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arangodb/arangod/Aql/IndexBlock.cpp

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////////////////////////////////////////////////////////////////////////////////
/// DISCLAIMER
///
/// Copyright 2014-2016 ArangoDB GmbH, Cologne, Germany
/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
///
/// 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.
///
/// Copyright holder is ArangoDB GmbH, Cologne, Germany
///
/// @author Jan Steemann
/// @author Michael Hackstein
////////////////////////////////////////////////////////////////////////////////
#include "IndexBlock.h"
#include "Aql/AqlItemBlock.h"
#include "Aql/Collection.h"
#include "Aql/Condition.h"
#include "Aql/ExecutionEngine.h"
#include "Aql/Functions.h"
#include "Aql/Query.h"
#include "Basics/Exceptions.h"
#include "Basics/ScopeGuard.h"
#include "Basics/StaticStrings.h"
#include "Cluster/ServerState.h"
#include "StorageEngine/DocumentIdentifierToken.h"
#include "Utils/OperationCursor.h"
#include "V8/v8-globals.h"
#include "VocBase/LogicalCollection.h"
#include "VocBase/ManagedDocumentResult.h"
#include "VocBase/vocbase.h"
#include <velocypack/Iterator.h>
#include <velocypack/velocypack-aliases.h>
using namespace arangodb;
using namespace arangodb::aql;
IndexBlock::IndexBlock(ExecutionEngine* engine, IndexNode const* en)
: ExecutionBlock(engine, en),
DocumentProducingBlock(en, _trx),
_collection(en->collection()),
_currentIndex(0),
_indexes(en->getIndexes()),
_cursor(nullptr),
_cursors(_indexes.size()),
_condition(en->_condition->root()),
_hasV8Expression(false),
_indexesExhausted(false),
_isLastIndex(false),
_returned(0) {
_mmdr.reset(new ManagedDocumentResult);
if (_condition != nullptr) {
// fix const attribute accesses, e.g. { "a": 1 }.a
for (size_t i = 0; i < _condition->numMembers(); ++i) {
auto andCond = _condition->getMemberUnchecked(i);
for (size_t j = 0; j < andCond->numMembers(); ++j) {
auto leaf = andCond->getMemberUnchecked(j);
if (leaf->numMembers() != 2) {
continue;
}
// We only support binary conditions
TRI_ASSERT(leaf->numMembers() == 2);
AstNode* lhs = leaf->getMember(0);
AstNode* rhs = leaf->getMember(1);
if (lhs->type == NODE_TYPE_ATTRIBUTE_ACCESS && lhs->isConstant()) {
lhs = const_cast<AstNode*>(Ast::resolveConstAttributeAccess(lhs));
leaf->changeMember(0, lhs);
}
if (rhs->type == NODE_TYPE_ATTRIBUTE_ACCESS && rhs->isConstant()) {
rhs = const_cast<AstNode*>(Ast::resolveConstAttributeAccess(rhs));
leaf->changeMember(1, rhs);
}
}
}
}
}
IndexBlock::~IndexBlock() { cleanupNonConstExpressions(); }
/// @brief adds a UNIQUE() to a dynamic IN condition
arangodb::aql::AstNode* IndexBlock::makeUnique(
arangodb::aql::AstNode* node) const {
if (node->type != arangodb::aql::NODE_TYPE_ARRAY || node->numMembers() >= 2) {
// an non-array or an array with more than 1 member
auto en = static_cast<IndexNode const*>(getPlanNode());
auto ast = en->_plan->getAst();
auto array = ast->createNodeArray();
array->addMember(node);
auto trx = transaction();
bool isSorted = false;
bool isSparse = false;
auto unused =
trx->getIndexFeatures(_indexes[_currentIndex], isSorted, isSparse);
if (isSparse) {
// the index is sorted. we need to use SORTED_UNIQUE to get the
// result back in index order
return ast->createNodeFunctionCall("SORTED_UNIQUE", array);
}
// a regular UNIQUE will do
return ast->createNodeFunctionCall("UNIQUE", array);
}
// presumably an array with no or a single member
return node;
}
void IndexBlock::executeExpressions() {
DEBUG_BEGIN_BLOCK();
TRI_ASSERT(_condition != nullptr);
TRI_ASSERT(!_nonConstExpressions.empty());
// The following are needed to evaluate expressions with local data from
// the current incoming item:
AqlItemBlock* cur = _buffer.front();
