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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.
/*
* 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.
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package org.apache.cassandra.cql3.selection;
import java.nio.ByteBuffer;
import java.util.*;
import com.google.common.base.MoreObjects;
import com.google.common.base.Predicate;
import com.google.common.collect.Iterables;
import com.google.common.collect.Iterators;
import com.google.common.collect.Lists;
import org.apache.cassandra.cql3.*;
import org.apache.cassandra.cql3.functions.Function;
import org.apache.cassandra.db.filter.ColumnFilter;
import org.apache.cassandra.db.marshal.UTF8Type;
import org.apache.cassandra.exceptions.InvalidRequestException;
import org.apache.cassandra.schema.ColumnMetadata;
import org.apache.cassandra.schema.TableMetadata;
import org.apache.cassandra.transport.ProtocolVersion;
public abstract class Selection
{
/**
* A predicate that returns true for static columns.
*/
private static final Predicate STATIC_COLUMN_FILTER = (column) -> column.isStatic();
private final TableMetadata table;
private final List columns;
private final SelectionColumnMapping columnMapping;
protected final ResultSet.ResultMetadata metadata;
protected final ColumnFilterFactory columnFilterFactory;
protected final boolean isJson;
// Columns used to order the result set for JSON queries with post ordering.
protected final List orderingColumns;
protected Selection(TableMetadata table,
List selectedColumns,
Set orderingColumns,
SelectionColumnMapping columnMapping,
ColumnFilterFactory columnFilterFactory,
boolean isJson)
{
this.table = table;
this.columns = selectedColumns;
this.columnMapping = columnMapping;
this.metadata = new ResultSet.ResultMetadata(columnMapping.getColumnSpecifications());
this.columnFilterFactory = columnFilterFactory;
this.isJson = isJson;
// If we order post-query, the sorted column needs to be in the ResultSet for sorting,
// even if we don't ultimately ship them to the client (CASSANDRA-4911).
this.columns.addAll(orderingColumns);
this.metadata.addNonSerializedColumns(orderingColumns);
this.orderingColumns = orderingColumns.isEmpty() ? Collections.emptyList() : new ArrayList<>(orderingColumns);
}
// Overriden by SimpleSelection when appropriate.
public boolean isWildcard()
{
return false;
}
/**
* Checks if this selection contains static columns.
* @return true if this selection contains static columns, false otherwise;
*/
public boolean containsStaticColumns()
{
if (table.isStaticCompactTable() || !table.hasStaticColumns())
return false;
if (isWildcard())
return true;
return !Iterables.isEmpty(Iterables.filter(columns, STATIC_COLUMN_FILTER));
}
/**
* Returns the corresponding column index used for post query ordering
* @param c ordering column
* @return
*/
public Integer getOrderingIndex(ColumnMetadata c)
{
if (!isJson)
return getResultSetIndex(c);
// If we order post-query in json, the first and only column that we ship to the client is the json column.
// In that case, we should keep ordering columns around to perform the ordering, then these columns will
// be placed after the json column. As a consequence of where the colums are placed, we should give the
// ordering index a value based on their position in the json encoding and discard the original index.
