Summary:
When running tck tests there was a peculiar behavior where sometimes some queries worked, and sometimes they failed. Nothing was failing when memgraph was restarted between each query (scenario) - which points to MATCH DETACH DELETE not working correctly.
What was happening is the following: some transaction would update the record in version list and set it's expiry to it's id. Along with that some transaction would query the mentioned record - and would set the hints flags for that expiration transaction status (which was aborted - which is fine at this moment). After some while, because the record is not really deleted because it's not aborted some other transaction would modify it's expiry transaction (this time making the transaction commited), but because the hints flags were not updated - they would still return the status for the old transaction - which was aborted. This made some records available even though they were deleted.
Reviewers: mislav.bradac, florijan, teon.banek, matej.gradicek, buda
Reviewed By: buda
Subscribers: buda, lion, pullbot
Differential Revision: https://phabricator.memgraph.io/D370
Summary:
Gradicek's Mvcc test have seen the following changes:
- provided a test infrastructure (fixture and macros) to facilitate testing and increase readability
- split tests into multi-transaction update, VersionList::find and general Mvcc testing
- multi-transaction update tests have been refactored (i *think* nothing got deleted, but it was a mess so I don't guarantee)
- changed all multithreaded tests to be single-threaded because multiple threads were not necessary
- changed transaction naming from T5, T8, T10 to T1, T2... for consistency with actual transaction indices
What still needs to be done:
- Gleich and Gradicek need to review the infrastructure (possible improvements)
- multi-transaction update tests need to be addressed by Gradicek (see "TODO gradicek" in code, discuss with Flor)
- the wiki/draw.io documentation needs to be updated. it is not imperative that all the tests be drawn in draw.io, only the general infrastructure explained. perhaps only a few examples drawn. Gradicek discuss with Flor
- Gleich see the "TODO Gleich" lines in the diff and discuss with flor
Suggested workflow:
- review this diff, hopefully land (before resolving all the TODOs)
- discard D169
- Gradicek and Gleich address the TODOs
- Flor reviews the results (in following diffs)
Reviewers: dgleich, matej.gradicek, buda
Reviewed By: matej.gradicek, buda
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D348
Summary: Changing mvcc again. This should be double-checked since it's quite a substantial change. The test here tests for the new behaviour - which should be correct.
Reviewers: matej.gradicek, dtomicevic, buda
Reviewed By: matej.gradicek, buda
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D156