auto en = static_cast<IndexNode const*>(getPlanNode());
auto ast = en->_plan->getAst();
for (size_t posInExpressions = 0;
posInExpressions < _nonConstExpressions.size(); ++posInExpressions) {
auto& toReplace = _nonConstExpressions[posInExpressions];
auto exp = toReplace->expression;
bool mustDestroy;
AqlValue a = exp->execute(_trx, cur, _pos, _inVars[posInExpressions],
_inRegs[posInExpressions], mustDestroy);
AqlValueGuard guard(a, mustDestroy);
AstNode* evaluatedNode = nullptr;
AqlValueMaterializer materializer(_trx);
VPackSlice slice = materializer.slice(a, false);
evaluatedNode = ast->nodeFromVPack(slice, true);
_condition->getMember(toReplace->orMember)
->getMember(toReplace->andMember)
->changeMember(toReplace->operatorMember, evaluatedNode);
}
DEBUG_END_BLOCK();
}
int IndexBlock::initialize() {
DEBUG_BEGIN_BLOCK();
int res = ExecutionBlock::initialize();
auto en = static_cast<IndexNode const*>(getPlanNode());
auto ast = en->_plan->getAst();
// instantiate expressions:
auto instantiateExpression = [&](size_t i, size_t j, size_t k,
AstNode* a) -> void {
// all new AstNodes are registered with the Ast in the Query
auto e = std::make_unique<Expression>(ast, a);
TRI_IF_FAILURE("IndexBlock::initialize") {
THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
}
_hasV8Expression |= e->isV8();
std::unordered_set<Variable const*> inVars;
e->variables(inVars);
auto nce = std::make_unique<NonConstExpression>(i, j, k, e.get());
e.release();
_nonConstExpressions.push_back(nce.get());
nce.release();
// Prepare _inVars and _inRegs:
_inVars.emplace_back();
std::vector<Variable const*>& inVarsCur = _inVars.back();
_inRegs.emplace_back();
std::vector<RegisterId>& inRegsCur = _inRegs.back();
for (auto const& v : inVars) {
inVarsCur.emplace_back(v);
auto it = en->getRegisterPlan()->varInfo.find(v->id);
TRI_ASSERT(it != en->getRegisterPlan()->varInfo.end());
TRI_ASSERT(it->second.registerId < ExecutionNode::MaxRegisterId);
inRegsCur.emplace_back(it->second.registerId);
}
};
if (_condition == nullptr) {
// This Node has no condition. Iterate over the complete index.
return TRI_ERROR_NO_ERROR;
}
auto outVariable = en->outVariable();
for (size_t i = 0; i < _condition->numMembers(); ++i) {
auto andCond = _condition->getMemberUnchecked(i);
for (size_t j = 0; j < andCond->numMembers(); ++j) {
auto leaf = andCond->getMemberUnchecked(j);
if (leaf->numMembers() != 2) {
continue;
}
// We only support binary conditions
TRI_ASSERT(leaf->numMembers() == 2);
AstNode* lhs = leaf->getMember(0);
AstNode* rhs = leaf->getMember(1);
if (lhs->isAttributeAccessForVariable(outVariable, false)) {
// Index is responsible for the left side, check if right side has to be
// evaluated
if (!rhs->isConstant()) {
if (leaf->type == NODE_TYPE_OPERATOR_BINARY_IN) {
rhs = makeUnique(rhs);
}
instantiateExpression(i, j, 1, rhs);
TRI_IF_FAILURE("IndexBlock::initializeExpressions") {
THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
}
}
} else {
// Index is responsible for the right side, check if left side has to be
// evaluated
if (!lhs->isConstant()) {
instantiateExpression(i, j, 0, lhs);
TRI_IF_FAILURE("IndexBlock::initializeExpressions") {
THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
}
}
}
}
}
return res;
// cppcheck-suppress style
DEBUG_END_BLOCK();
}
// init the ranges for reading, this should be called once per new incoming
// block!
//
// This is either called every time we get a new incoming block.
// If all the bounds are constant, then in the case of hash, primary or edges
// indexes it does nothing. In the case of a skiplist index, it creates a
// skiplistIterator which is used by readIndex. If at least one bound is
// variable, then this this also evaluates the IndexOrCondition required to
// determine the values of the bounds.
