com.datastax.driver.core.TokenRange Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of cassandra-driver-core Show documentation
Show all versions of cassandra-driver-core Show documentation
A driver for Apache Cassandra 1.2+ that works exclusively with the Cassandra Query Language version 3
(CQL3) and Cassandra's binary protocol.
/*
* Copyright (C) 2012-2015 DataStax Inc.
*
* Licensed 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 com.datastax.driver.core;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Objects;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;
import java.util.ArrayList;
import java.util.List;
/**
* A range of tokens on the Cassandra ring.
*
* A range is start-exclusive and end-inclusive. It is empty when start and end are the same token, except if that is the minimum
* token, in which case the range covers the whole ring (this is consistent with the behavior of CQL range queries).
*
* Note that CQL does not handle wrapping. To query all partitions in a range, see {@link #unwrap()}.
*/
public final class TokenRange implements Comparable {
private final Token start;
private final Token end;
@VisibleForTesting
final Token.Factory factory;
TokenRange(Token start, Token end, Token.Factory factory) {
this.start = start;
this.end = end;
this.factory = factory;
}
/**
* Return the start of the range.
*
* @return the start of the range (exclusive).
*/
public Token getStart() {
return start;
}
/**
* Return the end of the range.
*
* @return the end of the range (inclusive).
*/
public Token getEnd() {
return end;
}
/**
* Splits this range into a number of smaller ranges of equal "size" (referring to the number of tokens, not the actual amount of data).
*
* Splitting an empty range is not permitted. But note that, in edge cases, splitting a range might produce one or more empty ranges.
*
* @param numberOfSplits the number of splits to create.
* @return the splits.
* @throws IllegalArgumentException if the range is empty or if numberOfSplits < 1.
*/
public List splitEvenly(int numberOfSplits) {
if (numberOfSplits < 1)
throw new IllegalArgumentException(String.format("numberOfSplits (%d) must be greater than 0.", numberOfSplits));
if (isEmpty())
throw new IllegalArgumentException("Can't split empty range " + this);
List tokenRanges = new ArrayList();
List splitPoints = factory.split(start, end, numberOfSplits);
Token splitStart = start;
for (Token splitEnd : splitPoints) {
tokenRanges.add(new TokenRange(splitStart, splitEnd, factory));
splitStart = splitEnd;
}
tokenRanges.add(new TokenRange(splitStart, end, factory));
return tokenRanges;
}
/**
* Returns whether this range is empty.
*
* A range is empty when start and end are the same token, except if that is the minimum token,
* in which case the range covers the whole ring (this is consistent with the behavior of CQL
* range queries).
*
* @return whether the range is empty.
*/
public boolean isEmpty() {
return start.equals(end) && !start.equals(factory.minToken());
}
/**
* Returns whether this range wraps around the end of the ring.
*
* @return whether this range wraps around.
*/
public boolean isWrappedAround() {
return start.compareTo(end) > 0 && !end.equals(factory.minToken());
}
/**
* Splits this range into a list of two non-wrapping ranges. This will return the range itself if it is
* non-wrapping, or two ranges otherwise.
*
* For example:
*
* - {@code ]1,10]} unwraps to itself;
* - {@code ]10,1]} unwraps to {@code ]10,min_token]} and {@code ]min_token,1]}.
*
*
* This is useful for CQL range queries, which do not handle wrapping:
*
* {@code
* List rows = new ArrayList();
* for (TokenRange subRange : range.unwrap()) {
* ResultSet rs = session.execute("SELECT * FROM mytable WHERE token(pk) > ? and token(pk) <= ?",
* subRange.getStart(), subRange.getEnd());
* rows.addAll(rs.all());
* }
* }
*
* @return the list of non-wrapping ranges.
*/
public List unwrap() {
if (isWrappedAround()) {
return ImmutableList.of(
new TokenRange(start, factory.minToken(), factory),
new TokenRange(factory.minToken(), end, factory));
} else {
return ImmutableList.of(this);
}
}
/**
* Returns whether this range intersects another one.
*
* For example:
*
* - {@code ]3,5]} intersects {@code ]1,4]}, {@code ]4,5]}...
* - {@code ]3,5]} does not intersect {@code ]1,2]}, {@code ]2,3]}, {@code ]5,7]}...
*
*
* @param that the other range.
* @return whether they intersect.
*/
public boolean intersects(TokenRange that) {
// Empty ranges never intersect any other range
if (this.isEmpty() || that.isEmpty())
return false;
return this.contains(that.start, true)
|| this.contains(that.end, false)
|| that.contains(this.start, true)
|| that.contains(this.end, false);
}
/**
* Computes the intersection of this range with another one.
*
* If either of these ranges overlap the the ring, they are unwrapped and the unwrapped
* tokens are compared with one another.
