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/**
* 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.hadoop.hive.ql.exec.vector.mapjoin.fast;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hive.ql.exec.vector.mapjoin.hashtable.VectorMapJoinHashMapResult;
import org.apache.hadoop.hive.serde2.WriteBuffers;
import org.apache.hadoop.hive.serde2.WriteBuffers.ByteSegmentRef;
import org.apache.hadoop.hive.serde2.WriteBuffers.Position;;
// Supports random access.
public class VectorMapJoinFastValueStore {
private static final Log LOG = LogFactory.getLog(VectorMapJoinFastValueStore.class.getName());
private WriteBuffers writeBuffers;
/**
* A store for "lists" of arbitrary length values in memory.
*
* The memory is a "infinite" byte array or WriteBuffers object.
*
* We give the client a 64-bit (long) value reference to keep that has the offset within
* the "infinite" byte array of the last value inserted in a "list".
*
* We optimize the common case when "list"s are 1 element and values are short and store the
* value length in the value reference word.
*
* We also support keeping a count (up to a limit or cap) so help with join result generation
* algorithms.
*
* If the last value is big, the big length will be encoded as an integer at the beginning
* of the value followed by the big value bytes.
*
* Due to optimizing by keeping the last value's length in the value reference, when we have
* more than one value, a new value will need to keep the small value length of the next
* value.
*
* So, values after the first value have 4 parts: a relative offset word with flags, an
* optional length if the current value is big, an optional next value length if it is small,
* and the value bytes.
*
* Cases:
* 1) One element, small:
*
* Value Reference -------------
* |
* |
* v
* {Small Value Bytes}
*
* 2) One element, big:
*
* Value Reference --------------
* |
* |
* v
* {Big Value Len} {Big Value Bytes}
*
* 1) Multiple elements:
*
* Value Reference ----------------
* |
* | // Last value added.
* |
* v
* {Rel Offset Word} [Big Value Len] [Next Value Small Len] {Value Bytes}
* | optional optional
* |
* |
* --- . . . ---
* |
* | // 0 or more
* |
* v
* {Rel Offset Word} [Big Value Len] [Next Value Small Len] {Value Bytes}
* | optional optional
* |
* |
* --------------------
* |
* |
* v
* [Big Value Length] {Value Bytes}
* optional
*
* // First value added without Relative Offset Word, etc.
*/
public WriteBuffers writeBuffers() {
return writeBuffers;
}
public static class HashMapResult extends VectorMapJoinHashMapResult {
private VectorMapJoinFastValueStore valueStore;
private boolean hasRows;
private long valueRefWord;
private boolean isSingleRow;
private int cappedCount;
private boolean haveReadCurrent;
private int readIndex;
private boolean isEof;
private boolean isNextEof;
private boolean isNextLast;
long nextAbsoluteValueOffset;
boolean isNextValueLengthSmall;
int nextSmallValueLength;
private ByteSegmentRef byteSegmentRef;
private Position readPos;
public HashMapResult() {
super();
valueRefWord = -1;
hasRows = false;
byteSegmentRef = new ByteSegmentRef();
readPos = new Position();
}
public void set(VectorMapJoinFastValueStore valueStore, long valueRefWord) {
// LOG.debug("VectorMapJoinFastValueStore set valueRefWord " + Long.toHexString(valueRefWord));
this.valueStore = valueStore;
this.valueRefWord = valueRefWord;
hasRows = true;
isSingleRow = ((valueRefWord & IsLastFlag.flagOnMask) != 0);
cappedCount =
(int) ((valueRefWord & CappedCount.bitMask) >> CappedCount.bitShift);
// Position to beginning.
haveReadCurrent = false;
readIndex = 0;
isEof = false;
}
@Override
public boolean hasRows() {
return hasRows;
}
@Override
public boolean isSingleRow() {
if (!hasRows) {
return false;
}
return isSingleRow;
}
@Override
public boolean isCappedCountAvailable() {
return true;
}
@Override
public int cappedCount() {
if (!hasRows) {
return 0;
}
return cappedCount;
}
@Override
public ByteSegmentRef first() {
if (!hasRows) {
return null;
}
// Position to beginning.
haveReadCurrent = false;
readIndex = 0;
isEof = false;
return internalRead();
}
@Override
public ByteSegmentRef next() {
if (!hasRows) {
return null;
}
return internalRead();
}
public ByteSegmentRef internalRead() {
long absoluteValueOffset;
int valueLength;
if (readIndex == 0) {
/*
* Extract information from reference word from slot table.
