings longer than this limit are truncated. The `maxBytesPerValue` parameter should be set as low as possible, since high values will lead to wasted memory.<br/>If `maxBytesPerValue`is omitted; it defaults to `1024`. |`null` or `0`/`''` if `druid.generic.useDefaultValueForNull=true` (legacy mode)| -|`EARLIEST_BY(expr, timestampExpr, [maxBytesPerValue])`|Returns the earliest value of `expr`.<br />The earliest value of `expr` is taken from the row with the overall earliest non-null value of `timestampExpr`. <br />If the earliest non-null value of `timestampExpr` appears in multiple rows, the `expr` may be taken from any of those rows.<br /><br />If `expr` is a string or complex type `maxBytesPerValue` amount of space is allocated for the aggregation. Strings longer than this limit are truncated. The `maxBytesPerValue` parameter should be set as low as possible, since high values will lead to wasted memory.<br/>If `maxBytesPerValue`is omitted; it defaults to `1024`. |`null` or `0`/`''` if `druid.generic.useDefaultValueForNull=true` (legacy mode)| +|`EARLIEST_BY(expr, timestampExpr, [maxBytesPerValue])`|Returns the earliest value of `expr`.<br />The earliest value of `expr` is taken from the row with the overall earliest non-null value of `timestampExpr`. <br />If the earliest non-null value of `timestampExpr` appears in multiple rows, the `expr` may be taken from any of those rows.<br /><br />If `expr` is a string or complex type `maxBytesPerValue` amount of space is allocated for the aggregation. Strings longer than this limit are truncated. The `maxBytesPerValue` parameter should be set as low as possible, since high values will lead to wasted memory.<br/>If `maxBytesPerValue`is omitted; it defaults to `1024`. It cannot be used with the rollup tables created with any variant of the EARLIEST/LATEST/EARLIEST_BY/LATEST_BY aggregator since the intermediate type will already contain the timestamp and the one passed explicitly will get ignored by the native engine. USE `EARLIEST` in such scenario. |`null` or `0`/`''` if `druid.g eneric.useDefaultValueForNull=true` (legacy mode)| Review Comment: Suggesting rephrasing the new additions as follows: ``` <br /<br />Use `EARLIEST` instead of `EARLIEST_BY` on a table that has rollup enabled and was created with any variant of `EARLIEST`, `LATEST`, `EARLIEST_BY`, or `LATEST_BY`. In these cases, the intermediate type already stores the timestamp, and Druid ignores the value passed in `timestampExpr`. ``` * Is the behavior different between the native engine and multi-stage query engine? If yes, we should mention what MSQ does. If not, we can remove "by the native engine" from this description. * If Druid ignores the explicitly set timestamp, is EARLIEST_BY equivalent to using EARLIEST, or would it fail? -- 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]
