You are viewing a plain text version of this content. The canonical link for it is here.
Posted to commits@cassandra.apache.org by ty...@apache.org on 2014/12/19 19:23:44 UTC
[1/3] cassandra git commit: Fix DISTINCT on static columns with paging
Repository: cassandra
Updated Branches:
refs/heads/trunk 4a88249df -> a164de3be
Fix DISTINCT on static columns with paging
Patch by Tyler Hobbs; reviewed by Sylvain Lebresne for CASSANDRA-8087
Project: http://git-wip-us.apache.org/repos/asf/cassandra/repo
Commit: http://git-wip-us.apache.org/repos/asf/cassandra/commit/2acbab65
Tree: http://git-wip-us.apache.org/repos/asf/cassandra/tree/2acbab65
Diff: http://git-wip-us.apache.org/repos/asf/cassandra/diff/2acbab65
Branch: refs/heads/trunk
Commit: 2acbab6516fc6c8666d3bbff99c49f04b8499235
Parents: 351e35b
Author: Tyler Hobbs <ty...@apache.org>
Authored: Fri Dec 19 12:02:00 2014 -0600
Committer: Tyler Hobbs <ty...@apache.org>
Committed: Fri Dec 19 12:02:00 2014 -0600
----------------------------------------------------------------------
CHANGES.txt | 2 ++
.../cql3/statements/ColumnGroupMap.java | 27 ++++++++++++++++++
.../apache/cassandra/db/ColumnFamilyStore.java | 6 ++--
src/java/org/apache/cassandra/db/DataRange.java | 30 ++++++++++++++------
.../apache/cassandra/db/PagedRangeCommand.java | 13 +++------
.../cassandra/db/filter/SliceQueryFilter.java | 6 +++-
6 files changed, 64 insertions(+), 20 deletions(-)
----------------------------------------------------------------------
http://git-wip-us.apache.org/repos/asf/cassandra/blob/2acbab65/CHANGES.txt
----------------------------------------------------------------------
diff --git a/CHANGES.txt b/CHANGES.txt
index 1ad2de5..bd128f5 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -1,4 +1,6 @@
2.0.12:
+ * Fix non-distinct results in DISTNCT queries on static columns when
+ paging is enabled (CASSANDRA-8087)
* Move all hints related tasks to hints internal executor (CASSANDRA-8285)
* Fix paging for multi-partition IN queries (CASSANDRA-8408)
* Fix MOVED_NODE topology event never being emitted when a node
http://git-wip-us.apache.org/repos/asf/cassandra/blob/2acbab65/src/java/org/apache/cassandra/cql3/statements/ColumnGroupMap.java
----------------------------------------------------------------------
diff --git a/src/java/org/apache/cassandra/cql3/statements/ColumnGroupMap.java b/src/java/org/apache/cassandra/cql3/statements/ColumnGroupMap.java
index 58428ed..2fb9c5f 100644
--- a/src/java/org/apache/cassandra/cql3/statements/ColumnGroupMap.java
+++ b/src/java/org/apache/cassandra/cql3/statements/ColumnGroupMap.java
@@ -24,10 +24,13 @@ import java.util.HashMap;
import java.util.List;
import java.util.Map;
+import com.google.common.base.Objects;
import org.apache.cassandra.db.Column;
import org.apache.cassandra.db.marshal.AbstractType;
import org.apache.cassandra.db.marshal.CompositeType;
+import org.apache.cassandra.utils.ByteBufferUtil;
import org.apache.cassandra.utils.Pair;
+import org.apache.commons.lang3.StringUtils;
public class ColumnGroupMap
{
@@ -96,6 +99,24 @@ public class ColumnGroupMap
return map.containsKey(key);
}
+ @Override
+ public String toString()
+ {
+ List<String> fullStringPath = new ArrayList<>(fullPath.length);
+ for (ByteBuffer buffer : fullPath)
+ fullStringPath.add(ByteBufferUtil.bytesToHex(buffer));
+
+ List<String> stringMap = new ArrayList<>(fullPath.length);
+ for (Map.Entry<ByteBuffer, Value> entry : map.entrySet())
+ stringMap.add(ByteBufferUtil.bytesToHex(entry.getKey()) + ": " + entry.getValue());
+
+ return Objects.toStringHelper(this)