*
* This call will fail if the two ranges do not intersect, you must check by calling
* {@link #intersects(TokenRange)} beforehand.
*
* @param that the other range.
* @return the range(s) resulting from the intersection.
* @throws IllegalArgumentException if the ranges do not intersect.
*/
public List intersectWith(TokenRange that) {
if (!this.intersects(that))
throw new IllegalArgumentException("The two ranges do not intersect, use intersects() before calling this method");
List intersected = Lists.newArrayList();
// Compare the unwrapped ranges to one another.
List unwrappedForThis = this.unwrap();
List unwrappedForThat = that.unwrap();
for (TokenRange t1 : unwrappedForThis) {
for (TokenRange t2 : unwrappedForThat) {
if (t1.intersects(t2)) {
intersected.add(new TokenRange(
(t1.contains(t2.start, true)) ? t2.start : t1.start,
(t1.contains(t2.end, false)) ? t2.end : t1.end,
factory));
}
}
}
// If two intersecting ranges were produced, merge them if they are adjacent.
// This could happen in the case that two wrapped ranges intersected.
if (intersected.size() == 2) {
TokenRange t1 = intersected.get(0);
TokenRange t2 = intersected.get(1);
if (t1.end.equals(t2.start) || t2.end.equals(t1.start)) {
return ImmutableList.of(t1.mergeWith(t2));
}
}
return intersected;
}
/**
* Checks whether this range contains a given token.
*
* @param token the token to check for.
* @return whether this range contains the token, i.e. {@code range.start < token <= range.end}.
*/
public boolean contains(Token token) {
return contains(token, false);
}
// isStart handles the case where the token is the start of another range, for example:
// * ]1,2] contains 2, but it does not contain the start of ]2,3]
// * ]1,2] does not contain 1, but it contains the start of ]1,3]
private boolean contains(Token token, boolean isStart) {
boolean isAfterStart = isStart ? token.compareTo(start) >= 0 : token.compareTo(start) > 0;
boolean isBeforeEnd = end.equals(factory.minToken()) ||
(isStart ? token.compareTo(end) < 0 : token.compareTo(end) <= 0);
return isWrappedAround()
? isAfterStart || isBeforeEnd
: isAfterStart && isBeforeEnd;
}
/**
* Merges this range with another one.
*
* The two ranges should either intersect or be adjacent; in other words, the merged range
* should not include tokens that are in neither of the original ranges.
*
* For example:
*
* - merging {@code ]3,5]} with {@code ]4,7]} produces {@code ]3,7]};
* - merging {@code ]3,5]} with {@code ]4,5]} produces {@code ]3,5]};
* - merging {@code ]3,5]} with {@code ]5,8]} produces {@code ]3,8]};
* - merging {@code ]3,5]} with {@code ]6,8]} fails.
*
*
* @param that the other range.
* @return the resulting range.
* @throws IllegalArgumentException if the ranges neither intersect nor are adjacent.
*/
public TokenRange mergeWith(TokenRange that) {
if (this.equals(that))
return this;
if (!(this.intersects(that) || this.end.equals(that.start) || that.end.equals(this.start)))
throw new IllegalArgumentException(String.format(
"Can't merge %s with %s because they neither intersect nor are adjacent",
this, that));
if (this.isEmpty())
return that;
if (that.isEmpty())
return this;
// That's actually "starts in or is adjacent to the end of"
boolean thisStartsInThat = that.contains(this.start, true) || this.start.equals(that.end);
boolean thatStartsInThis = this.contains(that.start, true) || that.start.equals(this.end);
// This takes care of all the cases that return the full ring, so that we don't have to worry about them below
if (thisStartsInThat && thatStartsInThis)
return fullRing();
// Starting at this.start, see how far we can go while staying in at least one of the ranges.
Token mergedEnd = (thatStartsInThis && !this.contains(that.end, false))
? that.end
: this.end;
// Repeat in the other direction.
Token mergedStart = thisStartsInThat ? that.start : this.start;
return new TokenRange(mergedStart, mergedEnd, factory);
}
private TokenRange fullRing() {
return new TokenRange(factory.minToken(), factory.minToken(), factory);
}
@Override
public boolean equals(Object other) {
if (other == this)
return true;
if (other instanceof TokenRange) {
TokenRange that = (TokenRange) other;
return Objects.equal(this.start, that.start) &&
Objects.equal(this.end, that.end);
}
return false;
}
@Override
public int hashCode() {
return Objects.hashCode(start, end);
}
@Override
public String toString() {
return String.format("]%s, %s]", start, end);
}
@Override
public int compareTo(TokenRange other) {
if (this.equals(other)) {
return 0;
} else {
int compareStart = this.start.compareTo(other.start);
return compareStart != 0 ? compareStart : this.end.compareTo(other.end);
}
}
}