org.apache.cassandra.db

Class ReadCommand

java.lang.Object

org.apache.cassandra.db.monitoring.MonitorableImpl

org.apache.cassandra.db.ReadCommand

All Implemented Interfaces:

Monitorable, ReadQuery

Direct Known Subclasses:

PartitionRangeReadCommand, SinglePartitionReadCommand

public abstract class ReadCommand
extends MonitorableImpl

General interface for storage-engine read commands (common to both range and single partition commands).

This contains all the informations needed to do a local read.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected class	ReadCommand.CheckForAbort
protected static class	ReadCommand.Kind
protected static class	ReadCommand.SelectionDeserializer
static class	ReadCommand.Serializer

Field Summary

Fields

Modifier and Type	Field and Description
protected static org.slf4j.Logger	logger
static IVersionedSerializer<ReadCommand>	serializer

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	ReadCommand(ReadCommand.Kind kind, boolean isDigestQuery, int digestVersion, boolean acceptsTransient, TableMetadata metadata, int nowInSec, ColumnFilter columnFilter, RowFilter rowFilter, DataLimits limits, IndexMetadata index)

Method Summary

Modifier and Type	Method and Description
boolean	acceptsTransient()
protected abstract void	appendCQLWhereClause(java.lang.StringBuilder sb)
abstract ClusteringIndexFilter	clusteringIndexFilter(DecoratedKey key) The clustering index filter this command to use for the provided key.
ColumnFilter	columnFilter() A filter on which (non-PK) columns must be returned by the query.
abstract ReadCommand	copy() Returns a copy of this command.
protected abstract ReadCommand	copyAsDigestQuery()
ReadCommand	copyAsDigestQuery(java.lang.Iterable<Replica> replicas) Returns a copy of this command with isDigestQuery set to true.
ReadCommand	copyAsDigestQuery(Replica replica) Returns a copy of this command with isDigestQuery set to true.
protected abstract ReadCommand	copyAsTransientQuery()
ReadCommand	copyAsTransientQuery(java.lang.Iterable<Replica> replicas) Returns a copy of this command with acceptsTransient set to true.
ReadCommand	copyAsTransientQuery(Replica replica) Returns a copy of this command with acceptsTransient set to true.
Message<ReadCommand>	createMessage(boolean trackRepairedData) Creates a message for this command.
ReadResponse	createResponse(UnfilteredPartitionIterator iterator, org.apache.cassandra.db.RepairedDataInfo rdi)
int	digestVersion() If the query is a digest one, the requested digest version.
PartitionIterator	executeInternal(ReadExecutionController controller) Execute the query for internal queries (that is, it basically executes the query locally).
UnfilteredPartitionIterator	executeLocally(ReadExecutionController executionController) Executes this command on the local host.
ReadExecutionController	executionController() Starts a new read operation.
ReadExecutionController	executionController(boolean trackRepairedStatus)
Index	getIndex(ColumnFamilyStore cfs)
abstract long	getTimeout(java.util.concurrent.TimeUnit unit) The configured timeout for this command.
IndexMetadata	indexMetadata() Index (metadata) chosen for this query.
boolean	isDigestQuery() Whether this query is a digest one or not.
abstract boolean	isLimitedToOnePartition()
abstract boolean	isRangeRequest()
abstract boolean	isReversed() Whether the underlying ClusteringIndexFilter is reversed or not.
DataLimits	limits() The limits for the query.
void	maybeValidateIndex() If the index manager for the CFS determines that there's an applicable 2i that can be used to execute this command, call its (optional) validation method to check that nothing in this command's parameters violates the implementation specific validation rules.
TableMetadata	metadata() The metadata for the table this is a query on.
java.lang.String	name()
int	nowInSec() The time in seconds to use as "now" for this query.
protected abstract UnfilteredPartitionIterator	queryStorage(ColumnFamilyStore cfs, ReadExecutionController executionController)
protected abstract void	recordLatency(TableMetrics metric, long latencyNanos)
RowFilter	rowFilter() Filters/Resrictions on CQL rows.
protected abstract long	selectionSerializedSize(int version)
protected abstract void	serializeSelection(DataOutputPlus out, int version)
ReadCommand	setDigestVersion(int digestVersion) Sets the digest version, for when digest for that command is requested.
java.lang.String	toCQLString() Recreate the CQL string corresponding to this query.
abstract Verb	verb()
protected UnfilteredPartitionIterator	withoutPurgeableTombstones(UnfilteredPartitionIterator iterator, ColumnFamilyStore cfs, ReadExecutionController controller)
protected UnfilteredPartitionIterator	withStateTracking(UnfilteredPartitionIterator iter)
abstract ReadCommand	withUpdatedLimit(DataLimits newLimits) Creates a new ReadCommand instance with new limits.

