/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.cassandra.db.view;
import java.nio.ByteBuffer;
import java.util.*;
import com.google.common.collect.Iterators;
import com.google.common.collect.PeekingIterator;
import org.apache.cassandra.schema.ColumnMetadata;
import org.apache.cassandra.schema.Schema;
import org.apache.cassandra.schema.TableMetadata;
import org.apache.cassandra.db.*;
import org.apache.cassandra.db.rows.*;
import org.apache.cassandra.db.partitions.*;
import org.apache.cassandra.db.marshal.AbstractType;
import org.apache.cassandra.db.marshal.CompositeType;
/**
* Creates the updates to apply to a view given the existing rows in the base
* table and the updates that we're applying to them (this handles updates
* on a single partition only).
*
* This class is used by passing the updates made to the base table to
* {@link #addBaseTableUpdate} and calling {@link #generateViewUpdates} once all updates have
* been handled to get the resulting view mutations.
*/
public class ViewUpdateGenerator
{
private final View view;
private final int nowInSec;
private final TableMetadata baseMetadata;
private final DecoratedKey baseDecoratedKey;
private final ByteBuffer[] basePartitionKey;
private final TableMetadata viewMetadata;
private final Map<DecoratedKey, PartitionUpdate> updates = new HashMap<>();
// Reused internally to build a new entry
private final ByteBuffer[] currentViewEntryPartitionKey;
private final Row.Builder currentViewEntryBuilder;
/**
* The type of type update action to perform to the view for a given base table
* update.
*/
private enum UpdateAction
{
NONE, // There was no view entry and none should be added
NEW_ENTRY, // There was no entry but there is one post-update
DELETE_OLD, // There was an entry but there is nothing after update
UPDATE_EXISTING, // There was an entry and the update modifies it
SWITCH_ENTRY // There was an entry and there is still one after update,
// but they are not the same one.
};
/**
* Creates a new {@code ViewUpdateBuilder}.
*
* @param view the view for which this will be building updates for.
* @param basePartitionKey the partition key for the base table partition for which
* we'll handle updates for.
* @param nowInSec the current time in seconds. Used to decide if data are live or not
* and as base reference for new deletions.
*/
public ViewUpdateGenerator(View view, DecoratedKey basePartitionKey, int nowInSec)
{
this.view = view;
this.nowInSec = nowInSec;
this.baseMetadata = view.getDefinition().baseTableMetadata();
this.baseDecoratedKey = basePartitionKey;
this.basePartitionKey = extractKeyComponents(basePartitionKey, baseMetadata.partitionKeyType);
this.viewMetadata = Schema.instance.getTableMetadata(view.getDefinition().metadata.id);
this.currentViewEntryPartitionKey = new ByteBuffer[viewMetadata.partitionKeyColumns().size()];
this.currentViewEntryBuilder = BTreeRow.sortedBuilder();
}
private static ByteBuffer[] extractKeyComponents(DecoratedKey partitionKey, AbstractType<?> type)
{
return type instanceof CompositeType
? ((CompositeType)type).split(partitionKey.getKey())
: new ByteBuffer[]{ partitionKey.getKey() };
}
/**
* Adds to this generator the updates to be made to the view given a base table row
* before and after an update.
*
* @param existingBaseRow the base table row as it is before an update.
* @param mergedBaseRow the base table row after the update is applied (note that
* this is not just the new update, but rather the resulting row).
*/
public void addBaseTableUpdate(Row existingBaseRow, Row mergedBaseRow)
{
switch (updateAction(existingBaseRow, mergedBaseRow))
{
case NONE:
return;
case NEW_ENTRY:
createEntry(mergedBaseRow);
return;
case DELETE_OLD:
deleteOldEntry(existingBaseRow);
return;
case UPDATE_EXISTING:
updateEntry(existingBaseRow, mergedBaseRow);
return;
case SWITCH_ENTRY:
createEntry(mergedBaseRow);
deleteOldEntry(existingBaseRow);
return;
}
}
/**
* Returns the updates that needs to be done to the view given the base table updates
* passed to {@link #addBaseTableUpdate}.