+ .add("fullPath", "[" + StringUtils.join(fullStringPath, ", ") + "]")
+ .add("map", "{" + StringUtils.join(stringMap, ", ") + "}")
+ .add("isStatic", isStatic)
+ .toString();
+ }
+
private interface Value {};
private static class Simple implements Value
@@ -106,6 +127,12 @@ public class ColumnGroupMap
{
this.column = column;
}
+
+ @Override
+ public String toString()
+ {
+ return Objects.toStringHelper(this).add("column", ByteBufferUtil.bytesToHex(column.name())).toString();
+ }
}
private static class Collection extends ArrayList<Pair<ByteBuffer, Column>> implements Value {}
http://git-wip-us.apache.org/repos/asf/cassandra/blob/2acbab65/src/java/org/apache/cassandra/db/ColumnFamilyStore.java
----------------------------------------------------------------------
diff --git a/src/java/org/apache/cassandra/db/ColumnFamilyStore.java b/src/java/org/apache/cassandra/db/ColumnFamilyStore.java
index 0e7e5f2..7bd2a59 100644
--- a/src/java/org/apache/cassandra/db/ColumnFamilyStore.java
+++ b/src/java/org/apache/cassandra/db/ColumnFamilyStore.java
@@ -1649,12 +1649,12 @@ public class ColumnFamilyStore implements ColumnFamilyStoreMBean
/**
* Allows generic range paging with the slice column filter.
* Typically, suppose we have rows A, B, C ... Z having each some columns in [1, 100].
- * And suppose we want to page throught the query that for all rows returns the columns
+ * And suppose we want to page through the query that for all rows returns the columns
* within [25, 75]. For that, we need to be able to do a range slice starting at (row r, column c)
* and ending at (row Z, column 75), *but* that only return columns in [25, 75].
* That is what this method allows. The columnRange is the "window" of columns we are interested
* in each row, and columnStart (resp. columnEnd) is the start (resp. end) for the first
- * (resp. end) requested row.
+ * (resp. last) requested row.
*/
public ExtendedFilter makeExtendedFilter(AbstractBounds<RowPosition> keyRange,
SliceQueryFilter columnRange,
@@ -1694,6 +1694,8 @@ public class ColumnFamilyStore implements ColumnFamilyStoreMBean
assert columnFilter instanceof SliceQueryFilter;
SliceQueryFilter sfilter = (SliceQueryFilter)columnFilter;
assert sfilter.slices.length == 1;
+ // create a new SliceQueryFilter that selects all cells, but pass the original slice start and finish
+ // through to DataRange.Paging to be used on the first and last partitions
SliceQueryFilter newFilter = new SliceQueryFilter(ColumnSlice.ALL_COLUMNS_ARRAY, sfilter.isReversed(), sfilter.count);
dataRange = new DataRange.Paging(range, newFilter, sfilter.start(), sfilter.finish(), metadata.comparator);
}
http://git-wip-us.apache.org/repos/asf/cassandra/blob/2acbab65/src/java/org/apache/cassandra/db/DataRange.java
----------------------------------------------------------------------
diff --git a/src/java/org/apache/cassandra/db/DataRange.java b/src/java/org/apache/cassandra/db/DataRange.java
index b8e0bf5..b8b8daf 100644
--- a/src/java/org/apache/cassandra/db/DataRange.java
+++ b/src/java/org/apache/cassandra/db/DataRange.java
@@ -111,11 +111,19 @@ public class DataRange
return selectFullRow;
}
+ /**
+ * Returns a column filter that should be used for a particular row key. Note that in the case of paging,
+ * slice starts and ends may change depending on the row key.
+ */
public IDiskAtomFilter columnFilter(ByteBuffer rowKey)
{
return columnFilter;
}
+ /**
+ * Sets a new limit on the number of (grouped) cells to fetch. This is currently only used when the query limit applies
+ * to CQL3 rows.
