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Better size estimate for SpatialJoin #1555

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merged 3 commits into from
Oct 18, 2024
Merged

Better size estimate for SpatialJoin #1555

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202e888
better size estimate
Oct 15, 2024
edc01b4
Implement review and fix tests
Oct 17, 2024
fd8f807
Merge branch 'master' of ssh://github.com/ad-freiburg/qlever into spa…
Oct 17, 2024
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9 changes: 9 additions & 0 deletions src/engine/SpatialJoin.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -230,6 +230,15 @@ size_t SpatialJoin::getCostEstimate() {
// ____________________________________________________________________________
uint64_t SpatialJoin::getSizeEstimateBeforeLimit() {
if (childLeft_ && childRight_) {
// If we limit the number of results to k, even in the largest scenario, the
// result can be at most `|childLeft| * k`
auto maxResults = getMaxResults();
if (maxResults.has_value()) {
return childLeft_->getSizeEstimate() * maxResults.value();
}

// If we don't limit the number of results, we cannot draw conclusions about
// the size, other than the worst case `|childLeft| * |childRight|`
return childLeft_->getSizeEstimate() * childRight_->getSizeEstimate();
}
return 1; // dummy return if not both children are added
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