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foundationdb/fdbclient/WriteMap.h

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/*
* WriteMap.h
*
* This source file is part of the FoundationDB open source project
*
* Copyright 2013-2018 Apple Inc. and the FoundationDB project authors
*
* 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.
*/
#ifndef FDBCLIENT_WRITEMAP_H
#define FDBCLIENT_WRITEMAP_H
#pragma once
#include "fdbclient/FDBTypes.h"
#include "fdbclient/VersionedMap.h"
#include "fdbclient/SnapshotCache.h"
#include "fdbclient/Atomic.h"
struct RYWMutation {
Optional<ValueRef> value;
enum MutationRef::Type type;
RYWMutation(Optional<ValueRef> const& entry, MutationRef::Type type ) : value(entry), type(type) {}
RYWMutation() : value(), type(MutationRef::NoOp) {}
bool operator == (const RYWMutation& r) const {
return value == r.value && type == r.type;
}
bool operator!=(const RYWMutation& r) const { return !(*this == r); }
};
class OperationStack {
private:
RYWMutation singletonOperation;
Optional<std::vector<RYWMutation>> optionalOperations;
bool hasVector() const { return optionalOperations.present(); }
bool defaultConstructed;
public:
OperationStack () { defaultConstructed = true; } // Don't use this!
explicit OperationStack (RYWMutation initialEntry) { defaultConstructed = false; singletonOperation = initialEntry; }
void reset(RYWMutation initialEntry) { defaultConstructed = false; singletonOperation = initialEntry; optionalOperations = Optional<std::vector<RYWMutation>>(); }
void poppush(RYWMutation entry) { if(hasVector()) { optionalOperations.get().pop_back(); optionalOperations.get().push_back(entry); } else singletonOperation = entry; }
void push(RYWMutation entry) {
if(defaultConstructed) {
singletonOperation = entry;
defaultConstructed = false;
}
else if(hasVector())
optionalOperations.get().push_back(entry);
else {
optionalOperations = std::vector<RYWMutation>();
optionalOperations.get().push_back(entry);
}
}
bool isDependent() const {
if( !size() )
return false;
return singletonOperation.type != MutationRef::SetValue && singletonOperation.type != MutationRef::ClearRange && singletonOperation.type != MutationRef::SetVersionstampedValue && singletonOperation.type != MutationRef::SetVersionstampedKey;
}
const RYWMutation& top() const { return hasVector() ? optionalOperations.get().back() : singletonOperation; }
RYWMutation& operator[] (int n) { return (n==0) ? singletonOperation : optionalOperations.get()[n-1]; }
const RYWMutation& at(int n) const { return (n==0) ? singletonOperation : optionalOperations.get()[n-1]; }
int size() const { return defaultConstructed ? 0 : hasVector() ? optionalOperations.get().size() + 1 : 1; }
bool operator == (const OperationStack& r) const {
if (size() != r.size())
return false;
if (size() == 0)
return true;
if (singletonOperation != r.singletonOperation)
return false;
if (size() == 1)
return true;
for (int i = 0; i < optionalOperations.get().size(); i++) {
if (optionalOperations.get()[i] != r.optionalOperations.get()[i])
return false;
}
return true;
}
};
struct WriteMapEntry {
KeyRef key;
OperationStack stack;
bool following_keys_cleared;
bool following_keys_conflict;
bool is_conflict;
bool following_keys_unreadable;
bool is_unreadable;
WriteMapEntry( KeyRef const& key, OperationStack && stack, bool following_keys_cleared, bool following_keys_conflict, bool is_conflict, bool following_keys_unreadable, bool is_unreadable ) : key(key), stack(std::move(stack)), following_keys_cleared(following_keys_cleared), following_keys_conflict(following_keys_conflict), is_conflict(is_conflict), following_keys_unreadable(following_keys_unreadable), is_unreadable(is_unreadable) {}
