[GitHub] [druid] jihoonson commented on a diff in pull request #12396: Add support for authorizing query context params

[GitBox <gi...@apache.org>]

jihoonson commented on code in PR #12396:
URL: https://github.com/apache/druid/pull/12396#discussion_r852256537


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server/src/main/java/org/apache/druid/server/QueryHolder.java:
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@@ -0,0 +1,89 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.druid.server;
+
+import com.google.common.base.Preconditions;
+import org.apache.druid.query.DataSource;
+import org.apache.druid.query.Query;
+
+/**
+ * Holder of a native Druid query.
+ *
+ * The native Druid query object has query context parameters in it (see {@link Query#getContext()}).
+ * During query processing, Druid can add extra parameters as it needs. However, when authorizing context params,
+ * only the params that the user sets should be authorized. To separate user params from others,
+ * the Druid native query entry uses {@link QueryContext}. After user context params are authorized
+ * in {@link QueryLifecycle#authorize}, QueryLifecycle sets the query context back to this query holder
+ * using {@link #withContext(QueryContext)}. When callers use query context, they should check first
+ * if the query holder has a valid query context using {@link #isValidContext()}.
+ */
+public class QueryHolder<T>

Review Comment:
   I added `QueryHolder` at first because it was quite confusing which is the valid context between `Query.getContext()` and `QueryContext`. `QueryHolder` was a stateful object indicating whether `Query.getContext` is valid. `QueryLifecycle` could find a valid query context using `QueryHolder.isValidContext()`. A better approach is replacing the context map in `Query` with `QueryContext` as we can consolidate the query context stores. I didn't do it at first because it seems quite invasive. However, I was curious how invasive it would be, so went ahead and tried it. It actually doesn't seem that invasive, this PR is rather a little bit smaller than it was before.
   
   The `Query` interface now has `getQueryContext()` which returns `QueryContext`. This new interface is preferred over `Query.getContext()` which internally simply calls `QueryContext.getMergedParams()`. `QueryContext` in `Query` is "valid" only in the broker in a sense that `defaultParams`, `userParams`, and `systemParams` will not be kept after serialization. All parameters will be stored in `userParams` after it is deserialized. This should not cause any issue today.



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