Expression variables are calculated too often #60112
Comments
Joonalai
added
the
Bug
We already have set the layer scope for ALL layer types in the map renderer job preparation, so there's no need to add another layer scope in the vector layer renderer Refs qgis#60112
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This is possibly caused by a plugin or some other local configuration issue -- on my testing I only see this method called twice per layer per map draw (or once after #60367 is merged) |
We already have set the layer scope for ALL layer types in the map renderer job preparation, so there's no need to add another layer scope in the vector layer renderer Refs #60112
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I tried with your changes with newest master (9f7f9d7). I added the log line and with single GPKG layer and now there is still 41 calls for a single polygon memory layer after doing the steps in the issue.
I am using clean profile with no plugins or other configuration and I develop QGIS through Distrobox using official qgis3-build-deps image as a base image, so I think there should not be anything in my configuration causing this. Version information<style type="text/css"> p, li { white-space: pre-wrap; } </style>
Libraries Active Python plugins |
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@Joonalai I can't explain that -- maybe try a debug build and set a breakpoint and see what's calling it |
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Here is a callers.log that contains call stacks for each call. I used this code to get these: Codevoid logCallStack() {
const int maxFrames = 50;
void* framePointers[maxFrames];
// Capture stack frames
int frameCount = backtrace(framePointers, maxFrames);
// Transform frame addresses into readable symbols
char** symbolList = backtrace_symbols(framePointers, frameCount);
std::cerr << "Call stack:\n";
for (int i = 0; i < frameCount; i++) {
std::string symbol = symbolList[i]; // Convert to a std::string for manipulation
// Extract between the parentheses (demangling happens here)
size_t begin = symbol.find('(');
size_t plus = symbol.find('+', begin);
if (begin != std::string::npos && plus != std::string::npos) {
std::string mangledName = symbol.substr(begin + 1, plus - begin - 1); // Extract mangled name
int status;
char* demangledName = abi::__cxa_demangle(mangledName.c_str(), nullptr, nullptr, &status);
if (status == 0 && demangledName != nullptr) {
if (*demangledName != '\0') // Ensure the demangled name is not empty
std::cerr << " " << demangledName << std::endl; // Print demangled name
} else {
if (!mangledName.empty()) // Ensure the mangled name is not empty
std::cerr << " " << mangledName << std::endl; // If demangling fails, print mangled name
}
std::free(demangledName); // Free memory allocated by __cxa_demangle
}
}
std::free(symbolList); // Cleanup
} |
What is the bug or the crash?
When trying to figure out why QGIS gets frozen and really slow with more than 200 layers, I noticed expression variables are calculated really often.
Steps to reproduce the issue
To reproduce the issue it's easiest to add log line to
QgsExpressionContextUtils::layerScopemethod and then do following steps:These simple steps produce 85 lines for memory polygon layer, 123 lines for gpkg polygon layer and 226 lines for PostGIS layer.
Versions
Version details
<style type="text/css"> p, li { white-space: pre-wrap; } </style>Libraries
Qt version
5.15.13
Python version
3.12.3
GDAL/OGR version
3.8.4
PROJ version
9.4.0
EPSG Registry database version
v11.004 (2024-02-24)
GEOS version
3.12.1-CAPI-1.18.1
SQLite version
3.45.1
PostgreSQL client version
16.6 (Ubuntu 16.6-0ubuntu0.24.04.1)
SpatiaLite version
5.1.0
QWT version
6.1.4
QScintilla2 version
2.14.1
OS version
Ubuntu 24.04.1 LTS
Active Python plugins
db_manager
0.1.20
MetaSearch
0.3.6
processing
2.12.99
grassprovider
2.12.99
Supported QGIS version
New profile
Additional context
Maybe some kind of caching should be used to limit amount of times variables are calculated?
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