int compare(StringRef const& r) const { return key.compare(r); }
int compare(ExtStringRef const& r) const { return -r.compare(key); }
std::string toString() const { return printable(key); }
};
inline int compare(StringRef const& l, WriteMapEntry const& r) {
return l.compare(r.key);
}
inline int compare(ExtStringRef const& l, WriteMapEntry const& r) {
return l.compare(r.key);
}
inline bool operator < ( const WriteMapEntry& lhs, const WriteMapEntry& rhs ) { return lhs.key < rhs.key; }
inline bool operator < ( const WriteMapEntry& lhs, const StringRef& rhs ) { return lhs.key < rhs; }
inline bool operator < ( const StringRef& lhs, const WriteMapEntry& rhs ) { return lhs < rhs.key; }
inline bool operator<(const WriteMapEntry& lhs, const ExtStringRef& rhs) {
return rhs.compare(lhs.key) > 0;
}
inline bool operator<(const ExtStringRef& lhs, const WriteMapEntry& rhs) {
return lhs.compare(rhs.key) < 0;
}
class WriteMap {
private:
typedef PTreeImpl::PTree<WriteMapEntry> PTreeT;
typedef PTreeImpl::PTreeFinger<WriteMapEntry> PTreeFingerT;
typedef Reference<PTreeT> Tree;
public:
explicit WriteMap(Arena* arena) : arena(arena), ver(-1), scratch_iterator(this), writeMapEmpty(true) {
PTreeImpl::insert( writes, ver, WriteMapEntry( allKeys.begin, OperationStack(), false, false, false, false, false ) );
PTreeImpl::insert( writes, ver, WriteMapEntry( allKeys.end, OperationStack(), false, false, false, false, false ) );
PTreeImpl::insert( writes, ver, WriteMapEntry( afterAllKeys, OperationStack(), false, false, false, false, false ) );
}
WriteMap(WriteMap&& r) noexcept
: writeMapEmpty(r.writeMapEmpty), writes(std::move(r.writes)), ver(r.ver),
scratch_iterator(std::move(r.scratch_iterator)), arena(r.arena) {}
WriteMap& operator=(WriteMap&& r) noexcept {
writeMapEmpty = r.writeMapEmpty;
writes = std::move(r.writes);
ver = r.ver;
scratch_iterator = std::move(r.scratch_iterator);
arena = r.arena;
return *this;
}
//a write with addConflict false on top of an existing write with a conflict range will not remove the conflict
void mutate( KeyRef key, MutationRef::Type operation, ValueRef param, bool addConflict ) {
writeMapEmpty = false;
auto& it = scratch_iterator;
it.reset(writes, ver);
it.skip( key );
bool is_cleared = it.entry().following_keys_cleared;
bool following_conflict = it.entry().following_keys_conflict;
bool is_conflict = addConflict || it.is_conflict_range();
bool following_unreadable = it.entry().following_keys_unreadable;
bool is_unreadable = it.is_unreadable() || operation == MutationRef::SetVersionstampedValue || operation == MutationRef::SetVersionstampedKey;
bool is_dependent = operation != MutationRef::SetValue && operation != MutationRef::SetVersionstampedValue && operation != MutationRef::SetVersionstampedKey;
if (it.entry().key != key) {
if( it.is_cleared_range() && is_dependent ) {
it.tree.clear();
OperationStack op( RYWMutation( Optional<StringRef>(), MutationRef::SetValue ) );
coalesceOver(op, RYWMutation(param, operation), *arena);
PTreeImpl::insert( writes, ver, WriteMapEntry( key, std::move(op), true, following_conflict, is_conflict, following_unreadable, is_unreadable ) );
} else {
it.tree.clear();
PTreeImpl::insert( writes, ver, WriteMapEntry( key, OperationStack( RYWMutation( param, operation ) ), is_cleared, following_conflict, is_conflict, following_unreadable, is_unreadable ) );
}
} else {
if( !it.is_unreadable() && operation == MutationRef::SetValue ) {
it.tree.clear();
PTreeImpl::remove( writes, ver, key );