*
* @return the updates to do to the view.
*/
public Collection<PartitionUpdate> generateViewUpdates()
{
return updates.values();
}
/**
* Clears the current state so that the generator may be reused.
*/
public void clear()
{
updates.clear();
}
/**
* Compute which type of action needs to be performed to the view for a base table row
* before and after an update.
*/
private UpdateAction updateAction(Row existingBaseRow, Row mergedBaseRow)
{
// Having existing empty is useful, it just means we'll insert a brand new entry for mergedBaseRow,
// but if we have no update at all, we shouldn't get there.
assert !mergedBaseRow.isEmpty();
// Note that none of the base PK columns will differ since we're intrinsically dealing
// with the same base row. So we have to check 3 things:
// 1) that the clustering doesn't have a null, which can happen for compact tables. If that's the case,
// there is no corresponding entries.
// 2) if there is a column not part of the base PK in the view PK, whether it is changed by the update.
// 3) whether mergedBaseRow actually match the view SELECT filter
if (baseMetadata.isCompactTable())
{
Clustering clustering = mergedBaseRow.clustering();
for (int i = 0; i < clustering.size(); i++)
{
if (clustering.get(i) == null)
return UpdateAction.NONE;
}
}
assert view.baseNonPKColumnsInViewPK.size() <= 1 : "We currently only support one base non-PK column in the view PK";
if (view.baseNonPKColumnsInViewPK.isEmpty())
{
// The view entry is necessarily the same pre and post update.
// Note that we allow existingBaseRow to be null and treat it as empty (see MultiViewUpdateBuilder.generateViewsMutations).
boolean existingHasLiveData = existingBaseRow != null && existingBaseRow.hasLiveData(nowInSec);
boolean mergedHasLiveData = mergedBaseRow.hasLiveData(nowInSec);
return existingHasLiveData
? (mergedHasLiveData ? UpdateAction.UPDATE_EXISTING : UpdateAction.DELETE_OLD)
: (mergedHasLiveData ? UpdateAction.NEW_ENTRY : UpdateAction.NONE);
}
ColumnMetadata baseColumn = view.baseNonPKColumnsInViewPK.get(0);
assert !baseColumn.isComplex() : "A complex column couldn't be part of the view PK";
Cell before = existingBaseRow == null ? null : existingBaseRow.getCell(baseColumn);
Cell after = mergedBaseRow.getCell(baseColumn);
// If the update didn't modified this column, the cells will be the same object so it's worth checking
if (before == after)
return isLive(before) ? UpdateAction.UPDATE_EXISTING : UpdateAction.NONE;
if (!isLive(before))
return isLive(after) ? UpdateAction.NEW_ENTRY : UpdateAction.NONE;
if (!isLive(after))
return UpdateAction.DELETE_OLD;
return baseColumn.cellValueType().compare(before.value(), after.value()) == 0
? UpdateAction.UPDATE_EXISTING
: UpdateAction.SWITCH_ENTRY;
}
private boolean matchesViewFilter(Row baseRow)
{
return view.matchesViewFilter(baseDecoratedKey, baseRow, nowInSec);
}
private boolean isLive(Cell cell)
{
return cell != null && cell.isLive(nowInSec);
}
/**
* Creates a view entry corresponding to the provided base row.
* <p>
* This method checks that the base row does match the view filter before applying it.
*/
private void createEntry(Row baseRow)
{
// Before create a new entry, make sure it matches the view filter
if (!matchesViewFilter(baseRow))
return;
startNewUpdate(baseRow);
currentViewEntryBuilder.addPrimaryKeyLivenessInfo(computeLivenessInfoForEntry(baseRow));
currentViewEntryBuilder.addRowDeletion(baseRow.deletion());
for (ColumnData data : baseRow)
{
ColumnMetadata viewColumn = view.getViewColumn(data.column());
// If that base table column is not denormalized in the view, we had nothing to do.
