Summary:
My dear fellow Memgraphians. It's friday afternoon, and I am as ready to pop as WAL is to get reviewed...
What's done:
- Vertices and Edges have global IDs, stored in `VersionList`. Main storage is now a concurrent map ID->vlist_ptr.
- WriteAheadLog class added. It's based around buffering WAL::Op objects (elementraly DB changes) and periodically serializing and flusing them to disk.
- Snapshot recovery refactored, WAL recovery added. Snapshot format changed again to include necessary info.
- Durability testing completely reworked.
What's not done (and should be when we decide how):
- Old WAL file purging.
- Config refactor (naming and organization). Will do when we discuss what we want.
- Changelog and new feature documentation (both depending on the point above).
- Better error handling and recovery feedback. Currently it's all returning bools, which is not fine-grained enough (neither for errors nor partial successes, also EOF is reported as a failure at the moment).
- Moving the implementation of WAL stuff to .cpp where possible.
- Not sure if there are transactions being created outside of `GraphDbAccessor` and it's `BuildIndex`. Need to look into.
- True write-ahead logic (flag controlled): not committing a DB transaction if the WAL has not flushed it's data. We can discuss the gain/effort ratio for this feature.
Reviewers: buda, mislav.bradac, teon.banek, dgleich
Reviewed By: dgleich
Subscribers: mtomic, pullbot
Differential Revision: https://phabricator.memgraph.io/D958
Summary:
Warnings I ignored:
Creates a new stacktrace object and then dumps it
102.570384 (102.495075) E[1]: [src/utils/exceptions.hpp:116]: (performance) Variable 'stacktrace_' is assigned in constructor body. Consider performing initialization in initialization list.
102.570390 (102.495081) E[1]: [src/utils/exceptions.hpp:127]: (performance) Variable 'stacktrace_' is assigned in constructor body. Consider performing initialization in initialization list.
Used all over the codebase without explicit cast
102.570412 (102.495103) E[1]: [src/utils/stacktrace.hpp:14]: (style) Class 'Line' has a constructor with 1 argument that is not explicit.
Not really used anywhere before initialized:
102.570526 (102.495217) E[1]: [src/data_structures/concurrent/skiplist.hpp:467]: (warning) Member variable 'Accessor::preds' is not initialized in the constructor.
102.570530 (102.495221) E[1]: [src/data_structures/concurrent/skiplist.hpp:467]: (warning) Member variable 'Accessor::succs' is not initialized in the constructor.
Implicit conversions between types are used all over the codebase:
102.570548 (102.495239) E[1]: [src/storage/property_value.hpp:41]: (style) Class 'PropertyValue' has a constructor with 1 argument that is not explicit.
102.570552 (102.495243) E[1]: [src/storage/property_value.hpp:42]: (style) Class 'PropertyValue' has a constructor with 1 argument that is not explicit.
102.570557 (102.495248) E[1]: [src/storage/property_value.hpp:43]: (style) Class 'PropertyValue' has a constructor with 1 argument that is not explicit.
102.570561 (102.495252) E[1]: [src/storage/property_value.hpp:44]: (style) Class 'PropertyValue' has a constructor with 1 argument that is not explicit.
102.570566 (102.495257) E[1]: [src/storage/property_value.hpp:47]: (style) Class 'PropertyValue' has a constructor with 1 argument that is not explicit.
102.570570 (102.495261) E[1]: [src/storage/property_value.hpp:50]: (style) Class 'PropertyValue' has a constructor with 1 argument that is not explicit.
102.570578 (102.495269) E[1]: [src/storage/property_value.hpp:53]: (style) Class 'PropertyValue' has a constructor with 1 argument that is not explicit.
102.570582 (102.495273) E[1]: [src/storage/property_value.hpp:57]: (style) Class 'PropertyValue' has a constructor with 1 argument that is not explicit.
102.570591 (102.495282) E[1]: [src/query/typed_value.hpp:80]: (style) Class 'TypedValue' has a constructor with 1 argument that is not explicit.
