release-21.1: sql: Repartition tables before dropping regions #65896
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Previously we could get into a situation where on dropping a region, concurrent queries on REGIONAL BY ROW tables could fail. This was due to the fact that when resolving the partition tuple in the optimizer, we'd encounter a partition without a corresponding enum value. This issue was timing dependant, and would only be hit if the query had a leased type descriptor from after the drop region, along with a table descriptor from before the drop region. To get around this problem, we introduce a new transaction to the drop region schema changer which performs a pre-drop action of repartitioning all REGIONAL BY ROW tables, and updating their leases. This ensures that the table descriptors will be seen _before_ the modified type descriptors. Of note is the fact that this is only required on drop region. In the add region case, having this mismatch occur and seeing an extra region (with no corresponding partition) is not a problem for the query engine. Release note (sql change): Fix a bug where queries on REGIONAL BY ROW tables could fail in the brief window in which a DROP REGION operation is in progress.
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arulajmani
approved these changes
May 31, 2021
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Backport 1/1 commits from #64273.
/cc @cockroachdb/release
Previously we could get into a situation where on dropping a region,
concurrent queries on REGIONAL BY ROW tables could fail. This was due to
the fact that when resolving the partition tuple in the optimizer, we'd
encounter a partition without a corresponding enum value. This issue was
timing dependant, and would only be hit if the query had a leased type
descriptor from after the drop region, along with a table descriptor
from before the drop region.
To get around this problem, we introduce a new transaction to the drop
region schema changer which performs a pre-drop action of repartitioning
all REGIONAL BY ROW tables, and updating their leases. This ensures that
the table descriptors will be seen before the modified type
descriptors.
Of note is the fact that this is only required on drop region. In the
add region case, having this mismatch occur and seeing an extra region
(with no corresponding partition) is not a problem for the query engine.
Release note (sql change): Fix a bug where queries on REGIONAL BY ROW tables
could fail in the brief window in which a DROP REGION operation is in
progress.
Resolves: #64223