eric-maynard commented on code in PR #1938:
URL: https://github.com/apache/polaris/pull/1938#discussion_r2167144153
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polaris-core/src/main/java/org/apache/polaris/core/persistence/pagination/PageToken.java:
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@@ -18,82 +18,75 @@
*/
package org.apache.polaris.core.persistence.pagination;
-import java.util.List;
-import java.util.Objects;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
+import com.fasterxml.jackson.databind.annotation.JsonSerialize;
+import jakarta.annotation.Nullable;
+import java.util.Optional;
+import java.util.OptionalInt;
+import org.apache.polaris.immutables.PolarisImmutable;
-/**
- * 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 {
-
- /** Build a new PageToken that reads everything */
- public static PageToken readEverything() {
- return build(null, null);
- }
+/** A wrapper for pagination information passed in as part of a request. */
+@PolarisImmutable
+@JsonSerialize(as = ImmutablePageToken.class)
+@JsonDeserialize(as = ImmutablePageToken.class)
+public interface PageToken {
+ // Serialization property names are intentionally short to reduce the size
of the serialized
+ // paging token.
- /** Build a new PageToken from an input String, without a specified page
size */
- public static PageToken fromString(String token) {
- return build(token, null);
- }
-
- /** Build a new PageToken from a limit */
- public static PageToken fromLimit(Integer pageSize) {
- return build(null, pageSize);
- }
+ /** The requested page size (optional). */
+ @JsonProperty("p")
+ OptionalInt pageSize();
- /** Build a {@link PageToken} from the input string and page size */
- public static PageToken build(String token, Integer pageSize) {
- if (token == null || token.isEmpty()) {
- if (pageSize != null) {
- return new LimitPageToken(pageSize);
- } else {
- return new ReadEverythingPageToken();
- }
- } else {
- // TODO implement, split out by the token's prefix
- throw new IllegalArgumentException("Unrecognized page token: " + token);
- }
+ /** Convenience for {@code pageSize().isPresent()}. */
+ default boolean paginationRequested() {
+ return pageSize().isPresent();
}
- /** Serialize a {@link PageToken} into a string */
- public abstract String toTokenString();
-
/**
- * Builds a new page token to reflect new data that's been read. If the
amount of data read is
- * less than the pageSize, this will return a {@link DonePageToken}
+ * Paging token value, if present. Serialized paging tokens always have a
value, but "synthetic"
+ * paging tokens like {@link #readEverything()} or {@link #fromLimit(int)}
do not have a token
+ * value.
*/
- protected abstract PageToken updated(List<?> newData);
+ @JsonProperty("v")
+ Optional<Token> value();
+
+ // Note: another property can be added to contain a (cryptographic)
signature, if we want to
+ // ensure that a paging-token hasn't been tampered.
/**
- * Builds a {@link Page <T>} from a {@link List<T>}. The {@link PageToken}
attached to the new
- * {@link Page <T>} is the same as the result of calling {@link
#updated(List)} on this {@link
- * PageToken}.
+ * Paging token value, if it is present and an instance of the given {@code
type}. This is a
+ * convenience to prevent duplication of type casts.
*/
- public final <T> Page<T> buildNextPage(List<T> data) {
- return new Page<T>(updated(data), data);
+ default <T extends Token> Optional<T> valueAs(Class<T> type) {
+ return value()
+ .flatMap(
+ t ->
+ type.isAssignableFrom(t.getClass()) ?
Optional.of(type.cast(t)) : Optional.empty());
+ }
+
+ /** Represents a non-paginated request. */
+ static PageToken readEverything() {
+ return PageTokenUtil.READ_EVERYTHING;
Review Comment:
Is `READ_EVERYTHING` a `Util`? Seems like it would belong in `PageToken`
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