Re: Perform streaming logical transactions by background workers and parallel apply
Dilip Kumar <dilipbalaut@gmail.com>
On Wed, Jan 4, 2023 at 4:25 PM houzj.fnst@fujitsu.com <houzj.fnst@fujitsu.com> wrote: > > Attach the new patch set. > Apart from addressing Sawada-San's comments, I also did some other minor > changes in the patch: I have done a high-level review of 0001, and later I will do a detailed review of this while reading through the patch I think some of the comments need some changes.. 1. + The deadlock can happen in + * the following ways: + * + * 4) Lock types + * + * Both the stream lock and the transaction lock mentioned above are + * session-level locks because both locks could be acquired outside the + * transaction, and the stream lock in the leader needs to persist across + * transaction boundaries i.e. until the end of the streaming transaction. I think the Lock types should not be listed with the number 4). Because point number 1,2 and 3 are explaining the way how deadlocks can happen but 4) doesn't fall under that category. 2. + * Since the database structure (schema of subscription tables, constraints, + * etc.) of the publisher and subscriber could be different, applying + * transactions in parallel mode on the subscriber side can cause some + * deadlocks that do not occur on the publisher side. I think this paragraph needs to be rephrased a bit. It is saying that some deadlock can occur on subscribers which did not occur on the publisher. I think what it should be conveying is that the deadlock can occur due to concurrently applying the conflicting/dependent transactions which are not conflicting/dependent on the publisher due to <explain reason>. Because if we create the same schema on the publisher it might not have ended up in a deadlock instead it would have been executed in sequence (due to lock waiting). So the main point we are conveying is that the transaction which was independent of each other on the publisher could be dependent on the subscriber and they can end up in deadlock due to parallel apply. -- Regards, Dilip Kumar EnterpriseDB: http://www.enterprisedb.com
Commits
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the thread's linked commits as JSON, with link sources.
API reference →
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Fix invalid memory access during the shutdown of the parallel apply worker.
- 3d144c6c8602 16.0 landed
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Fix assertion failure in apply worker.
- de63f8dadee4 16.0 landed
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Use elog to report unexpected action in handle_streamed_transaction().
- 781ac42d43ab 16.0 landed
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Use appropriate wait event when sending data in the apply worker.
- d9d7fe68d35e 16.0 landed
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Allow the logical_replication_mode to be used on the subscriber.
- 9f2213a7c575 16.0 landed
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Rename GUC logical_decoding_mode to logical_replication_mode.
- 1e8b61735cfb 16.0 landed
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Display the leader apply worker's PID for parallel apply workers.
- d540a02a724b 16.0 landed
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Improve the code to decide and process the apply action.
- c981d9145dea 16.0 landed
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Document the newly added wait events added by commit 216a784829.
- cd06ccd78fcf 16.0 landed
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Perform apply of large transactions by parallel workers.
- 216a784829c2 16.0 landed
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Wake up a subscription's replication worker processes after DDL.
- c6e1f62e2cee 16.0 cited
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Add copyright notices to meson files
- 8284cf5f746f 16.0 cited
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Better document logical replication parameters
- a8500750ca0a 16.0 cited
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Add a common function to generate the origin name.
- 776e1c8a5d14 16.0 cited
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Harmonize parameter names in storage and AM code.
- bfcf1b34805f 16.0 cited
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Avoid using list_length() to test for empty list.
- efd0c16becbf 16.0 cited
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Improve two comments related to a boolean DefElem's value
- 8445f5a21d40 16.0 cited
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Fix partition table's REPLICA IDENTITY checking on the subscriber.
- 26b3455afaa9 15.0 cited
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Fix data inconsistency between publisher and subscriber.
- b7658c24c7c1 15.0 cited
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Fix cache look-up failures while applying changes in logical replication.
- 5a97b1325453 15.0 cited