path: root/src/mongo/db/ops/modifier_rename.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_rename.h"

#include "mongo/base/error_codes.h"
#include "mongo/bson/mutable/document.h"
#include "mongo/bson/mutable/algorithm.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 str = mongoutils::str;

struct ModifierRename::PreparedState {
    PreparedState(mutablebson::Element root)
        : doc(root.getDocument()),
          fromElemFound(doc.end()),
          toIdxFound(0),
          toElemFound(doc.end()),
          applyCalled(false) {}

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

    // The element to rename
    mutablebson::Element fromElemFound;

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

    // Element to remove (in the destination position)
    mutablebson::Element toElemFound;

    // Was apply called?
    bool applyCalled;
};

ModifierRename::ModifierRename() : _fromFieldRef(), _toFieldRef() {}

ModifierRename::~ModifierRename() {}

Status ModifierRename::init(const BSONElement& modExpr, const Options& opts, bool* positional) {
    if (modExpr.type() != String) {
        return Status(ErrorCodes::BadValue,
                      str::stream() << "The 'to' field for $rename must be a string: " << modExpr);
    }

    // Extract the field names from the mod expression

    _fromFieldRef.parse(modExpr.fieldName());
    Status status = fieldchecker::isUpdatable(_fromFieldRef);
    if (!status.isOK())
        return status;

    _toFieldRef.parse(modExpr.String());
    status = fieldchecker::isUpdatable(_toFieldRef);
    if (!status.isOK())
        return status;

    // TODO: Remove this restriction and make a noOp to lift restriction
    // Old restriction is that if the fields are the same then it is not allowed.
    if (_fromFieldRef == _toFieldRef)
        return Status(ErrorCodes::BadValue,
                      str::stream()
                          << "The source and target field for $rename must differ: " << modExpr);

    // TODO: Remove this restriction by allowing moving deeping from the 'from' path
    // Old restriction is that if the to/from is on the same path it fails
    if (_fromFieldRef.isPrefixOf(_toFieldRef) || _toFieldRef.isPrefixOf(_fromFieldRef)) {
        return Status(ErrorCodes::BadValue,
                      str::stream() << "The source and target field for $rename must "
                                       "not be on the same path: " << modExpr);
    }
    // TODO: We can remove this restriction as long as there is only one,
    //       or it is the same array -- should think on this a bit.
    //
    // If a $-positional operator was used it is an error
    size_t dummyPos;
    if (fieldchecker::isPositional(_fromFieldRef, &dummyPos))
        return Status(ErrorCodes::BadValue,
                      str::stream() << "The source field for $rename may not be dynamic: "
                                    << _fromFieldRef.dottedField());
    else if (fieldchecker::isPositional(_toFieldRef, &dummyPos))
        return Status(ErrorCodes::BadValue,
                      str::stream() << "The destination field for $rename may not be dynamic: "
                                    << _toFieldRef.dottedField());

    if (positional)
        *positional = false;

    return Status::OK();
}

Status ModifierRename::prepare(mutablebson::Element root,
                               StringData matchedField,
                               ExecInfo* execInfo) {
    // Rename doesn't work with positional fields ($)
    dassert(matchedField.empty());

    _preparedState.reset(new PreparedState(root));

    // Locate the to field name in 'root', which must exist.
    size_t fromIdxFound;
    Status status = pathsupport::findLongestPrefix(
        _fromFieldRef, root, &fromIdxFound, &_preparedState->fromElemFound);

    const bool sourceExists =
        (_preparedState->fromElemFound.ok() && fromIdxFound == (_fromFieldRef.numParts() - 1));

    // If we can't find the full element in the from field then we can't do anything.
    if (!status.isOK() || !sourceExists) {
        execInfo->noOp = true;
        _preparedState->fromElemFound = root.getDocument().end();

        // TODO: remove this special case from existing behavior
        if (status.code() == ErrorCodes::PathNotViable) {
            return status;
        }

        return Status::OK();
    }

    // Ensure no array in ancestry if what we found is not at the root
    mutablebson::Element curr = _preparedState->fromElemFound.parent();
    if (curr != curr.getDocument().root())
        while (curr.ok() && (curr != curr.getDocument().root())) {
            if (curr.getType() == Array)
                return Status(ErrorCodes::BadValue,
                              str::stream() << "The source field cannot be an array element, '"
                                            << _fromFieldRef.dottedField() << "' in doc with "
                                            << findElementNamed(root.leftChild(), "_id").toString()
                                            << " has an array field called '" << curr.getFieldName()
                                            << "'");
            curr = curr.parent();
        }

