[GitHub] [druid] loquisgon commented on a diff in pull request #11550: SQL: Add is_active to sys.segments, update examples and docs.

[GitBox <gi...@apache.org>]

loquisgon commented on code in PR #11550:
URL: https://github.com/apache/druid/pull/11550#discussion_r877379016


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docs/querying/sql.md:
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@@ -1123,20 +1123,23 @@ Segments table provides details on all Druid segments, whether they are publishe
 |version|STRING|Version string (generally an ISO8601 timestamp corresponding to when the segment set was first started). Higher version means the more recently created segment. Version comparing is based on string comparison.|
 |partition_num|LONG|Partition number (an integer, unique within a datasource+interval+version; may not necessarily be contiguous)|
 |num_replicas|LONG|Number of replicas of this segment currently being served|
-|num_rows|LONG|Number of rows in current segment, this value could be null if unknown to Broker at query time|
-|is_published|LONG|Boolean is represented as long type where 1 = true, 0 = false. 1 represents this segment has been published to the metadata store with `used=1`. See the [Architecture page](../design/architecture.md#segment-lifecycle) for more details.|
-|is_available|LONG|Boolean is represented as long type where 1 = true, 0 = false. 1 if this segment is currently being served by any process(Historical or realtime). See the [Architecture page](../design/architecture.md#segment-lifecycle) for more details.|
-|is_realtime|LONG|Boolean is represented as long type where 1 = true, 0 = false. 1 if this segment is _only_ served by realtime tasks, and 0 if any historical process is serving this segment.|
-|is_overshadowed|LONG|Boolean is represented as long type where 1 = true, 0 = false. 1 if this segment is published and is _fully_ overshadowed by some other published segments. Currently, is_overshadowed is always false for unpublished segments, although this may change in the future. You can filter for segments that "should be published" by filtering for `is_published = 1 AND is_overshadowed = 0`. Segments can briefly be both published and overshadowed if they were recently replaced, but have not been unpublished yet. See the [Architecture page](../design/architecture.md#segment-lifecycle) for more details.|
+|num_rows|LONG|Number of rows in this segment. This field is updated in the background and cached on the Broker. It may be null if the Broker has not gathered a row count for this segment yet. It may not match the result of `count(*)` queries on realtime data, because the cached value on the Broker may be out of date, and because different replicas of realtime segments may not be in sync with each other. Once a segment is published, its row count will settle and stop changing.|

Review Comment:
   It is unfortunate that the "we don't know the number of rows yet because we haven't check" state is zero. I rather have it null or some other indications ("?" or "processing"... I know is not easy to find an alternative. But until know I puzzled why there is a lag of time when rows are zero in the web console and suddenly they are not. And this happened when I was working in tombstones because "zero" rows was an indication to me that the segment might be a tombstone until it was not lol....



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