//
// It is guaranteed that
// _buffer is not empty, in particular _buffer.front() is defined
// _pos points to a position in _buffer.front()
// Therefore, we can use the register values in _buffer.front() in row
// _pos to evaluate the variable bounds.
bool IndexBlock::initIndexes() {
DEBUG_BEGIN_BLOCK();
// We start with a different context. Return documents found in the previous
// context again.
_alreadyReturned.clear();
// Find out about the actual values for the bounds in the variable bound case:
if (!_nonConstExpressions.empty()) {
TRI_ASSERT(_condition != nullptr);
if (_hasV8Expression) {
bool const isRunningInCluster =
arangodb::ServerState::instance()->isRunningInCluster();
// must have a V8 context here to protect Expression::execute()
auto engine = _engine;
arangodb::basics::ScopeGuard guard{
[&engine]() -> void { engine->getQuery()->enterContext(); },
[&]() -> void {
if (isRunningInCluster) {
// must invalidate the expression now as we might be called from
// different threads
for (auto const& e : _nonConstExpressions) {
e->expression->invalidate();
}
engine->getQuery()->exitContext();
}
}};
ISOLATE;
v8::HandleScope scope(isolate); // do not delete this!
executeExpressions();
TRI_IF_FAILURE("IndexBlock::executeV8") {
THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
}
} else {
// no V8 context required!
executeExpressions();
TRI_IF_FAILURE("IndexBlock::executeExpression") {
THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
}
}
}
IndexNode const* node = static_cast<IndexNode const*>(getPlanNode());
if (node->_reverse) {
_currentIndex = _indexes.size() - 1;
} else {
_currentIndex = 0;
}
createCursor();
if (_cursor->failed()) {
THROW_ARANGO_EXCEPTION(_cursor->code);
}
while (!_cursor->hasMore()) {
if (node->_reverse) {
--_currentIndex;
} else {
++_currentIndex;
}
if (_currentIndex < _indexes.size()) {
// This check will work as long as _indexes.size() < MAX_SIZE_T
createCursor();
if (_cursor->failed()) {
THROW_ARANGO_EXCEPTION(_cursor->code);
}
} else {
_cursor = nullptr;
_indexesExhausted = true;
// We were not able to initialize any index with this condition
return false;
}
}
_indexesExhausted = false;
return true;
// cppcheck-suppress style
DEBUG_END_BLOCK();
}
/// @brief create an OperationCursor object
void IndexBlock::createCursor() {
DEBUG_BEGIN_BLOCK();
_cursor = orderCursor(_currentIndex);
DEBUG_END_BLOCK();
}
/// @brief Forwards _iterator to the next available index
void IndexBlock::startNextCursor() {
DEBUG_BEGIN_BLOCK();
IndexNode const* node = static_cast<IndexNode const*>(getPlanNode());
if (node->_reverse) {
--_currentIndex;
_isLastIndex = (_currentIndex == 0);
} else {
++_currentIndex;
_isLastIndex = (_currentIndex == _indexes.size() - 1);
}
if (_currentIndex < _indexes.size()) {
// This check will work as long as _indexes.size() < MAX_SIZE_T
createCursor();
} else {
_cursor = nullptr;
}
DEBUG_END_BLOCK();
}
// this is called every time we just skip in the index
bool IndexBlock::skipIndex(size_t atMost) {
DEBUG_BEGIN_BLOCK();
if (_cursor == nullptr || _indexesExhausted) {
// All indexes exhausted
return false;
}
while (_cursor != nullptr) {
if (!_cursor->hasMore()) {
startNextCursor();
continue;
}
if (_returned == atMost) {
// We have skipped enough, do not check if we have more
return true;
}
TRI_IF_FAILURE("IndexBlock::readIndex") {
THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
}
uint64_t returned = static_cast<uint64_t>(_returned);
int res = _cursor->skip(atMost - returned, returned);
_returned = static_cast<size_t>(returned);
if (res == TRI_ERROR_NO_ERROR) {
// We have skipped enough.
// And this index could return more.