// (CASSANDRA-14286)
return orderingColumns.indexOf(c) + 1;
}
public ResultSet.ResultMetadata getResultMetadata()
{
if (!isJson)
return metadata;
ColumnSpecification firstColumn = metadata.names.get(0);
ColumnSpecification jsonSpec = new ColumnSpecification(firstColumn.ksName, firstColumn.cfName, Json.JSON_COLUMN_ID, UTF8Type.instance);
ResultSet.ResultMetadata resultMetadata = new ResultSet.ResultMetadata(Lists.newArrayList(jsonSpec));
resultMetadata.addNonSerializedColumns(orderingColumns);
return resultMetadata;
}
public static Selection wildcard(TableMetadata table, boolean isJson, boolean returnStaticContentOnPartitionWithNoRows)
{
List all = new ArrayList<>(table.columns().size());
Iterators.addAll(all, table.allColumnsInSelectOrder());
return new SimpleSelection(table, all, Collections.emptySet(), true, isJson, returnStaticContentOnPartitionWithNoRows);
}
public static Selection wildcardWithGroupBy(TableMetadata table,
VariableSpecifications boundNames,
boolean isJson,
boolean returnStaticContentOnPartitionWithNoRows)
{
return fromSelectors(table,
Lists.newArrayList(table.allColumnsInSelectOrder()),
boundNames,
Collections.emptySet(),
Collections.emptySet(),
true,
isJson,
returnStaticContentOnPartitionWithNoRows);
}
public static Selection forColumns(TableMetadata table, List columns, boolean returnStaticContentOnPartitionWithNoRows)
{
return new SimpleSelection(table, columns, Collections.emptySet(), false, false, returnStaticContentOnPartitionWithNoRows);
}
public void addFunctionsTo(List functions)
{
}
private static boolean processesSelection(List selectables)
{
for (Selectable selectable : selectables)
{
if (selectable.processesSelection())
return true;
}
return false;
}
public static Selection fromSelectors(TableMetadata table,
List selectables,
VariableSpecifications boundNames,
Set orderingColumns,
Set nonPKRestrictedColumns,
boolean hasGroupBy,
boolean isJson,
boolean returnStaticContentOnPartitionWithNoRows)
{
List selectedColumns = new ArrayList<>();
SelectorFactories factories =
SelectorFactories.createFactoriesAndCollectColumnDefinitions(selectables, null, table, selectedColumns, boundNames);
SelectionColumnMapping mapping = collectColumnMappings(table, factories);
Set filteredOrderingColumns = filterOrderingColumns(orderingColumns,
selectedColumns,
factories,
isJson);
return (processesSelection(selectables) || selectables.size() != selectedColumns.size() || hasGroupBy)
? new SelectionWithProcessing(table,
selectedColumns,
filteredOrderingColumns,
nonPKRestrictedColumns,
mapping,
factories,
isJson,
returnStaticContentOnPartitionWithNoRows)
: new SimpleSelection(table,
selectedColumns,
filteredOrderingColumns,
nonPKRestrictedColumns,
mapping,
isJson,
returnStaticContentOnPartitionWithNoRows);
}
/**
* Removes the ordering columns that are already selected.
*
* @param orderingColumns the columns used to order the results
* @param selectedColumns the selected columns
* @param factories the factory used to create the selectors
* @return the ordering columns that are not part of the selection
*/
private static Set filterOrderingColumns(Set orderingColumns,
List selectedColumns,
SelectorFactories factories,
boolean isJson)
{
// CASSANDRA-14286
if (isJson)
return orderingColumns;
Set filteredOrderingColumns = new LinkedHashSet<>(orderingColumns.size());
for (ColumnMetadata orderingColumn : orderingColumns)
{
int index = selectedColumns.indexOf(orderingColumn);
if (index >= 0 && factories.indexOfSimpleSelectorFactory(index) >= 0)
continue;
filteredOrderingColumns.add(orderingColumn);
}
return filteredOrderingColumns;
}
/**
* Returns the index of the specified column within the resultset
* @param c the column
* @return the index of the specified column within the resultset or -1
*/
public int getResultSetIndex(ColumnMetadata c)
{
return getColumnIndex(c);
}
/**
* Returns the index of the specified column
* @param c the column
* @return the index of the specified column or -1
*/
protected final int getColumnIndex(ColumnMetadata c)
{
return columns.indexOf(c);
}
private static SelectionColumnMapping collectColumnMappings(TableMetadata table,
SelectorFactories factories)
{
SelectionColumnMapping selectionColumns = SelectionColumnMapping.newMapping();
for (Selector.Factory factory : factories)
{
ColumnSpecification colSpec = factory.getColumnSpecification(table);
factory.addColumnMapping(selectionColumns, colSpec);
}
return selectionColumns;
}
public abstract Selectors newSelectors(QueryOptions options);
/**
* @return the list of CQL3 columns value this SelectionClause needs.