// Alose, if it's part of the view PK it's already been taken into account in the clustering.
if (viewColumn == null || viewColumn.isPrimaryKeyColumn())
continue;
addColumnData(viewColumn, data);
}
submitUpdate();
}
/**
* Creates the updates to apply to the existing view entry given the base table row before
* and after the update, assuming that the update hasn't changed to which view entry the
* row correspond (that is, we know the columns composing the view PK haven't changed).
* <p>
* This method checks that the base row (before and after) does match the view filter before
* applying anything.
*/
private void updateEntry(Row existingBaseRow, Row mergedBaseRow)
{
// While we know existingBaseRow and mergedBaseRow are corresponding to the same view entry,
// they may not match the view filter.
if (!matchesViewFilter(existingBaseRow))
{
createEntry(mergedBaseRow);
return;
}
if (!matchesViewFilter(mergedBaseRow))
{
deleteOldEntryInternal(existingBaseRow);
return;
}
startNewUpdate(mergedBaseRow);
// In theory, it may be the PK liveness and row deletion hasn't been change by the update
// and we could condition the 2 additions below. In practice though, it's as fast (if not
// faster) to compute those info than to check if they have changed so we keep it simple.
currentViewEntryBuilder.addPrimaryKeyLivenessInfo(computeLivenessInfoForEntry(mergedBaseRow));
currentViewEntryBuilder.addRowDeletion(mergedBaseRow.deletion());
// We only add to the view update the cells from mergedBaseRow that differs from
// existingBaseRow. For that and for speed we can just cell pointer equality: if the update
// hasn't touched a cell, we know it will be the same object in existingBaseRow and
// mergedBaseRow (note that including more cells than we strictly should isn't a problem
// for correction, so even if the code change and pointer equality don't work anymore, it'll
// only a slightly inefficiency which we can fix then).
// Note: we could alternatively use Rows.diff() for this, but because it is a bit more generic
// than what we need here, it's also a bit less efficient (it allocates more in particular),
// and this might be called a lot of time for view updates. So, given that this is not a whole
// lot of code anyway, it's probably doing the diff manually.
PeekingIterator<ColumnData> existingIter = Iterators.peekingIterator(existingBaseRow.iterator());
for (ColumnData mergedData : mergedBaseRow)
{
ColumnMetadata baseColumn = mergedData.column();
ColumnMetadata viewColumn = view.getViewColumn(baseColumn);
// If that base table column is not denormalized in the view, we had nothing to do.
// Alose, if it's part of the view PK it's already been taken into account in the clustering.
if (viewColumn == null || viewColumn.isPrimaryKeyColumn())
continue;
ColumnData existingData = null;
// Find if there is data for that column in the existing row
while (existingIter.hasNext())
{
int cmp = baseColumn.compareTo(existingIter.peek().column());
if (cmp < 0)
break;
ColumnData next = existingIter.next();
if (cmp == 0)
{
existingData = next;
break;
}
}
if (existingData == null)
{
addColumnData(viewColumn, mergedData);
continue;
}
if (mergedData == existingData)
continue;
if (baseColumn.isComplex())
{
ComplexColumnData mergedComplexData = (ComplexColumnData)mergedData;
ComplexColumnData existingComplexData = (ComplexColumnData)existingData;
if (mergedComplexData.complexDeletion().supersedes(existingComplexData.complexDeletion()))
currentViewEntryBuilder.addComplexDeletion(viewColumn, mergedComplexData.complexDeletion());
PeekingIterator<Cell> existingCells = Iterators.peekingIterator(existingComplexData.iterator());
for (Cell mergedCell : mergedComplexData)
{
Cell existingCell = null;
// Find if there is corresponding cell in the existing row
while (existingCells.hasNext())
{
int cmp = baseColumn.cellPathComparator().compare(mergedCell.path(), existingCells.peek().path());
if (cmp > 0)
break;
Cell next = existingCells.next();
if (cmp == 0)
{
existingCell = next;
break;
}
}
if (mergedCell != existingCell)
addCell(viewColumn, mergedCell);
}
}
else
{
// Note that we've already eliminated the case where merged == existing
addCell(viewColumn, (Cell)mergedData);
}
}
submitUpdate();
}
/**
* Deletes the view entry corresponding to the provided base row.