Methods inherited from class org.apache.cassandra.db.monitoring.MonitorableImpl

abort, complete, creationTimeNanos, isAborted, isCompleted, isCrossNode, isInProgress, isSlow, setMonitoringTime, slowTimeoutNanos, timeoutNanos

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.apache.cassandra.db.ReadQuery

empty, execute, getPager, isEmpty, selectsClustering, selectsFullPartition, selectsKey

Field Detail

logger

protected static final org.slf4j.Logger logger

serializer

public static final IVersionedSerializer<ReadCommand> serializer

Constructor Detail

ReadCommand

protected ReadCommand(ReadCommand.Kind kind,
                      boolean isDigestQuery,
                      int digestVersion,
                      boolean acceptsTransient,
                      TableMetadata metadata,
                      int nowInSec,
                      ColumnFilter columnFilter,
                      RowFilter rowFilter,
                      DataLimits limits,
                      IndexMetadata index)

Method Detail

serializeSelection

protected abstract void serializeSelection(DataOutputPlus out,
                                           int version)
                                    throws java.io.IOException

Throws:

java.io.IOException

selectionSerializedSize

protected abstract long selectionSerializedSize(int version)

isLimitedToOnePartition

public abstract boolean isLimitedToOnePartition()

isRangeRequest

public abstract boolean isRangeRequest()

withUpdatedLimit

public abstract ReadCommand withUpdatedLimit(DataLimits newLimits)

Creates a new ReadCommand instance with new limits.

Parameters:

newLimits - the new limits

Returns:

a new ReadCommand with the updated limits

getTimeout

public abstract long getTimeout(java.util.concurrent.TimeUnit unit)

The configured timeout for this command.

Returns:

the configured timeout for this command.

isDigestQuery

public boolean isDigestQuery()

Whether this query is a digest one or not.

Returns:

Whether this query is a digest query.

digestVersion

public int digestVersion()

If the query is a digest one, the requested digest version.

Returns:

the requested digest version if the query is a digest. Otherwise, this can return anything.

setDigestVersion

public ReadCommand setDigestVersion(int digestVersion)

Sets the digest version, for when digest for that command is requested.

Note that we allow setting this independently of setting the command as a digest query as this allows us to use the command as a carrier of the digest version even if we only call setIsDigestQuery on some copy of it.

Parameters:

digestVersion - the version for the digest is this command is used for digest query..

Returns:

this read command.

acceptsTransient

public boolean acceptsTransient()

Returns:

Whether this query expects only a transient data response, or a full response

indexMetadata

@Nullable
public IndexMetadata indexMetadata()

Index (metadata) chosen for this query. Can be null.

Returns:

index (metadata) chosen for this query

clusteringIndexFilter

public abstract ClusteringIndexFilter clusteringIndexFilter(DecoratedKey key)

The clustering index filter this command to use for the provided key.

Note that that method should only be called on a key actually queried by this command and in practice, this will almost always return the same filter, but for the sake of paging, the filter on the first key of a range command might be slightly different.

Parameters:

key - a partition key queried by this command.

Returns:

the ClusteringIndexFilter to use for the partition of key key.

copy

public abstract ReadCommand copy()

Returns a copy of this command.

Returns:

a copy of this command.

copyAsTransientQuery

public ReadCommand copyAsTransientQuery(Replica replica)

Returns a copy of this command with acceptsTransient set to true.

copyAsTransientQuery

public ReadCommand copyAsTransientQuery(java.lang.Iterable<Replica> replicas)

Returns a copy of this command with acceptsTransient set to true.

copyAsTransientQuery

protected abstract ReadCommand copyAsTransientQuery()

copyAsDigestQuery

public ReadCommand copyAsDigestQuery(Replica replica)

Returns a copy of this command with isDigestQuery set to true.

copyAsDigestQuery

public ReadCommand copyAsDigestQuery(java.lang.Iterable<Replica> replicas)

Returns a copy of this command with isDigestQuery set to true.

copyAsDigestQuery

protected abstract ReadCommand copyAsDigestQuery()

queryStorage

protected abstract UnfilteredPartitionIterator queryStorage(ColumnFamilyStore cfs,
                                                            ReadExecutionController executionController)

isReversed

public abstract boolean isReversed()

Whether the underlying ClusteringIndexFilter is reversed or not.