+ */
public void updateColumnsLimit(int count)
{
columnFilter.updateColumnsLimit(count);
@@ -123,12 +131,18 @@ public class DataRange
public static class Paging extends DataRange
{
+ // The slice of columns that we want to fetch for each row, ignoring page start/end issues.
private final SliceQueryFilter sliceFilter;
+
private final Comparator<ByteBuffer> comparator;
- private final ByteBuffer columnStart;
- private final ByteBuffer columnFinish;
- private Paging(AbstractBounds<RowPosition> range, SliceQueryFilter filter, ByteBuffer columnStart, ByteBuffer columnFinish, Comparator<ByteBuffer> comparator)
+ // used to restrict the start of the slice for the first partition in the range
+ private final ByteBuffer firstPartitionColumnStart;
+
+ // used to restrict the end of the slice for the last partition in the range
+ private final ByteBuffer lastPartitionColumnFinish;
+
+ private Paging(AbstractBounds<RowPosition> range, SliceQueryFilter filter, ByteBuffer firstPartitionColumnStart, ByteBuffer lastPartitionColumnFinish, Comparator<ByteBuffer> comparator)
{
super(range, filter);
@@ -138,8 +152,8 @@ public class DataRange
this.sliceFilter = filter;
this.comparator = comparator;
- this.columnStart = columnStart;
- this.columnFinish = columnFinish;
+ this.firstPartitionColumnStart = firstPartitionColumnStart;
+ this.lastPartitionColumnFinish = lastPartitionColumnFinish;
}
public Paging(AbstractBounds<RowPosition> range, SliceQueryFilter filter, ByteBuffer columnStart, ByteBuffer columnFinish, AbstractType<?> comparator)
@@ -184,11 +198,11 @@ public class DataRange
private ColumnSlice[] slicesForKey(ByteBuffer key)
{
// We don't call that until it's necessary, so assume we have to do some hard work
- // Also note that columnStart and columnFinish, when used, only "restrict" the filter slices,
+ // Also note that firstPartitionColumnStart and lastPartitionColumnFinish, when used, only "restrict" the filter slices,
// it doesn't expand on them. As such, we can ignore the case where they are empty and we do
// as it screw up with the logic below (see #6592)
- ByteBuffer newStart = equals(startKey(), key) && columnStart.hasRemaining() ? columnStart : null;
- ByteBuffer newFinish = equals(stopKey(), key) && columnFinish.hasRemaining() ? columnFinish : null;
+ ByteBuffer newStart = equals(startKey(), key) && firstPartitionColumnStart.hasRemaining() ? firstPartitionColumnStart : null;
+ ByteBuffer newFinish = equals(stopKey(), key) && lastPartitionColumnFinish.hasRemaining() ? lastPartitionColumnFinish : null;
List<ColumnSlice> newSlices = new ArrayList<ColumnSlice>(sliceFilter.slices.length); // in the common case, we'll have the same number of slices
http://git-wip-us.apache.org/repos/asf/cassandra/blob/2acbab65/src/java/org/apache/cassandra/db/PagedRangeCommand.java
----------------------------------------------------------------------
diff --git a/src/java/org/apache/cassandra/db/PagedRangeCommand.java b/src/java/org/apache/cassandra/db/PagedRangeCommand.java
index d6f3ca1..a8d7f49 100644
--- a/src/java/org/apache/cassandra/db/PagedRangeCommand.java
+++ b/src/java/org/apache/cassandra/db/PagedRangeCommand.java
@@ -97,15 +97,10 @@ public class PagedRangeCommand extends AbstractRangeCommand
public boolean countCQL3Rows()
{
- // We only use PagedRangeCommand for CQL3. However, for SELECT DISTINCT, we want to return false here, because
- // we just want to pick the first cell of each partition and returning true here would throw off the logic in
- // ColumnFamilyStore.filter().
- // What we do know is that for a SELECT DISTINCT the underlying SliceQueryFilter will have a compositesToGroup==-1
- // and a count==1. And while it would be possible for a normal SELECT on a COMPACT table to also have such
- // parameters, it's fine returning false since if we do count one cell for each partition, then each partition
- // will coincide with exactly one CQL3 row.
- SliceQueryFilter filter = (SliceQueryFilter)predicate;
- return filter.compositesToGroup >= 0 || filter.count != 1;
+ // For CQL3 queries, unless this is a DISTINCT query, the slice filter count is the LIMIT of the query.
+ // We don't page queries in the first place if their LIMIT <= pageSize and so we'll never page a query with
+ // a limit of 1. See CASSANDRA-8087 for more details.
