path: root/src/mongo/db/ops/modifier_inc.cpp

/**
 *    Copyright (C) 2013 10gen Inc.
 *
 *    This program is free software: you can redistribute it and/or  modify
 *    it under the terms of the GNU Affero General Public License, version 3,
 *    as published by the Free Software Foundation.
 *
 *    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
 *    GNU Affero General Public License for more details.
 *
 *    You should have received a copy of the GNU Affero General Public License
 *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *    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 GNU Affero General 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/db/ops/modifier_inc.h"

#include "mongo/base/error_codes.h"
#include "mongo/bson/mutable/algorithm.h"
#include "mongo/bson/mutable/document.h"
#include "mongo/db/ops/field_checker.h"
#include "mongo/db/ops/log_builder.h"
#include "mongo/db/ops/path_support.h"
#include "mongo/util/mongoutils/str.h"

namespace mongo {

namespace mb = mutablebson;
namespace str = mongoutils::str;

struct ModifierInc::PreparedState {
    PreparedState(mutablebson::Document& doc)
        : doc(doc), idxFound(0), elemFound(doc.end()), newValue(), noOp(false) {}

    // Document that is going to be changed.
    mutablebson::Document& doc;

    // Index in _fieldRef for which an Element exist in the document.
    size_t idxFound;

    // Element corresponding to _fieldRef[0.._idxFound].
    mutablebson::Element elemFound;

    // Value to be applied
    SafeNum newValue;

    // This $inc is a no-op?
    bool noOp;
};

ModifierInc::ModifierInc(ModifierIncMode mode)
    : ModifierInterface(), _mode(mode), _fieldRef(), _posDollar(0), _val() {}

ModifierInc::~ModifierInc() {}

Status ModifierInc::init(const BSONElement& modExpr, const Options& opts, bool* positional) {
    //
    // field name analysis
    //

    // Perform standard field name and updateable checks.
    _fieldRef.parse(modExpr.fieldName());
    Status status = fieldchecker::isUpdatable(_fieldRef);
    if (!status.isOK()) {
        return status;
    }

    // If a $-positional operator was used, get the index in which it occurred
    // and ensure only one occurrence.
    size_t foundCount;
    bool foundDollar = fieldchecker::isPositional(_fieldRef, &_posDollar, &foundCount);

    if (positional)
        *positional = foundDollar;

    if (foundDollar && foundCount > 1) {
        return Status(ErrorCodes::BadValue,
                      str::stream() << "Too many positional (i.e. '$') elements found in path '"
                                    << _fieldRef.dottedField() << "'");
    }

    //
    // value analysis
    //

    if (!modExpr.isNumber()) {
        // TODO: Context for mod error messages would be helpful
        // include mod code, etc.
        return Status(ErrorCodes::TypeMismatch,
                      str::stream() << "Cannot " << (_mode == MODE_INC ? "increment" : "multiply")
                                    << " with non-numeric argument: {" << modExpr << "}");
    }

    _val = modExpr;
    dassert(_val.isValid());

    return Status::OK();
}

Status ModifierInc::prepare(mutablebson::Element root,
                            StringData matchedField,
                            ExecInfo* execInfo) {
    _preparedState.reset(new PreparedState(root.getDocument()));

    // If we have a $-positional field, it is time to bind it to an actual field part.
    if (_posDollar) {
        if (matchedField.empty()) {
            return Status(ErrorCodes::BadValue,
                          str::stream() << "The positional operator did not find the match "
                                           "needed from the query. Unexpanded update: "
                                        << _fieldRef.dottedField());
        }
        _fieldRef.setPart(_posDollar, matchedField);
    }

    // Locate the field name in 'root'. Note that we may not have all the parts in the path
    // in the doc -- which is fine. Our goal now is merely to reason about whether this mod
    // apply is a noOp or whether is can be in place. The remaining path, if missing, will
    // be created during the apply.
    Status status = pathsupport::findLongestPrefix(
        _fieldRef, root, &_preparedState->idxFound, &_preparedState->elemFound);

    // FindLongestPrefix may say the path does not exist at all, which is fine here, or
    // that the path was not viable or otherwise wrong, in which case, the mod cannot
    // proceed.
    if (status.code() == ErrorCodes::NonExistentPath) {
        _preparedState->elemFound = root.getDocument().end();
    } else if (!status.isOK()) {
        return status;
    }

    // We register interest in the field name. The driver needs this info to sort out if
    // there is any conflict among mods.
    execInfo->fieldRef[0] = &_fieldRef;

    // Capture the value we are going to write. At this point, there may not be a value
    // against which to operate, so the result will be simply _val.
    _preparedState->newValue = _val;