// We are good.
return true;
}
}
return false;
}
// this is called every time we need to fetch data from the indexes
bool IndexBlock::readIndex(
size_t atMost,
IndexIterator::DocumentCallback const& callback) {
DEBUG_BEGIN_BLOCK();
// this is called every time we want to read the index.
// For the primary key index, this only reads the index once, and never
// again (although there might be multiple calls to this function).
// For the edge, hash or skiplists indexes, initIndexes creates an iterator
// and read*Index just reads from the iterator until it is done.
// Then initIndexes is read again and so on. This is to avoid reading the
// entire index when we only want a small number of documents.
if (_cursor == nullptr || _indexesExhausted) {
// All indexes exhausted
return false;
}
while (_cursor != nullptr) {
if (!_cursor->hasMore()) {
startNextCursor();
continue;
}
TRI_ASSERT(atMost >= _returned);
if (_returned == atMost) {
// We have returned enough, do not check if we have more
return true;
}
TRI_IF_FAILURE("IndexBlock::readIndex") {
THROW_ARANGO_EXCEPTION(TRI_ERROR_DEBUG);
}
TRI_ASSERT(atMost >= _returned);
if (_cursor->nextDocument(callback, atMost - _returned)) {
// We have returned enough.
// And this index could return more.
// We are good.
return true;
}
}
// if we get here the indexes are exhausted.
return false;
// cppcheck-suppress style
DEBUG_END_BLOCK();
}
int IndexBlock::initializeCursor(AqlItemBlock* items, size_t pos) {
DEBUG_BEGIN_BLOCK();
int res = ExecutionBlock::initializeCursor(items, pos);
if (res != TRI_ERROR_NO_ERROR) {
return res;
}
_alreadyReturned.clear();
_returned = 0;
_pos = 0;
_currentIndex = 0;
return TRI_ERROR_NO_ERROR;
// cppcheck-suppress style
DEBUG_END_BLOCK();
}
/// @brief getSome
AqlItemBlock* IndexBlock::getSome(size_t atLeast, size_t atMost) {
DEBUG_BEGIN_BLOCK();
traceGetSomeBegin();
if (_done) {
traceGetSomeEnd(nullptr);
return nullptr;
}
TRI_ASSERT(atMost > 0);
size_t curRegs;
std::unique_ptr<AqlItemBlock> res(
requestBlock(atMost,
getPlanNode()->getRegisterPlan()->nrRegs[getPlanNode()->getDepth()]));
_returned = 0; // here we count how many of this AqlItemBlock we have
// already filled
size_t copyFromRow; // The row to copy values from
// The following callbacks write one index lookup result into res at
// position _returned:
IndexIterator::DocumentCallback callback;
if (_indexes.size() > 1) {
// Activate uniqueness checks
callback = [&](DocumentIdentifierToken const& token, VPackSlice slice) {
TRI_ASSERT(res.get() != nullptr);
if (!_isLastIndex) {
// insert & check for duplicates in one go
if (!_alreadyReturned.emplace(token._data).second) {
// Document already in list. Skip this
return;
}
} else {
// only check for duplicates
if (_alreadyReturned.find(token._data) != _alreadyReturned.end()) {
// Document found, skip
return;
}
}
_documentProducer(res.get(), slice, curRegs, _returned, copyFromRow);
};
} else {
// No uniqueness checks
callback = [&](DocumentIdentifierToken const& token, VPackSlice slice) {
TRI_ASSERT(res.get() != nullptr);
_documentProducer(res.get(), slice, curRegs, _returned, copyFromRow);
};
}
do {
if (_buffer.empty()) {
size_t toFetch = (std::min)(DefaultBatchSize(), atMost);
if (!ExecutionBlock::getBlock(toFetch, toFetch) || (!initIndexes())) {
_done = true;
break;
}
TRI_ASSERT(!_indexesExhausted);
}
if (_indexesExhausted) {
AqlItemBlock* cur = _buffer.front();
if (++_pos >= cur->size()) {
_buffer.pop_front(); // does not throw
returnBlock(cur);
_pos = 0;
}
if (_buffer.empty()) {
if (!ExecutionBlock::getBlock(DefaultBatchSize(), DefaultBatchSize())) {
_done = true;
break;
}
}
if (!initIndexes()) {
_done = true;
break;
}
TRI_ASSERT(!_indexesExhausted);
}
// We only get here with non-exhausted indexes.
