opendev/gerrit
Code Issues Proposed changes

Try harder to choose index queries as a data source

Browse Source 
AndSource should be choosing which child as the primary data source
based on its cost, in order to make the cheapest query.

This improves the chances of a partial-index query actually being
answered from the index, because the query builder adds at least one
top-level index predicate (sortkey) to any query. If we treat the
cost of an index query as 0, this means that of a top-level AndSource
it should choose that rather than a non-index predicate.

This also papers over an issue where the index rewriter fails to wrap
a non-indexable predicate (e.g. ownerin) in a ChangeDataSource.

Change-Id: I56d9781743fe31e5cf8c309d62cd93fe0d886219
This commit is contained in:
Dave Borowitz
2013-09-13 14:53:26 -04:00
parent 2bd1cb12d1
commit 8828458f53
2 changed files with 10 additions and 4 deletions
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5
gerrit-server/src/main/java/com/google/gerrit/server/index/IndexedChangeQuery.java
View File

@@ -126,7 +126,10 @@ public class IndexedChangeQuery extends Predicate<ChangeData>
@Override
public int getCost() {
return pred.getCost();
// Index queries are assumed to be cheaper than any other type of query, so
// so try to make sure they get picked. Note that pred's cost may be higher
// because it doesn't know whether it's being used in an index query or not.
return 0;
}
@Override

9
gerrit-server/src/main/java/com/google/gerrit/server/query/change/AndSource.java
View File

@@ -162,12 +162,15 @@ public class AndSource extends AndPredicate<ChangeData>
}
private ChangeDataSource source() {
int minCost = Integer.MAX_VALUE;
Predicate<ChangeData> s = null;
for (Predicate<ChangeData> p : getChildren()) {
if (p instanceof ChangeDataSource) {
return (ChangeDataSource) p;
if (p instanceof ChangeDataSource && p.getCost() < minCost) {
s = p;
minCost = p.getCost();
}
}
return null;
return (ChangeDataSource) s;
}
@Override