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QuestDB is high performance SQL time series database

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 *  Copyright (c) 2014-2019 Appsicle
 *  Copyright (c) 2019-2024 QuestDB
 *
 *  Licensed 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,
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package io.questdb.cairo.sql;

import io.questdb.cairo.TableReader;
import io.questdb.std.QuietCloseable;
import org.jetbrains.annotations.Nullable;
import org.jetbrains.annotations.TestOnly;

/**
 * A cursor for navigating through partition frames.
 */
public interface PartitionFrameCursor extends QuietCloseable, SymbolTableSource {

    default void calculateSize(RecordCursor.Counter counter) {
    }

    // same TableReader is available on each partition frame
    TableReader getTableReader();

    /**
     * @return the next element in the partition frame
     * @throws io.questdb.cairo.DataUnavailableException when the queried partition is in cold storage
     */
    @Nullable
    PartitionFrame next();

    /**
     * Reload the partition frame and return the cursor to the beginning of
     * the partition frame
     *
     * @return true when reload data has changed, false otherwise
     */
    @TestOnly
    boolean reload();

    /**
     * @return number of rows in all partition frames.
     */
    long size();

    /**
     * @return true if cursor supports fast size calculation,
     * i.e. {@link #calculateSize(RecordCursor.Counter)} is properly implemented.
     */
    default boolean supportsSizeCalculation() {
        return false;
    }

    /**
     * Return the cursor to the first partition frame.
     */
    void toTop();
}