...

/**
 * Interactive query for issuing range queries and scans over KeyValue stores.
 * <p>
 *  A range query retrieves a set of records, specified using an upper and/or lower bound on the keys.
 * <p>
 * A scan query retrieves all records contained in the store.
 * <p>
 */
@Evolving
public final class RangeQuery<K, V> implements Query<KeyValueIterator<K, V>> {
    ...

    private final boolean isKeyAscending;

    /**
     * Determines if the query keys are in ascending order.
     * @return true if ascending, false otherwise.
     */
    public boolean isKeyAscending();
    ...

    /**
     * Set the query to return keys in descending order.
     * @return a new RangeQuery instance with descending flag set.
     */
    public RangeQuery<K, V> withDescendingKeys();

    ...
}

According to KIP-968, we introduce a public enum ResultOrder.

ResultOrder enum
It helps with specifying the order of the returned results by the query.

package org.apache.kafka.streams.query;
 
public enum ResultOrder {
    ANY,
    ASCENDING,
    DESCENDING
}

Test Plan

This time, our goal is to implement reverseRange and reverseAll functionalities. While these terms are used for clarity, in practice, they correspond to RangeQuery.withRange().withDescendingKeys() and RangeQuery.withNoBounds().withDescendingKeys(), respectively. To ensure the accurate retrieval of results for both functionalities, adjustments to IQv2StoreIntegrationTest are required. In our previous approach, we stored query results in a set, which doesn't maintain order. I've transitioned to using a list for storing query results, enabling us to distinguish between rangeQuery and reverseQuery. Here, rangeQuery refers to standard queries (those not using withDescendingKeys()) such as withRange(), withLowerBound(), withUpperBound(), and withNoBounds(). In contrast, reverseQuery denotes queries that employ the withDescendingKeys() method.

...