Refresh cagg uses min value for dimension when start_time is NULL #7546
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When the refresh_continuous_aggregate window's start is NULL, use the min value in the hypertable to determine the beginning of the range instead of the min value for the partition column.
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Additional details and impacted files@@ Coverage Diff @@
## main #7546 +/- ##
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+ Coverage 80.06% 82.15% +2.09%
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Files 190 230 +40
Lines 37181 43360 +6179
Branches 9450 10912 +1462
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+ Hits 29770 35624 +5854
- Misses 2997 3412 +415
+ Partials 4414 4324 -90 ☔ View full report in Codecov by Sentry. |
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The description of the PR explains what is done, but it is more important why it is done. In particular:
The old behavior take the minimum value of the type when NULL is provided to create an open-ended range. What is the situation that break prompting you to do this approach instead?
| appendStringInfo(command, | ||
| "SELECT pg_catalog.min(%s) FROM %s.%s", | ||
| quote_identifier(NameStr(dim->fd.column_name)), | ||
| quote_identifier(NameStr(ht->fd.schema_name)), | ||
| quote_identifier(NameStr(ht->fd.table_name))); |
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This does a full table scan of the entire hypertable. With a hypertable that is big, this is going to be a significant problem, especially if tiering is involved.
When the refresh_continuous_aggregate window's start is NULL, use the min value in the hypertable to determine the beginning of the range instead of the min value for the partition column.