PTreeImpl::insert( writes, ver, WriteMapEntry( key, OperationStack( RYWMutation( param, operation ) ), is_cleared, following_conflict, is_conflict, following_unreadable, is_unreadable ) );
} else {
WriteMapEntry e( it.entry() );
e.is_conflict = is_conflict;
e.is_unreadable = is_unreadable;
if (e.stack.size() == 0 && it.is_cleared_range() && is_dependent) {
e.stack.push(RYWMutation(Optional<StringRef>(), MutationRef::SetValue));
coalesceOver(e.stack, RYWMutation(param, operation), *arena);
} else if( !is_unreadable && e.stack.size() > 0 )
coalesceOver( e.stack, RYWMutation( param, operation ), *arena );
else
e.stack.push( RYWMutation( param, operation ) );
it.tree.clear();
PTreeImpl::remove( writes, ver, e.key ); // FIXME: Make PTreeImpl::insert do this automatically (see also VersionedMap.h FIXME)
PTreeImpl::insert( writes, ver, std::move(e) );
}
}
}
void clear( KeyRangeRef keys, bool addConflict ) {
writeMapEmpty = false;
if( !addConflict ) {
clearNoConflict( keys );
return;
}
auto& it = scratch_iterator;
it.reset(writes, ver);
it.skip( keys.begin );
bool insert_begin = !it.is_cleared_range() || !it.is_conflict_range() || it.is_unreadable();
if(it.endKey() == keys.end) {
++it;
} else if(it.endKey() < keys.end) {
it.skip( keys.end );
}
bool insert_end = ( it.is_unmodified_range() || !it.is_conflict_range() || it.is_unreadable() ) && ( !it.keyAtBegin() || it.beginKey() != keys.end );
bool end_coalesce_clear = it.is_cleared_range() && it.beginKey() == keys.end && it.is_conflict_range() && !it.is_unreadable();
bool end_conflict = it.is_conflict_range();
bool end_cleared = it.is_cleared_range();
bool end_unreadable = it.is_unreadable();
it.tree.clear();
PTreeImpl::remove( writes, ver, ExtStringRef(keys.begin, !insert_begin ? 1 : 0), ExtStringRef(keys.end, end_coalesce_clear ? 1 : 0) );
if (insert_begin)
PTreeImpl::insert( writes, ver, WriteMapEntry( keys.begin, OperationStack(), true, true, true, false, false ) );
if (insert_end)
PTreeImpl::insert( writes, ver, WriteMapEntry( keys.end, OperationStack(), end_cleared, end_conflict, end_conflict, end_unreadable, end_unreadable ) );
}
void addUnmodifiedAndUnreadableRange( KeyRangeRef keys ) {
auto& it = scratch_iterator;
it.reset(writes, ver);
it.skip( keys.begin );
bool insert_begin = !it.is_unmodified_range() || it.is_conflict_range() || !it.is_unreadable();
if(it.endKey() == keys.end) {
++it;
} else if(it.endKey() < keys.end) {
it.skip( keys.end );
}
bool insert_end = ( it.is_cleared_range() || it.is_conflict_range() || !it.is_unreadable() ) && ( !it.keyAtBegin() || it.beginKey() != keys.end );
bool end_coalesce_unmodified = it.is_unmodified_range() && it.beginKey() == keys.end && !it.is_conflict_range() && it.is_unreadable();
bool end_conflict = it.is_conflict_range();
bool end_cleared = it.is_cleared_range();
bool end_unreadable = it.is_unreadable();
it.tree.clear();
PTreeImpl::remove( writes, ver, ExtStringRef(keys.begin, !insert_begin ? 1 : 0), ExtStringRef(keys.end, end_coalesce_unmodified ? 1 : 0) );
if (insert_begin)
PTreeImpl::insert( writes, ver, WriteMapEntry( keys.begin, OperationStack(), false, false, false, true, true ) );
if (insert_end)
PTreeImpl::insert( writes, ver, WriteMapEntry( keys.end, OperationStack(), end_cleared, end_conflict, end_conflict, end_unreadable, end_unreadable ) );
}
void addConflictRange( KeyRangeRef keys ) {
writeMapEmpty = false;
auto& it = scratch_iterator;
it.reset(writes, ver);
it.skip( keys.begin );
std::vector<ExtStringRef> removals;
std::vector<WriteMapEntry> insertions;
if( !it.entry().following_keys_conflict || !it.entry().is_conflict ) {
if( it.keyAtBegin() && it.beginKey() == keys.begin ) {
removals.push_back( keys.begin );
}
