SERVER-28769 Implement PopNode.

1 files changed, 121 insertions, 0 deletions

diff --git a/src/mongo/db/update/pop_node.cpp b/src/mongo/db/update/pop_node.cpp
new file mode 100644
index 00000000000..c0a81132118
--- /dev/null
+++ b/src/mongo/db/update/pop_node.cpp
@@ -0,0 +1,121 @@
+/**
+ * Copyright (C) 2017 MongoDB 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/platform/basic.h"
+
+#include "mongo/db/update/pop_node.h"
+
+#include "mongo/db/update/path_support.h"
+
+namespace mongo {
+
+Status PopNode::init(BSONElement modExpr, const CollatorInterface* collator) {
+    _popFromFront = modExpr.isNumber() && modExpr.number() < 0;
+    return Status::OK();
+}
+
+void PopNode::apply(mutablebson::Element element,
+                    FieldRef* pathToCreate,
+                    FieldRef* pathTaken,
+                    StringData matchedField,
+                    bool fromReplication,
+                    const UpdateIndexData* indexData,
+                    LogBuilder* logBuilder,
+                    bool* indexesAffected,
+                    bool* noop) const {
+    *indexesAffected = false;
+    *noop = false;
+
+    if (pathTaken->empty()) {
+        // No components of the path existed. The pop is treated as a no-op in this case.
+        *noop = true;
+        return;
+    }
+
+    if (!pathToCreate->empty()) {
+        // There were path components which we could not traverse. If 'element' is a nested object
+        // which does not contain 'pathToCreate', then this is a no-op (e.g. {$pop: {"a.b.c": 1}}
+        // for document {a: {b: {}}}).
+        //
+        // If the element is an array, but the numeric path does not exist, then this is also a
+        // no-op (e.g. {$pop: {"a.2.b": 1}} for document {a: [{b: 0}, {b: 1}]}).
+        //
+        // Otherwise, this the path contains a blocking leaf or array element, which is an error.
+        if (element.getType() == BSONType::Object) {
+            *noop = true;
+            return;
+        }
+
+        size_t arrayIndex;
+        if (element.getType() == BSONType::Array &&
+            pathsupport::isNumericPathComponent(pathToCreate->getPart(0), &arrayIndex)) {
+            *noop = true;
+            return;
+        }
+
+        uasserted(ErrorCodes::PathNotViable,
+                  str::stream() << "Cannot use the part (" << pathToCreate->getPart(0) << ") of ("
+                                << pathTaken->dottedField()
+                                << "."
+                                << pathToCreate->dottedField()
+                                << ") to traverse the element ({"
+                                << element.toString()
+                                << "})");
+    }
+
+    invariant(!pathTaken->empty());
+    invariant(pathToCreate->empty());
+
+    // The full path existed, but we must fail if the element at that path is not an array.
+    invariant(element.ok());
+    uassert(ErrorCodes::TypeMismatch,
+            str::stream() << "Path '" << pathTaken->dottedField()
+                          << "' contains an element of non-array type '"
+                          << typeName(element.getType())
+                          << "'",
+            element.getType() == BSONType::Array);
+
+    if (!element.hasChildren()) {
+        // The path exists and contains an array, but the array is empty.
+        *noop = true;
+        return;
+    }
+
+    if (indexData && indexData->mightBeIndexed(pathTaken->dottedField())) {
+        *indexesAffected = true;
+    }
+
+    auto elementToRemove = _popFromFront ? element.leftChild() : element.rightChild();
+    invariantOK(elementToRemove.remove());
+
+    if (logBuilder) {
+        uassertStatusOK(logBuilder->addToSetsWithNewFieldName(pathTaken->dottedField(), element));
+    }
+}
+
+}  // namespace mongo