*/
public List getColumns()
{
return columns;
}
/**
* @return the mappings between resultset columns and the underlying columns
*/
public SelectionColumns getColumnMapping()
{
return columnMapping;
}
public abstract boolean isAggregate();
@Override
public String toString()
{
return MoreObjects.toStringHelper(this)
.add("columns", columns)
.add("columnMapping", columnMapping)
.add("metadata", metadata)
.toString();
}
private static List rowToJson(List row,
ProtocolVersion protocolVersion,
ResultSet.ResultMetadata metadata,
List orderingColumns)
{
ByteBuffer[] jsonRow = new ByteBuffer[orderingColumns.size() + 1];
StringBuilder sb = new StringBuilder("{");
for (int i = 0; i < metadata.names.size(); i++)
{
ColumnSpecification spec = metadata.names.get(i);
ByteBuffer buffer = row.get(i);
// If it is an ordering column we need to keep it in case we need it for post ordering
int index = orderingColumns.indexOf(spec);
if (index >= 0)
jsonRow[index + 1] = buffer;
// If the column is only used for ordering we can stop here.
if (i >= metadata.getColumnCount())
continue;
if (i > 0)
sb.append(", ");
String columnName = spec.name.toString();
if (!columnName.equals(columnName.toLowerCase(Locale.US)))
columnName = "\"" + columnName + "\"";
sb.append('"');
sb.append(Json.quoteAsJsonString(columnName));
sb.append("\": ");
if (buffer == null)
sb.append("null");
else
sb.append(spec.type.toJSONString(buffer, protocolVersion));
}
sb.append("}");
jsonRow[0] = UTF8Type.instance.getSerializer().serialize(sb.toString());
return Arrays.asList(jsonRow);
}
public static interface Selectors
{
/**
* Returns the {@code ColumnFilter} corresponding to those selectors
*
* @return the {@code ColumnFilter} corresponding to those selectors
*/
public ColumnFilter getColumnFilter();
/**
* Checks if one of the selectors perform some aggregations.
* @return {@code true} if one of the selectors perform some aggregations, {@code false} otherwise.
*/
public boolean isAggregate();
/**
* Returns the number of fetched columns
* @return the number of fetched columns
*/
public int numberOfFetchedColumns();
/**
* Checks if one of the selectors collect TTLs.
* @return {@code true} if one of the selectors collect TTLs, {@code false} otherwise.
*/
public boolean collectTTLs();
/**
* Checks if one of the selectors collect timestamps.
* @return {@code true} if one of the selectors collect timestamps, {@code false} otherwise.
*/
public boolean collectTimestamps();
/**
* Adds the current row of the specified ResultSetBuilder.
*
* @param rs the ResultSetBuilder
* @throws InvalidRequestException
*/
public void addInputRow(ResultSetBuilder rs);
public List getOutputRow();
public void reset();
}
// Special cased selection for when only columns are selected.
private static class SimpleSelection extends Selection
{
private final boolean isWildcard;
public SimpleSelection(TableMetadata table,
List selectedColumns,
Set orderingColumns,
boolean isWildcard,
boolean isJson,
boolean returnStaticContentOnPartitionWithNoRows)
{
this(table,
selectedColumns,
orderingColumns,
SelectionColumnMapping.simpleMapping(selectedColumns),
isWildcard ? ColumnFilterFactory.wildcard(table)
: ColumnFilterFactory.fromColumns(table, selectedColumns, orderingColumns, Collections.emptySet(), returnStaticContentOnPartitionWithNoRows),
isWildcard,
isJson);
}
public SimpleSelection(TableMetadata table,
List selectedColumns,
Set orderingColumns,
Set nonPKRestrictedColumns,
SelectionColumnMapping mapping,
boolean isJson,
boolean returnStaticContentOnPartitionWithNoRows)
{
this(table,
selectedColumns,
orderingColumns,
mapping,
ColumnFilterFactory.fromColumns(table, selectedColumns, orderingColumns, nonPKRestrictedColumns, returnStaticContentOnPartitionWithNoRows),
false,
isJson);
}
private SimpleSelection(TableMetadata table,
List selectedColumns,
Set orderingColumns,
SelectionColumnMapping mapping,
ColumnFilterFactory columnFilterFactory,
boolean isWildcard,
boolean isJson)
{
/*
* In theory, even a simple selection could have multiple time the same column, so we
* could filter those duplicate out of columns. But since we're very unlikely to
* get much duplicate in practice, it's more efficient not to bother.