insertions.push_back( WriteMapEntry( keys.begin, it.is_operation() ? OperationStack( it.op() ) : OperationStack(), it.entry().following_keys_cleared, true, true, it.entry().following_keys_unreadable, it.entry().is_unreadable ) );
}
while ( it.endKey() < keys.end ) {
++it;
if (it.keyAtBegin() && (!it.entry().following_keys_conflict || !it.entry().is_conflict) ) {
WriteMapEntry e( it.entry() );
e.following_keys_conflict = true;
e.is_conflict = true;
removals.push_back( e.key );
insertions.push_back( std::move(e) );
}
}
ASSERT( it.beginKey() != keys.end );
if( !it.entry().following_keys_conflict || !it.entry().is_conflict ) {
bool isCleared = it.entry().following_keys_cleared;
bool isUnreadable = it.entry().is_unreadable;
bool followingUnreadable = it.entry().following_keys_unreadable;
++it;
if ( !it.keyAtBegin() || it.beginKey() != keys.end ) {
insertions.push_back(WriteMapEntry(keys.end, OperationStack(), isCleared, false, false, followingUnreadable, isUnreadable));
}
}
it.tree.clear();
//SOMEDAY: optimize this code by having a PTree removal/insertion that takes and returns an iterator
for( int i = 0; i < removals.size(); i++ ) {
PTreeImpl::remove( writes, ver, removals[i] ); // FIXME: Make PTreeImpl::insert do this automatically (see also VersionedMap.h FIXME)
}
for( int i = 0; i < insertions.size(); i++ ) {
PTreeImpl::insert( writes, ver, std::move(insertions[i]) );
}
}
struct iterator {
// Iterates over three types of segments: unmodified ranges, cleared ranges, and modified keys.
// Modified keys may be dependent (need to be collapsed with a snapshot value) or independent (value is known regardless of the snapshot value)
// Every key will belong to exactly one segment. The first segment begins at "" and the last segment ends at \xff\xff.
explicit iterator( WriteMap* map ) : tree(map->writes), at( map->ver ), offset(false) { ++map->ver; }
// Creates an iterator which is conceptually before the beginning of map (you may essentially only call skip() or ++ on it)
// This iterator also represents a snapshot (will be unaffected by future writes)
enum SEGMENT_TYPE { UNMODIFIED_RANGE, CLEARED_RANGE, INDEPENDENT_WRITE, DEPENDENT_WRITE };
SEGMENT_TYPE type() const {
if (offset)
return entry().following_keys_cleared ? CLEARED_RANGE : UNMODIFIED_RANGE;
else
return entry().stack.isDependent() ? DEPENDENT_WRITE : INDEPENDENT_WRITE;
}
bool is_cleared_range() const { return offset && entry().following_keys_cleared; }
bool is_unmodified_range() const { return offset && !entry().following_keys_cleared; }
bool is_operation() const { return !offset; }
bool is_conflict_range() const { return offset ? entry().following_keys_conflict : entry().is_conflict; }
bool is_unreadable() const { return offset ? entry().following_keys_unreadable : entry().is_unreadable; }
bool is_independent() const {
ASSERT(is_operation());
return entry().following_keys_cleared || !entry().stack.isDependent();
}
ExtStringRef beginKey() const { return ExtStringRef(entry().key, offset && entry().stack.size()); }
ExtStringRef endKey() const { return offset ? nextEntry().key : ExtStringRef(entry().key, 1); }
OperationStack const& op() const {
ASSERT(is_operation());
return entry().stack;
}
iterator& operator++() {
if (!offset && !equalsKeyAfter( entry().key, nextEntry().key )) {
offset = true;
} else {
beginLen = endLen;
finger.resize( beginLen );
endLen = PTreeImpl::halfNext( at, finger );
offset = !entry().stack.size();
}
return *this;
}
iterator& operator--() {
if (offset && entry().stack.size() ) {
offset = false;
} else {
endLen = beginLen;
finger.resize(endLen);
beginLen = PTreeImpl::halfPrevious( at, finger );