*/
absoluteValueOffset =
(valueRefWord & AbsoluteValueOffset.bitMask);
// Position before the last written value.
valueStore.writeBuffers.setReadPoint(absoluteValueOffset, readPos);
if (isSingleRow) {
isNextEof = true;
valueLength =
(int) ((valueRefWord & SmallValueLength.bitMask) >> SmallValueLength.bitShift);
boolean isValueLengthSmall = (valueLength != SmallValueLength.allBitsOn);
if (!isValueLengthSmall) {
// And, if current value is big we must read it.
valueLength = valueStore.writeBuffers.readVInt(readPos);
}
} else {
isNextEof = false;
// 2nd and beyond records have a relative offset word at the beginning.
long relativeOffsetWord = valueStore.writeBuffers.readVLong(readPos);
long relativeOffset =
(relativeOffsetWord & NextRelativeValueOffset.bitMask) >> NextRelativeValueOffset.bitShift;
nextAbsoluteValueOffset = absoluteValueOffset - relativeOffset;
isNextLast = ((relativeOffsetWord & IsNextValueLastFlag.flagOnMask) != 0);
isNextValueLengthSmall =
((relativeOffsetWord & IsNextValueLengthSmallFlag.flagOnMask) != 0);
}
valueLength =
(int) ((valueRefWord & SmallValueLength.bitMask) >> SmallValueLength.bitShift);
boolean isValueLengthSmall = (valueLength != SmallValueLength.allBitsOn);
if (!isValueLengthSmall) {
// And, if current value is big we must read it.
valueLength = valueStore.writeBuffers.readVInt(readPos);
}
// 2nd and beyond have the next value's small length in the current record.
if (isNextValueLengthSmall) {
nextSmallValueLength = valueStore.writeBuffers.readVInt(readPos);
} else {
nextSmallValueLength = -1;
}
} else {
if (isNextEof) {
return null;
}
absoluteValueOffset = nextAbsoluteValueOffset;
// Position before the last written value.
valueStore.writeBuffers.setReadPoint(absoluteValueOffset, readPos);
if (isNextLast) {
isNextEof = true;
if (isNextValueLengthSmall) {
valueLength = nextSmallValueLength;
} else {
valueLength = (int) valueStore.writeBuffers.readVLong(readPos);
}
} else {
isNextEof = false;
// 2nd and beyond records have a relative offset word at the beginning.
long relativeOffsetWord = valueStore.writeBuffers.readVLong(readPos);
// Read current value's big length now, if necessary.
if (isNextValueLengthSmall) {
valueLength = nextSmallValueLength;
} else {
valueLength = (int) valueStore.writeBuffers.readVLong(readPos);
}
long relativeOffset =
(relativeOffsetWord & NextRelativeValueOffset.bitMask) >> NextRelativeValueOffset.bitShift;
nextAbsoluteValueOffset = absoluteValueOffset - relativeOffset;
isNextLast = ((relativeOffsetWord & IsNextValueLastFlag.flagOnMask) != 0);
isNextValueLengthSmall =
((relativeOffsetWord & IsNextValueLengthSmallFlag.flagOnMask) != 0);
if (isNextValueLengthSmall) {
// TODO: Write readVInt
nextSmallValueLength = (int) valueStore.writeBuffers.readVLong(readPos);
} else {
nextSmallValueLength = -1;
}
}
}
// Our reading is positioned to the value.
valueStore.writeBuffers.getByteSegmentRefToCurrent(byteSegmentRef, valueLength, readPos);
readIndex++;
return byteSegmentRef;
}
@Override
public boolean isEof() {
if (!hasRows) {
return true;
}
return isEof;
}
@Override
public void forget() {
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append("(" + super.toString() + ", ");
sb.append("cappedCount " + cappedCount() + ")");
return sb.toString();
}
}
/**
* Bit-length fields within a 64-bit (long) value reference.
