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postgresql/src/test/isolation/expected/read-write-unique-3.out

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Detect SSI conflicts before reporting constraint violations While prior to this patch the user-visible effect on the database of any set of successfully committed serializable transactions was always consistent with some one-at-a-time order of execution of those transactions, the presence of declarative constraints could allow errors to occur which were not possible in any such ordering, and developers had no good workarounds to prevent user-facing errors where they were not necessary or desired. This patch adds a check for serialization failure ahead of duplicate key checking so that if a developer explicitly (redundantly) checks for the pre-existing value they will get the desired serialization failure where the problem is caused by a concurrent serializable transaction; otherwise they will get a duplicate key error. While it would be better if the reads performed by the constraints could count as part of the work of the transaction for serialization failure checking, and we will hopefully get there some day, this patch allows a clean and reliable way for developers to work around the issue. In many cases existing code will already be doing the right thing for this to "just work". Author: Thomas Munro, with minor editing of docs by me Reviewed-by: Marko Tiikkaja, Kevin Grittner
2016-04-07 18:12:35 +02:00
Parsed test spec with 2 sessions
starting permutation: rw1 rw2 c1 c2
step rw1: SELECT insert_unique(1, '1');
Improve display of query results in isolation tests. Previously, isolationtester displayed SQL query results using some ad-hoc code that clearly hadn't had much effort expended on it. Field values longer than 14 characters weren't separated from the next field, and usually caused misalignment of the columns too. Also there was no visual separation of a query's result from subsequent isolationtester output. This made test result files confusing and hard to read. To improve matters, let's use libpq's PQprint() function. Although that's long since unused by psql, it's still plenty good enough for the purpose here. Like 741d7f104, back-patch to all supported branches, so that this isn't a stumbling block for back-patching isolation test changes. Discussion: https://postgr.es/m/582362.1623798221@sss.pgh.pa.us
2021-06-23 17:12:31 +02:00
insert_unique
-------------
(1 row)
Detect SSI conflicts before reporting constraint violations While prior to this patch the user-visible effect on the database of any set of successfully committed serializable transactions was always consistent with some one-at-a-time order of execution of those transactions, the presence of declarative constraints could allow errors to occur which were not possible in any such ordering, and developers had no good workarounds to prevent user-facing errors where they were not necessary or desired. This patch adds a check for serialization failure ahead of duplicate key checking so that if a developer explicitly (redundantly) checks for the pre-existing value they will get the desired serialization failure where the problem is caused by a concurrent serializable transaction; otherwise they will get a duplicate key error. While it would be better if the reads performed by the constraints could count as part of the work of the transaction for serialization failure checking, and we will hopefully get there some day, this patch allows a clean and reliable way for developers to work around the issue. In many cases existing code will already be doing the right thing for this to "just work". Author: Thomas Munro, with minor editing of docs by me Reviewed-by: Marko Tiikkaja, Kevin Grittner
2016-04-07 18:12:35 +02:00
step rw2: SELECT insert_unique(1, '2'); <waiting ...>
step c1: COMMIT;
step rw2: <... completed>
Use annotations to reduce instability of isolation-test results. We've long contended with isolation test results that aren't entirely stable. Some test scripts insert long delays to try to force stable results, which is not terribly desirable; but other erratic failure modes remain, causing unrepeatable buildfarm failures. I've spent a fair amount of time trying to solve this by improving the server-side support code, without much success: that way is fundamentally unable to cope with diffs that stem from chance ordering of arrival of messages from different server processes. We can improve matters on the client side, however, by annotating the test scripts themselves to show the desired reporting order of events that might occur in different orders. This patch adds three types of annotations to deal with (a) test steps that might or might not complete their waits before the isolationtester can see them waiting; (b) test steps in different sessions that can legitimately complete in either order; and (c) NOTIFY messages that might arrive before or after the completion of a step in another session. We might need more annotation types later, but this seems to be enough to deal with the instabilities we've seen in the buildfarm. It also lets us get rid of all the long delays that were previously used, cutting more than a minute off the runtime of the isolation tests. Back-patch to all supported branches, because the buildfarm instabilities affect all the branches, and because it seems desirable to keep isolationtester's capabilities the same across all branches to simplify possible future back-patching of tests. Discussion: https://postgr.es/m/327948.1623725828@sss.pgh.pa.us
2021-06-23 03:43:12 +02:00
ERROR: could not serialize access due to read/write dependencies among transactions
Detect SSI conflicts before reporting constraint violations While prior to this patch the user-visible effect on the database of any set of successfully committed serializable transactions was always consistent with some one-at-a-time order of execution of those transactions, the presence of declarative constraints could allow errors to occur which were not possible in any such ordering, and developers had no good workarounds to prevent user-facing errors where they were not necessary or desired. This patch adds a check for serialization failure ahead of duplicate key checking so that if a developer explicitly (redundantly) checks for the pre-existing value they will get the desired serialization failure where the problem is caused by a concurrent serializable transaction; otherwise they will get a duplicate key error. While it would be better if the reads performed by the constraints could count as part of the work of the transaction for serialization failure checking, and we will hopefully get there some day, this patch allows a clean and reliable way for developers to work around the issue. In many cases existing code will already be doing the right thing for this to "just work". Author: Thomas Munro, with minor editing of docs by me Reviewed-by: Marko Tiikkaja, Kevin Grittner
2016-04-07 18:12:35 +02:00
step c2: COMMIT;