102.570596 (102.495287) E[1]: [src/query/typed_value.hpp:81]: (style) Class 'TypedValue' has a constructor with 1 argument that is not explicit.
102.570601 (102.495292) E[1]: [src/query/typed_value.hpp:82]: (style) Class 'TypedValue' has a constructor with 1 argument that is not explicit.
102.570605 (102.495296) E[1]: [src/query/typed_value.hpp:83]: (style) Class 'TypedValue' has a constructor with 1 argument that is not explicit.
102.570609 (102.495300) E[1]: [src/query/typed_value.hpp:89]: (style) Class 'TypedValue' has a constructor with 1 argument that is not explicit.
102.570614 (102.495305) E[1]: [src/query/typed_value.hpp:92]: (style) Class 'TypedValue' has a constructor with 1 argument that is not explicit.
102.570618 (102.495309) E[1]: [src/query/typed_value.hpp:95]: (style) Class 'TypedValue' has a constructor with 1 argument that is not explicit.
102.570623 (102.495314) E[1]: [src/query/typed_value.hpp:98]: (style) Class 'TypedValue' has a constructor with 1 argument that is not explicit.
102.570627 (102.495318) E[1]: [src/query/typed_value.hpp:102]: (style) Class 'TypedValue' has a constructor with 1 argument that is not explicit.
102.570632 (102.495323) E[1]: [src/query/typed_value.hpp:105]: (style) Class 'TypedValue' has a constructor with 1 argument that is not explicit.
102.570636 (102.495327) E[1]: [src/query/typed_value.hpp:108]: (style) Class 'TypedValue' has a constructor with 1 argument that is not explicit.
102.570641 (102.495332) E[1]: [src/query/typed_value.hpp:109]: (style) Class 'TypedValue' has a constructor with 1 argument that is not explicit.
102.570645 (102.495336) E[1]: [src/communication/bolt/v1/decoder/decoded_value.hpp:88]: (style) Class 'DecodedValue' has a constructor with 1 argument that is not explicit.
102.570650 (102.495341) E[1]: [src/communication/bolt/v1/decoder/decoded_value.hpp:89]: (style) Class 'DecodedValue' has a constructor with 1 argument that is not explicit.
102.570654 (102.495345) E[1]: [src/communication/bolt/v1/decoder/decoded_value.hpp:90]: (style) Class 'DecodedValue' has a constructor with 1 argument that is not explicit.
102.570659 (102.495350) E[1]: [src/communication/bolt/v1/decoder/decoded_value.hpp:91]: (style) Class 'DecodedValue' has a constructor with 1 argument that is not explicit.
102.570663 (102.495354) E[1]: [src/communication/bolt/v1/decoder/decoded_value.hpp:94]: (style) Class 'DecodedValue' has a constructor with 1 argument that is not explicit.
102.570668 (102.495359) E[1]: [src/communication/bolt/v1/decoder/decoded_value.hpp:97]: (style) Class 'DecodedValue' has a constructor with 1 argument that is not explicit.
102.570672 (102.495363) E[1]: [src/communication/bolt/v1/decoder/decoded_value.hpp:100]: (style) Class 'DecodedValue' has a constructor with 1 argument that is not explicit.
102.570677 (102.495368) E[1]: [src/communication/bolt/v1/decoder/decoded_value.hpp:104]: (style) Class 'DecodedValue' has a constructor with 1 argument that is not explicit.
102.570681 (102.495372) E[1]: [src/communication/bolt/v1/decoder/decoded_value.hpp:107]: (style) Class 'DecodedValue' has a constructor with 1 argument that is not explicit.
102.570690 (102.495381) E[1]: [src/communication/bolt/v1/decoder/decoded_value.hpp:110]: (style) Class 'DecodedValue' has a constructor with 1 argument that is not explicit.
102.570694 (102.495385) E[1]: [src/communication/bolt/v1/decoder/decoded_value.hpp:113]: (style) Class 'DecodedValue' has a constructor with 1 argument that is not explicit.
