SERVER-42665 move ProjectionPolicies to top-level mongo namespace

1 files changed, 73 insertions, 0 deletions

diff --git a/src/mongo/db/query/projection_policies.h b/src/mongo/db/query/projection_policies.h
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+++ b/src/mongo/db/query/projection_policies.h
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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.
+ */
+
+#pragma once
+
+namespace mongo {
+
+struct ProjectionPolicies {
+    // Allows the caller to indicate whether the projection should default to including or
+    // excluding the _id field in the event that the projection spec does not specify the
+    // desired behavior. For instance, given a projection {a: 1}, specifying 'kExcludeId' is
+    // equivalent to projecting {a: 1, _id: 0} while 'kIncludeId' is equivalent to the
+    // projection {a: 1, _id: 1}. If the user explicitly specifies a projection on _id, then
+    // this will override the default policy; for instance, {a: 1, _id: 0} will exclude _id for
+    // both 'kExcludeId' and 'kIncludeId'.
+    enum class DefaultIdPolicy { kIncludeId, kExcludeId };
+
+    // Allows the caller to specify how the projection should handle nested arrays; that is, an
+    // array whose immediate parent is itself an array. For example, in the case of sample
+    // document {a: [1, 2, [3, 4], {b: [5, 6]}]} the array [3, 4] is a nested array. The array
+    // [5, 6] is not, because there is an intervening object between it and its closest array
+    // ancestor.
+    enum class ArrayRecursionPolicy { kRecurseNestedArrays, kDoNotRecurseNestedArrays };
+
+    // Allows the caller to specify whether computed fields should be allowed within inclusion
+    // projections. Computed fields are implicitly prohibited by exclusion projections.
+    enum class ComputedFieldsPolicy { kBanComputedFields, kAllowComputedFields };
+
+    static const DefaultIdPolicy kDefaultIdPolicyDefault = DefaultIdPolicy::kIncludeId;
+    static const ArrayRecursionPolicy kArrayRecursionPolicyDefault =
+        ArrayRecursionPolicy::kRecurseNestedArrays;
+    static const ComputedFieldsPolicy kComputedFieldsPolicyDefault =
+        ComputedFieldsPolicy::kAllowComputedFields;
+
+    ProjectionPolicies(DefaultIdPolicy idPolicy = kDefaultIdPolicyDefault,
+                       ArrayRecursionPolicy arrayRecursionPolicy = kArrayRecursionPolicyDefault,
+                       ComputedFieldsPolicy computedFieldsPolicy = kComputedFieldsPolicyDefault)
+        : idPolicy(idPolicy),
+          arrayRecursionPolicy(arrayRecursionPolicy),
+          computedFieldsPolicy(computedFieldsPolicy) {}
+
+    const DefaultIdPolicy idPolicy;
+    const ArrayRecursionPolicy arrayRecursionPolicy;
+    const ComputedFieldsPolicy computedFieldsPolicy;
+};
+
+}  // namespace mongo