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/**
* Copyright (C) 2019-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#include "mongo/platform/basic.h"
#include "mongo/db/auth/authorization_session.h"
#include "mongo/db/pipeline/expression_js_emit.h"
#include "mongo/db/pipeline/make_js_function.h"
#include "mongo/db/query/query_knobs_gen.h"
namespace mongo {
REGISTER_EXPRESSION(_internalJsEmit, ExpressionInternalJsEmit::parse);
namespace {
/**
* Helper for extracting fields from a BSONObj in one pass. This is a hot path
* for some map reduce workloads so be careful when changing.
*
* 'elts' must be an array of size >= 2.
*/
void extract2Args(const BSONObj& args, BSONElement* elts) {
const size_t nToExtract = 2;
auto fail = []() { uasserted(31220, "emit takes 2 args"); };
BSONObjIterator it(args);
for (size_t i = 0; i < nToExtract; ++i) {
if (!it.more()) {
fail();
}
elts[i] = it.next();
}
// There should be exactly two arguments, no more.
if (it.more()) {
fail();
}
}
/**
* This function is called from the JavaScript function provided to the expression.
*/
BSONObj emitFromJS(const BSONObj& args, void* data) {
BSONElement elts[2];
extract2Args(args, elts);
auto emitState = static_cast<ExpressionInternalJsEmit::EmitState*>(data);
if (elts[0].type() == Undefined) {
MutableDocument md;
// Note: Using MutableDocument::addField() is considerably faster than using
// MutableDocument::setField() or building a document by hand with the DOC() macros.
md.addField("k", Value(BSONNULL));
md.addField("v", Value(elts[1]));
emitState->emit(md.freeze());
} else {
MutableDocument md;
md.addField("k", Value(elts[0]));
md.addField("v", Value(elts[1]));
emitState->emit(md.freeze());
}
return BSONObj();
}
} // namespace
ExpressionInternalJsEmit::ExpressionInternalJsEmit(ExpressionContext* const expCtx,
boost::intrusive_ptr<Expression> thisRef,
std::string funcSource)
: Expression(expCtx, {std::move(thisRef)}),
_emitState{{}, internalQueryMaxJsEmitBytes.load(), 0},
_thisRef(_children[0]),
_funcSource(std::move(funcSource)) {
expCtx->sbeCompatible = false;
}
void ExpressionInternalJsEmit::_doAddDependencies(mongo::DepsTracker* deps) const {
_children[0]->addDependencies(deps);
}
boost::intrusive_ptr<Expression> ExpressionInternalJsEmit::parse(ExpressionContext* const expCtx,
BSONElement expr,
const VariablesParseState& vps) {
uassert(4660801,
str::stream() << kExpressionName << " cannot be used inside a validator.",
!expCtx->isParsingCollectionValidator);
uassert(31221,
str::stream() << kExpressionName
<< " requires an object as an argument, found: " << typeName(expr.type()),
expr.type() == BSONType::Object);
BSONElement evalField = expr["eval"];
uassert(31222, str::stream() << "The map function must be specified.", evalField);
uassert(31224,
"The map function must be of type string or code",
evalField.type() == BSONType::String || evalField.type() == BSONType::Code);
std::string funcSourceString = evalField._asCode();
BSONElement thisField = expr["this"];
uassert(
31223, str::stream() << kExpressionName << " requires 'this' to be specified", thisField);
boost::intrusive_ptr<Expression> thisRef = parseOperand(expCtx, thisField, vps);
return new ExpressionInternalJsEmit(expCtx, std::move(thisRef), std::move(funcSourceString));
}
Value ExpressionInternalJsEmit::serialize(bool explain) const {
return Value(
Document{{kExpressionName,
Document{{"eval", _funcSource}, {"this", _thisRef->serialize(explain)}}}});
}
Value ExpressionInternalJsEmit::evaluate(const Document& root, Variables* variables) const {
Value thisVal = _thisRef->evaluate(root, variables);
uassert(31225, "'this' must be an object.", thisVal.getType() == BSONType::Object);
// If the scope does not exist and is created by the following call, then make sure to
// re-bind emit() and the given function to the new scope.
ExpressionContext* expCtx = getExpressionContext();
auto jsExec = expCtx->getJsExecWithScope();
// Inject the native "emit" function to be called from the user-defined map function. This
// particular Expression/ExpressionContext may be reattached to a new OperationContext (and thus
// a new JS Scope) when used across getMore operations, so this method will handle that case for
// us by only injecting if we haven't already.
jsExec->injectEmitIfNecessary(emitFromJS, &_emitState);
// Although inefficient to "create" a new function every time we evaluate, this will usually end
// up being a simple cache lookup. This is needed because the JS Scope may have been recreated
// on a new thread if the expression is evaluated across getMores.
auto func = makeJsFunc(expCtx, _funcSource.c_str());
BSONObj thisBSON = thisVal.getDocument().toBson();
BSONObj params;
jsExec->callFunctionWithoutReturn(func, params, thisBSON);
auto returnValue = Value(std::move(_emitState.emittedObjects));
_emitState.reset();
return returnValue;
}
} // namespace mongo
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