Github user keith-turner commented on a diff in the pull request:
https://github.com/apache/accumulo/pull/275#discussion_r125107098
--- Diff:
core/src/main/java/org/apache/accumulo/core/iterators/system/LocalityGroupIterator.java
---
@@ -97,75 +133,116 @@ public static final int seek(HeapIterator hiter,
LocalityGroup[] groups, Set<Byt
else
cfSet = Collections.emptySet();
- for (LocalityGroup lgr : groups) {
- // when include is set to true it means this locality groups contains
- // wanted column families
- boolean include = false;
+ // determine the set of groups to use
+ Collection<LocalityGroup> groupsToUse = Collections.EMPTY_LIST;
- if (cfSet.size() == 0) {
- include = !inclusive;
- } else if (lgr.isDefaultLocalityGroup && lgr.columnFamilies == null)
{
- // do not know what column families are in the default locality
group,
- // only know what column families are not in it
+ // if no column families specified, then include all groups unless
!inclusive
+ if (cfSet.size() == 0) {
+ if (!inclusive) {
+ groupsToUse = groups.groups;
+ }
+ } else {
+ groupsToUse = new HashSet<LocalityGroup>();
+ // do not know what column families are in the default locality
group,
+ // only know what column families are not in it
+ if (groups.defaultGroup != null) {
if (inclusive) {
- if (!nonDefaultColumnFamilies.containsAll(cfSet)) {
+ if (!groups.groupByCf.keySet().containsAll(cfSet)) {
// default LG may contain wanted and unwanted column families
- include = true;
+ groupsToUse.add(groups.defaultGroup);
}// else - everything wanted is in other locality groups, so
nothing to do
} else {
- // must include, if all excluded column families are in other
locality groups
- // then there are not unwanted column families in default LG
- include = true;
+ // must include the default group as it may include cfs not in
our cfSet
+ groupsToUse.add(groups.defaultGroup);
+ }
+ }
+
+ /*
+ * Need to consider the following cases for inclusive and exclusive
(lgcf:locality group column family set, cf:column family set) lgcf and cf are
disjoint
+ * lgcf and cf are the same cf contains lgcf lgcf contains cf lgccf
and cf intersect but neither is a subset of the other
+ */
+ if (!inclusive) {
+ for (Entry<ByteSequence,LocalityGroup> entry :
groups.groupByCf.entrySet()) {
+ if (!cfSet.contains(entry.getKey())) {
+ groupsToUse.add(entry.getValue());
+ }
+ }
+ } else if (groups.groupByCf.size() <= cfSet.size()) {
+ for (Entry<ByteSequence,LocalityGroup> entry :
groups.groupByCf.entrySet()) {
+ if (cfSet.contains(entry.getKey())) {
+ groupsToUse.add(entry.getValue());
+ }
}
} else {
- /*
- * Need to consider the following cases for inclusive and
exclusive (lgcf:locality group column family set, cf:column family set) lgcf
and cf are
- * disjoint lgcf and cf are the same cf contains lgcf lgcf
contains cf lgccf and cf intersect but neither is a subset of the other
- */
-
- for (Entry<ByteSequence,MutableLong> entry :
lgr.columnFamilies.entrySet())
- if (entry.getValue().longValue() > 0)
- if (cfSet.contains(entry.getKey())) {
- if (inclusive)
- include = true;
- } else if (!inclusive) {
- include = true;
- }
+ for (ByteSequence cf : cfSet) {
+ LocalityGroup group = groups.groupByCf.get(cf);
+ if (group != null) {
+ groupsToUse.add(group);
+ }
+ }
}
+ }
- if (include) {
- lgr.getIterator().seek(range, EMPTY_CF_SET, false);
- hiter.addSource(lgr.getIterator());
- numLGSeeked++;
- }// every column family is excluded, zero count, or not present
+ for (LocalityGroup lgr : groupsToUse) {
+ lgr.getIterator().seek(range, EMPTY_CF_SET, false);
+ hiter.addSource(lgr.getIterator());
+ numLGSeeked++;
+ }
+
+ if (used != null) {
+ used.addAll(groupsToUse);
}
return numLGSeeked;
}
@Override
public void seek(Range range, Collection<ByteSequence> columnFamilies,
boolean inclusive) throws IOException {
- seek(this, groups, nonDefaultColumnFamilies, range, columnFamilies,
inclusive);
+ Set<ByteSequence> cfSet;
+ if (columnFamilies.size() > 0)
+ cfSet = new HashSet<>(columnFamilies);
--- End diff --
Always doing this copy is annoying. I wonder if the cost of this copy is
made up by the cost savings of checking against the last families. I suspect
it may be, but not sure. I think using the same set of columns for each seek
is common, so its nice to use the same decision. In the use case were seek is
repeatedly being called with a different set of families, this copy and later
equality check would be a lot of overhead with no gain. However I think this an
exotic use case??
I like Guava's `cfSet = ImmutableSet.of(columnFamilies)` because if the
input is already an ImmutableSet it just returns it. This would be beneficial
if code calling seek passed in ImmutableSet. We could avoid the copy without
worrying about correctness. Also another nice thing about using immutable set
is the equality check below will be super quick (because its the same instance
it can check for reference equality). Comparing two different hash set
instances that have the same content requires examining the content (I looked
and it calls `containsAll()`).
I am thinking we should change this to `cfSet =
ImmutableSet.of(columnFamilies)` and then have a follow on issue to make
Accumulo code that constructs these sets in the tablet server use `ImmutableSet`
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