+ return ((SliceQueryFilter)predicate).count != 1;
}
public List<Row> executeLocally()
http://git-wip-us.apache.org/repos/asf/cassandra/blob/2acbab65/src/java/org/apache/cassandra/db/filter/SliceQueryFilter.java
----------------------------------------------------------------------
diff --git a/src/java/org/apache/cassandra/db/filter/SliceQueryFilter.java b/src/java/org/apache/cassandra/db/filter/SliceQueryFilter.java
index e0ccc2f..58a0303 100644
--- a/src/java/org/apache/cassandra/db/filter/SliceQueryFilter.java
+++ b/src/java/org/apache/cassandra/db/filter/SliceQueryFilter.java
@@ -292,7 +292,11 @@ public class SliceQueryFilter implements IDiskAtomFilter
public int lastCounted()
{
- return columnCounter == null ? 0 : columnCounter.live();
+ // If we have a slice limit set, columnCounter.live() can overcount by one because we have to call
+ // columnCounter.count() before we can tell if we've exceeded the slice limit (and accordingly, should not
+ // add the cells to returned container). To deal with this overcounting, we take the min of the slice
+ // limit and the counter's count.
+ return columnCounter == null ? 0 : Math.min(columnCounter.live(), count);
}
public int lastIgnored()
[3/3] cassandra git commit: Merge branch 'cassandra-2.1' into trunk
Posted by ty...@apache.org.
Merge branch 'cassandra-2.1' into trunk
Project: http://git-wip-us.apache.org/repos/asf/cassandra/repo
Commit: http://git-wip-us.apache.org/repos/asf/cassandra/commit/a164de3b
Tree: http://git-wip-us.apache.org/repos/asf/cassandra/tree/a164de3b
Diff: http://git-wip-us.apache.org/repos/asf/cassandra/diff/a164de3b
Branch: refs/heads/trunk
Commit: a164de3bee53fe48cac8a7bae809a7b2f4a435e9
Parents: 4a88249 6fe6d65
Author: Tyler Hobbs <ty...@apache.org>
Authored: Fri Dec 19 12:20:02 2014 -0600
Committer: Tyler Hobbs <ty...@apache.org>
Committed: Fri Dec 19 12:20:02 2014 -0600
----------------------------------------------------------------------
CHANGES.txt | 2 ++
.../apache/cassandra/db/ColumnFamilyStore.java | 6 ++--
src/java/org/apache/cassandra/db/DataRange.java | 29 ++++++++++++++------
.../cassandra/db/filter/SliceQueryFilter.java | 6 +++-
4 files changed, 32 insertions(+), 11 deletions(-)
----------------------------------------------------------------------
http://git-wip-us.apache.org/repos/asf/cassandra/blob/a164de3b/CHANGES.txt
----------------------------------------------------------------------
http://git-wip-us.apache.org/repos/asf/cassandra/blob/a164de3b/src/java/org/apache/cassandra/db/ColumnFamilyStore.java
----------------------------------------------------------------------
http://git-wip-us.apache.org/repos/asf/cassandra/blob/a164de3b/src/java/org/apache/cassandra/db/filter/SliceQueryFilter.java
----------------------------------------------------------------------
[2/3] cassandra git commit: Merge branch 'cassandra-2.0' into
cassandra-2.1
Posted by ty...@apache.org.