    //
    // in-place and no-op logic
    //
    // If the field path is not fully present, then this mod cannot be in place, nor is a
    // noOp.
    if (!_preparedState->elemFound.ok() || _preparedState->idxFound < (_fieldRef.numParts() - 1)) {
        // For multiplication, we treat ops against missing as yielding zero. We take
        // advantage here of the promotion rules for SafeNum; the expression below will
        // always yield a zero of the same type of operand that the user provided
        // (e.g. double).
        if (_mode == MODE_MUL)
            _preparedState->newValue *= SafeNum(static_cast<int32_t>(0));

        return Status::OK();
    }

    // If the value being $inc'ed is the same as the one already in the doc, than this is a
    // noOp.
    if (!_preparedState->elemFound.isNumeric()) {
        mb::Element idElem = mb::findFirstChildNamed(root, "_id");
        return Status(ErrorCodes::TypeMismatch,
                      str::stream() << "Cannot apply " << (_mode == MODE_INC ? "$inc" : "$mul")
                                    << " to a value of non-numeric type. {" << idElem.toString()
                                    << "} has the field '"
                                    << _preparedState->elemFound.getFieldName()
                                    << "' of non-numeric type "
                                    << typeName(_preparedState->elemFound.getType()));
    }
    const SafeNum currentValue = _preparedState->elemFound.getValueSafeNum();

    // Update newValue w.r.t to the current value of the found element.
    if (_mode == MODE_INC)
        _preparedState->newValue += currentValue;
    else
        _preparedState->newValue *= currentValue;

    // If the result of the addition is invalid, we must return an error.
    if (!_preparedState->newValue.isValid()) {
        mb::Element idElem = mb::findFirstChildNamed(root, "_id");
        return Status(ErrorCodes::BadValue,
                      str::stream() << "Failed to apply $inc operations to current value ("
                                    << currentValue.debugString() << ") for document {"
                                    << idElem.toString() << "}");
    }

    // If the values are identical (same type, same value), then this is a no-op.
    if (_preparedState->newValue.isIdentical(currentValue)) {
        _preparedState->noOp = execInfo->noOp = true;
        return Status::OK();
    }

    return Status::OK();
}

Status ModifierInc::apply() const {
    dassert(_preparedState->noOp == false);

    // If there's no need to create any further field part, the $inc is simply a value
    // assignment.
    if (_preparedState->elemFound.ok() && _preparedState->idxFound == (_fieldRef.numParts() - 1)) {
        return _preparedState->elemFound.setValueSafeNum(_preparedState->newValue);
    }

    //
    // Complete document path logic
    //

    // Creates the final element that's going to be $set in 'doc'.
    mutablebson::Document& doc = _preparedState->doc;
    StringData lastPart = _fieldRef.getPart(_fieldRef.numParts() - 1);
    mutablebson::Element elemToSet = doc.makeElementSafeNum(lastPart, _preparedState->newValue);
    if (!elemToSet.ok()) {
        return Status(ErrorCodes::InternalError, "can't create new element");
    }

    // Now, we can be in two cases here, as far as attaching the element being set goes:
    // (a) none of the parts in the element's path exist, or (b) some parts of the path
    // exist but not all.
    if (!_preparedState->elemFound.ok()) {
        _preparedState->elemFound = doc.root();
        _preparedState->idxFound = 0;
    } else {
        _preparedState->idxFound++;
    }

    // createPathAt() will complete the path and attach 'elemToSet' at the end of it.
    return pathsupport::createPathAt(
        _fieldRef, _preparedState->idxFound, _preparedState->elemFound, elemToSet);
}

Status ModifierInc::log(LogBuilder* logBuilder) const {
    dassert(_preparedState->newValue.isValid());

    // We'd like to create an entry such as {$set: {<fieldname>: <value>}} under 'logRoot'.
    // We start by creating the {$set: ...} Element.
    mutablebson::Document& doc = logBuilder->getDocument();

    // Then we create the {<fieldname>: <value>} Element.
    mutablebson::Element logElement =
        doc.makeElementSafeNum(_fieldRef.dottedField(), _preparedState->newValue);

    if (!logElement.ok()) {
        return Status(ErrorCodes::InternalError,
                      str::stream() << "Could not append entry to "
                                    << (_mode == MODE_INC ? "$inc" : "$mul") << " oplog entry: "
                                    << "set '" << _fieldRef.dottedField() << "' -> "
                                    << _preparedState->newValue.debugString());
    }

    // Now, we attach the {<fieldname>: <value>} Element under the {$set: ...} segment.
    return logBuilder->addToSets(logElement);
}

}  // namespace mongo