Returns:

whether the underlying ClusteringIndexFilter is reversed or not.

createResponse

public ReadResponse createResponse(UnfilteredPartitionIterator iterator,
                                   org.apache.cassandra.db.RepairedDataInfo rdi)

getIndex

public Index getIndex(ColumnFamilyStore cfs)

maybeValidateIndex

public void maybeValidateIndex()

If the index manager for the CFS determines that there's an applicable 2i that can be used to execute this command, call its (optional) validation method to check that nothing in this command's parameters violates the implementation specific validation rules.

executeLocally

public UnfilteredPartitionIterator executeLocally(ReadExecutionController executionController)

Executes this command on the local host.

Parameters:

executionController - the execution controller spanning this command

Returns:

an iterator over the result of executing this command locally.

recordLatency

protected abstract void recordLatency(TableMetrics metric,
                                      long latencyNanos)

executionController

public ReadExecutionController executionController(boolean trackRepairedStatus)

executionController

public ReadExecutionController executionController()

Description copied from interface: ReadQuery

Starts a new read operation.

This must be called before executeInternal and passed to it to protect the read. The returned object must be closed on all path and it is thus strongly advised to use it in a try-with-ressource construction.

Returns:

a newly started execution controller for this ReadQuery.

withStateTracking

protected UnfilteredPartitionIterator withStateTracking(UnfilteredPartitionIterator iter)

createMessage

public Message<ReadCommand> createMessage(boolean trackRepairedData)

Creates a message for this command.

verb

public abstract Verb verb()

appendCQLWhereClause

protected abstract void appendCQLWhereClause(java.lang.StringBuilder sb)

withoutPurgeableTombstones

protected UnfilteredPartitionIterator withoutPurgeableTombstones(UnfilteredPartitionIterator iterator,
                                                                 ColumnFamilyStore cfs,
                                                                 ReadExecutionController controller)

toCQLString

public java.lang.String toCQLString()

Recreate the CQL string corresponding to this query.

Note that in general the returned string will not be exactly the original user string, first because there isn't always a single syntax for a given query, but also because we don't have all the information needed (we know the non-PK columns queried but not the PK ones as internally we query them all). So this shouldn't be relied too strongly, but this should be good enough for debugging purpose which is what this is for.

name

public java.lang.String name()

Specified by:

name in interface Monitorable

metadata

public TableMetadata metadata()

Description copied from interface: ReadQuery

The metadata for the table this is a query on.

Specified by:

metadata in interface ReadQuery

Returns:

the metadata for the table this is a query on.

executeInternal

public PartitionIterator executeInternal(ReadExecutionController controller)

Description copied from interface: ReadQuery

Execute the query for internal queries (that is, it basically executes the query locally).

Specified by:

executeInternal in interface ReadQuery

Parameters:

controller - the ReadExecutionController protecting the read.

Returns:

the result of the query.

limits

public DataLimits limits()

Description copied from interface: ReadQuery

The limits for the query.

Specified by:

limits in interface ReadQuery

Returns:

The limits for the query.

nowInSec

public int nowInSec()

Description copied from interface: ReadQuery

The time in seconds to use as "now" for this query.

We use the same time as "now" for the whole query to avoid considering different values as expired during the query, which would be buggy (would throw of counting amongst other things).

Specified by:

nowInSec in interface ReadQuery

Returns:

the time (in seconds) to use as "now".

rowFilter

public RowFilter rowFilter()

Description copied from interface: ReadQuery

Filters/Resrictions on CQL rows.

This contains the restrictions that are not directly handled by the ClusteringIndexFilter. More specifically, this includes any non-PK column restrictions and can include some PK columns restrictions when those can't be satisfied entirely by the clustering index filter (because not all clustering columns have been restricted for instance). If there is 2ndary indexes on the table, one of this restriction might be handled by a 2ndary index.

Specified by:

rowFilter in interface ReadQuery

Returns:

the filter holding the expression that rows must satisfy.

columnFilter

public ColumnFilter columnFilter()

Description copied from interface: ReadQuery

A filter on which (non-PK) columns must be returned by the query.

Specified by:

columnFilter in interface ReadQuery

Returns:

which columns must be fetched by this query.