Merge branch 'cassandra-2.0' into cassandra-2.1
Conflicts:
CHANGES.txt
src/java/org/apache/cassandra/cql3/statements/ColumnGroupMap.java
src/java/org/apache/cassandra/db/DataRange.java
src/java/org/apache/cassandra/db/PagedRangeCommand.java
Project: http://git-wip-us.apache.org/repos/asf/cassandra/repo
Commit: http://git-wip-us.apache.org/repos/asf/cassandra/commit/6fe6d65d
Tree: http://git-wip-us.apache.org/repos/asf/cassandra/tree/6fe6d65d
Diff: http://git-wip-us.apache.org/repos/asf/cassandra/diff/6fe6d65d
Branch: refs/heads/trunk
Commit: 6fe6d65d5a0cd670bcd4590fcad2db62699de028
Parents: 6f42afa 2acbab6
Author: Tyler Hobbs <ty...@apache.org>
Authored: Fri Dec 19 12:11:06 2014 -0600
Committer: Tyler Hobbs <ty...@apache.org>
Committed: Fri Dec 19 12:11:06 2014 -0600
----------------------------------------------------------------------
CHANGES.txt | 2 ++
.../apache/cassandra/db/ColumnFamilyStore.java | 6 ++--
src/java/org/apache/cassandra/db/DataRange.java | 29 ++++++++++++++------
.../cassandra/db/filter/SliceQueryFilter.java | 6 +++-
4 files changed, 32 insertions(+), 11 deletions(-)
----------------------------------------------------------------------
http://git-wip-us.apache.org/repos/asf/cassandra/blob/6fe6d65d/CHANGES.txt
----------------------------------------------------------------------
diff --cc CHANGES.txt
index ddc25cd,bd128f5..84becc0
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@@ -1,46 -1,6 +1,48 @@@
-2.0.12:
+2.1.3
+ * Fix regression in SSTableRewriter causing some rows to become unreadable
+ during compaction (CASSANDRA-8429)
+ * Run major compactions for repaired/unrepaired in parallel (CASSANDRA-8510)
+ * (cqlsh) Fix compression options in DESCRIBE TABLE output when compression
+ is disabled (CASSANDRA-8288)
+ * (cqlsh) Fix DESCRIBE output after keyspaces are altered (CASSANDRA-7623)
+ * Make sure we set lastCompactedKey correctly (CASSANDRA-8463)
+ * (cqlsh) Fix output of CONSISTENCY command (CASSANDRA-8507)
+ * (cqlsh) Fixed the handling of LIST statements (CASSANDRA-8370)
+ * Make sstablescrub check leveled manifest again (CASSANDRA-8432)
+ * Check first/last keys in sstable when giving out positions (CASSANDRA-8458)
+ * Disable mmap on Windows (CASSANDRA-6993)
+ * Add missing ConsistencyLevels to cassandra-stress (CASSANDRA-8253)
+ * Add auth support to cassandra-stress (CASSANDRA-7985)
+ * Fix ArrayIndexOutOfBoundsException when generating error message
+ for some CQL syntax errors (CASSANDRA-8455)
+ * Scale memtable slab allocation logarithmically (CASSANDRA-7882)
+ * cassandra-stress simultaneous inserts over same seed (CASSANDRA-7964)
+ * Reduce cassandra-stress sampling memory requirements (CASSANDRA-7926)
+ * Ensure memtable flush cannot expire commit log entries from its future (CASSANDRA-8383)
+ * Make read "defrag" async to reclaim memtables (CASSANDRA-8459)
+ * Remove tmplink files for offline compactions (CASSANDRA-8321)
+ * Reduce maxHintsInProgress (CASSANDRA-8415)
+ * BTree updates may call provided update function twice (CASSANDRA-8018)
+ * Release sstable references after anticompaction (CASSANDRA-8386)
+ * Handle abort() in SSTableRewriter properly (CASSANDRA-8320)
+ * Fix high size calculations for prepared statements (CASSANDRA-8231)
+ * Centralize shared executors (CASSANDRA-8055)
+ * Fix filtering for CONTAINS (KEY) relations on frozen collection
+ clustering columns when the query is restricted to a single
+ partition (CASSANDRA-8203)
+ * Do more aggressive entire-sstable TTL expiry checks (CASSANDRA-8243)
+ * Add more log info if readMeter is null (CASSANDRA-8238)
+ * add check of the system wall clock time at startup (CASSANDRA-8305)
+ * Support for frozen collections (CASSANDRA-7859)
+ * Fix overflow on histogram computation (CASSANDRA-8028)
+ * Have paxos reuse the timestamp generation of normal queries (CASSANDRA-7801)
+ * Fix incremental repair not remove parent session on remote (CASSANDRA-8291)
+ * Improve JBOD disk utilization (CASSANDRA-7386)
+ * Log failed host when preparing incremental repair (CASSANDRA-8228)
+ * Force config client mode in CQLSSTableWriter (CASSANDRA-8281)
+Merged from 2.0:
+ * Fix non-distinct results in DISTNCT queries on static columns when
+ paging is enabled (CASSANDRA-8087)
* Move all hints related tasks to hints internal executor (CASSANDRA-8285)
* Fix paging for multi-partition IN queries (CASSANDRA-8408)
* Fix MOVED_NODE topology event never being emitted when a node
http://git-wip-us.apache.org/repos/asf/cassandra/blob/6fe6d65d/src/java/org/apache/cassandra/db/ColumnFamilyStore.java
----------------------------------------------------------------------
http://git-wip-us.apache.org/repos/asf/cassandra/blob/6fe6d65d/src/java/org/apache/cassandra/db/DataRange.java
----------------------------------------------------------------------
diff --cc src/java/org/apache/cassandra/db/DataRange.java
index 31a9370,b8b8daf..a67105b
--- a/src/java/org/apache/cassandra/db/DataRange.java
+++ b/src/java/org/apache/cassandra/db/DataRange.java
@@@ -124,12 -131,18 +132,17 @@@ public class DataRang
public static class Paging extends DataRange
{
+ // The slice of columns that we want to fetch for each row, ignoring page start/end issues.