*/
super(table, selectedColumns, orderingColumns, mapping, columnFilterFactory, isJson);
this.isWildcard = isWildcard;
}
@Override
public boolean isWildcard()
{
return isWildcard;
}
public boolean isAggregate()
{
return false;
}
public Selectors newSelectors(QueryOptions options)
{
return new Selectors()
{
private List current;
public void reset()
{
current = null;
}
public List getOutputRow()
{
if (isJson)
return rowToJson(current, options.getProtocolVersion(), metadata, orderingColumns);
return current;
}
public void addInputRow(ResultSetBuilder rs) throws InvalidRequestException
{
current = rs.current;
}
public boolean isAggregate()
{
return false;
}
@Override
public int numberOfFetchedColumns()
{
return getColumns().size();
}
@Override
public boolean collectTTLs()
{
return false;
}
@Override
public boolean collectTimestamps()
{
return false;
}
@Override
public ColumnFilter getColumnFilter()
{
// In the case of simple selection we know that the ColumnFilter has already been computed and
// that by consequence the selectors argument has not impact on the output.
return columnFilterFactory.newInstance(null);
}
};
}
}
private static class SelectionWithProcessing extends Selection
{
private final SelectorFactories factories;
private final boolean collectTimestamps;
private final boolean collectTTLs;
public SelectionWithProcessing(TableMetadata table,
List columns,
Set orderingColumns,
Set nonPKRestrictedColumns,
SelectionColumnMapping metadata,
SelectorFactories factories,
boolean isJson,
boolean returnStaticContentOnPartitionWithNoRows)
{
super(table,
columns,
orderingColumns,
metadata,
ColumnFilterFactory.fromSelectorFactories(table, factories, orderingColumns, nonPKRestrictedColumns, returnStaticContentOnPartitionWithNoRows),
isJson);
this.factories = factories;
this.collectTimestamps = factories.containsWritetimeSelectorFactory();
this.collectTTLs = factories.containsTTLSelectorFactory();;
for (ColumnMetadata orderingColumn : orderingColumns)
{
factories.addSelectorForOrdering(orderingColumn, getColumnIndex(orderingColumn));
}
}
@Override
public void addFunctionsTo(List functions)
{
factories.addFunctionsTo(functions);
}
@Override
public int getResultSetIndex(ColumnMetadata c)
{
return factories.indexOfSimpleSelectorFactory(super.getResultSetIndex(c));
}
public boolean isAggregate()
{
return factories.doesAggregation();
}
public Selectors newSelectors(final QueryOptions options) throws InvalidRequestException
{
return new Selectors()
{
private final List selectors = factories.newInstances(options);
public void reset()
{
for (Selector selector : selectors)
selector.reset();
}
public boolean isAggregate()
{
return factories.doesAggregation();
}
public List getOutputRow()
{
List outputRow = new ArrayList<>(selectors.size());
for (Selector selector: selectors)
outputRow.add(selector.getOutput(options.getProtocolVersion()));
return isJson ? rowToJson(outputRow, options.getProtocolVersion(), metadata, orderingColumns) : outputRow;
}
public void addInputRow(ResultSetBuilder rs) throws InvalidRequestException
{
for (Selector selector : selectors)
selector.addInput(options.getProtocolVersion(), rs);
}
@Override
public int numberOfFetchedColumns()
{
return getColumns().size();
}
@Override
public boolean collectTTLs()
{
return collectTTLs;
}
@Override
public boolean collectTimestamps()
{
return collectTimestamps;
}
@Override
public ColumnFilter getColumnFilter()
{
return columnFilterFactory.newInstance(selectors);
}
};
}
}
}
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