offset = !entry().stack.size() || !equalsKeyAfter( entry().key, nextEntry().key );
}
return *this;
}
bool operator == ( const iterator& r ) const { return offset == r.offset && beginLen == r.beginLen && finger[beginLen-1] == r.finger[beginLen-1]; }
void skip( KeyRef key ) { // Changes *this to the segment containing key (so that beginKey()<=key && key < endKey())
finger.clear();
if( key == allKeys.end )
PTreeImpl::last(tree, at, finger);
else
PTreeImpl::upper_bound( tree, at, key, finger );
endLen = finger.size();
beginLen = PTreeImpl::halfPrevious( at, finger );
offset = !entry().stack.size() || (entry().key != key);
}
private:
friend class WriteMap;
void reset( Tree const& tree, Version ver ) { this->tree = tree; this->at = ver; this->finger.clear(); beginLen=endLen=0; offset = false; }
WriteMapEntry const& entry() const { return finger[beginLen - 1]->data; }
WriteMapEntry const& nextEntry() const { return finger[endLen - 1]->data; }
bool keyAtBegin() { return !offset || !entry().stack.size(); }
Tree tree;
Version at;
int beginLen, endLen;
PTreeFingerT finger;
bool offset; // false-> the operation stack at entry(); true-> the following cleared or unmodified range
};
bool empty() const { return writeMapEmpty; }
static RYWMutation coalesce(RYWMutation existingEntry, RYWMutation newEntry, Arena& arena) {
ASSERT(newEntry.value.present());
if (newEntry.type == MutationRef::SetValue)
return newEntry;
else if (newEntry.type == MutationRef::AddValue) {
switch(existingEntry.type) {
case MutationRef::SetValue:
return RYWMutation(doLittleEndianAdd(existingEntry.value, newEntry.value.get(), arena), MutationRef::SetValue);
case MutationRef::AddValue:
return RYWMutation(doLittleEndianAdd(existingEntry.value, newEntry.value.get(), arena), MutationRef::AddValue);
default:
throw operation_failed();
}
} else if (newEntry.type == MutationRef::CompareAndClear) {
switch (existingEntry.type) {
case MutationRef::SetValue:
if (doCompareAndClear(existingEntry.value, newEntry.value.get(), arena).present()) {
return existingEntry;
} else {
return RYWMutation(Optional<ValueRef>(), MutationRef::SetValue);
}
default:
throw operation_failed();
}
} else if (newEntry.type == MutationRef::AppendIfFits) {
switch(existingEntry.type) {
case MutationRef::SetValue:
return RYWMutation(doAppendIfFits(existingEntry.value, newEntry.value.get(), arena), MutationRef::SetValue);
case MutationRef::AppendIfFits:
return RYWMutation(doAppendIfFits(existingEntry.value, newEntry.value.get(), arena), MutationRef::AppendIfFits);
default:
throw operation_failed();
}
} else if (newEntry.type == MutationRef::And) {
switch(existingEntry.type) {
case MutationRef::SetValue:
return RYWMutation(doAnd(existingEntry.value, newEntry.value.get(), arena), MutationRef::SetValue);
case MutationRef::And:
return RYWMutation(doAnd(existingEntry.value, newEntry.value.get(), arena), MutationRef::And);
default:
throw operation_failed();
}
} else if (newEntry.type == MutationRef::Or) {
switch(existingEntry.type) {
case MutationRef::SetValue:
return RYWMutation(doOr(existingEntry.value, newEntry.value.get(), arena), MutationRef::SetValue);
case MutationRef::Or:
return RYWMutation(doOr(existingEntry.value, newEntry.value.get(), arena), MutationRef::Or);
default:
throw operation_failed();
}
} else if (newEntry.type == MutationRef::Xor) {
switch(existingEntry.type) {
case MutationRef::SetValue:
return RYWMutation(doXor(existingEntry.value, newEntry.value.get(), arena), MutationRef::SetValue);
case MutationRef::Xor:
return RYWMutation(doXor(existingEntry.value, newEntry.value.get(), arena), MutationRef::Xor);
default:
throw operation_failed();
}
} else if (newEntry.type == MutationRef::Max) {
switch (existingEntry.type) {
case MutationRef::SetValue:
return RYWMutation(doMax(existingEntry.value, newEntry.value.get(), arena), MutationRef::SetValue);
case MutationRef::Max:
return RYWMutation(doMax(existingEntry.value, newEntry.value.get(), arena), MutationRef::Max);
default:
throw operation_failed();
}
} else if (newEntry.type == MutationRef::Min) {
switch (existingEntry.type) {
case MutationRef::SetValue:
return RYWMutation(doMin(existingEntry.value, newEntry.value.get(), arena), MutationRef::SetValue);
case MutationRef::Min:
return RYWMutation(doMin(existingEntry.value, newEntry.value.get(), arena), MutationRef::Min);
default:
throw operation_failed();
}
} else if (newEntry.type == MutationRef::ByteMin) {
switch (existingEntry.type) {
case MutationRef::SetValue:
return RYWMutation(doByteMin(existingEntry.value, newEntry.value.get(), arena), MutationRef::SetValue);
case MutationRef::ByteMin:
return RYWMutation(doByteMin(existingEntry.value, newEntry.value.get(), arena), MutationRef::ByteMin);
default:
throw operation_failed();
}
} else if (newEntry.type == MutationRef::ByteMax) {
switch (existingEntry.type) {
case MutationRef::SetValue:
return RYWMutation(doByteMax(existingEntry.value, newEntry.value.get(), arena), MutationRef::SetValue);
case MutationRef::ByteMax:
return RYWMutation(doByteMax(existingEntry.value, newEntry.value.get(), arena), MutationRef::ByteMax);
default:
throw operation_failed();
}
} else if (newEntry.type == MutationRef::MinV2) {
switch (existingEntry.type) {
case MutationRef::SetValue:
return RYWMutation(doMinV2(existingEntry.value, newEntry.value.get(), arena), MutationRef::SetValue);
case MutationRef::MinV2:
return RYWMutation(doMinV2(existingEntry.value, newEntry.value.get(), arena), MutationRef::MinV2);
default:
throw operation_failed();
}
} else if (newEntry.type == MutationRef::AndV2) {
switch (existingEntry.type) {
case MutationRef::SetValue:
return RYWMutation(doAndV2(existingEntry.value, newEntry.value.get(), arena), MutationRef::SetValue);
case MutationRef::AndV2:
return RYWMutation(doAndV2(existingEntry.value, newEntry.value.get(), arena), MutationRef::AndV2);
default:
throw operation_failed();
}
} else
throw operation_failed();
}
static void coalesceOver(OperationStack& stack, RYWMutation newEntry, Arena& arena) {
RYWMutation existingEntry = stack.top();
if (existingEntry.type == newEntry.type && newEntry.type != MutationRef::CompareAndClear) {
if (isNonAssociativeOp(existingEntry.type) && existingEntry.value.present() && existingEntry.value.get().size() != newEntry.value.get().size()) {
stack.push(newEntry);
}
else {
stack.poppush(coalesce(existingEntry, newEntry, arena));
}
}
else {
if (isAtomicOp(newEntry.type) && isAtomicOp(existingEntry.type)) {
stack.push(newEntry);
}
else {
stack.poppush(coalesce(existingEntry, newEntry, arena));
}
}
}
static RYWMutation coalesceUnder(OperationStack const& stack, Optional<ValueRef> const& value, Arena& arena) {
if( !stack.isDependent() && stack.size() == 1 )
return stack.at(0);
RYWMutation currentEntry = RYWMutation( value, MutationRef::SetValue);
for(int i = 0; i < stack.size(); ++i) {
currentEntry = coalesce(currentEntry, stack.at(i), arena);
}
return currentEntry;
}
private:
friend class ReadYourWritesTransaction;
Arena* arena;
bool writeMapEmpty;
Tree writes;
Version ver; // an internal version number for the tree - no connection to database versions! Currently this is incremented after reads, so that consecutive writes have the same version and those separated by reads have different versions.