CypherParser:
102.570767 (102.495458) E[1]: [src/query/frontend/opencypher/generated/CypherParser.h:69]: (style) Class 'CypherParser' has a constructor with 1 argument that is not explicit.
102.570772 (102.495463) E[1]: [src/query/frontend/opencypher/generated/CypherLexer.h:40]: (style) Class 'CypherLexer' has a constructor with 1 argument that is not explicit.
102.570776 (102.495467) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:86]: (style) The scope of the variable '_la' can be reduced.
102.570781 (102.495472) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:311]: (style) The scope of the variable '_la' can be reduced.
102.570785 (102.495476) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:402]: (style) The scope of the variable '_la' can be reduced.
102.570789 (102.495480) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:497]: (style) The scope of the variable '_la' can be reduced.
102.570797 (102.495488) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:778]: (style) The scope of the variable '_la' can be reduced.
102.570802 (102.495493) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:895]: (style) The scope of the variable '_la' can be reduced.
102.570806 (102.495497) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:991]: (style) The scope of the variable '_la' can be reduced.
102.570811 (102.495502) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:1190]: (style) The scope of the variable '_la' can be reduced.
102.570815 (102.495506) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:1274]: (style) The scope of the variable '_la' can be reduced.
102.570820 (102.495511) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:1393]: (style) The scope of the variable '_la' can be reduced.
102.570824 (102.495515) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:1570]: (style) The scope of the variable '_la' can be reduced.
102.570829 (102.495520) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:1695]: (style) The scope of the variable '_la' can be reduced.
102.570834 (102.495525) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:1800]: (style) The scope of the variable '_la' can be reduced.
102.570839 (102.495530) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:1903]: (style) The scope of the variable '_la' can be reduced.
102.570843 (102.495534) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:2019]: (style) The scope of the variable '_la' can be reduced.
102.570848 (102.495539) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:2228]: (style) The scope of the variable '_la' can be reduced.
102.570852 (102.495543) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:2542]: (style) The scope of the variable '_la' can be reduced.
102.570857 (102.495548) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:2797]: (style) The scope of the variable '_la' can be reduced.
102.570861 (102.495552) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:2966]: (style) The scope of the variable '_la' can be reduced.
102.570866 (102.495557) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:3067]: (style) The scope of the variable '_la' can be reduced.
102.570870 (102.495561) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:3289]: (style) The scope of the variable '_la' can be reduced.
102.570875 (102.495566) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:3295]: (style) The scope of the variable 'alt' can be reduced.
102.570879 (102.495570) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:3419]: (style) The scope of the variable '_la' can be reduced.
102.570884 (102.495575) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:3596]: (style) The scope of the variable '_la' can be reduced.
102.570888 (102.495579) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:3688]: (style) The scope of the variable '_la' can be reduced.
102.570893 (102.495584) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:3963]: (style) The scope of the variable '_la' can be reduced.
102.570897 (102.495588) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:4452]: (style) The scope of the variable '_la' can be reduced.
102.570902 (102.495593) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:4586]: (style) The scope of the variable '_la' can be reduced.
102.570906 (102.495597) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:4813]: (style) The scope of the variable '_la' can be reduced.
102.570911 (102.495602) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:4943]: (style) The scope of the variable '_la' can be reduced.
102.570918 (102.495609) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:5026]: (style) The scope of the variable '_la' can be reduced.
102.570923 (102.495614) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:5569]: (style) The scope of the variable '_la' can be reduced.
102.570928 (102.495619) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:5664]: (style) The scope of the variable '_la' can be reduced.
102.570932 (102.495623) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:5755]: (style) The scope of the variable '_la' can be reduced.
102.570937 (102.495628) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:5888]: (style) The scope of the variable '_la' can be reduced.
102.570941 (102.495632) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:6045]: (style) The scope of the variable '_la' can be reduced.
102.570946 (102.495637) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:6142]: (style) The scope of the variable '_la' can be reduced.
102.570950 (102.495641) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:6347]: (style) The scope of the variable '_la' can be reduced.
102.570955 (102.495646) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:6523]: (style) The scope of the variable '_la' can be reduced.