*
* Lowest field: An absolute byte offset the value in the WriteBuffers.
*
* 2nd field: For short values, the length of the value. Otherwise, a special constant
* indicating a big value whose length is stored with the value.
*
* 3rd field: A value count, up to a limit (a cap). Have a count helps the join result
* algorithms determine which optimization to use for M x N result cross products.
* A special constant indicates if the value count is >= the cap.
*
* Last field: an bit indicating whether there is only one value.
*/
// Lowest field.
private final class AbsoluteValueOffset {
private static final int bitLength = 40;
private static final long allBitsOn = (1L << bitLength) - 1;
private static final long bitMask = allBitsOn;
// Make it a power of 2.
private static final long maxSize = 1L << (bitLength - 2);
}
private final class SmallValueLength {
private static final int bitLength = 10;
private static final int allBitsOn = (1 << bitLength) - 1;
private static final int threshold = allBitsOn; // Lower this for big value testing.
private static final int bitShift = AbsoluteValueOffset.bitLength;
private static final long bitMask = ((long) allBitsOn) << bitShift;
private static final long allBitsOnBitShifted = ((long) allBitsOn) << bitShift;
}
private final class CappedCount {
private static final int bitLength = 10;
private static final int allBitsOn = (1 << bitLength) - 1;
private static final int limit = allBitsOn;
private static final int bitShift = SmallValueLength.bitShift + SmallValueLength.bitLength;
private static final long bitMask = ((long) allBitsOn) << bitShift;
}
private final class IsLastFlag {
private static final int bitShift = CappedCount.bitShift + CappedCount.bitLength;;
private static final long flagOnMask = 1L << bitShift;
}
// This bit should not be on for valid value references. We use -1 for a no value marker.
private final class IsInvalidFlag {
private static final int bitShift = 63;
private static final long flagOnMask = 1L << bitShift;
}
/**
* Relative Offset Word stored at the beginning of all but the last value that has a
* relative offset and 2 flags.
*
* We put the flags at the low end of the word so the variable length integer will
* encode smaller.
*
* First bit is a flag indicating if the next value (not the current value) has a small length.
* When the first value is added and it has a small length, that length is stored in the
* value reference and not with the value. So, when we have multiple values, we need a way to
* know to keep the next value's small length with the current value.
*
* Second bit is a flag indicating if the next value (not the current value) is the last value.
*
* The relative offset *backwards* to the next value.
*/
private final class IsNextValueLengthSmallFlag {
private static final int bitLength = 1;
private static final long flagOnMask = 1L;
}
private final class IsNextValueLastFlag {
private static final int bitLength = 1;
private static final int bitShift = IsNextValueLengthSmallFlag.bitLength;
private static final long flagOnMask = 1L << bitShift;
}
private final class NextRelativeValueOffset {
private static final int bitLength = 40;
private static final long allBitsOn = (1L << bitLength) - 1;
private static final int bitShift = IsNextValueLastFlag.bitShift + IsNextValueLastFlag.bitLength;
private static final long bitMask = allBitsOn << bitShift;
}
public long addFirst(byte[] valueBytes, int valueStart, int valueLength) {
// First value is written without: next relative offset, next value length, is next value last
// flag, is next value length small flag, etc.
/*
* We build up the Value Reference Word we will return that will be kept by the caller.
*/
long valueRefWord = IsLastFlag.flagOnMask;
valueRefWord |= ((long) 1 << CappedCount.bitShift);
long newAbsoluteOffset;
if (valueLength < SmallValueLength.threshold) {
// Small case: Just write the value bytes only.
if (valueLength == 0) {
// We don't write a first empty value.
