dimas-b commented on code in PR #1528: URL: https://github.com/apache/polaris/pull/1528#discussion_r2078553909
########## polaris-core/src/main/java/org/apache/polaris/core/persistence/pagination/PageToken.java: ########## @@ -0,0 +1,179 @@ +/* + * 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.nio.charset.StandardCharsets; +import java.util.Arrays; +import java.util.Base64; +import java.util.List; +import java.util.stream.Collectors; +import java.util.stream.Stream; + +/** + * Represents a page token that can be used by operations like `listTables`. Clients that specify a + * `pageSize` (or a `pageToken`) may receive a `next-page-token` in the response, the content of + * which is a serialized PageToken. + * + * <p>By providing that in the next query's `pageToken`, the client can resume listing where they + * left off. If the client provides a `pageToken` or `pageSize` but `next-page-token` is null in the + * response, that means there is no more data to read. + */ +public abstract class PageToken { + + public int pageSize; + + public static final PageToken END = null; + public static final int DEFAULT_PAGE_SIZE = 1000; + + protected void validate() { + if (pageSize <= 0) { + throw new IllegalArgumentException("Page size must be greater than zero"); + } + } + + /** + * Get a new PageTokenBuilder from a PageToken. The PageTokenBuilder type should match the + * PageToken type. Implementations may also provide a static `builder` method to obtain the same + * PageTokenBuilder. + */ + protected abstract PageTokenBuilder<?> getBuilder(); + + /** Allows `PageToken` implementations to implement methods like `fromLimit` */ + public abstract static class PageTokenBuilder<T extends PageToken> { + + /** + * A prefix that tokens are expected to start with, ideally unique across `PageTokenBuilder` + * implementations. + */ + public abstract String tokenPrefix(); + + /** + * The number of expected components in a token. This should match the number of components + * returned by getComponents and shouldn't account for the prefix or the checksum. + */ + public abstract int expectedComponents(); + + /** Deserialize a string into a {@link PageToken} */ + public final PageToken fromString(String tokenString) { + if (tokenString == null) { + throw new IllegalArgumentException("Cannot build page token from null string"); + } else if (tokenString.isEmpty()) { + if (this instanceof ReadEverythingPageToken.ReadEverythingPageTokenBuilder) { + return ReadEverythingPageToken.get(); Review Comment: Specs are not infallible :) Quoting from the REST API [spec](https://github.com/apache/iceberg/blob/f7c6d57a03282516c6f988fa23a809416cd765b1/open-api/rest-catalog-open-api.yaml#L1699-L1701) ``` Servers that support pagination must return all results in a single response with the value of `next-page-token` set to `null` if the query parameter `pageToken` is not set in the request. ``` IMHO, this requirement is a recipe for disaster if, for example, a catalog has millions of entries. I would not want to force Polaris into following this statement by the letter. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: issues-unsubscr...@polaris.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