102.570959 (102.495650) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:6614]: (style) The scope of the variable '_la' can be reduced.
102.570964 (102.495655) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:6899]: (style) The scope of the variable '_la' can be reduced.
102.570968 (102.495659) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:6992]: (style) The scope of the variable '_la' can be reduced.
102.570973 (102.495664) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:7147]: (style) The scope of the variable '_la' can be reduced.
102.570977 (102.495668) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:7680]: (style) The scope of the variable '_la' can be reduced.
102.570982 (102.495673) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:7759]: (style) The scope of the variable '_la' can be reduced.
102.570986 (102.495677) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:7938]: (style) The scope of the variable '_la' can be reduced.
102.570991 (102.495682) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:8126]: (style) The scope of the variable '_la' can be reduced.
102.570995 (102.495686) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:8220]: (style) The scope of the variable '_la' can be reduced.
102.571000 (102.495691) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:8313]: (style) The scope of the variable '_la' can be reduced.
102.571004 (102.495695) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:8491]: (style) The scope of the variable '_la' can be reduced.
102.571009 (102.495700) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:8703]: (style) The scope of the variable '_la' can be reduced.
102.571013 (102.495704) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:8783]: (style) The scope of the variable '_la' can be reduced.
102.571018 (102.495709) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:8914]: (style) The scope of the variable '_la' can be reduced.
102.571022 (102.495713) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:9119]: (style) The scope of the variable '_la' can be reduced.
102.571027 (102.495718) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:9220]: (style) The scope of the variable '_la' can be reduced.
102.571034 (102.495725) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:9414]: (style) The scope of the variable '_la' can be reduced.
102.571039 (102.495730) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:9660]: (style) The scope of the variable '_la' can be reduced.
102.571043 (102.495734) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:10008]: (style) The scope of the variable '_la' can be reduced.
102.571048 (102.495739) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:10158]: (style) The scope of the variable '_la' can be reduced.
102.571052 (102.495743) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:10250]: (style) The scope of the variable '_la' can be reduced.
102.571057 (102.495748) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:10370]: (style) The scope of the variable '_la' can be reduced.
102.571061 (102.495752) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:10637]: (style) The scope of the variable '_la' can be reduced.
102.571065 (102.495756) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:10749]: (style) The scope of the variable '_la' can be reduced.
102.571070 (102.495761) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:10815]: (style) The scope of the variable '_la' can be reduced.
102.571075 (102.495766) E[1]: [src/query/frontend/opencypher/generated/CypherParser.cpp:10881]: (style) The scope of the variable '_la' can be reduced.
We know that we represented it correctly in memory:
102.571079 (102.495770) E[1]: [src/communication/bolt/v1/decoder/decoder.hpp:252]: (portability) Casting between integer* and double* which have an incompatible binary data representation.
Cont assigned but not used after:
102.571101 (102.495792) E[1]: [src/query/frontend/ast/ast.hpp:1008]: (style) Variable 'cont' is assigned a value that is never used.
Reviewers: teon.banek, buda, mferencevic
Reviewed By: teon.banek
Subscribers: mferencevic, pullbot
Differential Revision: https://phabricator.memgraph.io/D967
Summary: Locked version. There are some benchmarks, it seems the lock won't be the bottleneck in the WAL (DB ops causing WAL delta insertions into it will be slower, flushing the WAL be slower).
Reviewers: buda, mislav.bradac, dgleich
Reviewed By: mislav.bradac
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D919
Summary: In the current state, it was not possible to iterate, or even access a const map, or const set structure because of an incorrect implementation of "ConstAccessors".