// Get an offset to reduce the relative offset later if there are more than 1 value.
newAbsoluteOffset = writeBuffers.getWritePoint();
} else {
newAbsoluteOffset = writeBuffers.getWritePoint();
writeBuffers.write(valueBytes, valueStart, valueLength);
}
// The caller remembers the small value length.
valueRefWord |= ((long) valueLength) << SmallValueLength.bitShift;
} else {
// Big case: write the length as a VInt and then the value bytes.
newAbsoluteOffset = writeBuffers.getWritePoint();
writeBuffers.writeVInt(valueLength);
writeBuffers.write(valueBytes, valueStart, valueLength);
// Use magic length value to indicate big.
valueRefWord |= SmallValueLength.allBitsOnBitShifted;
}
// LOG.debug("VectorMapJoinFastValueStore addFirst valueLength " + valueLength + " newAbsoluteOffset " + newAbsoluteOffset + " valueRefWord " + Long.toHexString(valueRefWord));
// The lower bits are the absolute value offset.
valueRefWord |= newAbsoluteOffset;
return valueRefWord;
}
public long addMore(long oldValueRef, byte[] valueBytes, int valueStart, int valueLength) {
if ((oldValueRef & IsInvalidFlag.flagOnMask) != 0) {
throw new RuntimeException("Invalid optimized hash table reference");
}
/*
* Extract information about the old value.
*/
long oldAbsoluteValueOffset =
(oldValueRef & AbsoluteValueOffset.bitMask);
int oldSmallValueLength =
(int) ((oldValueRef & SmallValueLength.bitMask) >> SmallValueLength.bitShift);
boolean isOldValueLengthSmall = (oldSmallValueLength != SmallValueLength.allBitsOn);
int oldCappedCount =
(int) ((oldValueRef & CappedCount.bitMask) >> CappedCount.bitShift);
boolean isOldValueLast =
((oldValueRef & IsLastFlag.flagOnMask) != 0);
// LOG.debug("VectorMapJoinFastValueStore addMore isOldValueLast " + isOldValueLast + " oldSmallValueLength " + oldSmallValueLength + " oldAbsoluteValueOffset " + oldAbsoluteValueOffset + " oldValueRef " + Long.toHexString(oldValueRef));
/*
* Write information about the old value (which becomes our next) at the beginning
* of our new value.
*/
long newAbsoluteOffset = writeBuffers.getWritePoint();
long relativeOffsetWord = 0;
if (isOldValueLengthSmall) {
relativeOffsetWord |= IsNextValueLengthSmallFlag.flagOnMask;
}
if (isOldValueLast) {
relativeOffsetWord |= IsNextValueLastFlag.flagOnMask;
}
int newCappedCount = oldCappedCount;
if (newCappedCount < CappedCount.limit) {
newCappedCount++;
}
long relativeOffset = newAbsoluteOffset - oldAbsoluteValueOffset;
relativeOffsetWord |= (relativeOffset << NextRelativeValueOffset.bitShift);
writeBuffers.writeVLong(relativeOffsetWord);
// When the next value is small it was not recorded with the old (i.e. next) value and we
// have to remember it.
if (isOldValueLengthSmall) {
writeBuffers.writeVInt(oldSmallValueLength);
}
// Now, we have written all information about the next value, work on the *new* value.
long newValueRef = ((long) newCappedCount) << CappedCount.bitShift;
boolean isNewValueSmall = (valueLength < SmallValueLength.threshold);
if (!isNewValueSmall) {
// Use magic value to indicating we are writing the big value length.
newValueRef |= ((long) SmallValueLength.allBitsOn << SmallValueLength.bitShift);
writeBuffers.writeVInt(valueLength);
} else {
// Caller must remember small value length.
newValueRef |= ((long) valueLength) << SmallValueLength.bitShift;
}
writeBuffers.write(valueBytes, valueStart, valueLength);
// The lower bits are the absolute value offset.
newValueRef |= newAbsoluteOffset;
// LOG.debug("VectorMapJoinFastValueStore addMore valueLength " + valueLength + " newAbsoluteOffset " + newAbsoluteOffset + " newValueRef " + Long.toHexString(newValueRef));
return newValueRef;
}
public VectorMapJoinFastValueStore(int writeBuffersSize) {
writeBuffers = new WriteBuffers(writeBuffersSize, AbsoluteValueOffset.maxSize);
}
}