* <p>
* This method checks that the base row does match the view filter before bothering.
*/
private void deleteOldEntry(Row existingBaseRow)
{
// Before deleting an old entry, make sure it was matching the view filter (otherwise there is nothing to delete)
if (!matchesViewFilter(existingBaseRow))
return;
deleteOldEntryInternal(existingBaseRow);
}
private void deleteOldEntryInternal(Row existingBaseRow)
{
startNewUpdate(existingBaseRow);
DeletionTime dt = new DeletionTime(computeTimestampForEntryDeletion(existingBaseRow), nowInSec);
currentViewEntryBuilder.addRowDeletion(Row.Deletion.shadowable(dt));
submitUpdate();
}
/**
* Computes the partition key and clustering for a new view entry, and setup the internal
* row builder for the new row.
*
* This assumes that there is corresponding entry, i.e. no values for the partition key and
* clustering are null (since we have eliminated that case through updateAction).
*/
private void startNewUpdate(Row baseRow)
{
ByteBuffer[] clusteringValues = new ByteBuffer[viewMetadata.clusteringColumns().size()];
for (ColumnMetadata viewColumn : viewMetadata.primaryKeyColumns())
{
ColumnMetadata baseColumn = view.getBaseColumn(viewColumn);
ByteBuffer value = getValueForPK(baseColumn, baseRow);
if (viewColumn.isPartitionKey())
currentViewEntryPartitionKey[viewColumn.position()] = value;
else
clusteringValues[viewColumn.position()] = value;
}
currentViewEntryBuilder.newRow(Clustering.make(clusteringValues));
}
private LivenessInfo computeLivenessInfoForEntry(Row baseRow)
{
/*
* We need to compute both the timestamp and expiration.
*
* For the timestamp, it makes sense to use the bigger timestamp for all view PK columns.
*
* This is more complex for the expiration. We want to maintain consistency between the base and the view, so the
* entry should only exist as long as the base row exists _and_ has non-null values for all the columns that are part
* of the view PK.
* Which means we really have 2 cases:
* 1) either the columns for the base and view PKs are exactly the same: in that case, the view entry should live
* as long as the base row lives. This means the view entry should only expire once *everything* in the base row
* has expired. Which means the row TTL should be the max of any other TTL.
* 2) or there is a column that is not in the base PK but is in the view PK (we can only have one so far, we'll need
* to slightly adapt if we allow more later): in that case, as long as that column lives the entry does too, but
* as soon as it expires (or is deleted for that matter) the entry also should expire. So the expiration for the
* view is the one of that column, irregarding of any other expiration.
* To take an example of that case, if you have:
* CREATE TABLE t (a int, b int, c int, PRIMARY KEY (a, b))
* CREATE MATERIALIZED VIEW mv AS SELECT * FROM t WHERE c IS NOT NULL AND a IS NOT NULL AND b IS NOT NULL PRIMARY KEY (c, a, b)
* INSERT INTO t(a, b) VALUES (0, 0) USING TTL 3;
* UPDATE t SET c = 0 WHERE a = 0 AND b = 0;
* then even after 3 seconds elapsed, the row will still exist (it just won't have a "row marker" anymore) and so
* the MV should still have a corresponding entry.