iterator scratch_iterator; // Avoid unnecessary memory allocation in write operations
void dump() {
iterator it( this );
it.skip(allKeys.begin);
while( it.beginKey() < allKeys.end ) {
TraceEvent("WriteMapDump").detail("Begin", it.beginKey().toStandaloneStringRef())
.detail("End", it.endKey())
.detail("Cleared", it.is_cleared_range())
.detail("Conflicted", it.is_conflict_range())
.detail("Operation", it.is_operation())
.detail("Unmodified", it.is_unmodified_range())
.detail("Independent", it.is_operation() && it.is_independent())
.detail("StackSize", it.is_operation() ? it.op().size() : 0);
++it;
}
}
//SOMEDAY: clearNoConflict replaces cleared sets with two map entries for everyone one item cleared
void clearNoConflict( KeyRangeRef keys ) {
auto& it = scratch_iterator;
it.reset(writes, ver);
//Find all write conflict ranges within the cleared range
it.skip( keys.begin );
bool insert_begin = !it.is_cleared_range() || it.is_unreadable();
bool lastConflicted = it.is_conflict_range();
bool conflicted = lastConflicted;
std::vector<ExtStringRef> conflict_ranges;
if( insert_begin ) {
conflict_ranges.push_back( keys.begin );
} else {
conflicted = !conflicted;
}
while( it.endKey() < keys.end ) {
++it;
if ( lastConflicted != it.is_conflict_range() ) {
conflict_ranges.push_back( it.beginKey() );
lastConflicted = it.is_conflict_range();
}
}
if( it.endKey() == keys.end )
++it;
ASSERT( it.beginKey() <= keys.end && keys.end < it.endKey() );
bool insert_end = ( ( it.is_unmodified_range() || it.is_unreadable() ) && ( !it.keyAtBegin() || it.beginKey() != keys.end ) ) || ( it.entry().is_conflict && !it.entry().following_keys_conflict && it.beginKey() == keys.end && !it.keyAtBegin() );
bool end_cleared = it.is_cleared_range();
bool end_coalesce_clear = it.is_cleared_range() && it.beginKey() == keys.end && it.is_conflict_range()==lastConflicted && !it.is_unreadable();
bool end_conflict = it.is_conflict_range();
bool end_unreadable = it.is_unreadable();
TEST( it.is_conflict_range() != lastConflicted );
it.tree.clear();
PTreeImpl::remove( writes, ver, ExtStringRef(keys.begin, !insert_begin ? 1 : 0), ExtStringRef(keys.end, end_coalesce_clear ? 1 : 0) );
for( int i = 0; i < conflict_ranges.size(); i++ ) {
PTreeImpl::insert( writes, ver, WriteMapEntry( conflict_ranges[i].toArenaOrRef(*arena), OperationStack(), true, conflicted, conflicted, false, false ) );
conflicted = !conflicted;
}
ASSERT( conflicted != lastConflicted );
if (insert_end)
PTreeImpl::insert( writes, ver, WriteMapEntry( keys.end, OperationStack(), end_cleared, end_conflict, end_conflict, end_unreadable, end_unreadable ) );
}
};
/*
for write in writes: # write.type in [ 'none', 'clear', 'independent', 'dependent' ]
for read in reads[ write.begin : write.end ]: # read.type in [ 'unknown', 'empty', 'value' ]
if write.type == "none":
yield read
elif write.type == "clear":
yield empty()
elif write.type == "independent":
yield value( write )
else: # Dependent write
if read.type == "unknown":
yield read
else:
yield value( collapse( read, write ) )
*/
#endif
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