Provide framework for generic lazily evaluated operation results #1350

RobinTF · 2024-05-18T00:32:19Z

Still WIP. Currently missing:

Discussion about remaining TODOs
Lots of unit tests
Also most likely some functions need to be broken up into smaller pieces once we found everything else to be working "correctly".
Documentation of all newly introduced functions once they're becoming somewhat "final"
Cold Fusion & World domination?

src/engine/Operation.cpp

RobinTF · 2024-05-18T00:36:16Z

src/engine/Operation.cpp

+ result._resultPointer->resultTable()->idTable().numColumns();
+ LOG(DEBUG) << "Computed result of size " << resultNumRows << " x "
+ << resultNumCols << std::endl;
+ }


Does this debug message provide any real benefit to make it worth somehow incorporating it into lazily evaluated operations?

codecov · 2024-05-18T00:56:07Z

Codecov Report

Attention: Patch coverage is 78.61446% with 142 lines in your changes missing coverage. Please review.

Project coverage is 89.35%. Comparing base (3fad814) to head (603a48b).

Files	Patch %	Lines
src/engine/Result.cpp	71.09%	67 Missing and 7 partials ⚠️
src/engine/Operation.cpp	79.62%	18 Missing and 4 partials ⚠️
src/util/CacheableGenerator.h	87.40%	0 Missing and 17 partials ⚠️
src/engine/IndexScan.cpp	5.88%	15 Missing and 1 partial ⚠️
src/util/Cache.h	84.84%	0 Missing and 5 partials ⚠️
src/engine/ExportQueryExecutionTrees.cpp	93.33%	0 Missing and 3 partials ⚠️
src/util/ConcurrentCache.h	70.00%	0 Missing and 3 partials ⚠️
src/engine/QueryExecutionTree.cpp	87.50%	0 Missing and 1 partial ⚠️
src/util/IteratorWrapper.h	88.88%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1350      +/-   ##
==========================================
- Coverage   89.63%   89.35%   -0.29%     
==========================================
  Files         343      345       +2     
  Lines       29951    30472     +521     
  Branches     3315     3393      +78     
==========================================
+ Hits        26847    27227     +380     
- Misses       1957     2063     +106     
- Partials     1147     1182      +35

☔ View full report in Codecov by Sentry.
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@hannahbast

This PR contains all the changes from the infrastructure for lazy operation evaluation (#1350) that are simple and repetitive, but touch many files. In particular: * Rename the `ResultTable` class to `Result` (a TODO suggested by @hannahbast some time ago). * Add a new parameter `bool requestLaziness` to `Operation::computeResult`. This parameter is currently unused.

src/engine/Operation.cpp

RobinTF · 2024-07-11T17:02:50Z

src/engine/Operation.cpp

 updateRuntimeInformationOnSuccess(
- *resultAndCacheStatus._resultPointer->resultTable(),
+ // TODO<RobinTF> find a better representation for "unknown" than 0.


This concept doesn't 100% make sense for lazy evaluation. We could of course provide a lower bound for qlever-ui to display by adding this to the onSizeChanged listener or something

For now this is not the primary concern:)

src/engine/QueryExecutionContext.h

RobinTF · 2024-07-11T17:07:13Z

src/util/ConcurrentCache.h

@@ -38,6 +37,8 @@ class WaitedForResultWhichThenFailedException : public std::exception {
 enum struct CacheStatus {
 cachedNotPinned,
 cachedPinned,
+ // TODO<RobinTF> Rename to notCached, the name is just confusing. Can
+ // potentially be merged with notInCacheAndNotComputed.


Task for a follow-up PR

joka921

A first round of comments.
I haven't looked at the whole caching stuff yet.

src/util/IteratorWrapper.h

src/util/CacheableGenerator.h

joka921 · 2024-07-22T15:21:27Z

src/util/CacheableGenerator.h

+ return;
+ }
+ if (masterState_ == MasterIteratorState::MASTER_STARTED && !isMaster) {
+ conditionVariable_.wait(lock, [this, index]() {


You should implement a time limit here, especially if you synchronously block a thread here.
We need to handle the case of slow masters. I still think that the easiest way to do this is that also the master can receive a IteratorExpired because there is no conceptual difference between a master and a non-master.

I agree on the time limit, but as I told you in person the master/slave system does have some benefits so having only slaves pass a time limit would be an option, but this might be a task for a follow-up PR.

I still think that the non-master approach + everybody having a timeout is better. We can probably dispute this further, the current state (forever blocking until the slow master times out) is a blocker for this PR.

src/util/CacheableGenerator.h

joka921 · 2024-07-22T15:37:46Z

src/engine/Result.h

+ sortedBy_{std::move(sortedBy)},
+ localVocab_{std::move(localVocab)} {}
+
+ bool isDataEvaluated() const noexcept {


isn't this rather isMaterialized as opposed to isLazy?

The name can be changed to everything you want once everything else is settled

src/engine/Operation.cpp

joka921 · 2024-07-22T15:59:59Z

src/engine/Operation.cpp

 updateRuntimeInformationOnSuccess(
- *resultAndCacheStatus._resultPointer->resultTable(),
+ // TODO<RobinTF> find a better representation for "unknown" than 0.