// At least one of them is prepared and ready to read.
TRI_ASSERT(!_indexesExhausted);
AqlItemBlock* cur = _buffer.front();
curRegs = cur->getNrRegs();
TRI_ASSERT(curRegs <= res->getNrRegs());
// only copy 1st row of registers inherited from previous frame(s)
inheritRegisters(cur, res.get(), _pos, _returned);
copyFromRow = _returned;
// Read the next elements from the indexes
auto saveReturned = _returned;
_indexesExhausted = !readIndex(atMost, callback);
if (_returned == saveReturned) {
// No results. Kill the registers:
for (arangodb::aql::RegisterId i = 0; i < curRegs; ++i) {
res->destroyValue(_returned, i);
}
} else {
// Update statistics
_engine->_stats.scannedIndex += _returned - saveReturned;
}
} while (_returned < atMost);
// Now there are three cases:
// (1) The AqlItemBlock is empty (no result for any input or index)
// (2) The AqlItemBlock is half-full (0 < _returned < atMost)
// (3) The AqlItemBlock is full (_returned == atMost)
if (_returned == 0) {
AqlItemBlock* dummy = res.release();
returnBlock(dummy);
return nullptr;
}
if (_returned < atMost) {
res->shrink(_returned, false);
}
// Clear out registers no longer needed later:
clearRegisters(res.get());
traceGetSomeEnd(res.get());
return res.release();
// cppcheck-suppress style
DEBUG_END_BLOCK();
}
/// @brief skipSome
size_t IndexBlock::skipSome(size_t atLeast, size_t atMost) {
DEBUG_BEGIN_BLOCK();
if (_done) {
return 0;
}
_returned = 0;
while (_returned < atLeast) {
if (_buffer.empty()) {
size_t toFetch = (std::min)(DefaultBatchSize(), atMost);
if (!ExecutionBlock::getBlock(toFetch, toFetch) || (!initIndexes())) {
_done = true;
break;
}
TRI_ASSERT(!_indexesExhausted);
_pos = 0; // this is in the first block
}
if (_indexesExhausted) {
AqlItemBlock* cur = _buffer.front();
if (++_pos >= cur->size()) {
_buffer.pop_front(); // does not throw
returnBlock(cur);
_pos = 0;
}
if (_buffer.empty()) {
if (!ExecutionBlock::getBlock(DefaultBatchSize(), DefaultBatchSize())) {
_done = true;
break;
}
_pos = 0; // this is in the first block
}
if (!initIndexes()) {
_done = true;
break;
}
TRI_ASSERT(!_indexesExhausted);
}
// We only get here with non-exhausted indexes.
// At least one of them is prepared and ready to read.
TRI_ASSERT(!_indexesExhausted);
_indexesExhausted = !skipIndex(atMost);
}
return _returned;
// cppcheck-suppress style
DEBUG_END_BLOCK();
}
/// @brief frees the memory for all non-constant expressions
void IndexBlock::cleanupNonConstExpressions() {
for (auto& it : _nonConstExpressions) {
delete it;
}
_nonConstExpressions.clear();
}
/// @brief order a cursor for the index at the specified position
arangodb::OperationCursor* IndexBlock::orderCursor(size_t currentIndex) {
AstNode const* conditionNode = nullptr;
if (_condition != nullptr) {
TRI_ASSERT(_indexes.size() == _condition->numMembers());
TRI_ASSERT(_condition->numMembers() > currentIndex);
conditionNode = _condition->getMember(currentIndex);
}
TRI_ASSERT(_indexes.size() > currentIndex);
// TODO: if we have _nonConstExpressions, we should also reuse the
// cursors, but in this case we have to adjust the iterator's search condition
// from _condition
if (!_nonConstExpressions.empty() || _cursors[currentIndex] == nullptr) {
// yet no cursor for index, so create it
IndexNode const* node = static_cast<IndexNode const*>(getPlanNode());
_cursors[currentIndex].reset(_trx->indexScanForCondition(
_indexes[currentIndex], conditionNode, node->outVariable(), _mmdr.get(),
UINT64_MAX, transaction::Methods::defaultBatchSize(), node->_reverse));
} else {
// cursor for index already exists, reset and reuse it
_cursors[currentIndex]->reset();
}
return _cursors[currentIndex].get();
}
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