    // "To" side validation below

    status = pathsupport::findLongestPrefix(
        _toFieldRef, root, &_preparedState->toIdxFound, &_preparedState->toElemFound);

    // FindLongestPrefix may return not viable or any other error and then we cannot proceed.
    if (status.code() == ErrorCodes::NonExistentPath) {
        // Not an error condition as we will create the "to" path as needed.
    } else if (!status.isOK()) {
        return status;
    }

    const bool destExists = _preparedState->toElemFound.ok() &&
        (_preparedState->toIdxFound == (_toFieldRef.numParts() - 1));

    // Ensure no array in ancestry of "to" Element
    // Set to either parent, or node depending on if the full path element was found
    curr = (destExists ? _preparedState->toElemFound.parent() : _preparedState->toElemFound);
    if (curr != curr.getDocument().root()) {
        while (curr.ok()) {
            if (curr.getType() == Array)
                return Status(ErrorCodes::BadValue,
                              str::stream() << "The destination field cannot be an array element, '"
                                            << _fromFieldRef.dottedField() << "' in doc with "
                                            << findElementNamed(root.leftChild(), "_id").toString()
                                            << " has an array field called '" << curr.getFieldName()
                                            << "'");
            curr = curr.parent();
        }
    }

    // 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] = &_fromFieldRef;
    execInfo->fieldRef[1] = &_toFieldRef;

    execInfo->noOp = false;

    return Status::OK();
}

Status ModifierRename::apply() const {
    dassert(_preparedState->fromElemFound.ok());

    _preparedState->applyCalled = true;

    // Remove from source
    Status removeStatus = _preparedState->fromElemFound.remove();
    if (!removeStatus.isOK()) {
        return removeStatus;
    }

    // If there's no need to create any further field part, the op is simply a value
    // assignment.
    const bool destExists = _preparedState->toElemFound.ok() &&
        (_preparedState->toIdxFound == (_toFieldRef.numParts() - 1));

    if (destExists) {
        removeStatus = _preparedState->toElemFound.remove();
        if (!removeStatus.isOK()) {
            return removeStatus;
        }
    }

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

    // Find the new place to put the "to" element:
    // createPathAt does not use existing prefix elements so we
    // need to get the prefix match position for createPathAt below
    size_t tempIdx = 0;
    mutablebson::Element tempElem = doc.end();
    Status status = pathsupport::findLongestPrefix(_toFieldRef, doc.root(), &tempIdx, &tempElem);

    // createPathAt will complete the path and attach 'elemToSet' at the end of it.
    return pathsupport::createPathAt(_toFieldRef,
                                     tempElem == doc.end() ? 0 : tempIdx + 1,
                                     tempElem == doc.end() ? doc.root() : tempElem,
                                     elemToSet);
}

Status ModifierRename::log(LogBuilder* logBuilder) const {
    // If there was no element found then it was a noop, so return immediately
    if (!_preparedState->fromElemFound.ok())
        return Status::OK();

    // debug assert if apply not called, since we found an element to move.
    dassert(_preparedState->applyCalled);

    const bool isPrefix = _fromFieldRef.isPrefixOf(_toFieldRef);
    const StringData setPath = (isPrefix ? _fromFieldRef : _toFieldRef).dottedField();
    const StringData unsetPath = isPrefix ? StringData() : _fromFieldRef.dottedField();
    const bool doUnset = !isPrefix;

    // 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();

    // Create the {<fieldname>: <value>} Element. Note that we log the mod with a
    // dotted field, if it was applied over a dotted field. The rationale is that the
    // secondary may be in a different state than the primary and thus make different
    // decisions about creating the intermediate path in _fieldRef or not.
    mutablebson::Element logElement =
        doc.makeElementWithNewFieldName(setPath, _preparedState->fromElemFound.getValue());

    if (!logElement.ok()) {
        return Status(ErrorCodes::InternalError, "cannot create details for $rename mod");
    }

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

    if (status.isOK() && doUnset) {
        // Create the {<fieldname>: <value>} Element. Note that we log the mod with a
        // dotted field, if it was applied over a dotted field. The rationale is that the
        // secondary may be in a different state than the primary and thus make different
        // decisions about creating the intermediate path in _fieldRef or not.
        status = logBuilder->addToUnsets(unsetPath);
    }

    return status;
}

}  // namespace mongo