release-20.2: sql: fix or disallow TRUNCATE and concurrent schema changes #63153
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…ma changes Prior to this change, the truncate implementation since 20.2 was totally broken. The code creates new indexes for all existing indexes. It also makes all mutations public. The problem with this is that it makes the mutations public *after* deciding which indexes to clone. Because of this it just makes currently being backfilled or validated indexes public. This leads to inconsistency between the old secondary index and the newly truncated indexes. The code is also problematic in that it does not do anything about the mutation jobs. The code assumes that these jobs will happily continue and detect that they correspond to no mutations and stop doing things as well as clean themselves up. Unfortunately, it seems that these changes can lead to certain failures. For example, new index validation may now fail. Reverting that index build will now also fail because the index is public. This will leave the descriptor in a state where it has an orphaned mutation job. We fix this by only permitting TRUNCATE to run concurrently with mutations we deem safe and then to fix the behavior for those cases. Fixes cockroachdb#62842. Release note (bug fix): Fixed bugs where TRUNCATE concurrent with index construction and other schema changes could result in corruption.
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jordanlewis
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Backport 1/1 commits from #62944.
/cc @cockroachdb/release
Prior to this change, the truncate implementation since 20.2 was totally
broken. The code creates new indexes for all existing indexes. It also
makes all mutations public. The problem with this is that it makes the
mutations public after deciding which indexes to clone. Because of this
it just makes currently being backfilled or validated indexes public. This
leads to inconsistency between the old secondary index and the newly
truncated indexes.
The code is also problematic in that it does not do anything about the mutation
jobs. The code assumes that these jobs will happily continue and detect that
they correspond to no mutations and stop doing things as well as clean
themselves up. Unfortunately, it seems that these changes can lead to certain
failures. For example, new index validation may now fail. Reverting that index
build will now also fail because the index is public. This will leave the
descriptor in a state where it has an orphaned mutation job. We fix this by
only permitting TRUNCATE to run concurrently with mutations we deem safe and
then to fix the behavior for those cases.
Fixes #62842.
Release note (bug fix): Fixed bugs where TRUNCATE concurrent with index
construction and other schema changes could result in corruption.