private final SliceQueryFilter sliceFilter;
-
- private final Comparator<ByteBuffer> comparator;
+ private final Comparator<Composite> comparator;
- private final Composite columnStart;
- private final Composite columnFinish;
- private Paging(AbstractBounds<RowPosition> range, SliceQueryFilter filter, Composite columnStart, Composite columnFinish, Comparator<Composite> comparator)
+ // used to restrict the start of the slice for the first partition in the range
- private final ByteBuffer firstPartitionColumnStart;
++ private final Composite firstPartitionColumnStart;
+
+ // used to restrict the end of the slice for the last partition in the range
- private final ByteBuffer lastPartitionColumnFinish;
++ private final Composite lastPartitionColumnFinish;
+
- private Paging(AbstractBounds<RowPosition> range, SliceQueryFilter filter, ByteBuffer firstPartitionColumnStart, ByteBuffer lastPartitionColumnFinish, Comparator<ByteBuffer> comparator)
++ private Paging(AbstractBounds<RowPosition> range, SliceQueryFilter filter, Composite firstPartitionColumnStart, Composite lastPartitionColumnFinish, Comparator<Composite> comparator)
{
super(range, filter);
@@@ -139,13 -152,13 +152,13 @@@
this.sliceFilter = filter;
this.comparator = comparator;
- this.columnStart = columnStart;
- this.columnFinish = columnFinish;
+ this.firstPartitionColumnStart = firstPartitionColumnStart;
+ this.lastPartitionColumnFinish = lastPartitionColumnFinish;
}
- public Paging(AbstractBounds<RowPosition> range, SliceQueryFilter filter, ByteBuffer columnStart, ByteBuffer columnFinish, AbstractType<?> comparator)
+ public Paging(AbstractBounds<RowPosition> range, SliceQueryFilter filter, Composite columnStart, Composite columnFinish, CellNameType comparator)
{
- this(range, filter, columnStart, columnFinish, filter.isReversed() ? comparator.reverseComparator : comparator);
+ this(range, filter, columnStart, columnFinish, filter.isReversed() ? comparator.reverseComparator() : comparator);
}
@Override
@@@ -184,11 -197,12 +197,11 @@@
private ColumnSlice[] slicesForKey(ByteBuffer key)
{
-- // We don't call that until it's necessary, so assume we have to do some hard work
+ // Also note that firstPartitionColumnStart and lastPartitionColumnFinish, when used, only "restrict" the filter slices,
// it doesn't expand on them. As such, we can ignore the case where they are empty and we do
// as it screw up with the logic below (see #6592)
- Composite newStart = equals(startKey(), key) && !columnStart.isEmpty() ? columnStart : null;
- Composite newFinish = equals(stopKey(), key) && !columnFinish.isEmpty() ? columnFinish : null;
- ByteBuffer newStart = equals(startKey(), key) && firstPartitionColumnStart.hasRemaining() ? firstPartitionColumnStart : null;
- ByteBuffer newFinish = equals(stopKey(), key) && lastPartitionColumnFinish.hasRemaining() ? lastPartitionColumnFinish : null;
++ Composite newStart = equals(startKey(), key) && !firstPartitionColumnStart.isEmpty() ? firstPartitionColumnStart : null;
++ Composite newFinish = equals(stopKey(), key) && !lastPartitionColumnFinish.isEmpty() ? lastPartitionColumnFinish : null;
List<ColumnSlice> newSlices = new ArrayList<ColumnSlice>(sliceFilter.slices.length); // in the common case, we'll have the same number of slices
http://git-wip-us.apache.org/repos/asf/cassandra/blob/6fe6d65d/src/java/org/apache/cassandra/db/filter/SliceQueryFilter.java
----------------------------------------------------------------------