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Reworded the documentation for lastByKeyColumns. #1935

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Reworded the documentation for lastByKeyColumns. #1935

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39ac447
Reworded the documentation for lastByKeyColumns.
jcferretti Feb 4, 2022
5aa9e55
Fixed grammar.
jcferretti Feb 4, 2022
d77b0ac
Fixed typo.
jcferretti Feb 4, 2022
56820e6
Spotlessfy.
jcferretti Feb 4, 2022
c28462b
Small cosmetic javadoc fix.
jcferretti Feb 8, 2022
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10 changes: 7 additions & 3 deletions extensions/kafka/src/main/java/io/deephaven/kafka/KafkaTools.java
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Expand Up @@ -1381,9 +1381,13 @@ private static String[] getColumnNames(
* @param keySpec Conversion specification for Kafka record keys from table column data.
* @param valueSpec Conversion specification for Kafka record values from table column data.
* @param lastByKeyColumns Whether to publish only the last record for each unique key. Ignored when {@code keySpec}
* is {@code IGNORE}. If {@code keySpec != null && !lastByKeyColumns}, it is expected that {@code table} will
* not produce any row shifts; that is, the publisher expects keyed tables to be streams, add-only, or
* aggregated.
* is {@code IGNORE}. If {@code lastByKeyColumns == true}, it is expected that {@code table} is an add-only
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This is backwards. If {@code lastByKeyColumns == true} we will apply the aggregation ourselves, and so none of this wording applies.

* stream, or the result of an aggregation; a general refreshing table where rows can change position in
* arbitrary ways (eg, the result of {@code sort}) is not allowed. In DH engine technical terms, when
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e.g.

* {@code lastByKeyColumns == true} the updates to {@code table} should not produce any row shifts. A table
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There is a debate to be had about whether we actually want to restrict shifts for keyed tables. I remain convinced that the answer is yes. @cpwright should weigh in as well.

* generated from a Kafka stream via {@code consumeToTable} trivially satisfies this constraint. Any
* operations over such a table that do not reorder rows also satisfy the constraint.
*
* @return a callback to stop producing and shut down the associated table listener; note a caller should keep a
* reference to this return value to ensure liveliness.
*/
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