eric-maynard commented on code in PR #1555:
URL: https://github.com/apache/polaris/pull/1555#discussion_r2112255474


##########
polaris-core/src/main/java/org/apache/polaris/core/persistence/pagination/EntityIdPageToken.java:
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@@ -0,0 +1,120 @@
+/*
+ * 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.polaris.core.persistence.pagination;
+
+import java.util.List;
+import java.util.Optional;
+import org.apache.polaris.core.entity.EntityNameLookupRecord;
+import org.apache.polaris.core.entity.PolarisBaseEntity;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class EntityIdPageToken extends PageToken implements HasPageSize {
+  private static final Logger LOGGER = 
LoggerFactory.getLogger(EntityIdPageToken.class);
+
+  public static final String PREFIX = "entity-id";
+
+  /** The minimum ID that could be attached to an entity */
+  private static final long MINIMUM_ID = 0;
+
+  /** The entity ID to use to start with. */
+  public static final long BASE_ID = MINIMUM_ID - 1;
+
+  private final long entityId;
+  private final int pageSize;
+
+  public EntityIdPageToken(int pageSize) {
+    this.entityId = BASE_ID;
+    this.pageSize = pageSize;
+  }
+
+  public EntityIdPageToken(long entityId, int pageSize) {
+    this.entityId = entityId;
+    this.pageSize = pageSize;
+  }
+
+  /**
+   * Build an {@link EntityIdPageToken} from a {@link PageRequest}, or else a 
{@link
+   * ReadEverythingPageToken} if the request doesn't require pagination.
+   */
+  public static PageToken fromPageRequest(PageRequest pageRequest) {
+    if (pageRequest.getPageTokenString().isEmpty()) {
+      if (pageRequest.getPageSize().isEmpty()) {
+        return PageToken.readEverything();

Review Comment:
   > I mean, the code that needs to extract a specific token from PageRequest 
already knows the exact token class. The "read everything" case is the only 
exception.
   
   It's not the only exception -- to make this more clear I've added the limit 
token type I mentioned above. Now in the current state of the code we have two 
"exceptions".
   
   > Each Persistence uses only one token type.
   
   Each one uses 3 now, and even if you exclude the 2 simple types it's obvious 
that we will need another type soon for paginating non-entity requests.



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