For now this is not the primary concern:)

…t-table

joka921

Some small comments.

joka921 · 2024-08-02T11:37:33Z

src/util/Cache.h

+ if (_maxSizeSingleEntry < newSize ||
+ _maxSize - std::min(_totalSizePinned, _maxSize) < newSize) {


This I don't understand/believe:

why not

sizeDiff = newSize - oldSize; // check for underflow... if (totalSizePinnedPlusNonPinnedEverything + sizeDiff > _maxSize) erase(key); ```. (+ The `_maxSizeSingleEntry` check of course, that one is undisputed.

Because _maxSize is of type MemorySize which will throw an exception instead of becoming a negative size value. I remember fiddling around with this a lot until it worked and this is what my changes converged to. I must admit that I don't know anymore why I settled on these exact changes.

src/util/Cache.h

joka921 · 2024-08-02T11:47:18Z

src/util/CacheableGenerator.h

+ return;
+ }
+ if (masterState_ == MasterIteratorState::MASTER_STARTED && !isMaster) {
+ conditionVariable_.wait(lock, [this, index]() {


I still think that the non-master approach + everybody having a timeout is better. We can probably dispute this further, the current state (forever blocking until the slow master times out) is a blocker for this PR.

…t-table

sonarcloud · 2024-08-02T18:29:36Z

Quality Gate passed

Issues
21 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

…tead of `Result` (#1433) This is a small preparation for lazy operations (see #1350)

RobinTF commented May 18, 2024

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RobinTF commented May 18, 2024

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RobinTF mentioned this pull request May 21, 2024

Refactoring preliminaries for lazy operations (Part 1) #1352

Merged

RobinTF added 25 commits May 23, 2024 16:26

Rename ResultTable -> Result

80667bd

Wrap idTable in variant

31b2c11

Add ability to create Result from generator

4d0204c

Start fixing caching issues

515ed0c

Avoid another class of exceptions

ca1cbed

Optimize imports

9e7f3cb

Introduce ReusableGenerator class

4c75d42

Try to make caching work

892e4a5

Fiddle around with const a bit

586365c

Add more TODOs

80e2dbd

Fix TextLimit code after rebase

18ca5b1

Fix compilation issues for ReusableGenerator

86a9f4b

Remove offset calculations from exporter

7f0a5e7

Fix typo

aee20dd

Add comments

7576b2e

Make supportsLimit private to avoid misuse

7765a25

Properly use minimum limit if present

f815be8

Start adding code to manipulate code after cache extraction

90cca50

Implement fallback mechanism for failed cache share

694c21f

Fix accidental edit of Usage.md

ea8b81f

Consume result as master

50e4529

Add proper condition variables

16eedd8

Implement code that allows for proper recomputation of cache size

bf8f085

Refactor a bit

771eb5b

Aggregate tables at the end of lazy results

8aa9060

Clarify currently buggy behaviour

27e451e

RobinTF commented Jul 11, 2024

View reviewed changes

src/engine/Operation.cpp Outdated Show resolved Hide resolved

RobinTF commented Jul 11, 2024

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src/engine/QueryExecutionContext.h Outdated Show resolved Hide resolved

RobinTF commented Jul 11, 2024

View reviewed changes

Fix macOS build

96982aa

joka921 reviewed Jul 22, 2024

View reviewed changes

Merge remote-tracking branch 'ad-freiburg/master' into refactor-resul…

58a193d

…t-table

RobinTF mentioned this pull request Jul 23, 2024

Refactoring preliminaries for lazy operations (Part 2) #1413

Merged

RobinTF added 13 commits July 24, 2024 13:10

Merge remote-tracking branch 'ad-freiburg/master' into refactor-resul…

93a71cc

…t-table

Fix wrong merge conflict resolution

9c07e4f

Use #pragma once

1da9b17

Simplify caching structure to fix bugs

c6aa641

Merge remote-tracking branch 'ad-freiburg/master' into refactor-resul…

838a97e

…t-table

Fix size calculation

d74b89d

Remove complicated atomic mutex check mechanism

bfc9d8f

Merge remote-tracking branch 'ad-freiburg/master' into refactor-resul…

592c670

…t-table

Avoid copy

564d54b

Use timer class to simplify calls

d566d5b

Start adding some documentation

a164ef4

Merge remote-tracking branch 'ad-freiburg/master' into refactor-resul…

f9f22f4

…t-table

Unlock before notifying

23713cc

joka921 reviewed Aug 2, 2024

View reviewed changes

RobinTF added 2 commits August 2, 2024 18:25

Merge remote-tracking branch 'ad-freiburg/master' into refactor-resul…

c56dd82

…t-table

Adjust Cache to simplify code a bit

603a48b

This was referenced Aug 2, 2024

Refactor ConstructExportContext to use IdTable and LocalVocab instead of Result #1433

Merged

Allow cache to manage entries of varying size #1434

Open

Add helper types for #1350 #1435

Open

joka921 pushed a commit that referenced this pull request Aug 2, 2024

Refactor ConstructExportContext to use IdTable and LocalVocab ins…

76bb412

…tead of `Result` (#1433) This is a small preparation for lazy operations (see #1350)

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Provide framework for generic lazily evaluated operation results #1350

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sonarcloud bot commented Aug 2, 2024

		if (_maxSizeSingleEntry < newSize \|\|
		_maxSize - std::min(_totalSizePinned, _maxSize) < newSize) {

Provide framework for generic lazily evaluated operation results #1350

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Provide framework for generic lazily evaluated operation results #1350

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sonarcloud bot commented Aug 2, 2024

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