97a71a4adc
Since NotesMigration now returns only constant values, this check is redundant. Change-Id: Ib4d89e01f1dc50192ee3fca8f8501272c5a4838d
74 lines
3.4 KiB
Java
74 lines
3.4 KiB
Java
// Copyright (C) 2016 The Android Open Source Project
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package com.google.gerrit.server.schema;
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import com.google.gerrit.reviewdb.server.DisallowedReviewDb;
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import com.google.gerrit.reviewdb.server.ReviewDb;
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import com.google.gerrit.server.notedb.NotesMigration;
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import com.google.gwtorm.server.OrmException;
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import com.google.gwtorm.server.SchemaFactory;
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import com.google.inject.Inject;
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import com.google.inject.Singleton;
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@Singleton
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public class NotesMigrationSchemaFactory implements SchemaFactory<ReviewDb> {
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private final NotesMigration migration;
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@Inject
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NotesMigrationSchemaFactory(NotesMigration migration) {
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this.migration = migration;
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}
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@Override
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public ReviewDb open() throws OrmException {
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// There are two levels at which this class disables access to Changes and related tables,
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// corresponding to two phases of the NoteDb migration:
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//
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// 1. When changes are read from NoteDb but some changes might still have their primary storage
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// in ReviewDb, it is generally programmer error to read changes from ReviewDb. However,
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// since ReviewDb is still the primary storage for most or all changes, we still need to
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// support writing to ReviewDb. This behavior is accomplished by wrapping in a
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// DisallowedReviewDb.
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//
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// Some codepaths might need to be able to read from ReviewDb if they really need to,
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// because they need to operate on the underlying source of truth, for example when reading
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// a change to determine its primary storage. To support this, ReviewDbUtil#unwrapDb can
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// detect and unwrap databases of this type.
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//
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// 2. After all changes have their primary storage in NoteDb, we can completely shut off access
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// to the change tables. At this point in the migration, we are by definition not using the
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// ReviewDb tables at all; we could even delete the tables at this point, and Gerrit would
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// continue to function.
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//
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// This is accomplished by setting the delegate ReviewDb *underneath*
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// DisallowReadFromChanges to be a complete no-op, with NoChangesReviewDb. With this
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// stub implementation, all read operations return no results, and write operations silently
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// do nothing. This implementation is not a public class and callers couldn't do anything
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// useful with it even if it were.
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// Disable writes to change tables in ReviewDb (ReviewDb access for changes are No-Ops); all
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// other table accesses throw runtime exceptions.
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ReviewDb db = new NoChangesReviewDb();
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// Second create the wrappers which can be removed by ReviewDbUtil#unwrapDb(ReviewDb).
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if (migration.readChanges()) {
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// If reading changes from NoteDb is configured, changes should not be read from ReviewDb.
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// Make sure that any attempt to read a change from ReviewDb anyway fails with an exception.
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db = new DisallowedReviewDb(db);
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}
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return db;
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}
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}
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