schemachanger: enable reverting failed schema change jobs #61466
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This PR prevents new-style schema changes from running concurrently with any other schema changes, in two ways: 1. If there are mutations in progress (from either new or old schema changes) when attempting to plan a new-style schema change, we wait and poll until there are no mutations, and then restart the transaction. 2. If we try to write an old-style schema change job while there is a new-style schema change on the table, which is detected via a new field on the table descriptor for the new-style schema change job ID, an error is returned. This effectively prevents all schema changes, even the ones without mutations. Most of this commit consists of testing. Testing knobs for the new schema changer are introduced. We also now accumulate the statements involved in the schema change, as strings, in the schema changer state in `extraTxnState`. The executor now takes an argument to inject more relevant state into the testing knobs, including the aforementioned statements. Release justification: Non-production code change (the new schema changer is disabled for 21.1) Release note: None
Release justification: Non-production code change (the schema changer is not enabled by default for 21.1). Release note: None
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I think the code changes are pretty simple, but the main thing this is missing is testing. It'd be nice to have some data-driven/declarative planning tests for the stages generated when reverting a schema change, with DDL statements as the input. But it's not clear what the best way would be to specify in the test input the exact stage at which we'd want to stop and revert. Maybe we could specify the number of stages to run. |
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First commit is #61042.