// Copyright (C) 2013 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package com.google.gerrit.server.index;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Objects;
import com.google.common.collect.Lists;
import com.google.common.collect.Sets;
import com.google.gerrit.reviewdb.client.Change;
import com.google.gerrit.reviewdb.client.Change.Status;
import com.google.gerrit.server.query.AndPredicate;
import com.google.gerrit.server.query.NotPredicate;
import com.google.gerrit.server.query.OrPredicate;
import com.google.gerrit.server.query.Predicate;
import com.google.gerrit.server.query.QueryParseException;
import com.google.gerrit.server.query.change.AndSource;
import com.google.gerrit.server.query.change.BasicChangeRewrites;
import com.google.gerrit.server.query.change.ChangeData;
import com.google.gerrit.server.query.change.ChangeQueryBuilder;
import com.google.gerrit.server.query.change.ChangeQueryRewriter;
import com.google.gerrit.server.query.change.ChangeStatusPredicate;
import com.google.gerrit.server.query.change.OrSource;
import com.google.inject.Inject;
import java.util.BitSet;
import java.util.EnumSet;
import java.util.List;
import java.util.Set;
/** Rewriter that pushes boolean logic into the secondary index. */
public class IndexRewriteImpl implements ChangeQueryRewriter {
/** Set of all open change statuses. */
public static final Set<Change.Status> OPEN_STATUSES;
/** Set of all closed change statuses. */
public static final Set<Change.Status> CLOSED_STATUSES;
static {
EnumSet<Change.Status> open = EnumSet.noneOf(Change.Status.class);
EnumSet<Change.Status> closed = EnumSet.noneOf(Change.Status.class);
for (Change.Status s : Change.Status.values()) {
if (s.isOpen()) {
open.add(s);
} else {
closed.add(s);
}
}
OPEN_STATUSES = Sets.immutableEnumSet(open);
CLOSED_STATUSES = Sets.immutableEnumSet(closed);
}
@VisibleForTesting
static final int MAX_LIMIT = 1000;
/**
* Get the set of statuses that changes matching the given predicate may have.
*
* @param in predicate
* @return the maximal set of statuses that any changes matching the input
* predicates may have, based on examining boolean and
* {@link ChangeStatusPredicate}s.
*/
public static EnumSet<Change.Status> getPossibleStatus(Predicate<ChangeData> in) {
EnumSet<Change.Status> s = extractStatus(in);
return s != null ? s : EnumSet.allOf(Change.Status.class);
}
private static EnumSet<Change.Status> extractStatus(Predicate<ChangeData> in) {
if (in instanceof ChangeStatusPredicate) {
return EnumSet.of(((ChangeStatusPredicate) in).getStatus());
} else if (in instanceof NotPredicate) {
EnumSet<Status> s = extractStatus(in.getChild(0));
return s != null ? EnumSet.complementOf(s) : null;
} else if (in instanceof OrPredicate) {
EnumSet<Change.Status> r = null;
int childrenWithStatus = 0;
for (int i = 0; i < in.getChildCount(); i++) {
EnumSet<Status> c = extractStatus(in.getChild(i));
if (c != null) {
if (r == null) {
r = EnumSet.noneOf(Change.Status.class);
}
r.addAll(c);
childrenWithStatus++;
}
}
if (r != null && childrenWithStatus < in.getChildCount()) {
// At least one child supplied a status but another did not.
// Assume all statuses for the children that did not feed a
// status at this part of the tree. This matches behavior if
// the child was used at the root of a query.
return EnumSet.allOf(Change.Status.class);
}
return r;
} else if (in instanceof AndPredicate) {
EnumSet<Change.Status> r = null;
for (int i = 0; i < in.getChildCount(); i++) {
EnumSet<Change.Status> c = extractStatus(in.getChild(i));
if (c != null) {
if (r == null) {
r = EnumSet.allOf(Change.Status.class);
}
r.retainAll(c);
}
}
return r;
}
return null;
}
private final IndexCollection indexes;
private final BasicChangeRewrites basicRewrites;
@Inject
IndexRewriteImpl(IndexCollection indexes,
BasicChangeRewrites basicRewrites) {
this.indexes = indexes;
this.basicRewrites = basicRewrites;
}
@Override
public Predicate<ChangeData> rewrite(Predicate<ChangeData> in, int start)
throws QueryParseException {
ChangeIndex index = indexes.getSearchIndex();
in = basicRewrites.rewrite(in);
int limit =
Objects.firstNonNull(ChangeQueryBuilder.getLimit(in), MAX_LIMIT);
// Increase the limit rather than skipping, since we don't know how many
// skipped results would have been filtered out by the enclosing AndSource.
limit += start;
limit = Math.max(limit, 1);
limit = Math.min(limit, MAX_LIMIT);
Predicate<ChangeData> out = rewriteImpl(in, index, limit);
if (in == out || out instanceof IndexPredicate) {
return new IndexedChangeQuery(index, out, limit);
} else if (out == null /* cannot rewrite */) {
return in;
} else {
return out;
}
}
/**
* Rewrite a single predicate subtree.