*/
assert view.baseNonPKColumnsInViewPK.size() <= 1; // This may change, but is currently an enforced limitation
LivenessInfo baseLiveness = baseRow.primaryKeyLivenessInfo();
if (view.baseNonPKColumnsInViewPK.isEmpty())
{
int ttl = baseLiveness.ttl();
int expirationTime = baseLiveness.localExpirationTime();
for (Cell cell : baseRow.cells())
{
if (cell.ttl() > ttl)
{
ttl = cell.ttl();
expirationTime = cell.localDeletionTime();
}
}
return ttl == baseLiveness.ttl()
? baseLiveness
: LivenessInfo.withExpirationTime(baseLiveness.timestamp(), ttl, expirationTime);
}
ColumnMetadata baseColumn = view.baseNonPKColumnsInViewPK.get(0);
Cell cell = baseRow.getCell(baseColumn);
assert isLive(cell) : "We shouldn't have got there if the base row had no associated entry";
long timestamp = Math.max(baseLiveness.timestamp(), cell.timestamp());
return LivenessInfo.withExpirationTime(timestamp, cell.ttl(), cell.localDeletionTime());
}
private long computeTimestampForEntryDeletion(Row baseRow)
{
// We delete the old row with it's row entry timestamp using a shadowable deletion.
// We must make sure that the deletion deletes everything in the entry (or the entry will
// still show up), so we must use the bigger timestamp found in the existing row (for any
// column included in the view at least).
// TODO: We have a problem though: if the entry is "resurected" by a later update, we would
// need to ensure that the timestamp for then entry then is bigger than the tombstone
// we're just inserting, which is not currently guaranteed.
// This is a bug for a separate ticket though.
long timestamp = baseRow.primaryKeyLivenessInfo().timestamp();
for (ColumnData data : baseRow)
{
if (!view.getDefinition().includes(data.column().name))
continue;
timestamp = Math.max(timestamp, data.maxTimestamp());
}
return timestamp;
}
private void addColumnData(ColumnMetadata viewColumn, ColumnData baseTableData)
{
assert viewColumn.isComplex() == baseTableData.column().isComplex();
if (!viewColumn.isComplex())
{
addCell(viewColumn, (Cell)baseTableData);
return;
}
ComplexColumnData complexData = (ComplexColumnData)baseTableData;
currentViewEntryBuilder.addComplexDeletion(viewColumn, complexData.complexDeletion());
for (Cell cell : complexData)
addCell(viewColumn, cell);
}
private void addCell(ColumnMetadata viewColumn, Cell baseTableCell)
{
assert !viewColumn.isPrimaryKeyColumn();
currentViewEntryBuilder.addCell(baseTableCell.withUpdatedColumn(viewColumn));
}
/**
* Finish building the currently updated view entry and add it to the other built
* updates.
*/
private void submitUpdate()
{
Row row = currentViewEntryBuilder.build();
// I'm not sure we can reach there is there is nothing is updated, but adding an empty row breaks things
// and it costs us nothing to be prudent here.
if (row.isEmpty())
return;
DecoratedKey partitionKey = makeCurrentPartitionKey();
PartitionUpdate update = updates.get(partitionKey);
if (update == null)
{
// We can't really know which columns of the view will be updated nor how many row will be updated for this key
// so we rely on hopefully sane defaults.
update = new PartitionUpdate(viewMetadata, partitionKey, viewMetadata.regularAndStaticColumns(), 4);
updates.put(partitionKey, update);
}
update.add(row);
}
private DecoratedKey makeCurrentPartitionKey()
{
ByteBuffer rawKey = viewMetadata.partitionKeyColumns().size() == 1
? currentViewEntryPartitionKey[0]
: CompositeType.build(currentViewEntryPartitionKey);
return viewMetadata.partitioner.decorateKey(rawKey);
}
private ByteBuffer getValueForPK(ColumnMetadata column, Row row)
{
switch (column.kind)
{
case PARTITION_KEY:
return basePartitionKey[column.position()];
case CLUSTERING:
return row.clustering().get(column.position());
default:
// This shouldn't NPE as we shouldn't get there if the value can be null (or there is a bug in updateAction())
return row.getCell(column).value();
}
}
}