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make use of selectivity estimates in hash, skiplist and persistent indexes (#2703)

This commit is contained in:
Jan 2017-06-30 18:11:58 +02:00 committed by Frank Celler
parent 94b4a9ec4b
commit c7c8910c7c
1 changed files with 13 additions and 10 deletions
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23
arangod/RocksDBEngine/RocksDBVPackIndex.cpp
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@ -1044,17 +1044,11 @@ bool RocksDBVPackIndex::supportsFilterCondition(
if (attributesCoveredByEquality == _fields.size() && unique()) {
// index is unique and condition covers all attributes by equality
if (estimatedItems >= values) {
// reduce costs due to uniqueness
estimatedItems = values;
estimatedCost = static_cast<double>(estimatedItems);
} else {
// cost is already low... now slightly prioritize the unique index
estimatedCost *= 0.995;
}
estimatedItems = values;
estimatedCost = 0.995 * values;
return true;
}
if (attributesCovered > 0 &&
(!_sparse || attributesCovered == _fields.size())) {
// if the condition contains at least one index attribute and is not
@ -1064,7 +1058,16 @@ bool RocksDBVPackIndex::supportsFilterCondition(
// sparse indexes are contained in Index::canUseConditionPart)
estimatedItems = static_cast<size_t>((std::max)(
static_cast<size_t>(estimatedCost * values), static_cast<size_t>(1)));
estimatedCost *= static_cast<double>(values);
// check if the index has a selectivity estimate ready
if (attributesCoveredByEquality == _fields.size()) {
StringRef ignore;
double estimate = this->selectivityEstimate(&ignore);
if (estimate > 0.0) {
estimatedItems = static_cast<size_t>(1.0 / estimate);
}
}
estimatedCost = static_cast<double>(estimatedItems);
return true;
}