*
* @param in predicate to rewrite.
* @param index index whose schema determines which fields are indexed.
* @param limit maximum number of results to return.
* @return {@code null} if no part of this subtree can be queried in the
* index directly. {@code in} if this subtree and all its children can be
* queried directly in the index. Otherwise, a predicate that is
* semantically equivalent, with some of its subtrees wrapped to query the
* index directly.
* @throws QueryParseException if the underlying index implementation does not
* support this predicate.
*/
private Predicate<ChangeData> rewriteImpl(Predicate<ChangeData> in,
ChangeIndex index, int limit) throws QueryParseException {
if (isIndexPredicate(in, index)) {
return in;
} else if (!isRewritePossible(in)) {
return null; // magic to indicate "in" cannot be rewritten
}
int n = in.getChildCount();
BitSet isIndexed = new BitSet(n);
BitSet notIndexed = new BitSet(n);
BitSet rewritten = new BitSet(n);
List<Predicate<ChangeData>> newChildren = Lists.newArrayListWithCapacity(n);
for (int i = 0; i < n; i++) {
Predicate<ChangeData> c = in.getChild(i);
Predicate<ChangeData> nc = rewriteImpl(c, index, limit);
if (nc == c) {
isIndexed.set(i);
newChildren.add(c);
} else if (nc == null /* cannot rewrite c */) {
notIndexed.set(i);
newChildren.add(c);
} else {
rewritten.set(i);
newChildren.add(nc);
}
}
if (isIndexed.cardinality() == n) {
return in; // All children are indexed, leave as-is for parent.
} else if (notIndexed.cardinality() == n) {
return null; // Can't rewrite any children, so cannot rewrite in.
} else if (rewritten.cardinality() == n) {
return in.copy(newChildren); // All children were rewritten.
}
return partitionChildren(in, newChildren, isIndexed, index, limit);
}
private boolean isIndexPredicate(Predicate<ChangeData> in, ChangeIndex index) {
if (!(in instanceof IndexPredicate)) {
return false;
}
IndexPredicate<ChangeData> p = (IndexPredicate<ChangeData>) in;
return index.getSchema().getFields().containsKey(p.getField().getName());
}
private Predicate<ChangeData> partitionChildren(
Predicate<ChangeData> in,
List<Predicate<ChangeData>> newChildren,
BitSet isIndexed,
ChangeIndex index,
int limit) throws QueryParseException {
if (isIndexed.cardinality() == 1) {
int i = isIndexed.nextSetBit(0);
newChildren.add(
0, new IndexedChangeQuery(index, newChildren.remove(i), limit));
return copy(in, newChildren);
}
// Group all indexed predicates into a wrapped subtree.
List<Predicate<ChangeData>> indexed =
Lists.newArrayListWithCapacity(isIndexed.cardinality());
List<Predicate<ChangeData>> all =
Lists.newArrayListWithCapacity(
newChildren.size() - isIndexed.cardinality() + 1);
for (int i = 0; i < newChildren.size(); i++) {
Predicate<ChangeData> c = newChildren.get(i);
if (isIndexed.get(i)) {
indexed.add(c);
} else {
all.add(c);
}
}
all.add(0, new IndexedChangeQuery(index, in.copy(indexed), limit));
return copy(in, all);
}
private Predicate<ChangeData> copy(
Predicate<ChangeData> in,
List<Predicate<ChangeData>> all) {
if (in instanceof AndPredicate) {
return new AndSource(all);
} else if (in instanceof OrPredicate) {
return new OrSource(all);
}
return in.copy(all);
}
private static boolean isRewritePossible(Predicate<ChangeData> p) {
return p.getChildCount() > 0 && (
p instanceof AndPredicate
|| p instanceof OrPredicate
|| p instanceof NotPredicate);
}
}