Reviewers: mislav.bradac, teon.banek, buda
Reviewed By: teon.banek, buda
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D902
Summary:
It's purpose is to illustrate that currently expansion from a single node (with a fixed degree) does not execute in consistent time, but the execution time depends on the rest of the graph (that's disconnected). Current benchmark results:
```
florijan@florxps:~/Memgraph/memgraph/build$ ./tests/benchmark/expansion
Run on (8 X 3500 MHz CPU s)
2017-08-17 16:06:30
***WARNING*** CPU scaling is enabled, the benchmark real time measurements may be noisy and will incur extra overhead.
***WARNING*** Library was built as DEBUG. Timings may be affected.
Benchmark Time CPU Iterations
-------------------------------------------------------------------------
ExpansionBenchFixture/Match/1 0 ms 0 ms 4903
ExpansionBenchFixture/Match/1024 0 ms 0 ms 4785
ExpansionBenchFixture/Match/1024k 0 ms 0 ms 4623
ExpansionBenchFixture/Expand/1 9 ms 9 ms 83
ExpansionBenchFixture/Expand/1024 20 ms 20 ms 41
ExpansionBenchFixture/Expand/1024k 3430 ms 3430 ms 1
```
Reviewers: mislav.bradac, buda
Reviewed By: mislav.bradac
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D676
Summary: Fixed bug for SkipList::position_and_count for an item lesser then all skiplist elements.
Reviewers: mislav.bradac
Reviewed By: mislav.bradac
Differential Revision: https://phabricator.memgraph.io/D629
Summary:
- GraphDbAccessor - index range API added
- index api tests refactored
- skiplist minor cleanup.
Reviewers: teon.banek, buda, mislav.bradac
Reviewed By: teon.banek
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D533
Summary:
- added functionality to `GraphDbAccessor` for cardinality estimates
- changed all `GraphDbAccessor::Count...` functions to return `int64_t`
- added the need functionality into `LabelPropertyIndex`
- modified `SkipList::position_and_count` to accept a custom `equals` function. Equality could not be implemented using only the custom `less` because it compares a templated `TItem` with skiplist element type `T`, and is therefore not symetrical.
Reviewers: teon.banek, buda, mislav.bradac
Reviewed By: teon.banek
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D521
Summary:
- refactored so `less` is used instead of `greater`
- added a fuzzy unit test
Reviewers: mislav.bradac, buda, teon.banek
Reviewed By: teon.banek
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D519
Summary: This is the first implementation that seems to work. I am not happy with it's complexity. Might attempt a simpler implementation, at the cost of some performance.
Reviewers: dgleich, buda
Reviewed By: dgleich
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D502
Summary:
PushQueue with concurrent lock-free pushing, and single-threaded deletion. Iteration without modification can also be concurrent. Deletion should NOT be concurrent with iteration and other deletions, but can be concurrent with pushing.
There is no const iteraton at the moment, we can add it when necessary. Also I've not handled std::iterator_traits, might be fun getting into that :D
Reviewers: buda, dgleich, mislav.bradac
Reviewed By: dgleich
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D420
Summary: There was a big performance hit induced when removing consecutive nodes from the concurrent list. The reason why it was happening is that the iterator has a pointer to previous node, and uses that pointer to re-link the whole list after the deletion. That node wasn't alive because it was deleted earlier and was always being updated to the next deleted entry in the list while incrementing the iterator. This behaviour caused find_and_disconnect method to be invoked, which has an O(n) complexity. That made our removal of O(n) entries from the list run in O(n^2) time, which is obviously slow.
Reviewers: buda, mislav.bradac, florijan
Reviewed By: mislav.bradac
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D483
Summary: An unpleasant race-condition detected. Solution proposed. It's not very pretty. Perhaps consider using the ConcurrentPushQueue. Not 100% sure, but it should make the GC code easier to work with.
Reviewers: buda, mislav.bradac, teon.banek, dgleich
Reviewed By: buda
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D469
Summary:
Jenkins would hang at a random time while running all the tests.
The reason for that is a bug in skiplist implementation.
Skiplist method find_or_larger was never ending and would continuously stay in the while loop because the next node (with the queried value) onto which it would try to jump would be marked as deleted and that would stop it from jumping on it, or ending on that node.
Reviewers: buda, teon.banek, mislav.bradac
Reviewed By: buda
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D334
Summary: data_structures moved from src/
Test Plan: manual
Reviewers: sale
Subscribers: buda, sale
Differential Revision: https://memgraph.phacility.com/D14
